Cold Climate Building 

Enclosure Solutions

Jan Kosny, Ali Fallahi, and Nitin Shukla

Fraunhofer CSE

January 2013
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iii 

Cold Climate Building Enclosure Solutions

Prepared for: 

The National Renewable Energy Laboratory 

On behalf of the U.S. Department of Energy’s Building America Program 

Office of Energy Efficiency and Renewable Energy 

15013 Denver West Parkway 

Golden, CO 80401 

NREL Contract No. DE-AC36-08GO28308 

Prepared by: 

Fraunhofer CSE 

25 First Street

Cambridge, MA 02141 

NREL Technical Monitor: Chuck Booten 

Prepared under Subcontractor No. KNDJ-0-40345-00 

January 2013 
iv

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v 

Contents

List of Figures ................................................................................................................................. vi

List of Tables ................................................................................................................................ viii

Definitions ....................................................................................................................................... ix

Executive Summary .......................................................................................................................... i

1 Introduction................................................................................................................................2

2 Insulation Technologies .............................................................................................................3

2.1 Deep Energy Wall Retrofit ..................................................................................................3

2.2 Vacuum Insulation Panel .....................................................................................................3

2.3 Aerogel .................................................................................................................................4

2.4 Relevance to Building America’s Goals ..............................................................................5

3 Cost-Effectiveness Analysis .......................................................................................................6

3.1 VIP Cost Analysis ................................................................................................................6

3.1.1 Installed Cost Estimation .........................................................................................6

3.1.2 Target R-Value.........................................................................................................8

3.1.3 Equivalent Thickness ...............................................................................................8

3.1.4 Retrofit Tasks ...........................................................................................................8

3.1.5 Discussion ................................................................................................................9

3.2 Aerogel Cost Analysis .........................................................................................................9

3.2.1 Retrofit Cost Estimation ..........................................................................................9

3.2.2 Cost Comparisons ..................................................................................................12

3.2.3 Future Cost Comparisons .......................................................................................13

3.2.4 Aerogel Production Cost ........................................................................................13

3.2.5 Approaches to Lower Production Cost ..................................................................14

3.2.6 Discussion ..............................................................................................................15

4 Blown-In Aerogel Technology .................................................................................................17

4.1 Thermal Testing of Shredded Spaceloft Aerogel Blankets ................................................17

4.2 Discussion ..........................................................................................................................18

5 Conclusions and Future Work .................................................................................................19

References ......................................................................................................................................20
vi

List of Figures

Figure 1. Emerging building insulation technologies considered: (a) VIP-based EIFS, (b) aerogel 

applied on the interior surface of the wall, (c) aerogel applied on the exterior surface of the 

wall, (d) blown-in aerogel applied to completely and partially filled cavities. Only thermal 

components are shown and drainage design is omitted. .............................................................. 22

Figure 2. 3D thermal modeling of modeled VIP encapsulated with XPS protection layers: (a) plan 

view of 1 ft × 1 ft ×1 in. VIP panel with XPS protection dividers, (b) VIP layer sandwiched 

between two 1-in. layers of XPS. The whole assembly has an effective thermal resistance of R35. (c) Temperature mapping of VIP. The panel size is 1 ft × 1 ft ×1 in. and composed of three 

VIPs divided by XPS protection layers............................................................................................. 23

Figure 3. Equivalent thicknesses and installed cost of different exterior wall insulation systems to 

achieve R-35. The thicknesses in this figure are rounded from the manufactured thickness 

(rigid board with at least 1 in. thickness and spray foam with at least 0.5 in. thickness). The 

equivalent thickness for PU takes into account the thermal bridging effect of wood studs. VIP 

encapsulated in XPS insulation has effective thermal resistance of R-35 (Figures 4 and 5). The 

VIP cost was collected either directly from manufacturers or from published data on the 

internet for U.S., European, and Chinese markets.......................................................................... 24

Figure 4. Modeled thermal resistance of PU foam sprayed into studs 2 × 6; 16 in. o.c. The effective 

thermal resistance of 5.5 in. PU foam is R-25 (excluding air film resistances). To reach target 

R-35, it was assumed that the studs are installed on the exterior and standing off 2 in. away 

from the exterior sheeting. The 2 in. gap is filled with PU spray foam and collectively with the 

5.5 in. stud spaces provides the required target R-value. Therefore, approximately 7.5 in. PU 

foam is required to reach target R-35............................................................................................... 26

Figure 5. Modeled thermal resistance of PU foam sprayed into studs 2 × 4; 16 in. o.c. The effective 

thermal resistance of 3.5 in. PU foam is R-16.3 (excluding air film resistances). To reach target 

R-35, it was assumed that the studs are installed on the exterior and standing off 3.5 in. away 

from the exterior sheeting. The 3.5 in. gap is filled with PU spray foam and collectively with the 

3.5 in. stud spaces provides the required target R-value. Therefore, approximately 7 in. PU 

foam is required to reach target R-35............................................................................................... 27

Figure 6. Equivalent thicknesses and total cost of aerogel and foam insulation techniques to 

retrofit the wall of a baseline house to achieve target R-values of (a) R-4, (b) R-20, and (c) R-35. 

The thicknesses in this figure are rounded from the manufactured thickness (rigid board with 

at least 1 in. thickness, spray foam with at least 0.5 in. thickness, and blanket aerogel with 

minimum of 10 mm thickness). The material cost was collected either from manufacturers or 

published data on the internet. Costs of the exterior wall finishes are not included in analysis 

for all considered cases of wall retrofits; only the insulation part of the retrofit strategy is 

analyzed............................................................................................................................................... 30

Figure 7. Equivalent thicknesses and total cost of aerogel and conventional insulation techniques 

to retrofit the wall of a baseline house from interior to achieve target R-values of (a) R-4, (b) R8, (c) R-12 (compared with interior installation case), and (d) R-12 (compared with exterior 

installation case). Blanket aerogel installed from the interior side on top of the existing 

gypsum board. Conventional insulations installed from interior. For the case of R-12, both 

interior and exterior installations analyzed and shown. The thicknesses in this figure are 
vii

rounded values of the manufactured thickness (rigid board with at least 1 in. thickness, spray 

foam with at least 0.5 in. thickness and blanket aerogel with minimum of 3/8 in. thickness). The 

material cost was collected either from manufacturers or published data on the internet........ 34

Figure 8. Equivalent thickness and thermal resistance of aerogel and conventional insulations 

installed in a 2 × 4 stud cavity with R-5 existing insulation to retrofit the wall of a baseline 

house. The team assumed the existing R-5 took approximately 1.5 in. thickness of the cavity 

and the remaining 2 in. is filled with blown cellulose, blown fiberglass, injected PU foam, or 

aerogel. ................................................................................................................................................ 35

Figure 9. Equivalent thicknesses and total cost of XPS foam insulations installed into a 2 × 4 stud 

cavity that already has R-5 existing insulation to retrofit the wall of a baseline house. For 

comparison purposes, the team assumed the R-5 insulation already existing in the wall cavity 

took approximately 1.5 in. of the cavity and the remaining 2 in. is filled with aerogel. Based on 

this estimation, proposed installation of the blown aerogel into a 2 × 4 stud cavity would be 

cost competitive if its price would be lower than $12.1–$12.8/ft2

. ................................................ 36

Figure 10 . Equivalent thickness and thermal resistance of aerogel and conventional insulations 

installed into an empty 2 × 4 stud cavity to retrofit the wall of a baseline house. The 3.5 in. stud 

cavity is filled with blown cellulose, blown fiberglass, injected PU foam, or aerogel. To reach 

the target R-values, the team assumed that exterior XPS foam was installed in addition to PU 

foam cavity injection. Aerogel, open cell PU, closed cell PU, and XPS have R-values of R-8/in., 

R-3.6/in., R-6/in., and R-5/in., respectively. Blown cellulose has an R-value between R-3.2 and 

R-3.8/in. and blown fiberglass between R-2.2 and R-2.7/in. 

(http://www.energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11650). 

For this study, blown cellulose and blown fiberglass have R-values of R-3.5/in. and R-2.45/in., 

respectively......................................................................................................................................... 37

Figure 11. Equivalent thicknesses and total cost of aerogel and conventional insulations installed 

in empty 2 × 4 stud cavity to retrofit the wall of a baseline house. The 3.5 in. stud cavity is 

filled with blown cellulose, blown fiberglass, injected PU foam, or aerogel. To reach the target 

R-values, the team assumed XPS exterior installation in addition to PU cavity injection. Based 

on this estimation, proposed blown aerogel into a 2 × 4 stud cavity would be cost competitive 

if the price is within or lower than $12–$14/ft2

. ............................................................................... 38

Figure 12. Shredding of Spaceloft aerogel blankets: (a) finely chopped pieces of aerogel blanket 

as they exit the shredder, and (b) final product. ............................................................................. 39

Figure 13. R-value per inch as a function of effective packing density for shredded aerogel 

samples (three leftmost data points). Data for Spaceloft aerogel blanket are included as well 

[42] (rightmost data point). literature data on the thermal performance of shredded aerogels 

are lacking. To develop an approximate relation between conductivity and packing density, 

the team measured thermal conductivity for three effective packing densities. Then a very 

approximate extrapolation was made between measured data and Spaceloft aerogel data to 

predict R-values in the intermediate density range. The red line marks the density value 

required to obtain R-value of 8/in. .................................................................................................... 39

 Unless otherwise noted, all figures were created by Fraunhofer CSE. 
viii

List of Tables

Table 1. Installed cost estimates for conventional and emerging insulation techniques to retrofit 

the wall of a baseline house. Aerogel or VIP retrofit techniques do not require all retrofit tasks 

because of low thickness. Costs of the exterior wall finishes are not included in analysis for all 

considered cases of deep energy retrofits; only the insulation part of the retrofit strategy is 

analyzed............................................................................................................................................... 40

Table 2. Total cost of aerogel and conventional insulation techniques to retrofit the wall of 

baseline house to exterior R-4 target value. Aerogel retrofit technique does not require all 

retrofit tasks because of low thickness. The retrofit tasks are not in order. ............................... 43

Table 3. Total cost of aerogel and conventional insulation techniques to retrofit the wall of 

baseline house to exterior R-20 target value. Aerogel retrofit technique does not require all 

retrofit tasks because of low thickness. The retrofit tasks are not in order. ............................... 44

Table 4. Total cost of aerogel and conventional insulation techniques to retrofit the wall of 

baseline house to exterior R-35 target value. Aerogel retrofit technique does not require all 

retrofit tasks because of low thickness. The retrofit tasks are not in order. ............................... 45

Table 5. Total cost of aerogel and conventional insulation techniques to retrofit the wall of 

baseline house to interior R-4 target value. The aerogel retrofit technique does not require all 

retrofit tasks because of its lower thickness. The retrofit tasks are not in order........................ 47

Table 6. Total cost of aerogel and conventional insulation techniques to retrofit the wall of 

baseline house to interior R-8 target value. The aerogel retrofit technique does not require all 

retrofit tasks because of its lower thickness. The retrofit tasks are not in order........................ 49

Table 7. Total cost of aerogel and conventional insulation techniques to retrofit the wall of 

baseline house to interior R-12. The aerogel retrofit technique does not require all retrofit 

tasks because of its lower thickness. The retrofit tasks are not in order. ................................... 51

Table 8. Total cost of aerogel and conventional insulation techniques to retrofit the wall of 

baseline house to interior R-12 target value. Aerogel retrofit technique does not require all 

retrofit tasks because of its low thickness. The retrofit tasks are not in order. .......................... 52

Table 9. Total cost of aerogel and foam insulation techniques to retrofit the wall of baseline house 

to blown R-16 target value. The aerogel retrofit technique does not require all retrofit tasks 

because of its lower thickness. Required thicknesses were calculated based on effective Rvalue of cavity insulations. The retrofit tasks are not in order...................................................... 53

Table 10. Total cost of aerogel and foam insulation techniques to retrofit the wall of baseline 

house to blown R-20 target value. The aerogel retrofit technique does not require all retrofit 

tasks because of its lower thickness. The retrofit tasks are not in order. ................................... 55

Table 11. Thermal performance test data for aerogel samples. Data for Spaceloft aerogel blanket 

are taken from reference [50]. ........................................................................................................... 56

Unless otherwise noted, all tables were created by Fraunhofer CSE.
ix

Definitions

APD

EIFS

EPS

PIC

PU

U.S. DOE

VIP

XPS 

Atmospheric pressure drying

External insulation finishing system

Expanded polystyrene 

Polyisocyanurate 

Polyurethane

U.S. Department of Energy 

Vacuum insulation panel 

Extruded polystyrene 
i 

Executive Summary

The main goal of this project is to investigate the energy performance and cost effectiveness of

several state-of-the-art retrofit strategies that could be used in residential houses in the Boston 

and New England area. To realize this goal, Fraunhofer CSE evaluated the application of several 

emerging building enclosure technologies, including high performance (i.e., high R-value) 

aerogel and vacuum insulations, in forms that would be energy efficient, flexible for different 

retrofit scenarios, durable, and potentially cost competitive for deep energy retrofits. Historically, 

high performance thermal insulation has been an expensive material. With recent advancements 

in the fields of material processing and production technology, however, their prices have been 

falling, making them a more attractive option for building insulation. In this project, the team 

focused on the following building enclosure technologies: (i) R-30 vacuum insulation panels 

(VIP)-based exterior insulation finishing system (EIFS) system technology, (ii) aerogel exterior 

and interior wall surface insulations, and (iii) R-8 blown-cavity aerogel insulation. A detailed 

cost analysis was performed for each case. 

In the first phase of the project, the team developed detailed cost data that included material 

costs, labor costs, equivalent cost reductions from space savings and elimination of construction 

tasks, etc. The cost analysis indicates that the proposed method for VIP wall retrofit could be 

cost competitive with current deep energy retrofit strategies for walls using foam insulations. In 

the near future, further advancements in VIP manufacturing technology, larger volume 

production, and higher reliability through quality control of cores and films will enhance VIP 

cost effectiveness as a superior retrofit option for providing thermal insulation and mitigating 

thermal bridging effects in building envelopes. 

Next, we evaluated aerogel insulation application on the interior and exterior surfaces of the 

building envelope. Aerogel nanoinsulations are gels whose liquid component is completely 

removed and replaced with air or gas. They are highly porous materials with pore sizes on the 

order of nanometers, resulting in high thermal resistivity, about R-10 per inch. As-produced 

aerogels are fragile and unsuitable for use in most building applications; therefore, they are 

produced in blanket form by reinforcing them with a mechanically stronger material such as 

fiberglass. The team found that wall insulation retrofits using aerogel blankets could become cost

competitive in certain scenarios, such as interior thermal insulation installation. 

