8-B-i

APPENDIX 8-B. INSTALLATION COST DETERMINATION FOR FURNACES

TABLE OF CONTENTS

8-B.1 INTRODUCTION ................................................................................................. 8-B-1

8-B.2 NON-WEATHERIZED GAS FURNACES.......................................................... 8-B-2

8-B.2.1 Introduction............................................................................................................ 8-B-2

8-B.2.2 Basic Installation Costs.......................................................................................... 8-B-4

8-B.2.3 Venting................................................................................................................... 8-B-6

8-B.2.3.2 Replacement Installations.............................................................. 8-B-8

8-B.2.3.3 New Construction Installations.................................................... 8-B-19

8-B.2.4 Condensate Removal for Condensing Furnaces.................................................. 8-B-21

8-B.2.5 Advanced Controls............................................................................................... 8-B-22

8-B.2.6 Summary of NWGF Installation Costs................................................................ 8-B-22

8-B.3 MANUFACTURED HOME GAS FURNACES................................................. 8-B-23

8-B.3.1 Basic Installation Costs........................................................................................ 8-B-23

8-B.3.2 Venting................................................................................................................. 8-B-23

8-B.3.3 Condensate removal............................................................................................. 8-B-24

8-B.3.4 Additional Costs Associated with Space Constraints.......................................... 8-B-24

8-B.4 OIL-FIRED FURNACES.................................................................................... 8-B-25

8-B.4.1 Basic Installation.................................................................................................. 8-B-25

8-B.4.2 Venting................................................................................................................. 8-B-25

8-B.4.3 Condensate Removal ........................................................................................... 8-B-25

8-B.4.4 Additional Labor for Condensing Furnaces......................................................... 8-B-26

8-B.5 RS MEANS 2010 REGIONAL LABOR COSTS ............................................... 8-B-26

8-B.6 CONSULTANT REPORT (EER CONSULTING)............................................. 8-B-28

8-B.6.1 FURNACE Installation Requirements................................................................. 8-B-28

8-B.6.1.2 Furnace Installation Issues........................................................... 8-B-32

8-B.6.2 Furnace Installation Costs.................................................................................... 8-B-36

8-B.6.2.1 Additional Installation Costs........................................................ 8-B-37

8-B.6.3 Regional Differences ........................................................................................... 8-B-37

8-B.6.4 Furnace Installation Locations............................................................................. 8-B-38

8-B.6.5 Fraction of Common Vents.................................................................................. 8-B-40

8-B.6.6 Additional Information about Weatherized Furnaces.......................................... 8-B-40

8-B.6.7 Appendix A: Examples of vent and chimney sizing based on the National Fuel 

Gas Code table ..................................................................................................... 8-B-40

LIST OF TABLES

Table 8-B.1.1 Example Installation Cost Table................................................................ 8-B-1

Table 8-B.2.1 Summary of GRI 1992 Study on Furnace Installation Locations.............. 8-B-4

Table 8-B.2.2 Comparison of Furnace Installation Location Fractions............................ 8-B-4

Table 8-B.2.3 Basic Installation Cost: New Construction................................................ 8-B-5

Table 8-B.2.4 Basic Installation Costs: Replacement....................................................... 8-B-5

Table 8-B.2.5 Fraction of Existing Masonry Chimney Installations................................ 8-B-9
8-B-ii

Table 8-B.2.6 Fraction of Commonly Vented Furnace and Water Heater Installations... 8-B-9

Table 8-B.2.7 RECS 2005 Furnace Equipment Age Data.............................................. 8-B-11

Table 8-B.2.8 Fraction of Natural Draft Non-Condensing Non-Weatherized Gas 

Furnace for 2006 through 2010................................................................ 8-B-12

Table 8-B.2.9 Non-Condensing to Non-Condensing Venting Issues, Fraction 

Impacted, and Average Installation Cost................................................. 8-B-12

Table 8-B.2.10 Chimney Relining or Vent Resizing (Non-Condensing to NonCondensing)............................................................................................. 8-B-13

Table 8-B.2.11 Vent Connector Costs (Furnace): Replacement....................................... 8-B-13

Table 8-B.2.12 Vent Connector Costs (Water Heater): Replacement .............................. 8-B-14

Table 8-B.2.13 Condensing Non-Weatherized Gas Furnace Vent Length: Replacement 8-B-15

Table 8-B.2.14 Plastic (PVC) Venting Costs: Replacement Cost Example ..................... 8-B-15

Table 8-B.2.15 Fraction of Direct Vent Condensing Furnace Installations...................... 8-B-16

Table 8-B.2.16 Plastic (PVC) Venting Costs: Replacement Cost Example ..................... 8-B-16

Table 8-B.2.17 Concealing Ductwork Costs: Replacement Cost Example...................... 8-B-17

Table 8-B.2.18 Non-Condensing to Condensing Venting Issues, Fraction Impacted 

and Average Installation Cost.................................................................. 8-B-18

Table 8-B.2.19 Chimney Relining or Vent Resizing (Orphaned Water Heater).............. 8-B-18

Table 8-B.2.20 Vent Connector Costs (Furnace): Replacement....................................... 8-B-19

Table 8-B.2.21 Vent Connector Costs (Water Heater): Replacement .............................. 8-B-19

Table 8-B.2.22 Non-condensing Venting Costs (Typical 2-Story House): New 

Construction............................................................................................. 8-B-20

Table 8-B.2.23 Plastic Venting Costs: New Construction................................................ 8-B-20

Table 8-B.2.24 Installation Fractions and Average Costs for Condensate Removal........ 8-B-21

Table 8-B.2.25 Replacement Installations: Average Installation Costs for NonWeatherized Gas Furnaces....................................................................... 8-B-22

Table 8-B.2.26 New Construction Installations: Average Installation Costs for NonWeatherized Gas Furnaces....................................................................... 8-B-23

Table 8-B.3.1 Installation Fractions for Condensing Furnaces that Encounter Space 

Constraints............................................................................................... 8-B-24

Table 8-B.4.1 Stainless Steel Venting Installation Fractions by AFUE level ................ 8-B-25

Table 8-B.5.1 RS Means 2010 National Average Labor Costs by Crew (Standard 

Union) ...................................................................................................... 8-B-26

Table 8-B.5.2 RS Means Labor Costs Markups by Trade (Standard Union)................. 8-B-26

Table 8-B.5.3 Final Labor Cost Factors by Census Division and Four Large States..... 8-B-27

Table 8-B.5.4 Final Labor Cost Factors and Fraction of Households in RECS 2005 

Sample...................................................................................................... 8-B-28

Table 8-B.6.1 Furnace Installation Requirements (New Construction).......................... 8-B-30

Table 8-B.6.2 Furnace Installation Requirements (Replacement).................................. 8-B-31

Table 8-B.6.3 Additional Installation Issues and Frequencies........................................ 8-B-32

Table 8-B.6.4 Differences of Direct Vent fractions by location..................................... 8-B-34

Table 8-B.6.5 Scenarios for Venting Systems and Frequencies..................................... 8-B-35

Table 8-B.6.6 Estimated Furnace Installations, 2009 ..................................................... 8-B-38
8-B-iii

LIST OF FIGURES

Figure 8-B.2.1 Furnace Installation Locations by Region ................................................. 8-B-3

Figure 8-B.2.2 Relationship Between Labor Hours and Gas Furnace Input Capacity 

(RS Means) ................................................................................................ 8-B-6

Figure 8-B.2.1 Masonry Chimney Venting Installation (Non-Condensing Furnace)........ 8-B-7

Figure 8-B.2.2 Metal Venting Installation (Non-Condensing Furnace) ............................ 8-B-8

Figure 8-B.2.3 Plastic PVC Installation (Condensing Furnace) ........................................ 8-B-8
8-B-1

APPENDIX 8-B. INSTALLATION COST DETERMINATION FOR FURNACES

8-B.1 INTRODUCTION

This appendix provides further details about the derivation of installation costs for 

furnaces. The installation cost is the price to the consumer of labor and materials (other than the 

cost of the actual product) needed to install a furnace product. 

The Department of Energy (DOE) estimated installation costs for furnaces based on RS 

Means, a well known and respected construction cost estimation method, as well as manufacturer 

literature and information from expert consultants. Table 8-B.1.1 offers an example of the 

installation cost calculation. All labor costs are derived using the latest residential 2010 RS 

Means labor costs by crew type.1 Replacement installation cost tables include a trip charge,

which is often charged by contractors and calculated to be equal to one half hour of labor per 

crew member. Labor hours (or person-hours) are based on RS Means data, expert data, or 

engineering judgment. Bare costs are all the costs without any markups. Material costs are based 

on RS Means data, expert data, or internet sources. The total includes overhead and profit 

(O&P), which is calculated using labor and material markups from RS Means. Values reported in 

this appendix are based on national average labor costs. The labor costs shown in the tables in 

this appendix are the national average values. In its analysis, DOE used regional labor costs to 

more accurately estimate installation costs by region. Section 8-B.5 describes the derivation of 

regional labor costs. DOE then applied the appropriate regional labor cost to each RECS sample 

household. The total costs include O&P. (Note that the unit “L.F.” in the tables means “linear 

foot.”)