Further, the team proposed a novel concept of blown-in aerogel technology. Although this 

technology does not exist today, it might improve the thermal performance of typical woodframed walls, vaulted ceilings, and attics in the future. The preliminary cost estimates for this 

blown-cavity aerogel method show that this could become a cost-competitive option in niche 

areas of building thermal insulation, such as wall cavity insulation. The team conducted initial 

thermal testing on samples consisting of shredded aerogel blanket pieces to understand the 

insulation behavior of proposed blown-in aerogel technology. Thermal testing reveals that the Rvalue of these shredded aerogel samples increases as the effective packing density of aerogel 

pieces increases. This testing result shows a pathway for future development of blown-in aerogel 

technology by optimizing the processing method and packing density of the aerogel.
2 

1 Introduction 

This Building America project performed by Fraunhofer CSE investigates the performance of 

state-of-the-art, high R-value, deep energy retrofit strategies that could be applied to tripledeckers1

 and similar historic houses in the Boston and the New England area [1]. These 

strategies are based on high performance insulation materials such as vacuum insulation panels 

(VIPs) and aerogels, enabling achievement of high R-value in retrofits of walls with a very

minimal loss of the living space caused by the installation itself. In deep energy retrofit projects, 

target R-values for building envelopes are usually about R-30 for walls (R-value units in 

h·ft2·°F/Btu). This research project has been devised under the assumption that the target market 

is “deep” energy retrofits that aim to reduce envelope-related energy consumption by at least 

50%.2,3

The team investigated the potential integration of several high performing building enclosure 

technologies in forms that are expected to be energy efficient, flexible for different retrofit 

scenarios, durable, and cost competitive for deep energy retrofits. The focus was on three 

building enclosure technologies: 

• R-35 VIP-based external insulation finishing system (EIFS) system technology 

• Aerogel-based wall insulation 

• R-8 blown-in aerogel insulation

During the first phase of the project, the team developed detailed cost data for these 

technologies, including material costs, labor costs, potential time savings, equivalent cost 

reductions caused by space savings and elimination of construction tasks. In addition, Fraunhofer 

CSE, in collaboration with local government institutions, utilities, design offices, and 

contractors, is actively exploring different methods of cost reduction in residential retrofit 

projects performed in the Greater Boston area. 

The blown-in aerogel insulation technology is a new concept proposed in this report. Although 

this technology has potential for deep energy retrofit applications, it is at an early development 

stage. This initial analysis of R-8 blown cavity aerogel insulation indicated that, if fully 

developed, this method could be one of the easiest to apply and most labor-saving approaches to 

improve the thermal performance of typical wood-framed walls using a drill-and-fill technique. 

 

1 The triple-decker (or three-decker) is a unique housing type characteristic of New England cities in early 20th 

century. Generally defined, the triple-decker is a free standing, wood frame structure on its own narrow lot, three 

stories high and one family unit at each floor.

2 National Grid. Super Insulation Upgrades. 

See https://www1.nationalgridus.com/DeepEnergyRetrofit-MA-RES for more information.

3 Castle Square. Deep Energy Retrofit. 

See http://www.castledeepenergy.com/?page_id=185 for more information.
3 

2 Insulation Technologies

Emerging insulation technologies are slowly finding their way into buildings. VIP and aerogels 

are among the most promising of these building insulation technologies. Future success of these 

two technologies depends on their cost effectiveness in addition to their thermal performance and 

durability as compared to existing conventional technologies. 

In this report, the team analyzed the cost attributes of these two high R-value insulation 

technologies in combination with novel labor-saving installation techniques. Both technologies 

offer thermal conductivities several times lower than the conventional fiber and plastic foam 

insulations, which allows for the application of significantly thinner retrofit solutions, thus 

saving on space. In addition, thinner retrofit installations reduce costs for altering window and 

door openings, which is often necessary when using thick layers of conventional insulations for 

deep energy retrofit projects. Another advantage of these technologies is that both are 

nonflammable; this could be important if the United States adopts more restrictive building fire 

codes in the future, such as those that are already adopted in Europe, Japan, and China [2− 6]. 

2.1 Deep Energy Wall Retrofit

The target R-value of framed wall assemblies for deep energy retrofits in colder climates is 

typically R-30 or greater [7]. High R-value building envelopes reduce energy consumption for 

space heating and cooling, in addition to enhancing thermal comfort for the occupants. Advanced 

framing and exterior insulating sheathings can significantly improve thermal continuity to 

achieve high R-value walls [8]. There are space constraints for wall cavities or exterior 

installations of insulations, however, particularly in retrofit projects. In addition, very thick 

building envelopes are not desirable for several reasons: reduction of internal floor area for 

internal insulation retrofit, zoning regulations in cases of the exterior foam sheathing, a common 

need for alteration of window and door openings, architectural restrictions, and material use [9].

To achieve the highest possible thermal insulation resistance with existing space limitations of 

retrofit projects, new thermal insulation materials with low thermal conductivity, such as VIPs 

and aerogels, are reasonable alternatives to conventional insulation materials. As mentioned 

before, the main barrier to the application of these new materials is low production volume and 

high cost.

2.2 Vacuum Insulation Panel

VIPs are promising candidates for building thermal insulation because of their ultra-low thermal 

conductivity. Their thermal conductivity is four to eight times less than foam insulation 

materials, resulting in a substantially thinner solution to the building envelope relative to 

conventional insulation [10]. A VIP consists of a core panel enclosed in an air-tight envelope, to 

which a vacuum is applied. The common core materials are fumed and precipitated silica, open 

cell polyurethane (PU), and several types of fiberglass. The core is wrapped in a metallic or 

mylar foil, and then a vacuum is applied. The metallic film is sealed to maintain the vacuum for a 

long period of time; there may be some loss of insulation value as the panel ages, depending on 

the design of the installation [10].

Unfortunately, during the last two decades, high cost has been a major barrier to wide-scale 

adoption of silica-based VIPs. Currently, the price remains dominated by the typical dynamics of 
4 

the product introduction phase. Furthermore, the products themselves are still being developed 

and continually improved. 

2.3 Aerogel

Aerogel was invented in 1931 by Samuel Stephens Kistle. It is made up of a gel that has had its 

liquid component replaced by air—in fact, the material is 99% air by volume. Aerogels have 

considerably higher thermal resistivity values of about R-10/in. compared to the commonly used 

plastic foams such as extruded polystyrene (XPS, R-5/in.), expanded polystyrene (EPS, R-4/in.), 

polyisocyanurate (PIC, R-6.5/in.), and PU (R-6/in.).4,5,6 Therefore, in building retrofit 

applications where thickness of the envelope matters, they are considered a promising candidate 

for replacing conventional building thermal insulations. In addition, they are low flammable, 

lightweight, nontoxic, and water repellent, all highly desirable properties for a building thermal 

insulating material.

Aerogels have found application as thermal insulation material in subsea pipelines, shipping 

vessels, and the space exploration industry.7,8,9 Unfortunately, because of relatively low 

production volumes, this material is still expensive. Currently two U.S. companies, Aspen 

Aerogels Inc. and Cabot, have commercial products available in the market, and their production 

volumes are increasing as demand for aerogels grows. Meanwhile, ongoing research seeks to 

achieve a 50% decrease in the cost of this high performance insulation.10 Another market 

research report indicates that emerging insulation technologies such as aerogels will find small 

but profitable niches in the thermal envelope market, with 2020 market sizes of $230 million and 

$130 million, respectively.11

The thermal and cost analysis of the aerogel insulation presented in this report was prepared in 

collaboration with Aspen Aerogels, a member of the Fraunhofer CSE Building America team. 

 

4 Lawrence Berkley National Lab. Environmental Energy Technologies Division. See 

http://eetd.lbl.gov/ECS/aerogels/kistler-desert.html for more information. 5 Lawrence Berkley National Lab. Environmental Energy Technologies Division. See 

http://eetd.lbl.gov/ecs/aerogels/sa-thermal.html for more information. 6 TAASI Corporation. Insulation Properties of Aerogels. 

http://www.taasi.com/pdf/insul.pdf?token=5353a86ccb6eef3136ec51964fea78a49c67a75a|1317301391#PDFP

7 Aspen Aerogels. See http://www.aerogel.com/ for more information. 8

 NASA. Jet Propulsion Laboratory. California Institute of Technology. Preventing Heat Escape Through Insulation 

Called “Aerogel”. See http://marsrover.nasa.gov/mission/sc_rover_temp_aerogel.html for more information. 9 Woods, T. NASA (2011). Aerogels: Thinner, Lighter, Stronger. See 

http://www.nasa.gov/topics/technology/features/aerogels.html for more information 10 Kanellos, M. Green Tech Media (2011). Aerogel Prices to Drop by 90%?. See 

http://www.greentechmedia.com/articles/read/aerogels-to-drop-by-90-percent-in-price/ for more information. 11 McCutcheon, M. (2011). Opening the Thermal Envelope: Emerging Innovation in Dynamic Windows and 

Advanced Insulation. State of the Market Report. https://portal.luxresearchinc.com/research/report_excerpt/8469
5 

2.4 Relevance to Building America’s Goals

The overall goal of the U.S. Department of Energy's (DOE) Building America program is to 

“reduce home energy use by 30–50% (compared to 2009 energy codes for new homes and preretrofit energy use for existing homes)”.12 To this end, the team conducted research to “develop 

market-ready energy solutions that improve efficiency of new and existing homes in each U.S. 

climate zone, while increasing comfort, safety, and durability”.12

This research investigates the need for deep energy retrofits of residential walls in cold climates 

of the Northeast. 

 

12 US DOE (2012). Energy Efficiency and Renewable Energy. Building America – Resources for Energy Efficient 

Homes. http://www1.eere.energy.gov/buildings/building_america/program_goals.html. 
6 

3 Cost-Effectiveness Analysis

This project aims to develop and demonstrate advanced building enclosure strategies (based on 

VIP, aerogel, etc.) that improve energy savings, flexibility for different retrofit scenarios, speed 

of work, and cost competiveness for deep energy retrofits. We anticipate that the high R-value 

technologies for retrofitting residential walls and flat roofs could be used on thousands of 

historical triple-decker and colonial houses in the Boston and New England area. 

Affordability is a key aspect of high performance wall cavity insulations and sheathing insulation 

systems, because it helps ensure large-scale deployment of the systems. The design of the high 

R-value retrofit strategies focuses on simplicity, easy installation, and high performance 

materials. The team designed candidate systems and then performed an economic feasibility 

study to ensure that the design is competitive with the price of existing deep energy retrofit 

approaches. As part of the economic analysis, the team consulted with contractors to obtain 

estimates of the installation process and a bill of material to itemize the costs of the materials 

used in installation of the roof and wall retrofit systems.

It is important to mention here that the main focus of this report is to assess the economic 

feasibility of certain retrofit strategies that employ advanced insulation technologies. Therefore, 

hygrothermal performance of these advanced retrofit strategies, which is a key design parameter, 

is not investigated in this report. In fact, hygrothermal performance is beyond the scope of this

cost study. To advance understanding of this topic, Fraunhofer CSE is partnering with Dow 

Corning Inc. and Dryvit Inc. on a DOE-funded project and with Aspen Aerogel Inc. on a 

Department of Defense funded project to investigate the hygrothermal behavior of high 

performance materials such as VIPs and aerogel.

13,14

3.1 VIP Cost Analysis

This study compares the current cost of wall retrofit projects using VIPs to that of conventional 

foam applications. Foam insulations were chosen for comparison because they are most

commonly used in exterior wall retrofits and provide higher thermal resistance per unit thickness 

than fiber insulations. 

3.1.1 Installed Cost Estimation 

We estimated and compared the total cost15 to deep energy wall retrofitting of a baseline house16

using conventional foam insulations [11].17 The conventional foam insulations include rigid 

board (XPS, EPS, and PIC foams) and spray-applied (closed-cell PU foam) options. The team 

assumed that the rigid boards are installed in the form of an exterior sheathing, and the foam is 

sprayed either in between added studs or between exterior furrings. 

 

13 See http://apps1.eere.energy.gov/buildings/publications/pdfs/building_america/ns/plenary_2_emerging_tech.pdf

for more information.

14 See http://www.sbir.gov/sbirsearch/detail/12181 for more information. 15 The total cost is the sum of the bare material cost, the bare labor cost, the bare equipment cost plus 10% for profit. 16 The baseline house is a two-story average class residential house with 2,000 ft2 floor surface area and 2,700 ft2

wall surface area (RSMeans Residential Cost Data 2011, page 29).

17 The main source of cost data to estimate total cost is RSMeans Construction Cost Data (2011) and RSMeans 

Residential Cost Data (2011).
7 

Although retrofit applications can apply combined cavity and exterior insulations to reach R-35 

thermal resistance, this study considers only exterior installation as compared to VIPs. This is 

because for the cases considered in this study, the installed cost of combined cavity and exterior 

installation is higher than the installed cost of just exterior insulation. Table 1 shows an example

comparison. 

This report considers a new retrofit method of installing VIPs insulation that takes advantage of 

exterior cladding of a wall assembly to achieve continuity of thermal insulation in addition to the 

convenience of quick and easy installations. In this method, a 1 in. thick VIP is encapsulated 

between two layers of 1-in. XPS layers (Figure 1). Then the 3 in. thick VIP-based EIFS is

installed on the exterior sheathing using adhesives. For deep retrofit projects, VIP-based EIFS 

provides several advantages over conventional foam based EIFS: higher R-value per unit 

thickness, improved thermal continuity and avoidance of numerous added thickness-related 

costly tasks such as window alteration because it directly adheres to the existing wall. For 

example, in deep retrofits of walls using conventional foam insulations, adding thick layers of 

thermal insulation is necessary (often 6−10 in.). Thick layers of insulation usually require special 

attachment methods (long screws or additional furring). In addition, window and door openings 

need to be altered to allow window replacements closer to the exterior surface, reduce local 

thermal bridging, and improve water drainage, for example. Further work is very often necessary 

to adjust roof overhangs because the original wall surface moves notably toward the outside 

when the thick foam layers are installed. When using significantly thinner high performance 

insulations such as VIPs, these tasks are not necessary. 

We used the following approach to estimate the total cost of each retrofit strategy: 

1. A target R-value is estimated. 

2. An equivalent thickness is calculated to achieve the target R-value. 

3. A list of required retrofit tasks is determined. The retrofit work depending on insulation 

type and equivalent thickness includes a series of tasks from altering the existing walls 

and roof to installing the insulation and exterior cladding. 

4. The cost of each retrofit task and the installed cost are estimated. 

It is important to recognize that the market for the VIP technology is immature, and the prices 

are expected to decrease as demand grows. Therefore, it is more appropriate to compare this 

technology with conventional insulation methods assuming thermal performance or target Rvalue as the criterion rather than finding an optimum balance between R-value and cost/savings.

Furthermore, as mentioned previously, the hygrothermal aspects of VIPs are not considered in 

this report. As stated previously, VIP-based panels are usually sandwiched within protective 

layers of foam insulation. The cost of this foam was included in the total cost of the VIP 

application. Table 1 lists more details.
8 

3.1.2 Target R-Value

VIPs in the market have thermal resistance in the range of R-25 to R-50/in. depending on the 

core material type and thickness. For the purpose of this study, the team assumed that the VIP 

has a nominal center-of-the-panel thermal resistance of R-40.18 HEATING 7.3 software modeled

the effective R-value for the case where the VIP is sandwiched between two layers of XPS 

insulation layers (1-in. XPS + 1-in. VIP + 1-in. XPS) to protect it from impact and damage. An

effective thermal resistance of R-35 was determined by taking into account all thermal bridging 

effects of XPS and foil layers. This number also includes R-value reduction caused by possible 

inserts of XPS in the remaining areas where modular dimensions of VIPs do not exactly cover 

the whole wall (Figure 2). 