Table 8-B.1.1 Example Installation Cost Table

Description Crew Labor

Hours Unit

Bare Costs (2009$)

Quantity

Total 

incl. 

Material O&P Labor Total

Trip Charge CREW1 0.5 - 0.00 23.00 23.00 1 35.00

Description of Installation Item CREW1 0.5 Ea. 15.00 23.00 48.00 1 51.50

Total 1.0 15.00 46.00 71.00 86.50

The installation cost calculations for furnaces encompass a broad array of product 

classes, installation sizes, and venting configurations, including:

• non-weatherized gas furnaces, mobile home gas furnaces, and oil-fired furnaces;

• new and replacement markets;

• single-family, multi-family, and mobile home dwellings;

• venting systems that are Category I (non-condensing), Category III (stainless vents), and 

Category IV (condensing);

• various vents, such as masonry chimneys, type B metal, or plastic (polyvinylchloride 

(PVC));
8-B-2

• single-wall or double-wall vent connectors;

• gas or oil water heaters that are vented in common with a furnace or isolated; and

• special situations, such as the need to reline a chimney or vent an orphaned water heater.

Applying the RS Means methodology to a furnace installation requires knowledge of its 

details, including the vent length, venting material, vent type, diameter, number of elbows, etc. 

To estimate these quantities, DOE reviewed relevant literature, data, and installation manuals. 

Each estimate was a distribution of values derived from available data; a Crystal Ball Monte 

Carlo simulationa

8-B.2 NON-WEATHERIZED GAS FURNACES

was used to model the resultant costs for each individual household.

8-B.2.1 Introduction

DOE developed installation cost data for gas furnaces using RS Means cost data, DOE 

technical support documents, and consultant reports prepared for this analysis.2, 3, 4, 5, 62, 3, 4, 5, 6

The installation cost was divided into the following four components:

• basic installation,

• venting,

• condensate removal, and

• advanced controls.

The following information about market shares, technologies, and installation location

helped to shape the installation cost calculations.

New Construction and Replacement Market Shares. As determined in the shipment 

analysis portion of the national impact analysis (NIA) (see Chapter 9), for non-weatherized gas 

furnaces approximately 25% of the market will be new construction and 75% will be

replacements in 2016.

Non-Weatherized Gas Furnace Technologies. There are two main furnace designs: 

non-condensing and condensing. Almost all of the non-condensing furnaces have an annual fuel 

utilization efficiency (AFUE) of 80%, which represents the analysis baseline. Condensing 

furnaces have an AFUE of 90% or greater. Non-condensing furnaces usually use Category I 

venting systems, while condensing furnaces are vented using Category IV venting systems. A 

Category I venting system relies on negative pressure and uses either a masonry chimney or a 

metal vent. A Category IV venting system uses positive pressure and a plastic (PVC) vent.

 a

 See Chapter 8 for a description of the Monte Carlo simulation methodology.
8-B-3

Installation Locations. Figure 8-B.2.1 shows the fraction of installations by installation 

location in the North and South regions. The installation fractions are derived using RECS 2005 

household characteristics together with the following assumptions:7

1) If a household has a basement, then the furnace is installed in the basement.

2) If a household has an attic and was built after 1980, then the majority of the furnaces are

installed in the attic (75% of the time). If a household has an attic and was built before 

1980, then the furnaces are installed in the attic 25% of the time.

3) If the household has a crawl space, then the furnace is installed in the crawl space 75% of 

the time.

4) If the household has a garage, then the furnace is installed in the garage 75% of the time.

5) For all other cases the furnace is assumed to be installed indoors. 

Figure 8-B.2.1 Furnace Installation Locations by Region

For comparison, DOE reviewed another reference that examined furnace installations.

8

Table 8-B.2.1 shows a summary of the study results. This survey was completed in 1992 and is 

Unheated

North: 0.5%

South: 1.5%

Garage,

North: 5.0%

South: 21.4%

Indoor

North: 16.2%

South: 29.3%

Unheated

Basement

North: 16.7%

South: 6.7%

Heated

Basement

North: 49.9%

South: 15.0%

Heated

North: 2.1%

South: 12.0%

Crawl Space

North: 9.4%

South: 13.6%

Attic
8-B-4

based on unweighted regional field data. Although directly comparing the data from the two 

references is difficult, the overall national results appear to be similar (see Table 8-B.2.2). Table 

8-B.2.2 also includes numbers provided by the consultant report (see Table 8-B.7.6).

Table 8-B.2.1 Summary of GRI 1992 Study on Furnace Installation Locations

Furnace 

Location

Northwest

(n = 219)

Midwest

(n = 60)

Northeast

(n = 734)

South 

(n = 114)

Southern 

California 

(n = 204)

Overall 

(n=1408)

Basement 41.55% 68.33% 79.29% 14.91% 57.32%

Closet 14.61% 6.67% 1.77% 18.42% 65.20% 14.42%

Garage 25.57% 1.67% 0.41% 21.05% 16.18% 8.31%

Crawl Space 2.74% 0.82% 7.02% 1.42%

Utility 5.48% 18.33% 6.27% 4.90%

Other 9.13% 5.00% 11.17% 33.33% 7.84% 11.36%

Attic 0.91% 0.27% 5.26% 10.78% 2.27%

Table 8-B.2.2 Comparison of Furnace Installation Location Fractions

Furnace 

Location

GRI 1992 Study 

[Overall (n=1408)]

Consultant Report DOE Fractions

80% 

AFUE HH

90%+ 

AFUE HH

Basement 57.32% 40% 67% 48.47%

Garage 8.31% 8% 5% 14.09%

Crawl Space 1.42% 11% 10% 12.43%

Utility 4.90%

Other 11.36%

Attic 2.27% 27% 8% 3.68%

Indoor 14.42% 13% 9% 21.33%

Exterior 1% 1%

8-B.2.2 Basic Installation Costs

For non-weatherized gas furnaces, DOE estimated basic installation costs that are 

applicable to both replacement and new home installations. These costs, which apply to both 

condensing and non-condensing gas furnaces, include putting in place and setting up the furnace, 

gas piping, ductwork, electrical hookup for the thermostat, permit, removal or disposal fees, and, 

where applicable, additional labor hours for an attic installation. Table 8-B.2.3 shows the 

installation costs for new construction calculated using RS Means. Table 8-B.2.4 shows the basic 

installation cost for replacement cases. In addition to the costs presented in the table, for 

installations in the attic DOE assumed an additional labor hour ($48.21) for replacements and 

half an hour ($32.54) for new construction.
8-B-5

Table 8-B.2.3 Basic Installation Cost: New Construction

Description Crew Labor

Hours Unit

Bare Costs (2009$)

Quantity

Total

incl.

Material O&P Labor Total

Furnace Installation Q9 5.25* Ea. $0.00 $153.01 $153.01 1 $341.65 

Gas Piping 1 Plum 0.698 Ea. $17.56 $23.98 $41.54 1 $79.13

Ductwork Q10 0.102 Ea. $0.47 $2.97 $3.44 1 $87.21

Electrical Hookup (Thermostat) 1 Elec 0.4 Ea. $12.30 $13.14 $25.44 1 $47.13

Totals 6.45 $555.11 

* Labor hours vary by input capacity.

Table 8-B.2.4 Basic Installation Costs: Replacement

Description Crew Labor

Hours Unit

Bare Costs (2009$)

Quantity

Total

incl.

Material O&P Labor Total

Trip Charge Q9 1.00 Ea. $0.00 $29.15 $29.15 1 $48.21 

Remove Furnace Q9 2.62 Ea. $0.00 $76.50 $76.50 1 $126.54 

Furnace Installation Q9 5.25* Ea. $0.00 $153.01 $153.01 1 $253.07 

Unit Start-up, Check, and Clean up Q9 2.00 Ea. $0.00 $58.30 $58.30 1 $96.43 

Gas Piping 1 Plum 0.698 Ea. $17.56 $23.98 $41.54 1 $58.61

Ductwork Q10 0.102 Ea. $0.47 $2.97 $3.44 1 $64.60

Electrical Hookup (Thermostat) 1 Elec 0.4 Ea. $12.30 $13.14 $25.44 1 $34.91

Removal/Disposal and Permit Fees - $50.00 

Totals 12.07 $732.37

* Labor hours vary by input capacity.

Furnace installation cost varies by the furnace’s input capacity. Based on 2010 RS 

Means, DOE applied the following relationship shown in Figure 8-B.2.2 between labor hours for 

the “Furnace Installation” item and input capacity.