For this study, only the effective thermal resistance of R-35 was considered, and cases with Rvalue losses from aging and puncturing were not included. It is reported that R-value of VIPs 

with fumed silica core at atmospheric pressure is about R-12 [10], and therefore it is estimated 

that the punctured VIPs sandwiched between two layers of XPS will have effective thermal 

resistance of minimum R-22. (Note: Two layers of XPS foam provide R-10.) 

It should be noted that to accurately simulate VIPs’ R-value, a 3-D heat transfer computer 

program is required to take into account all the complexity of heat transfer phenomena. The 

HEATING 7.3 computer code was used in this project. It is a dynamic 3-D heat transfer, finitedifference program that has been extensively validated by ORNL and is capable of solving 

steady-state and transient heat conduction problems in one-, two-, or three-dimensional 

Cartesian, cylindrical, or spherical coordinates. 

In this report, R-35 is taken as the target R-value to find equivalent thickness of other insulations. 

3.1.3 Equivalent Thickness

The VIP is sandwiched between two layers of XPS rigid board protection layers. The foam-VIPfoam panel considered has a total thickness of 3 in. For thermally equivalent conventional 

insulations, however, the thickness can vary between 6 and 9 in. For foam insulations, the 

effective R-value was calculated by taking into account the thermal bridging effect of exterior 

wood studs or furring (Figure 4 and ). Figure 3 shows the equivalent thickness that is required to 

achieve R-35 for different insulations. 

3.1.4 Retrofit Tasks

A VIP-based EIFS can be quickly and easily installed. Because VIPs are sandwiched between

foam, the overall installation and drainage system for this technology are almost identical to 

those of conventional EIFS applications (exterior insulation and finish system). In contrast, 

installing thermally equivalent foam insulation involves several additional costly and laborintensive retrofit tasks. Moreover, because the equivalent thickness of foam insulation is greater 

than 6 in., the retrofit tasks are limited to not only the walls but also fenestration openings and 

roof overhangs that might need to be readjusted or extended. This adds to the cost as well. Table 

1 shows the required wall retrofit tasks of a baseline house for VIPs and foam insulations (refer

to Figure 1). 

 

18 Nonaged condition.
9 

3.1.5 Discussion

In this cost analysis, for foam insulation retrofits, the costs of material, installation, and labor 

were taken from the RSMeans Cost Data 2011 book. For VIP retrofits, the price quotations were 

obtained from several VIP manufacturers around the world and used as material cost. Data from 

manufacturers’ websites and technical publications were also included. The labor cost for VIPbased EIFS installation was assumed to be the same as the cost of installing 3 in. of foam 

insulation. There is a large variation in VIP prices among manufacturers and references. 

Figure 3 shows cost estimates for wall retrofit strategies with VIP and foam insulations.19 VIP 

retrofit cost is the installed cost and not just the material cost. Wall retrofits with foam insulation 

costs between $14 and $17/ft2, while VIP retrofits vary between $12 and $41/ft2, depending on 

the manufacturer. This wide range in VIP-based EIFS retrofit cost reflects the large variability in 

the VIP prices across different manufacturers. Taking the lower range of VIP-based EIFS cost, 

an R-35 VIP-based wall retrofit costs almost 15% less than that using foam insulation. In fact, it 

is interesting to note that majority of the VIP-based solutions covered in this study are very cost 

competitive with foam-based retrofits, and at the same time provide the convenience of easy and 

quick installation with minimum disruption to the occupants. 

3.2 Aerogel Cost Analysis

This section describes the results of examining the economic feasibility of applying aerogels to 

supplement existing building thermal insulation materials for specific retrofit scenarios. To 

evaluate the potential cost effectiveness of aerogels as thermal insulation for wall retrofit 

applications, the team first estimated and compared the cost of applying the aerogel to that of 

installing conventional building insulations for residential retrofit projects.

20 Next, several 

approaches to lower the production costs to make aerogel technology more cost effective are 

proposed. 

To estimate the cost of wall retrofit projects using aerogel, different aerogel configurations, both 

interior and exterior installations are considered. In addition, the team proposes a novel, quick, 

and simple application of aerogel into the stud cavity for retrofit projects and estimate a price 

that might make this new application of aerogel cost competitive with conventional insulations.

Because of the relatively limited availability of referenced research, engineering, and cost data to 

conduct a broader study on this subject, this report includes data from websites and technical 

publications that might not have established scientific standing. The team encourages readers to 

use their discretion. 

3.2.1 Retrofit Cost Estimation

The total costs21 to retrofit the wall of a baseline house22 with conventional insulations and 

aerogels were estimated and compared using RS Means Cost Data [11]. The aerogel blanket cost 

 

19 Exterior cladding installation cost is not included in the cost estimation. 20 R-value was used to indicate performance criteria of foam insulations and aerogel in this report. Future reports 

need to employ energy performance to account for more comprehensive performance aspects of these insulations.

21 The total cost is the sum of the bare material cost, the bare labor cost, the bare equipment cost plus 10% for profit. 22 The baseline house is a two story average class residential house with 2,000 ft2 floor surface area, 135 ft 

perimeter, and 2,700 ft2 wall surface area as defined by RS Means Residential Cost Data (2011, page 42).
10

is based on the current cost of commercially available aerogel in the U.S. market and short-term 

cost reduction predictions. Based on communications with Aspen Aerogels, in the United States

the cost of an aerogel blanket with R-4 per 10 mm will be between $2.50 and $3.00/ft2

 in the 

near future (considering coming improvements in the production method and production volume 

increase). This evaluation used a price level of $2.75/ft2, which might be slightly lower from the 

current U.S. market prices. 

Conventional insulations considered in this analysis include cellulose, fiberglass, rigid foam 

products (XPS, EPS, and PIC), and spray-applied foam (open or closed-cell PU). Aerogel is 

applied as blankets or using the proposed blown-in application. 

To estimate the total cost of each retrofit strategy, the team followed the steps described in 

section 3.1.1. 

In this study, the following aerogel insulating retrofit strategies are proposed: 

Aerogel blankets installed on the exterior side of the existing exterior wall sheathing: A 

relatively thick insulation system made of conventional foam is replaced with a thermally 

equivalent aerogel material with approximately half the total thickness. In this case, the aerogel 

insulation adheres directly to the existing wall sheathing and does not require several costly 

installation tasks that are normally required in retrofits with thicker layers of conventional 

insulations (long connectors, alteration of window and door openings, extension of roof 

overhangs, and so on). To assess the cost effectiveness of this proposed retrofit strategy, the total 

(installed) cost for this approach is compared to that of the thermally equivalent wall retrofit 

strategies where conventional insulation is installed on the exterior wall surface. For the purpose 

of the cost estimation, we used three target R-values: R-4, R-20, and R-35. The three levels of 

insulation reflect a typical re-siding project, a high efficiency solution, and a deep energy retrofit 

approach. Knowledge of the target R-value and the equivalent thicknesses of the conventional 

foam insulations (see Figure 6) allowed for an estimation of the associated costs, as shown in 

Table 2-. 

Aerogel blankets installed on the interior side of the existing gypsum board: Because aerogel is 

nontoxic, low flammable, and air permeable, and provides high R-value in thinner layers, it is a 

good candidate for interior installation. Three target R-values were assessed: R-4, R-8, and R-12. 

These were selected as practical and potentially cost-effective approaches for an interior retrofit.

The three R-value targets reflect one, two, and three layers of an aerogel blanket, respectively 

(each 10 mm thick with thermal resistance of R-4 per layer). This is a quick retrofit method that 

requires limited alteration of the interior space (corners, electrical, heating unit relocation, and 

window and door openings) and minimizes occupant disruption. This method could also be a 

solution for internal retrofits of vaulted ceilings, cathedralized attics, knee walls, and exterior 

walls when exterior insulation is more costly or is not possible because of technical or code 

reasons. To evaluate the cost effectiveness of this retrofit method, the team compared its cost to 

that of the conventional insulation installed on the interior wall surface. The conventional 

insulations considered were fiberglass batt, spray-applied foam, and foam board insulations. 

Fiberglass batt available in the market has a minimum thickness of 3 1⁄2 in.; however, for the sake 

of comparison, 1 1⁄2 in. batts were also evaluated. With the exception of the latter fiberglass case, 

other materials require a new internal frame wall build-up. Additionally, we also compared the 
11

cost of adding conventional insulation installed on the exterior wall surface for R-12. Figure 7

shows the calculated equivalent thicknesses for conventional insulations; Table 5 through Table 

8 show the estimated and compared costs. At present, there is a limited understanding of the 

hygrothermal behavior of the wall system where aerogel blankets are installed on the interior 

side. To further understanding on this topic, Fraunhofer CSE is conducting a long-term moisture 

measurement and durability study on a wall that is retrofitted with aerogel.

23

Blown-cavity aerogel: At present, residential retrofit applications use cavity insulations as lowcost insulation techniques. The R-value of these applications, however, is limited because of the 

cavity space restrictions. Typically, blown-in cellulose is the most common option; however, it is 

not the best-performing one. Other alternatives involve foam cavity injections. These 

applications can damage cavities (expanding foams) or create undesired air voids (shrinking in 

time, so-called nonexpanding foams). In that light, blown-in aerogel insulation can be considered 

an attractive potential alternative. Blown aerogel for existing 2 × 4 stud wall cavity using a drilland-fill technique is not yet commercially available. Fraunhofer CSE has worked with its 

Building America partners to evaluate this technique as a potential wall retrofit measure. 

At this stage of technology development, the team assumes that the blown aerogel is produced 

from chopped aerogel blankets. In the future, it is anticipated that a new formulation of aerogel 

will be developed specifically for this application. In addition, using the cost reducing 

approaches outlined later in this report would reduce material costs by 30% to 50%. Moreover, 

the blown aerogel insulation could be easily blended with other fiber insulations—bringing lowcost alternatives to the U.S. building insulation market. 

Estimating conservatively that thermal conductivity will increase by about 20% both during the 

synthesis of a new blown aerogel formula and while blowing it into the wall cavity, we assumed 

that the blown aerogel has a thermal resistivity of R-8/in.. This yields an effective thermal 

resistance of R-20 installed in a 2 × 4 at 16 in. o.c. stud wall cavity, assuming the existing stud 

cavity is completely empty. Note that R-20 is an effective thermal resistance and takes into 

account the thermal bridging effects in a 2 × 4 at 16 in. stud wall.

It is very common, however, that old walls are partially insulated in home retrofit projects; 

therefore, stud cavities already contain existing insulation. For cost comparison with exterior 

foam sheathing insulations or sprayed foam applications, the team considered the following 

thermal insulation cases:

• Blown-in aerogel applied in a 2 × 4 stud cavity with R-5 existing insulation compared 

with the case of the exterior XPS insulation. The team assumed the existing R-5 took 

approximately 1.5 in. thickness of the cavity and the remaining 2 in. is filled with the 

blown-in aerogel insulation. Using finite difference thermal modeling, the team 

determined an equivalent thermal resistance of R-16 for this configuration (see Figure 8). 

This is an effective thermal resistance of the cavity filled partially with R-5 and 

remaining with aerogel and takes into account thermal bridging effect due to studs. 

 

23 See http://cse.fraunhofer.org/5cc/project-overview/ for more information.
12

Exterior XPS insulation was considered as the only comparative case because other 

conventional insulations filled into remaining 2 in. cavity cannot reach the target of R-16. 

Figure 8 and 9 show the equivalent thicknesses and estimated costs. Table 9 lists the retrofit 

tasks and cost estimation details. 

Blown-in aerogel applied in an empty 2 × 4 stud cavity compared with the case of the blown 

fiber and sprayed applied foam insulation into the stud cavity. As mentioned, blown-in aerogel 

into an empty 2 × 4 stud cavity yields an effective thermal resistance of R-20. For comparative

cases, the team considered filling a 3.5 in. stud cavity with blown-in fiber, sprayed applied foam, 

or aerogel insulations. Figure 10 and 11 show the equivalent thicknesses and estimated costs.

Table 10 lists the retrofit tasks and cost estimation details. 

3.2.2 Cost Comparisons

For the three retrofit strategies described, the cost model yields the following cost values: 

The exterior installation using aerogel to achieve a target of R-4 is close to the price range of the 

conventional insulations. The cost of wall retrofit project using aerogel to achieve R-20 and R-35 

is, however, 1.5–2 times more expensive than retrofit with conventional fiber and foam 

insulations (see Figure 6). 

If conventional insulation is installed from the interior side of a retrofitted wall, interior 

installation of aerogel to achieve a target R-value of R-4 or R-8 is cost competitive or within the 

current price range of conventional insulations (see Figure 7). The cost of a wall retrofit project 

to achieve R-12 using aerogel is, however, 1.5–2 times more expensive than retrofit with fiber 

and foam insulations (see Figure 7). 

If conventional insulation is installed from the exterior side of a retrofitted wall, interior 

installation of aerogel to achieve target of R-12 is cost competitive (see Figure 7). 

Blown-in aerogel installed into 3.5 in. empty space of a 2 × 4 stud cavity would become cost 

competitive with blown-in fiber and spray-applied foam insulation into the stud cavity if the cost 

is below or in the range of $12 to $14/ft2. 

Blown-in aerogel installed into an R-5 partially insulated 2 × 4 stud cavity would be cost 

competitive compared with the case of the blown fiber and spray applied foam insulation if the 

cost is less than about $12 /ft2. 

Although both 2 × 4 stud wall cases have very close price ranges, the latter case where blown 

aerogel is filled into a 2 in. stud cavity thickness is more cost effective than the case of filling 

aerogel into an empty 3.5 in. stud cavity. 

Therefore, based on the current cost of the aerogel, the wall insulation retrofit using aerogel is 

cost competitive for a target of R-4 for both the interior and the exterior installation cases. R-8 

aerogel interior insulation is within the range of current conventional insulation prices; however, 

for the other interior and exterior wall retrofit applications considered here, aerogels seem to be 

1.5−2 times more expensive than the current conventional fiber and foam insulation. The 

proposed blown-in aerogel into a 2 × 4 stud cavity would be cost competitive if its price were
13

lower than $12/ft2 in cases with a partially insulated cavity and within the range of $12−$14/ft2

for the empty cavity case. All aerogel insulating techniques do not require additional furrings or 

wall opening alterations, and they seem to be more suitable than conventional insulations for 

confined spaces. 

3.2.3 Future Cost Comparisons

Several current publications report the possible reduction of aerogel cost. These reports predict 

that the manufacturing cost could be reduced by as much as 50% in the near future by modifying

the production process. Such reductions would make aerogel a cost-effective solution for a larger 

portion of retrofit projects. Based on a 50% reduction in the current price of the aerogel (as 

shown in Figure 6 and ), the future cost of the blanket and blown-in installations could be well 

below the current cost of conventional retrofit strategies. Moreover, blown-in aerogel is the only 

retrofit method that provides a high R-value with a single application into stud cavities. The

existing competing retrofit methods require a combination of stud cavity and exterior sheeting 

insulation to achieve similar R-values, which adds to retrofit project cost, duration, and subtasks. 

3.2.4 Aerogel Production Cost

Aerogel production has remained costly mainly because of high costs of raw materials and 

relatively smaller production volumes. 

Usually, aerogel synthesis involves the following three steps [12]:

Sol-Gel preparation. The gel is prepared using silicon precursors such as 

tetramethylorthosilicate, tetraethylorthosilicate, polyethoxydisiloxane, methyltriethoxysilane, and 

silicon alkaoxide. 

Gel aging. The gel prepared in step 1 is aged in a solvent for long periods of time to improve the 

mechanical and permeability properties of the gel network. The concentration, aging time, 

temperature, pH, and polarity have a strong influence on the strength and porosity of the aerogel. 

In laboratory settings, a batch process is adopted for the aging step, which is inherently a slow 

process. When scaling to the production phase, the batch processing step could increase product 

cost because of increased process line downtime and frequent stopping/starting of the production 

line. A continuous process is desirable because it helps increase the output. As with any 

multistep process, however, the individual step only adds time to the overall process if it is the 

bottleneck. Because aging is not the capitally intensive part of the process, more aging vessels 

can be used to reduce the aging time. 

Gel drying. In this step, the liquid inside the gel network is removed using a liquid to gas phase 

change process. Because of the surface tension of the liquid in contact with the solid, however, 

the liquid changing phase tends to pull the gel network along with it. This causes gel network to 

shrink and collapse. To retain the integrity of the gel structure during the drying process, the 

aged gel is brought to the supercritical condition. Under the supercritical condition, surface 

tension vanishes because there is no distinct liquid-vapor phase boundary. The supercritical 

condition can be realized at either low or high temperatures, depending on the liquid (e.g., CO2, 

ethanol), but high pressures are always required. 
14

As-produced aerogels are fragile and unsuitable for use in any practical application unless they 

are reinforced with some other material such as glass fiber, mineral fiber, and carbon fiber, or 

cross-linked with polymers.24 Although the reinforcement process gives mechanical strength 

and flexibility to the aerogel, it can result in an undesirable increase in the thermal conductivity 

and density of the resulting aerogel composite [13].25 This thermal conductivity increase can be 

minimized by using lower volume fractions of inferior, thermally conductive fibers as long as the 

mechanical requirements for the areogel application are satisfied. IR opacifiers such as carbon 

black, titanium oxide, and iron oxide with suitable fiber diameters can also be added during the 

sol-gel process to reduce the radiative part of the thermal conductivity [14]. The radiative 

contribution can be further reduced by using IR opacified fibers such as PET fibers coated with 

carbon black. 

3.2.5 Approaches to Lower Production Cost

The expensive raw materials used in step 1 and the large amounts of energy consumed to create 

high pressures in step 3 lead to high costs of production. In each of the synthesis steps, however, 

there is considerable potential to lower the cost:

Step 1: Use cheaper, more abundant raw materials such as rice husk, clay, and oil shale ash, and 

recycle process materials.

The market prices for silicon precursors are exorbitant; for example, tetraethylorthosilicate costs 

$1.8−3.0/kg.26 Rice husk is an inexpensive precursor source that is rich in silica; e.g., its ash can

contain up to 92−97% of amorphous silica [15]. Clay is another less costly and more plentiful 

substitute. Clay aerogel is produced using a freeze-drying process [16] and consists of stacked 

sheets of clay with occasional struts connecting these sheets. The thermal resistivity values have 

been reported to vary between R-4 and R-6/in. depending on the orientation of the stacked layers

[17]. Oil shale ash, a waste product from the oil shale refinement process, is another low-cost 

alternative that contains large quantities of silica (~50%) [18]. 

Although these options have potential, they require additional steps to arrive at the final product. 

For example, ash needs to be converted and then processed through more steps than currently

required. This could add to the cost rather than reduce it. Aspen Aerogel has developed an 

approach to reduce the cost of raw material sand process by recycling the two main process 

chemicals that are used in a supercritical drying process for aerogel: alcohol and CO2. Aspen 

reclaims and recycles 100% of the alcohol and approximately 97% of the CO2 [19].

 

24 Strong and Flexible Aerogels. See http://www.aerogel.org/?p=1058 for more information. 25 Aspen Aerogels. 2012. Pyrogel XT. See http://www.aerogel.com/products/pdf/Pyrogel_XT_DS.pdf for more 

information.

26 Anhui Huishang International Ltd. Tetraethyl Orthosilicate TEOS. See 

http://ahhs.en.alibaba.com/product/475123281-0/tetraethyl_orthosilicate_TEOS.html for more information.
15

Step 2: Use low vapor pressure solvents.

The commonly used solvents such as siloaxane, H2O/ethanol, tetraethylorthosilicate /ethanol, 

and polyethoxydisiloxane evaporate during the aging process, adding to the cost of the product. 

The evaporation also causes a slight shrinkage in the gel network, hence compromising the 

mechanical integrity of the final aerogel product. To address these issues, solvents with low 

vapor pressure such as ionic liquids should be considered in the future. These solvents will not 

be lost during the aging process, and can be recycled, resulting in a cost reduction. Ionic liquids, 

however, suffer from stability and corrosion issues and a detailed R&D effort will be needed to 

find a suitable type of ionic solvent for silica aerogel processing. 

Water, an abundant and cheap resource, has also been considered an aging solvent that improves 

the mechanical stability of the aerogel [20]. Another direction to reduce the cost is to minimize 

the aging time, which can be achieved by aging in a simulated pore solvent [21] or increasing the 

solvent temperature.

Step 3: Use atmospheric pressure drying. 

There are alternative cost-effective routes to achieve drying without resorting to high pressures: 

freeze drying and atmospheric pressure drying (APD). In freeze drying, the gel is frozen and 

subsequently sublimated. The freeze-drying process produces cracked and powder-like products, 

rendering this process unsuitable for large-scale mass production. APD is the most promising 

alternative to replace supercritical drying. It is a subcritical method where the capillary force 

between the pore liquid and the pore walls is minimized by modifying the surface chemistry of 

the pore walls. The surface is functionalized in such a manner that it becomes hydrophobic, and 

in the process expels water out of the pores. Because APD is an atmospheric pressure method, it 

consumes significantly less energy. In addition, APD does not require the expensive autoclave 

system used in supercritical drying, thus saving greatly on capital equipment cost [22]. At this 

time, an APD process cannot be fully employed for the large-scale production of powdered 

aerogels because fine aerogel particles will be lost to the open atmosphere. To avoid the mass 

loss and make the production process a continuous one, a closed type of drying process, such as 

a fluidized bed drying technique, can be a possible solution [23]. 

The fibers used in the reinforcement steps add to the aerogel production cost. Depending on the 

reinforcement material and the fraction content, the thermal conductivity can increase slightly or 

significantly. The same applies to the mechanical strength. For many building thermal insulation 

applications, however (e.g., blown-cavity or attic floor insulation), the thermal performance is 

the main performance criterion rather than the mechanical stiffness. The team believes that 

incorporating relatively mechanically weaker yet cheaper and low conductivity alternatives such 

as organic and biological fibers and using less fiber content will appreciably reduce the cost 

while achieving the thermal performance required for typical building insulations. 

3.2.6 Discussion

For this project, Fraunhofer CSE partnered with Aspen Aerogel. Aspen holds significant 

knowledge and technical expertise in optimizing the process parameters for aerogel production in 

order to decrease the production cost. According to Aspen, there is further potential to lower the 
16

cost of aerogel products by as much as 50% through approaches such as APD and implementing 

their strategic programs.

There are claims of developing a rice husk-based aerogel processing method that will decrease 

aerogel production cost by 80% [24]. The team believes that such dramatic cost reduction can be 

achieved primarily from the cheaper cost of rice husks and using a subcritical drying method. 

The team is unable, however, to find any new development on this product since 2010, 

suggesting serious production and cost challenges might be associated with the realization of this 

product. 

Svenska Aerogel Inc. recently claimed to have discovered a method that would reduce the price 

of their aerogels by 90% compared to their current baseline cost [10]. The company is highly 

secretive about their technology and it is not clear how such a high cost reduction has been 

achieved. Their current baseline cost is not available in the literature. Because their current 

baseline is not based on a production process, their baseline cost could be much higher compared 

to the production cost of U.S. aerogel manufacturers. The company plans to launch its products 

in 2012.27

Clay aerogels are also an attractive option because they are prepared from cheap and abundant 

clay material, although the process requires a potentially expensive freeze drying process. The 

thermal resistivity value of R-4–R-6/in. for clay aerogel is relatively inferior compared to R-8–R10/in. for current silica-based aerogels;

28 however, their production cost is expected to be 

significantly lower than the current high-end aerogels available on the market.

Although claims made by these aerogel manufacturers are encouraging, they lack scientific 

veracity and credible demonstration of the performance benefits and cost reductions. 

Considering this fact along with the fluctuating market demands, it is unlikely that aerogels will 

become a commonplace thermal insulation material for the U.S. building envelope industry in 

the near future. The team believes, however, that even today, aerogels may become a costeffective option for local insulation and for mitigation of thermal bridging effects in building 

envelopes such as in window and steel frames, and complex architectural details. 

 

27 CleanTech Investor (2011). Svenska Aerogel – Low cost aerogel solutions. See 

http://www.cleantechinvestor.com/portal/mainmenucomp/companiesa/2813-aerogel/9446-

aerogelprofile1june11.html for more information. 28 Cabot Aerogel, Inc. See http://www.cabot-corp.com/ for more information.
17

4 Blown-In Aerogel Technology

Today, aerogel blankets are the most common application of aerogel insulation. The team

anticipates that R-8 or even R-10 blown-cavity insulation based on aerogel has the potential to 

become one of the most effective methods to improve the thermal performance of typical woodframed walls, vaulted ceilings, and attics. The blown-in aerogel technology does not exist yet, 

but this concept has the potential for deep retrofit applications. If successfully developed, this 

technology might be an entirely new application of aerogel insulation. When the application 

space is very limited, small aerogel particles or aerogel blended with other fiber insulation would 

be blown into the wall cavity or into the vaulted ceiling instead of using significantly less 

thermally efficient conventional insulations. This application will not require strong fiber 

reinforcement unlike aerogel blankets.

The team proposes to mix cheaper and renewable fibers such as cellulose during the sol-gel 

process, and then carry out atmospheric condition drying. Here, the production process might be 

continuous because the reinforcement step will become an inherent part of the aerogel 

preparation process. The expected thermal conductivity of aerogels strengthened with cellulose 

will be only slightly higher than the thermal conductivity of silica aerogels [25]. This approach 

could bring cost savings by reducing processing costs and using less expensive fiber 

reinforcement and drying steps. 

The thermal resistivity of blown insulation made of the aerogel blankets will be at least 10% to 

25% lower than current products’ R-10 to R-11/in. because of current fiber reinforcement levels. 

In the short term, aerogel blown insulation would be made with significantly fewer fiber 

reinforcements. This would reduce insulation cost and improve its thermal resistivity with only 

incremental capital investments. Taken together, this would yield at least a 20% cost reduction. 

4.1 Thermal Testing of Shredded Spaceloft Aerogel Blankets

The thermal performance and density of proposed blowable aerogel would need to be optimized 

for cavity applications so that aerogel can meet thermal and structural requirements. This would 

require intensive research efforts before implementation in real building applications. As a 

preliminary step to understand the trends between thermal performance and density for the 

proposed blown aerogel, the team conducted ASTM C-518 thermal testing on a series of aerogel 

samples that were created by shredding aerogel blankets into small pieces and then packing these 

small pieces inside a container. The purpose was to explore the thermal performance of packed 

aerogel material such as blowable aerogel and shredded aerogel. The shredded aerogel samples 

do not represent future technology; the final blowable aerogel product and the technology will 

use different material formulation, density, and much improved performance compared to the 

shredded aerogel discussed in this section. 

To prepare shredded aerogel samples, a large Spaceloft aerogel blanket was chopped into small 

pieces about 1−2 in. in size using a commercial shredder (see Figure 12). Next, a container with 

side walls was made out of Styrofoam (outside dimension of 12 × 12 × 1.65 in. with wall 

thickness of ~1 in.), with the top and bottom sides covered with very thin paper sheets. Three 

aerogel samples varied in effective packing density, with three different amounts of shredded 

aerogels in this container. Here, effective packing density is defined as the ratio of aerogel mass 

placed inside the container to the internal volume of the container. A Lasercomp FOX305 heat 
18

flow meter apparatus measured the thermal conductivity of the chopped aerogel samples. The hot 

and cold plates were set to 37.5°C and 12.5°C, respectively, with an average temperature of 25°C 

for the experiments.

Table 11 and Figure 13 present R-value/in. as a function of aerogel sample effective packing 

density. R-value/in. increases as more shredded aerogel pieces are packed inside the given 

container volume. This trend can be explained using effective medium theory, which implies that 

adding a lower thermal conductivity material to a medium decreases the overall thermal 

conductivity of the composite. The Spaceloft aerogel blanket has lower thermal conductivity 

than air; therefore, packing more shredded aerogel mass in the same volume will yield a reduced 

overall thermal conductivity (or increase in R-value) of aerogel samples. The R-value for 

Spaceloft aerogel blanket is about 10/in.,29 and is included in Figure 13. As effective packing 

density increases, R-value is predicted to also increase. Following the trend in Figure 13, in order 

to obtain an R-value of 8/in. for shredded aerogel, density should be approximately 115 kg/m−3

(7.18 lb/ft−3). Future blown-in aerogel insulation will have a significantly lower application 

density. 

4.2 Discussion

The thermal testing results on shredded aerogel samples suggest that for blown-cavity 

applications it is critical to develop an aerogel synthesis process that would produce small-sized 

aerogel particles and avoid the need to shred aerogel blankets, which results in loss of valuable 

aerogel material. The strength of the fibers or mesh would be adjusted such that they will break 

into the desired size during the subsequent processing steps. Thermal testing also underlines the 

importance of optimizing the size of these aerogel particles to achieve a desired R-value 

performance.

 

29 Aspen Aerogels. Spaceloft 6250. See http://www.aerogel.com/products/pdf/Spaceloft_6250_DS.pdf for 

more information. 
19

5 Conclusions and Future Work

This report analyzes and compares the cost and performance of emerging high performance 

insulation technologies with conventional insulation methods in home energy retrofit situations. 

In particular, the team investigated the economic feasibility of applying VIPs and aerogels as a 

potential building thermal insulation material for wall retrofit applications. Surprisingly, very 

little has been done so far to evaluate their cost effectiveness, although this is a crucial factor to 

determine the potential application and limitation of these technologies. 

We evaluated the cost of VIPs as building envelope insulation relative to conventional building 

foam insulations in wall deep energy retrofit projects. Data from websites, technical publications, 

and quotes from manufacturers from the United States, Europe, and China show a wide range of 

prices for VIPs. We find that the proposed method for VIP wall retrofit can be cost competitive 

with current deep retrofit strategies using foam insulations. Based on this finding, further 

advancements in VIP manufacturing technology, larger volume production, and higher reliability 

through quality control of cores and films could enhance VIP cost effectiveness as a retrofit 

option for local insulation and mitigation of thermal bridging effects in building envelopes. 

Wall insulation retrofit using aerogel technology could become cost competitive in certain 

scenarios such as where a target R-4 is desired for both the interior and the exterior installation. 

In light of the recent technological advancements in aerogel processing, a novel approach of 

blown-cavity aerogel insulation, pending significant research and development, has the potential 

to become a cost-competitive option in niche areas of building thermal insulation, such as in 

cavity insulation and local insulations in areas of restricted space. Thermal testing on a series of 

samples consisting of shredded aerogel blanket pieces allowed the team to understand the 

insulation behavior of proposed blown aerogel technology. These tests showed that the R-value 

of these shredded aerogel samples increases as the effective packing density of aerogel pieces

increases. 

This report also gave an overview of the aerogel synthesis process. Currently, aerogel production 

is an expensive business, mainly because of the high cost associated with process chemicals and 

the drying procedure. A two-stage effort would reduce the aerogel production cost: 

1. Short term: Evaluate different ways to reduce the cost of processing materials. This 

would involve using less expensive source materials and processing solvents, and using 

less reinforcement material to reduce production cost. 

2. Longer term: Decrease the production process related costs by implementing a 

continuous production methodology and employing APD. 

The rising demand for insulation materials along with tight space limitations will be favorable 

factors for aerogel industry growth and lowering the production cost. 

In the future, the team, plans to apply the insights gained through cost analysis and thermal lab 

testing to evaluate the in-field performance of aerogel and VIP based retrofit strategies for 

northern U.S. climates. 
20

References

 

[1] Krim, A. J. (1977). The Three-Deckers of Dorchester: An Architectural Historical Survey. 

Paper submitted to Boston Redevelopment Authority. 

http://www.sidewalkmemories.org/archives/The%20Three-Deckers%20of%20Dorchester.pdf

[2] (2002). ISO 1182 Reaction to fire tests for building products - Non- combustibility test. 

[3] (2002). ISO 1716 Reaction to fire tests for building products - Determination of the heat of 

combustion. 

[4] (2002). ISO 5660-1 Reaction to fire tests - Heat release, smoke production and mass loss rate 

- Part 1: Heat release rate (cone calorimeter method).

[5] (2002). ISO 9239-1 Reaction to fire tests for floorings - Part 1: Determination of the burning 

behaviour using a radiant heat source. 

[6] (2002). ISO 11925-2 Reaction to fire tests - Ignitability of building products subjected to 

direct impingement of flame - Part 2: Single-flame source test.

[7] Aldrich, R.A., Arena, L., and Zoeller, W. (2010). Practical Residential Wall Systems: R-30 

and Beyond. Research report prepared by Steven Winter Associates, Inc for the Consortium for 

Advanced Residential Buildings (CARB). 

[8] Straube, J. and Smegal J. (2009). Building America Special Research Project: High-R Walls 

Case Study Analysis. Building Science Corporation. 

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HouseGas Abetment Cost Curve. McKinsey & Company. Full report available at 

https://solutions.mckinsey.com/climatedesk/. 

[10] ECBCS/IEA Annex 39. (2005). Vacuum Insulation Panels, Study on VIP-components and 

Panels for Service Life Prediction of VIP in Building Applications (Subtask A). Available at: 

http://www.ecbcs.org/annexes/annex39.htm

[11] Waier, P. R., Babbitt, C., Baker, T., Balboni, B., Bastoni, R.A. (2011). RS Means 

Residential Cost Data 2011, 30th Annual Addition 

[12] Soleimani Dorcheh, A., Abbas, M.H. (2008). Silica aerogel; synthesis, properties and 

characterization. Journal of Materials Processing Technology 199, 10-26. 

[13] Deng, Z., Wang, J., Wu, A., Shen, J., Zhou, B. (1998). High strength SiO2 aerogel 

insulation. Journal of Non-Crystalline Solids 225, 101–104. 

[14] Frank et al. (1998). Aerogel Composites Process for Producing the Same and Their Use. 

United States Patent Number 5789075. August, 1998. 

[15] Silica Aerogels. United States Patent Application 20070276051. 2007 

[16] Bandi, S., Bell, M., Schiraldi,D.A. (2004). Temperature-responsive clay aerogel–polymer 

Composites. Macromolecules 38, 6001–6003. 
21

 

[17] Hostler, S.R., Abramson, A.R., Gawryla, M.D., Bandi, S.A., Schiraldi, D.A. (2009). 

Thermal conductivity of a clay-based aerogel. International Journal of Heat and Mass Transfer

52, 665–669. 

[18] Gao, G.M., Liu, D.R., Zou, H.F., Zou, L.C., Gan, S.C. (2010). Preparation of silica aerogel 

from oil shale ash by fluidized bed drying. Powder Technology 197, 283–287.

[19] Rhine, W. Tang, Y. Dong, W. Trifu, R. Begag, R (2003−2008). Highly Insulating Windows 

with a U-Value less than 0.6 W/m2K. Final Report. Contract No. DE-FC26-03NT41950. 

http://sites.energetics.com/buildingenvelope/pdfs/Aerogel_Windows.pdf. 

[20] Reichenauer, G. (2004). Thermal aging of silica gels in water. Journal of Non-Crystalline 

Solids 350, 189–195. 

[21] Strøm, R.A., Masmoudi, Y., Rigacci, A., Petermann, G., Gullberg, L., Chevalier, B., 

Einarsrud, M.-A. (2007). Strengthening and aging of wet silica gels for up-scaling of aerogel 

preparation. Journal of Sol-Gel Science and Technology 41, 291–298. 

[22] Rao, A.V., Rao, A.P., Kulkarni, M.M. (2004). Influence of gel aging and Na2SiO3/H2O 

molar ratio on monolithicity and physical properties of water-glass-based aerogels dried at 

atmospheric pressure. Journal of Non-Crystalline Solids, Vol. 350, pp. 224–229. 

[23] Bhagat, S.D., Park, K.T., Kim, Y.M., Kim, J.S., Han, J.H. (2008). A continuous production 

process for silica aerogel powders based on sodium silicate by fluidized bed drying of wet-gel 

slurry. Solid State Sciences Vol. 10, pp. 1113-1116. 

[24] Joshi, V (2008). MSNBC Innovation. High-Tech Insulator Created from Rice Husks. 

http://www.msnbc.msn.com/id/23398379/ns/technology_and_science-innovation/t/high-techinsulator-created-rice-husks/#.TpMMo-xC_Xp

[25] Innerlohinger, J., Weber, H.K., Kraft, G. (2006). Lenzinger Berichte, 86, 137-143 
22

(a) (b)

(c) (d)

Figure 1. Emerging building insulation technologies considered: (a) VIP-based EIFS, (b) aerogel 

applied on the interior surface of the wall, (c) aerogel applied on the exterior surface of the wall, 

(d) blown-in aerogel applied to completely and partially filled cavities. Only thermal components 

are shown and drainage design is omitted.

Cementitious 

finish

Gypsum 

board

XPS

VIP 

insulation

Existing 

cladding

Gypsum 

board

Interior 

blanket 

aerogel

Gypsum 

board

Replaced 

Cladding

Exterior 

blanket 

aerogel

Existing 

cladding

Existing R-5 

cavity 

insulation

R-8/in. blownin aerogel 

into 2 × 4 wall 

cavity 

Gypsum 

board
23

(a)

(b)

(c)

Figure 2. 3D thermal modeling of modeled VIP encapsulated with XPS protection layers: (a) plan 

view of 1 ft × 1 ft ×1 in. VIP panel with XPS protection dividers, (b) VIP layer sandwiched between 

two 1-in. layers of XPS. The whole assembly has an effective thermal resistance of R-35. (c) 

Temperature mapping of VIP. The panel size is 1 ft × 1 ft ×1 in. and composed of three VIPs 

divided by XPS protection layers. 
24

Figure 3. Equivalent thicknesses and installed cost of different exterior wall insulation systems to achieve R-35. The thicknesses in this 

figure are rounded from the manufactured thickness (rigid board with at least 1 in. thickness and spray foam with at least 0.5 in. 

thickness). The equivalent thickness for PU takes into account the thermal bridging effect of wood studs. VIP encapsulated in XPS 

insulation has effective thermal resistance of R-35 (Figures 4 and 5). The VIP cost was collected either directly from manufacturers or 

from published data on the internet for U.S., European, and Chinese markets. 
25

PU1: Closed cell polyurethane foam was applied inside of 2 × 4 wood studs.

PU2: Closed cell polyurethane foam was applied inside of 2 × 6 wood studs.

For both cases, the added stud is installed from inside and standing off few inches from existing stud.

PU3: Closed cell polyurethane foam was applied in exterior furring.

VIP1 - Glacier Bay (according to http://passivehousetoronto.blogspot.com/2011/03/vacuum-insulated-panels-and-prices.html)

VIP2 - Dow Corning - Silica Core (according to Dow Corning’s quoting)

VIP3 - Popular Mechanics (according to Popular Mechanics magazine, Oct 2009)

VIP4 - Richard T. Bynum (according to Richard T. Bynum, Technology and engineering)

VIP5 - Dow Corning - Mineral Wool Core (according to Dow Corning’s quoting)

VIP6 - University of Chicago (according to Alan Feinerman)

VIP7 - Thermal Vision (according to Thermal Vision company’s quoting)

VIP8- Dow Corning Future price (estimated by Dow Corning)

VIP9 - Alam et al. (published paper)

VIP10 - Qingdao Kerui New Environmental Materials Co. (according to company’s quoting for R-30 VIP)

VIP11 - Sinoarch Shanghai Co. ; http://www.alibaba.com/showroom/vip-insulation.html

VIP12 - hangzhou Sanyou Dior Insulation Materials MFG Co., Ltd (according to company’s quoting)
26

Figure 4. Modeled thermal resistance of PU foam sprayed into studs 2 × 6; 16 in. o.c. The effective 

thermal resistance of 5.5 in. PU foam is R-25 (excluding air film resistances). To reach target R-35, 

it was assumed that the studs are installed on the exterior and standing off 2 in. away from the 

exterior sheeting. The 2 in. gap is filled with PU spray foam and collectively with the 5.5 in. stud 

spaces provides the required target R-value. Therefore, approximately 7.5 in. PU foam is required 

to reach target R-35.
27

Figure 5. Modeled thermal resistance of PU foam sprayed into studs 2 × 4; 16 in. o.c. The effective 

thermal resistance of 3.5 in. PU foam is R-16.3 (excluding air film resistances). To reach target R35, it was assumed that the studs are installed on the exterior and standing off 3.5 in. away from 

the exterior sheeting. The 3.5 in. gap is filled with PU spray foam and collectively with the 3.5 in.

stud spaces provides the required target R-value. Therefore, approximately 7 in. PU foam is 

required to reach target R-35.
28

(a)
29

(b)
30

(c)

Figure 6. Equivalent thicknesses and total cost of aerogel and foam insulation techniques to 

retrofit the wall of a baseline house to achieve target R-values of (a) R-4, (b) R-20, and (c) R-35. 

The thicknesses in this figure are rounded from the manufactured thickness (rigid board with at 

least 1 in. thickness, spray foam with at least 0.5 in. thickness, and blanket aerogel with minimum 

of 10 mm thickness). The material cost was collected either from manufacturers or published data 

on the internet. Costs of the exterior wall finishes are not included in analysis for all considered 

cases of wall retrofits; only the insulation part of the retrofit strategy is analyzed. 
31

(a)
32

(b)
33

(c)
34 

(d)

Figure 7. Equivalent thicknesses and total cost of aerogel and conventional insulation techniques 

to retrofit the wall of a baseline house from interior to achieve target R-values of (a) R-4, (b) R-8, 

(c) R-12 (compared with interior installation case), and (d) R-12 (compared with exterior 

installation case). Blanket aerogel installed from the interior side on top of the existing gypsum 

board. Conventional insulations installed from interior. For the case of R-12, both interior and 

exterior installations analyzed and shown. The thicknesses in this figure are rounded values of 

the manufactured thickness (rigid board with at least 1 in. thickness, spray foam with at least 0.5

in. thickness and blanket aerogel with minimum of 3/8 in. thickness). The material cost was 

collected either from manufacturers or published data on the internet.
35

To achieve target R-values, we assumed XPS exterior installation. Aerogel, open cell PU, closed cell PU 

and XPS have R-values of R-8/in., R-3.6/in., R-6/in. and R-5/in., respectively. Blown cellulose has Rvalue between R-3.2 to R-3.8 per inch and blown fiberglass between R-2.2 and R-2.7/in.

(http://www.energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11650). For this study, 

blown cellulose and blown fiberglass have R-values of R-3.5/in. and R-2.45/in., respectively. Note that the 

thermal resistance bar in the chart is composed of two parts. The blue part is an effective R-value of initial 

R-5 plus 2” conventional insulation (either blown cellulose, blown fiberglass, open-cell PU, closed-cell PU, 

or blown aerogel); the red part is the minimum required R-value to reach target R-16. Therefore, the total 

effective R-value of the cavity and XPS might exceed the minimum required R-16.

Figure 8. Equivalent thickness and thermal resistance of aerogel and conventional insulations 

installed in a 2 × 4 stud cavity with R-5 existing insulation to retrofit the wall of a baseline house. 

The team assumed the existing R-5 took approximately 1.5 in. thickness of the cavity and the 

remaining 2 in. is filled with blown cellulose, blown fiberglass, injected PU foam, or aerogel. 
36

Figure 9. Equivalent thicknesses and total cost of XPS foam insulations installed into a 2 × 4 stud 

cavity that already has R-5 existing insulation to retrofit the wall of a baseline house. For 

comparison purposes, the team assumed the R-5 insulation already existing in the wall cavity

took approximately 1.5 in. of the cavity and the remaining 2 in. is filled with aerogel. Based on this 

estimation, proposed installation of the blown aerogel into a 2 × 4 stud cavity would be cost 

competitive if its price would be lower than $12.1–$12.8/ft2

. 
37

Figure 10 . Equivalent thickness and thermal resistance of aerogel and conventional insulations 

installed into an empty 2 × 4 stud cavity to retrofit the wall of a baseline house. The 3.5 in. stud 

cavity is filled with blown cellulose, blown fiberglass, injected PU foam, or aerogel. To reach the 

target R-values, the team assumed that exterior XPS foam was installed in addition to PU foam 

cavity injection. Aerogel, open cell PU, closed cell PU, and XPS have R-values of R-8/in., R-3.6/in., 

R-6/in., and R-5/in., respectively. Blown cellulose has an R-value between R-3.2 and R-3.8/in. and 

blown fiberglass between R-2.2 and R-2.7/in. (See 

http://www.energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11650 for more 

information). For this study, blown cellulose and blown fiberglass have R-values of R-3.5/in. and 

R-2.45/in., respectively. 
38

Figure 11. Equivalent thicknesses and total cost of aerogel and conventional insulations installed 

in empty 2 × 4 stud cavity to retrofit the wall of a baseline house. The 3.5 in. stud cavity is filled 

with blown cellulose, blown fiberglass, injected PU foam, or aerogel. To reach the target R-values, 

the team assumed XPS exterior installation in addition to PU cavity injection. Based on this 

estimation, proposed blown aerogel into a 2 × 4 stud cavity would be cost competitive if the price 

is within or lower than $12–$14/ft2

. 
39

(a) (b)

Figure 12. Shredding of Spaceloft aerogel blankets: (a) finely chopped pieces of aerogel blanket 

as they exit the shredder, and (b) final product.

Figure 13. R-value per inch as a function of effective packing density for shredded aerogel 

samples (three leftmost data points). Data for Spaceloft aerogel blanket are included as well [Error! 

ookmark not defined.] (rightmost data point). Literature data on the thermal performance of 

shredded aerogels are lacking. To develop an approximate relation between conductivity and 

packing density, the team measured thermal conductivity for three effective packing densities. 

Then a very approximate extrapolation was made between measured data and Spaceloft aerogel 

data to predict R-values in the intermediate density range. The red line marks the density value

required to obtain R-value of 8/in.

y = 0.0009x2 - 0.0985x + 6.9796

R2 = 0.9987

0

2

4

6

8

10

12

40 60 80 100 120 140

R-value per inch

Effective Packing Density (kg m−3) 

Spaceloft 

blanket
40

Table 1. Installed cost estimates for conventional and emerging insulation techniques to retrofit the wall of a baseline house. Aerogel or 

VIP retrofit techniques do not require all retrofit tasks because of low thickness. Costs of the exterior wall finishes are not included in 

analysis for all considered cases of deep energy retrofits; only the insulation part of the retrofit strategy is analyzed. 

Insulation 

Type Retrofit Tasks and Cost ($/SqFt) Total Cost 

($/SqFt)

Rigid 

Insulation 

Removal of 

Exterior 

Cladding 

(vinyl 

siding) [1]

Furring 

[1]

Framing 

(2 × 4; 

OC 16) 

Framing 

(2 × 6; 

OC 16)

Window 

Relocation 

for deep 

window 

wells[2]

Insulation 

Installation 

(material & 

labor) [3]

Insulation 

protection 

layers (2 

XPS layers)

EIFS with 

1/2" 

cement 

board 

sheathing 

and 

2.5#/S.Y 

metal 

lath 

subtrate

Removal 

of 

shingles 

(two 

layers) 

[8]

Removal 

of OSB 

Deck [9]

Rafter 

extension 

(4 feet)

[10]

Fascia 

Boards 

Installation 

[9]

Soffit 

Nailer 

[4]

Replacement of 

OSB 

Deck [9]

Replace

ment of 

shingles 

[9]

Rake 

Overhang 

[5]

Building 

Kraft 

Paper [1]

Strapping 

Screws 

[11]

Installation 

of exterior 

cladding 

(vinyl 

siding) [1]

XPS(7") $0.59 $0.92 - - $0.52 $5.81 - - $0.04 $0.03 $0.129 $0.01 $0.01 $0.03 $0.09 $0.39 $0.22 $0.39 $7.79 $16.98

EPS(9") $0.59 $0.92 - - $0.52 $5.04 - - $0.04 $0.03 $0.129 $0.01 $0.01 $0.03 $0.09 $0.39 $0.22 $0.39 $7.79 $16.21

PIC(6.0") $0.59 $0.92 - - $0.52 $4.51 - - $0.04 $0.03 $0.129 $0.01 $0.01 $0.03 $0.09 $0.39 $0.22 $0.25 $7.79 $15.54

Sprayed 

Applied 

Foam 

Insulation

Removal of 

Exterior 

Cladding 

(vinyl 

siding) [1]

Furring 

[1]

Framing 

(2 × 4; 

OC 16) 

[4]

Framing 

(2 × 6; 

OC 16) 

[4]

Window 

Relocation 

for deep 

window 

wells[2]

Insulation 

Installation 

(material &

labor)[3]

Insulation 

protection 

layers (2 

XPS layers)

EIFS with 

1/2" 

cement 

board 

sheathing 

and 

2.5#/S.Y 

metal 

lath 

subtrate

Removal 

of 

shingles 

(two 

layers) 

[8]

Removal 

of OSB 

Deck [9]

Rafter 

extension 

(4 feet)

[10]

Fascia 

Boards 

Installation 

[4]

Soffit 

Nailer 

[4]

Replacement of 

OSB 

Deck [9]

Replace

ment of 

shingles 

[9]

Rake 

Overhang 

[5]

Building 

Kraft 

Paper [1]

Strapping 

Screws 

[11]

Installation 

of exterior 

cladding 

(vinyl 

siding) [1]

PU1 (7.5") $0.59 - - $1.91 $0.52 $5.39 - - $0.04 $0.03 $0.129 $0.01 $0.01 $0.03 $0.09 $0.39 $0.22 $0.39 $7.79 $16.34

PU2 (7.0") $0.59 - $1.50 - $0.52 $5.78 - - $0.04 $0.03 $0.129 $0.01 $0.01 $0.03 $0.09 $0.39 $0.22 $0.39 $7.79 $16.32

PU3 (6.0") $0.59 $0.92 - - $0.52 $4.62 - - $0.04 $0.03 $0.129 $0.01 $0.01 $0.03 $0.09 $0.39 $0.22 $0.25 $7.79 $14.59

Comboined 

Cavity & 

Exterior 

Insulations

Removal of 

Exterior 

Cladding 

(vinyl 

siding) [1]

Furring 

[1]

Framing 

(2 × 4; 

OC 16) 

[4]

Framing 

(2 × 6; 

OC 16) 

[4]

Window 

Relocation 

for deep 

window 

wells 

Cavity 

Insulation 

(material & 

labor) [12]

Insulation 

protection 

layers (2 

XPS layers)

EIFS with 

1/2" 

cement 

board 

sheathing 

and 

2.5#/S.Y 

metal 

lath 

subtrate

Removal 

of 

shingles 

(two 

layers) 

[8]

Removal 

of OSB 

Deck [9]

Rafter 

extension 

(4 feet)

[10]

Fascia 

Boards 

Installation 

[4]

Soffit 

Nailer 

[4]

Replacement of 

OSB 

Deck [9]

Replace

ment of 

shingles 

[9]

Rake 

Overhang 

[5]

Building 

Kraft 

Paper [1]

Strapping 

Screws 

[11]

Installation 

of exterior 

cladding 

(vinyl 

siding) [1]

Blown 

Cellulose (5 

3/16") [1]

$0.59 - - - $1.88 - - - - - - - - - - - - - 

XPS (3") - $0.92 - $2.30 - - - - - - - - - - - - $7.79 $13.48
41

VIP 

Insulation

Removal 

of 

Exterior 

Cladding 

(vinyl 

siding) 

[1]

Furring Framing 

(2 × 4; 

OC 16)

Framing 

(2 × 6; 

OC 16)

Window 

Relocation 

for deep 

window 

wells

VIP 

Insulation

Insulation 

protection 

layers for 

VIPs 

(2 XPS 

layers) [6]

Installed cost 

of EIFS with 

1/2" cement 

board 

sheathing and 

2.5#/S.Y metal 

lath subtrate 

(material & 

labor); Cost 

of foam 

insulation is 

not included 

[7]

Removal 

of 

shingles 

(two 

layers)

Removal 

of OSB 

Deck

Rafter 

extension 

(4 feet)

Fascia 

Boards 

Installation

Soffit 

Nailer

Replacement of 

OSB Deck

Replacement of 

shingles

Rake 

Overhang

Building 

Kraft 

Paper

Strapping 

Screws

Installation 

of exterior 

cladding 

(vinyl 

siding)

VIP1 (3.0") $0.59 - - - - $30.00 $2.42 $8.44 - - - - - - - - - - - $41.45 

VIP2 (3.0") $0.59 - - - - $11.43 $2.42 $8.44 - - - - - - - - - - - $22.88 

VIP3 (3.0") $0.59 - - - - $7.00 $2.42 $8.44 - - - - - - - - - - - $18.45 

VIP4 (3.0") $0.59 - - - - $4.27 $2.42 $8.44 - - - - - - - - - - - $15.72 

VIP5 (3.0") $0.59 - - - - $3.50 $2.42 $8.44 - - - - - - - - - - - $14.95 

VIP6 (3.0") $0.59 - - - - $3.00 $2.42 $8.44 - - - - - - - - - - - $14.45 

VIP7 (3.0") $0.59 - - - - $1.23 $2.42 $8.44 - - - - - - - - - - - $12.68 

VIP8 (3.0") $0.59 - - - - $1.15 $2.42 $8.44 - - - - - - - - - - - $12.60 

VIP9 (3.0") $0.59 - - - - $4.25 $2.42 $8.44 - - - - - - - - - - - $15.70 

VIP10 

(3.0") $0.59 - - - - $3.25 $2.42 $8.44 - - - - - - - - - - - $14.70

VIP11 

(3.0") $0.59 - - - - $2.78 $2.42 $8.44 - - - - - - - - - - - $14.23

VIP12 

(3.0") $0.59 - - - - $5.18 $2.42 $8.44 - - - - - - - - - - - $16.63

PU2: Closed cell polyurtheane foam was applied inside of 2 × 6 wood studs.

Both cases: the added stud is installed from inside and standing off a few inches from existing stud.

PU3: Closed cell polyurtheane foam was applied in exterior furring.

VIP1 - Glacier Bay (according to http://passivehousetoronto.blogspot.com/2011/03/vacuum-insulated-panels-and-prices.html).

VIP2 - Dow Corning - Silica Core (based on price quotations from Dow Corning’s).

VIP3 - Popular Mechanics (according to Popular Mechanics magazine, Oct 2009).

 (See http://www.popularmechanics.com/home/improvement/3455301 for more information)

VIP4 – Richard T. Bynum (according to Richard T. Bynum, Technology and Engineering).

VIP5 - Dow Corning - Mineral Wool Core (according to Dow Corning’s quoting).

VIP6 - University of Chicago (personal communication with Dr. Alan Feinerman, Associate Professor, University of Illinois at Chicago).

VIP7 - Thermal Vision (according to Thermal Vision company’s quoting).

VIP8- Dow Corning Future price (estimated by Dow Corning).

VIP9 – Based on the following paper:

Alam, M., Singh, H., and Limbachiya, M. C. (2011). Vacuum Insulation Panels (VIPs) for building construction industry - A review of the contemporary 

developments and future directions. Applied Energy, 88(11), 3592–3602.
42

VIP10 - Qingdao Kerui New Environmental Materials Co. (according to company’s quoting for R-30 VIP).

VIP11 - Sinoarch Shanghai Co. (according to company’s quoting); http://www.alibaba.com/showroom/vip-insulation.html.

VIP12 - hangzhou Sanyou Dior Insulation Materials MFG Co.,Ltd (according to company’s price quotation).

Aerogel1: According to Aspen Aerogel. The unit price is $2.75/ft2 with 3/8 in. thickness from Aspen Aerogel.

Aerogel2: Assuming 80% cost drop in future.

[1] According to RSMeans Building Construction Cost Data 2011. 

[2] According to Building Science Corporation (BSC). Estimated as $100/window × 14 windows of base case house / 2,700 ( total façade area of the base case 

house).

[3] According to RSMeans Building Construction Cost Data 2011, which includes material, equipment, and labor costs; the cheapest combination of rigid 

board insulation thickness was assumed for the cost analysis (e.g., 9 in. was assumed as 3 × 3 in. layer instead of 4 × 2 + 1 in.). For PU, thermal bridging 

effect was taken into account while calculating required thickness to achieve target R-value.

[4] According to RSMeans Building Residential Cost Data 2011.

[5] According to William A. Zoeller from Steven Winter Associates, Inc., Norwalk, CT.

[6] VIPs are encapsulated between two layers of XPS protection layers to reduce lateral damages. The cost includes material and labor costs.

[7] According to RSMeans Building Construction Cost Data 2011. The cost estimated for EIFS with 1⁄2 in. cement board sheathing and 2.5#/S.Y metal lathe

substrate (material and labor). The cost of 3 in. EPS foam insulation is not included because in VIP-based EIFS the foam insulation is replaced with 3 in.

encapsulated VIPs.

[8] According to RSMeans Building Construction Cost Data 2011. Estimated as 2 × 40 ft (removed area) × 2 (shingle layers) × $0.35 ( removal unit price /ft2) × 

2 ( both eave sides) / 2,700 ft2 (total façade area).

[9] According to RSMeans Building Construction Cost Data 2011. Estimated the same way as [8].

[10] According to RSMeans Building Construction Cost Data 2011. The rafter extension is 4 in.; 2 in. overlap and 2 in. extension from its existing length.

[11] According to http://www.bestmaterials.com/SearchResult.aspx?CategoryID=750.

[12] According to Steven Winter Associates, Inc. (https://www.google.com/search?q=Practical+Residential+Wall+Systems%3A+R-30+and+Beyond&ie=utf8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a). This is the cost of blown cellulose insulation including material and labor into 2 × 6 

framing wall ( $1,500 for 100 × 8 ft wall).
43

Table 2. Total cost of aerogel and conventional insulation techniques to retrofit the wall of baseline house to exterior R-4 target value. 

Aerogel retrofit technique does not require all retrofit tasks because of low thickness. The retrofit tasks are not in order.

Target Rvalue Insulation Type Retrofit Tasks and Cost ($/SqFt) Total Cost 

($/SqFt) 

Exterior R-4

Conventional 

Insulation 

Furring [1] Insulation 

Installation 

(material & 

labor) [2]

Adhesive 

to attach 

aerogel to 

subtrate

Removal 

of 

Exterior 

Cladding 

(vinyl 

siding) [1]

Building 

Kraft 

Paper [1]

Strapping 

Screws [4]

Installation 

of exterior 

cladding 

(vinyl siding) 

[1]

EPS (1.0") $0.92 $0.98 - $0.59 $0.22 $0.06 $7.79 $10.56 

Aerogel Blanket

[5]

Furring [1] Insulation 

Installation 

(material & 

labor) [3]

Adhesive 

to attach 

aerogel to 

subtrate [6]

Removal 

of 

Exterior 

Cladding 

(vinyl 

siding) [1]

Building 

Kraft 

Paper [1]

Strapping 

Screws [4]

Installation 

of exterior 

cladding 

(vinyl siding) 

[1]

Aerogel (0.4") - $3.26 $0.01 $0.59 $0.22 $0.06 $7.79 $11.93 

[1] According to RSMeans Building Construction Cost Data 2011.

[2] According to RSMeans Building Construction Cost Data 2011; the cheapest combination of rigid board insulation thickness was assumed for the cost 

analysis (e.g., 9 in. was assumed as 3 × 3 in. layer instead of 4 × 2 in. + 1 in.). For PU, thermal bridging effect was taken into account while calculating required 

thickness to achieve the target R-value. This cost includes material and labor costs. The labor cost varies from $0.43/ft2 to $0.47/ft2

, depending on insulation 

type.

[3] This cost is composed of $2.75/ ft2 material cost and $0.51/ ft2 labor cost; labor cost assumed the same as 1 in. rigid foam board installation cost from 

RSMeans Building Construction Cost Data 2011. 

[4] According to http://www.bestmaterials.com/SearchResult.aspx?CategoryID=750.

[5] After conversation with aerogel manufacturers and reviewing cost data, the team assumed that in short-term prognosis, a cost of an R-4/10 mm blanket 

can be chosen at $2.75/ft2.

[6] According to RSMeans Building Residential Cost Data 2011. Estimated based on $10.40/ 5 gal. and 18 (S.Y/gal.) coverage
44

Table 3. Total cost of aerogel and conventional insulation techniques to retrofit the wall of baseline house to exterior R-20 target value. 

Aerogel retrofit technique does not require all retrofit tasks because of low thickness. The retrofit tasks are not in order.

Target 

R-value

 

Insulation 

Type Retrofit Tasks and Cost ($/SqFt)

Total 

Cost 

($/SqFt)

Exterior 

R-20

Conventional 

Insulation 

Furring 

[1]

Window 

Relocation 

for deep 

window 

wells[2]

Insulation 

Installation 

[3]

Adhesive 

to attach 

aerogel 

to 

substrate

Removal 

of 

shingles 

(two 

layers) [1]

Removal 

of OSB 

Deck [1]

Rafter 

extensi

on (4 

feet) [1]

Fascia 

Boards 

Installation 

[4]

Soffit 

Nailer 

[4]

Replace

-ment 

of OSB 

Deck [1]

Replace

-ment 

of 

shingles 

[1]

Rake 

Over

hang 

[5]

Removal 

of 

Exterior 

Cladding 

(vinyl 

siding) [1]

Building 

Kraft 

Paper [1]

Strapping 

Screws [7]

Installation 

of exterior 

cladding 

(vinyl 

siding) [1]

XPS (4.0") $0.92 $0.52 $3.51 - $0.04 $0.03 $0.129 $0.01 $0.01 $0.03 $0.09 

$0.3

9 $0.59 $0.22 $0.16 $7.79 $14.45 

EPS (5.0") $0.92 $0.52 $3.04 - $0.04 $0.03 $0.129 $0.01 $0.01 $0.03 $0.09 

$0.3

9 $0.59 $0.22 $0.11 $7.79 $13.92 

PIC (3.0") $0.92 $0.52 $2.68 - $0.04 $0.03 $0.129 $0.01 $0.01 $0.03 $0.09 

$0.3

9 $0.59 $0.22 $0.12 $7.79 $13.57 

Aerogel 

Blanket[8]

Furring

[1]

Window 

Relocation 

for deep 

window 

wells

Insulation 

Installation 

(material & 

labor) [6]

Adhesive 

to attach 

aerogel 

to 

substrate [9]

Removal 

of 

shingles 

(two 

layers)

Removal 

of OSB 

Deck

Rafter 

extensi

on (4 

feet)

Fascia 

Boards 

Installation

Soffit 

Nailer

Replace

-ment 

of OSB 

Deck

Replace

-ment 

of 

shingles

Rake 

Over

hang

Removal 

of 

Exterior 

Cladding 

(vinyl 

siding) [1]

Building 

Kraft 

Paper 

[1]

Strapping 

Screws [7]

Installation 

of exterior 

cladding 

(vinyl 

siding) [1]

Aerogel (2.0") - $0.52 $14.26 $0.01 - - - - - - - - $0.59 $0.22 $0.06 $7.79 $23.45 

[1] According to RSMeans Building Construction Cost Data 2011.

[2] According to Building Science Corporation (BSC). Estimated as $100/window × 14 windows of base case house / 2,700 ft2 (total façade area of the base 

case house).

[3] According to RSMeans Building Construction Cost Data 2011; the cheapest combination of rigid board insulation thickness was assumed for the cost 

analysis (e.g., 9 in. was assumed as 3 × 3 in. layer instead of 4 × 2 in. + 1 in.). For PU, thermal bridging effect was taken into account while calculating required 

thickness to achieve the target R-value. This cost includes material and labor costs. The labor cost varies from $0.43/ft2 to $0.47/ft2

, depending on insulation 

type.

[4] According to RSMeans Building Residential Cost Data 2011.

[5] According to William A. Zoeller from Steven Winter Associates, Inc., Norwalk, CT.

[6] This cost is composed of $13.75/ ft2 material cost and $0.51/ ft2 labor cost; labor cost assumed the same as 1 in. rigid foam board installation cost from 

RSMeans Building Construction Cost Data 2011. 

[7] According to http://www.bestmaterials.com/SearchResult.aspx?CategoryID=750.

[8] After conversation with aerogel manufacturers and reviewing cost data, the team assumed that in short-term prognosis a cost of R-4/10mm blanket can 

be chosen at $2.75/ft2.

[9] According to RSMeans Building Residential Cost Data 2011. Estimated based on $10.40/ 5 gal. adhesive for 18 (S.Y/gal.) coverage.
45

Table 4. Total cost of aerogel and conventional insulation techniques to retrofit the wall of baseline house to exterior R-35 target value. 

Aerogel retrofit technique does not require all retrofit tasks because of low thickness. The retrofit tasks are not in order.

Target 

Rvalue 

Insulation 

Type Retrofit Tasks and Cost ($/SqFt)

Total 

Cost 

($/SqFt)

Exterior 

R-35 

Conventional 

Insulation 

Furring 

[1]

Framin

g (2 × 

4; OC 

16) [12] 

Framing 

(2 × 6; 

OC 16) 

[12]

Window 

Relocation for 

deep 

window 

wells [2]

Insulation 

Installa

-tion 

(materi

al & 

labor) 

[3]

Adhe-sive 

to attach 

aerogel to 

substrate

Removal 

of 

shingles 

(two 

layers) 

[4]

Remov

al of 

OSB 

Deck [5]

Rafter 

extension (4 

feet) [6]

Fascia 

Boards 

Installa

-tion [4]

Soffit 

Nailer 

[1]

Replacement of 

OSB 

Deck [5]

Replacement of 

shingles 

[5]

Rake 

Over

hang 

[7]

Removal 

of 

Exterior 

Cladding 

(vinyl 

siding) [1]

Building 

Kraft 

Paper [1]

Strapping 

Screws [8]

Installation 

of exterior 

cladding 

(vinyl 

siding) [1]

XPS (7.0") $0.92 - - $0.52 $5.81 - $0.04 $0.03 $0.129 $0.01 $0.01 $0.03 $0.09 $0.39 $0.59 $0.22 $0.20 $7.79 $16.78 

EPS (9.0") $0.92 - - $0.52 $5.04 - $0.04 $0.03 $0.129 $0.01 $0.01 $0.03 $0.09 $0.39 $0.59 $0.22 $0.20 $7.79 $16.01 

PIC (6.0") $0.92 - - $0.52 $4.51 - $0.04 $0.03 $0.129 $0.01 $0.01 $0.03 $0.09 $0.39 $0.59 $0.22 $0.12 $7.79 $15.41 

PU1 (7.5") - $1.50 - $0.52 $5.78 - $0.04 $0.03 $0.129 $0.01 $0.01 $0.03 $0.09 $0.39 $0.59 $0.22 $0.20 $7.79 $17.33 

PU2 (7.5") - - $1.91 $0.52 $5.78 - $0.04 $0.03 $0.129 $0.01 $0.01 $0.03 $0.09 $0.39 $0.59 $0.22 $0.20 $7.79 $17.74 

PU3 (6.0") $0.92 - - $0.52 $4.62 - $0.04 $0.03 $0.129 $0.01 $0.01 $0.03 $0.09 $0.39 $0.59 $0.22 $0.12 $7.79 $15.52 

Aerogel 

Blanket[9]

Furring

[1]

Framin

g (2 × 

4; OC 

16)

Framing 

(2 × 6; 

OC 16)

Window 

Relocati

on for 

deep 

window 

wells

Insulation 

Installa

-tion 

(materi

al & 

labor)

[10]

Adh-esive 

to attach 

aerogel to 

substrate [11]

Removal 

of 

shingles 

(two 

layers)

Remov

al of 

OSB 

Deck

Rafter 

extension (4 

feet)

Fascia 

Boards 

Installa

tion

Soffit 

Nailer

Replacement of 

OSB 

Deck

Replacement of 

shingles

Rake 

Over

hang

Removal 

of 

Exterior

Cladding 

(vinyl 

siding) 

[1]

Building 

Kraft 

Paper [1]

Strapping 

Screws 

Installation 

of exterior 

cladding 

(vinyl 

siding) [1]

Aerogel 

(3.4") - - - $0.52 $25.26 $0.01 - - - - - - - - $0.59 $0.22 $0.06 $7.79 $34.45

PU1: Closed cell polyurethane foam was applied inside of 2 × 4 wood studs.

PU2: Closed cell polyurethane foam was applied inside of 2 × 6 wood studs.

Both cases the added studs are standing off a few inches from existing stud.

PU3: Closed cell polyurethane foam was applied in exterior furring.

[1] According to RSMeans Building Construction Cost Data 2011.

[2] According to Building Science Corporation (BSC). Estimated as $100/window × 14 windows of base case house / 2,700 ft2 (total façade area of the base 

case house).

[3] According to RSMeans Building Construction Cost Data 2011; the cheapest combination of rigid board insulation thickness was assumed for the cost 

analysis (e.g., 9 in. was assumed as 3 × 3 in. layer instead of 4 × 2 in. + 1 in.). For PU, thermal bridging effect was taken into account while calculating required 

thickness to achieve the target R-value. This cost includes material and labor costs. The labor cost varies from $0.43/ft2 to $0.47/ft2

, depending on insulation 

type.

[4] According to RSMeans Building Construction Cost Data 2011. Estimated as 2 × 40 ft (removed area) × 2 ( shingle layers) × $0.35 ( removal unit price /ft2) ×
46

2 ( both eave sides) / 2,700 ft2 (total façade area).

[5] According to RSMeans Building Construction Cost Data 2011. Estimated the same way as [4].

[6] According to RSMeans Building Construction Cost Data 2011. The rafter extension is 4 in.; 2 in. overlap and 2 in. extension from its existing length.

[7] According to William A. Zoeller from Steven Winter Associates, Inc., Norwalk, CT.

[8] According to http://www.bestmaterials.com/SearchResult.aspx?CategoryID=750.

[9] After conversation with aerogel manufacturers and reviewing cost data, the team assumed that in short-term prognosis, a cost of an R-4/10 mm blanket 

can be chosen at $2.75/ft2. Aerogel is adhered to the substrate.

[10] This cost is composed of $24.75/ ft2 material cost (nine layers of blanket aerogel $2.75/ft2 per layer) and $0.51/ ft2 labor cost; labor cost assumed the 

same as 1 in. rigid foam board installation cost from RSMeans Building Construction Cost Data 2011. 

[11] According to RSMeans Building Residential Cost Data 2011. Estimated based on $10.40/ 5 gal. adhesive for 18 (S.Y/gal.) coverage.

[12] According to RSMeans Building Residential Cost Data 2011.
47

Table 5. Total cost of aerogel and conventional insulation techniques to retrofit the wall of baseline house to interior R-4 target value. 

The aerogel retrofit technique does not require all retrofit tasks because of its lower thickness. The retrofit tasks are not in order.

Target R-value

Insulation 

Type Retrofit Tasks and Cost ($/SqFt)

Total 

Cost 

($/SqFt)

Interior R-4 

(vs. Interior 

Installation)

Rigid 

Insulation 

Framing (2 

× 4; OC 16) 

[1]

Furring 

[1]

Window Interior 

Rearrangement [2]

Insulation 

Installation 

(material & 

labor) [3]

Adhesive to 

attach 

aerogel to 

substrate

Readjustment of 

electric outlets [4]

Installation of 

gypsum board 

[1]

Readjustment of 

Radiators and 

pipes [5]

Living area loss 

by application 

of furring or 2 

× 4 interior 

framing [6]

Fiberglass 

Batt 1[8] $1.50 - $0.24 $0.57 - $0.15 $0.66 $1.04 $2.68 $6.83 

Fiberglass 

Batt 2[9] - $0.92 $0.24 $0.72 - $0.15 $0.66 - $1.34 $4.03 

Aerogel 

Blanket[10]

Framing (2 

× 4; OC 16)

Furring 

[1]

Window Interior 

Rearrangement

Insulation 

Installation 

(material & 

labor) [7]

Adhesive to 

attach 

aerogel to 

substrate [11]

Readjustment of 

electric outlets [4]

Installation of 

gypsum board 

[1]

Readjustment of 

Radiators and 

pipes 

Living area loss 

by application 

of blanket 

aerogel [6]

Aerogel 

(0.4") - - - $3.26 $0.01 $0.15 $0.66 - $0.25 $4.33 

Fiberglass batt 2: 1 1⁄2 in. thick and R-5.

[1] According to RSMeans Building Construction Cost Data 2011.

[2] Includes interior trim and casing and estimated based on RSMeans Building Residential Cost Data 2011.

[3] According to RSMeans Building Construction Cost Data 2011; the cheapest combination of rigid board insulation thickness was assumed for the cost 

analysis (e.g., 9 in. was assumed as 3 × 3 in. layer instead of 4 × 2 in. + 1 in.). For PU, thermal bridging effect was taken into account while caclulating 

required thickness to achieve the target R-value. This cost is composed of material and labor costs. The labor cost varies from $0.43/ft2 to $0.47/ ft2

depending on insulation type.

[4] According to RSMeans Building Residential Cost Data 2011.

[5] Assumed seven radiatiors for the base case house (one radiator for each two windows) and average cost of $180/radiator. According to 

http://answers.yahoo.com/question/index?qid=20080306132958AApZtBL and http://ths.gardenweb.com/forums/load/hvac/msg0219104426118.html.

[6] According to RSMeans Building Residential Cost Data 2011; the cost per square foot of living area of baseline house is $80.25. The leaving area loss = 

(furring/ framing/blanket aerogel thickness + 0.5 in. dry wall thickness) × 135 ft (base case house perimeter) × 2 floors × unit price (based on RS Means

Building Residential Cost Data 2011 page 29) / total wall area (2,700 ft2).

[7] This cost is composed of $2.75/ ft2 material cost and $0.51/ ft2 labor cost; labor cost assumed the same as 1 in. rigid foam board installation cost from 

RSMeans Building Construction Cost Data 2011.

[8] 3 1⁄2 in. thick and R-13, according to RSMeans Building Construction Cost Data 2011. This is the minimum thickness of fiberglass batt available in the 
48

market.

[9] The minimum fiberglass thickness available in the market is 3 1⁄2 in. Less than this thickness is not common and is used just for odd jobs. For the sake 

of comparison, the cost of 1 1⁄2 in. thick and R-5 was considered according to http://www.acehardwareoutlet.com/productdetails.aspx?sku=45791.

[10] After conversation with aerogel manufacturers and reviewing cost data, the team assumed that in short-term prognosis, a cost of an R-4/10 mm 

blanket can be chosen at $2.75/ft2.

[11] According to RSMeans Building Residential Cost Data 2011. Estimated based on $10.40/ 5 gal. and 18 (S.Y/gal.) coverage.
49

Table 6. Total cost of aerogel and conventional insulation techniques to retrofit the wall of baseline house to interior R-8 target value. 

The aerogel retrofit technique does not require all retrofit tasks because of its lower thickness. The retrofit tasks are not in order.

Target R-value Insulation Type Retrofit Tasks and Cost ($/SqFt) Total Cost 

($/SqFt)

Interior 

R-8 

(vs. Interior 

Installation)

Rigid Insulation Framing 

(2 × 4; 

OC 16) 

[1]

Window Interior 

Rearrangement

[2]

Insulation 

Installation 

(material & 

labor) [3]

Adhesive to 

attach 

aerogel to 

substrate

Readjustment 

of electric 

outlets [4]

Installation 

of gypsum 

board [1]

Readjustment 

of Radiators 

and pipes [5]

Living area loss 

by application 

of 2 × 4

interior 

framing [6]

Fiberglass Batt[8] 

(3.5") $1.50 $0.24 $0.57 - $0.15 $0.66 $1.04 $2.67 $6.83

XPS (2.0") $1.50 $0.24 $1.82 - $0.15 $0.66 $1.04 $2.67 $8.08

EPS (3.0") $1.50 $0.24 $1.68 - $0.15 $0.66 $1.04 $2.67 $7.94

PIC (2.0") $1.50 $0.24 $1.59 - $0.15 $0.66 $1.04 $2.67 $7.85

PU [11] (2.0") $1.50 $0.24 $1.54 - $0.15 $0.66 $1.04 $2.67 $7.80

Aerogel Blanket[9] Framing 

(2 × 4; 

OC 16)

Window Interior 

Rearrangement

Insulation 

Installation 

(material & 

labor) [7]

Adhesive to 

attach 

aerogel to 

substrate [10]

Readjustment 

of electric 

outlets [4]

Installation 

of gypsum 

board [1]

Readjustment 

of Radiators 

and pipes 

Living area loss 

by application 

of blanket 

aerogel [6]

Aerogel (0.8") - - $6.01 $0.01 $0.15 $0.66 - $0.58 $7.41

[1] According to RSMeans Building Construction Cost Data 2011.

[2] Includes interior trim and casing and estimated based on RSMeans Building Residential Cost Data 2011.

[3] According to RSMeans Building Construction Cost Data 2011; the cheapest combination of rigid board insulation thickness was assumed for the cost

analysis (e.g., 9 in. was assumed as 3 × 3 in. layer instead of 4 × 2 in. + 1 in.). For PU, thermal bridging effect was taken into account while caclulating required 

thickness to achieve the target R-value. This cost is composed of material and labor costs. The labor cost varies from $0.43/ft2 to $0.47/ ft2 depending on 

insulation type.

[4] According to RSMeans Building Residential Cost Data 2011.

[5] Assumed seven radiators for the base case house (one radiator for each two windows and average cost of $180/radiator). According to 

http://answers.yahoo.com/question/index?qid=20080306132958AApZtBL and http://ths.gardenweb.com/forums/load/hvac/msg0219104426118.html.
50

[6] According to RSMeans Building Residential Cost Data 2011; the cost per square foot of living area of baseline house is $80.25. The leaving area loss = 

(framing/blanket aerogel thickness + 0.5 in. dry wall thickness) × 135 ft (base case house perimeter) × 2 floors × unit price (based on RS Means Building 

Residential Cost Data 2011, page 29) / total wall area (2,700 ft2).

[7] This cost is composed of $5.50/ ft2 material cost and $0.51/ ft2 labor cost; labor cost assumed the same as 1 in. rigid foam board installation cost from 

RSMeans Building Construction Cost Data 2011.

[8] 3 1⁄2 in. thick and R-13, according to RSMeans Building Construction Cost Data 2011. This is the minimum thickness of fiberglass batt available in the 

market.

[9] After conversation with aerogel manufacturers and reviewing cost data, the team assumed that in short-term prognosis, a cost of an R-4/10 mm blanket 

can be chosen at $2.75/ft2.

[10] According to RSMeans Building Residential Cost Data 2011. Estimated based on $10.40/ 5 gal. adhesive for 18 (S.Y/gal.) coverage.

[11] Required tackiness to reach effective R-8.
51

Table 7. Total cost of aerogel and conventional insulation techniques to retrofit the wall of baseline house from the interior side to a 

target insulation of R-12. The aerogel retrofit technique does not require all retrofit tasks because of its lower thickness. The retrofit 

tasks are not in order.

Target Rvalue Insulation Type Retrofit Tasks and Cost ($/SqFt) Total Cost 

($/SqFt)

Interior R12 

(vs. Interior 

Installation)

Rigid Insulation Framing 

(2 × 4; OC 

16) [1]

Window Interior 

Rearrangement

[2]

Insulation 

Installation 

(material & 

labor) [3]

Adhesive 

to attach 

aerogel to 

substrate

Readjustment 

of electric 

outlets [4]

Installation 

of gypsum 

board [1]

Readjustment 

of Radiators 

and pipes [5]

Living area 

loss by 

application 

of 2 × 4

interior 

framing [6]

Fiberglass Batt[8]

(3.5") $1.50 $0.24 $0.71 - $0.15 $0.66 $1.04 $2.67 $6.97

XPS [11] (3.0") $1.50 $0.24 $2.30 - $0.15 $0.66 $1.04 $2.67 $8.56

Aerogel Blanket[9] Framing 

(2 × 4; OC 

16)

Window Interior 

Rearrangement

Insulation 

Installation 

(material & 

labor) [7]

Adhesive 

to attach 

aerogel to 

substrate 

[10]

Readjustment 

of electric 

outlets [4]

Installation 

of gypsum 

board [1]

Readjustment 

of Radiators 

and pipes 

Living area 

loss by 

application 

of blanket 

aerogel [6]

Aerogel (1.2") - - $8.76 $0.01 $0.15 $0.66 - $1.75 $11.33

[1] According to RSMeans Building Construction Cost Data 2011.

[2] Includes interior trim and casing and estimated based on RSMeans Building Residential Cost Data 2011.

[3] According to RSMeans Building Construction Cost Data 2011; the cheapest combination of rigid board insulation thickness was assumed for the cost 

analysis (e.g., 9 in. was assumed as 3 × 3 in. layer instead of 4 × 2 in. + 1 in.). For PU, thermal bridging effect was taken into account while calculating 

required thickness to achieve the target R-value. This cost is composed of material and labor costs. The labor cost varies from $0.43/ft2 to $0.47/ ft2

depending on insulation type.

[4] According to RSMeans Building Residential Cost Data 2011.

[5] Assumed seven radiatiors for the base case house (one radiator for each two windows) and average cost of $180/radiator. According to 

http://answers.yahoo.com/question/index?qid=20080306132958AApZtBL and http://ths.gardenweb.com/forums/load/hvac/msg0219104426118.html.

[6] According to RSMeans Building Residential Cost Data 2011, the cost per square foot of living area of baseline house is $80.25. The leaving area loss = 

(framing/blanket aerogel thickness + 0.5 in. dry wall thickness) × 135 ft (base case house perimeter) × 2 floors × unit price (based on RS Means Building 
52

Residential Cost Data 2011, page 29) / total wall area (2,700 ft2).

[7] This cost is composed of $8.25/ ft2 material cost and $0.51/ ft2 labor cost; labor cost assumed the same as 1 in. rigid foam board installation cost from 

RSMeans Building Construction Cost Data 2011.

[8] 3 1⁄2 in. thick and R-15, to account for thermal bridging effect of the studs. The cost is according to RSMeans Building Construction Cost Data 2011.

[9] After conversation with aerogel manufacturers and reviewing cost data, the team assumed that in short-term prognosis, a cost of an R-4/10 mm blanket 

can be chosen at $2.75/ft2.

[10] According to RSMeans Building Residential Cost Data 2011. Estimated based on $10.40/ 5 gal. adhesive for 18 (S.Y/gal.) coverage.

[11] 3 in. thick and R-15, to account for thermal bridging effect of the studs. The cost is according to RSMeans Building Construction Cost Data 2011.

Table 8. Total cost of aerogel and conventional insulation techniques to retrofit the wall of baseline house to interior R-12 target value. 

Aerogel retrofit technique does not require all retrofit tasks because of its low thickness. The retrofit tasks are not in order.

Target R-value Insulation Type Retrofit Tasks and Cost ($/SqFt) Total Cost 

($/SqFt)

Interior 

R-12 (vs. 

Exterior 

Installation)

Conventional 

Insulation 

Furring [1]Window 

Relocation for 

deep window 

wells [2]

Insulation 

Installation 

(material & 

labor) [3]

Adhesive to 

attach 

aerogel to 

substrate

Readjustment 

of electric 

outlets [4]

Installation 

of gypsum 

board [1]

Removal of 

Exterior 

Cladding (vinyl 

siding) [1]

Building 

Kraft 

Paper [1]

Strapping 

Screws [5]

Installation of 

exterior cladding 

(vinyl siding) [1]

XPS (3.0") $0.92 $0.52 $2.30 - - - $0.59 $0.22 $0.12 $7.79 $12.46 

EPS (3.0") $0.92 $0.52 $1.68 - - - $0.59 $0.22 $0.12 $7.79 $11.84 

PIC (2.0") $0.92 $0.52 $1.59 - - - $0.59 $0.22 $0.10 $7.79 $11.73 

PU [6] (2.0") $0.92 $0.52 $1.54 - - - $0.59 $0.22 $0.10 $7.79 $11.68 

Aerogel Blanket

[7]

Furring Window 

Relocation for 

deep window 

wells

Insulation 

Installation 

(material & 

labor) [8]

Adhesive to 

attach 

aerogel to 

substrate [9]

Readjustment 

of electric 

outlets [4]

Installation 

of gypsum 

board [1]

Removal of 

Exterior 

Cladding (vinyl 

siding) 

Building 

Kraft 

Paper 

Strapping 

Screws 

Installation of 

exterior cladding 

(vinyl siding) 

Aerogel (1.2") - - $8.76 $0.01 $0.15 $0.66 - - - - $9.58 

[1] According to RSMeans Building Construction Cost Data 2011.

[2] According to Building Science Corporation (BSC). Estimated as $100/window × 14 windows of base case house / 2,700 ft2 (total façade area of the base 

case house).

[3] According to RSMeans Building Construction Cost Data 2011, the cheapest combination of rigid board insulation thickness was assumed for the cost 

analysis (e.g., 9 in. was assumed as 3 × 3 in. layer instead of 4 × 2 in. + 1 in.). For PU, thermal bridging effect was taken into account while caclulating required 

thickness to achieve the target R-value. This cost includes material and labor costs. The labor cost varies from $0.43/ft2 to $0.47/ft2

, depending on insulation 

type.
53

[4] According to RSMeans Building Residential Cost Data 2011.

[5] According to http://www.bestmaterials.com/SearchResult.aspx?CategoryID=750.

[6] Closed cell polyurethane foam was applied in extrior furring.

[7] After conversation with aerogel manufacturers and reviewing cost data, we assumed that in short-term prognosis, a cost of an R-4/10 mm blanket can be 

chosen at $2.75/ft2.

[8] This cost is composed of $8.25/ ft2 material cost and $0.51/ ft2 labor cost; labor cost assumed the same as 1 in. rigid foam board installation cost from 

RSMeans Building Construction Cost Data 2011. 

[9] According to RSMeans Building Residential Cost Data 2011. Estimated based on $10.40/ 5 gal. adhesive for 18 (S.Y/gal.) coverage.

Table 9. Total cost of aerogel and foam insulation techniques to retrofit the wall of baseline house to blown R-16 target value. The 

aerogel retrofit technique does not require all retrofit tasks because of its lower thickness. Required thicknesses were calculated based 

on effective R-value of cavity insulations. The retrofit tasks are not in order.

Target R-value Insulation Type Retrofit Tasks and Cost ($/SqFt) Total Cost 

($/SqFt)

Blown R-16 

(into Partially 

Insulated R-5 

Cavity)

Application of 

conventional insulation 

into 2 × 4 Studs, 16 o.c. 

in conjunction with 

exterior XPS

Exterior 

Furring [1]

Insulation 

Installation 

(material & 

labor) [1]

Window 

Relocation 

for deep 

window 

wells [2]

Removal of 

exterior 

cladding 

(Vinyl 

siding)[1]

Building 

Kraft 

Paper[1]

Installation of 

exterior cladding 

(Vinyl siding)[1]

Strapping 

Screws [3]

Blown Cellulose (2")[4] - $0.23 - - - - - $12.19

Exterior XPS (2") $0.92 $1.82 $0.52 $0.59 $0.22 $7.79 $0.10

Blown Fiberglass(2")[4] - $0.16 - - - - - $12.12

Exterior XPS (2") $0.92 $1.82 $0.52 $0.59 $0.22 $7.79 $0.10

Open-cell PU (2")[4] - $1.00 - - - - - $12.96

Exterior XPS (2") $0.92 $1.82 $0.52 $0.59 $0.22 $7.790 $0.10

Closed-cell PU (2")[4] - $1.54 - - - - - $12.85

Exterior XPS(1") $0.92 $1.21 $0.52 $0.59 $0.22 $7.79 $0.06

[1] According to RSMeans Building Construction Cost Data 2011.

[2] According to Building Science Corporation (BSC). Estimated as $100/window × 14 windows of base case house / 2,700 ft2 (total façade area of the base 
54

case house).

[3] According to http://www.bestmaterials.com/SearchResult.aspx?CategoryID=750.

[4] Effective R-value after taking into account thermal bridging effect.
55

Table 10. Total cost of aerogel and foam insulation techniques to retrofit the wall of baseline house to blown R-20 target value. The 

aerogel retrofit technique does not require all retrofit tasks because of its lower thickness. The retrofit tasks are not in order.

Target 

R-value Insulation Type Retrofit Tasks and Cost ($/SqFt)

Total 

Cost 

($/SqFt)

Blown 

R-20 

(into 

Empty 

Cavity)

Application of 

conventional insulation 

into 2 × 4 Studs, 16 o.c. in 

conjunction with exterior 

XPS

Exterior 

Furring 

[1]

Insulation 

Installation 

(material 

& labor) [1]

Window 

relocation 

for deep 

window 

wells [2]

Removal 

of exterior 

cladding 

(Vinyl 

siding) [1]

Building 

Kraft 

Paper [1]

Installation 

of exterior 

cladding 

(Vinyl siding)

[1]

Strapping 

Screws 

[3]

Blown Cellulose [4] (2.0") - $0.40 - - - - - $12.36 

Exterior XPS (2.0") $0.92 $1.82 $0.52 $0.59 $0.22 $7.79 $0.10 

Blown Fiberglass[4] (2.0") - $0.28 - - - - - $12.74 

Exterior XPS (2.0") $0.92 $2.30 $0.52 $0.59 $0.22 $7.79 $0.12 

Open-cell PU [4] (2.0") - $1.75 - - - - - $13.71 

Exterior XPS (2.0") $0.92 $1.82 $0.52 $0.59 $0.22 $7.790 $0.10 

Closed-cell PU (2.0")[4] - $2.70 - - - - - $14.00 

Exterior XPS (1.0") $0.92 $1.21 $0.52 $0.59 $0.22 $7.79 $0.06 

[1] According to RSMeans Building Construction Cost Data 2011.

[2] According to Building Science Corporation (BSC). Estimated as $100/window × 14 windows of base case house / 2,700 ft2 (total façade area of the base case 

house).

[3] According to http://www.bestmaterials.com/SearchResult.aspx?CategoryID=750.

[4] Effective R-value after taking into account thermal bridging effect.
56

Table 11. Thermal performance test data for aerogel samples. Data for Spaceloft aerogel blanket 

are taken from reference listed in footnote Error! Bookmark not defined..

Density

(kg m−3

) 

Thermal 

Conductivity

(W m−1 K−1)

R-Value/in.

130 0.014 10.00

76 0.030 4.84

65 0.031 4.68

54 0.033 4.33
DOE/GO-102013-3718 ▪ January 2013

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