1 Larger input capacity furnace are usually 

heavier and have larger dimensions, which require more labor hours.
8-B-6

Figure 8-B.2.2 Relationship Between Labor Hours and Gas 

Furnace Input Capacity (RS Means)

8-B.2.3 Venting

Estimating venting costs is complex, because there are a large variety of installation 

scenarios that are possible. DOE calculated venting costs for each household in the RECS 

furnace sample. To determine venting costs for both new construction and replacement 

installations, DOE used a number of parameters that have an impact on the venting installation 

cost, including vent location, installation type (replacement or new construction), region, vents 

(metal or plastic), vent connectors, and chimney type. 

Non-condensing furnaces exhaust high-temperature flue gas, which heats the inside of the 

vent above the dew point to ensure that water vapor in the flue gas does not condense; if it does 

condense and doesn’t re-evaporate quickly during the furnace firing cycle, it could corrode the 

vent, the furnace heat exchanger, or both, thus reducing the lifetime of the vent system or the 

furnace itself. Typically a small amount of condensate at cold startup is acceptable as long as it 

dries out quickly. More efficient low-temperature condensing furnaces condense the water vapor 

in a secondary heat exchanger, thus increasing furnace efficiency by reducing latent heat loss. 

The condensate is fed to a drain. Because the flue gas temperature is relatively low, condensing 

furnaces can be vented through PVC piping.

y = 0.0168x + 3.2329

R2 = 0.9945

0

1

2

3

4

5

6

7

0 50 100 150 200

Labor Hours (hours)

Input Capacity (kBtu/h)
8-B-7

Masonry chimneys, metal vents, and PVC piping are the most common venting 

assemblies. Details of these types of installation follow.

Masonry Chimney. Some non-condensing furnaces are vented using masonry chimneys, either 

lined or unlined. Figure 8-B.2.1 shows a lined masonry chimney venting a non-condensing 

furnace and a water heater. For unlined chimneys, the flexible liner shown is not present, and a

clay tile liner is used instead. Since the 1970s chimney construction techniques have changed. 

For newer chimneys, the chimney and clay tile liner is usually replaced by a masonry facade on 

the exterior that covers a wooden chase with a flexible metal liner on the interior. (These are 

faster to build compared to brick by brick.) If the water heater is isolatedb, the common water 

heater vent shown in Figure 8-B.2.1 would not be present.

Figure 8-B.2.1 Masonry Chimney Venting Installation (NonCondensing Furnace)

Metal Vents. Some non-condensing furnaces are vented using metal vents, either single wall or 

Type B double wall. Figure 8-B.2.2 shows a Type B double-wall metal vent. The combination 

of wall thimbles, storm collar, and flashing replace the chimney. Most metal vents go straight 

through the roof. If the water heater is isolated, the common water heater vent shown would not 

be present.

 b There are a number of water heater types that would not be vented in common with a furnace. These include 

electric, gas direct side-vented, and gas power-vented water heaters. In this appendix, the term “isolated” water 

heater is defined to include all of these possibilities, but only the most prevalent (more than 90%) option – electric 

water heaters – is modeled.
8-B-8

Figure 8-B.2.2 Metal Venting Installation (Non-Condensing 

Furnace)

Plastic PVC. All condensing furnaces are vented using PVC vents, either horizontal or vertical. 

Figure 8-B.2.3 shows a horizontal side-wall plastic vent. The furnace installation shown below

utilizes a two-plastic-pipe venting system. One of the vents exhausts the flue gases and the other

brings combustion air from the outside to the furnace. Flue gas piping is sloped downward 

toward the furnace so that condensate drips back into the furnace condensate drain. This 

installation includes a gas water heater (analogous to the common vented scenario above), which 

requires a separate flue gas exhaust vent. If the water heater is isolated, this exhaust vent will not 

be present.

Figure 8-B.2.3 Plastic PVC Installation (Condensing Furnace)

8-B.2.3.2 Replacement Installations

For replacements, DOE evaluated two cases. One involves switching from a non 

condensing natural draft furnace (less than 75% AFUE) to a non-condensing fan-assisted furnace 
8-B-9

(80% AFUE) and the other involves switching from a non-condensing (natural draft and fanassisted) to a condensing furnace (90% or greater AFUE).

Table 8-B.2.4 provides the fraction of existing masonry chimneys and metal vent 

installations by region, based on the 1994 GRI Furnace Survey.

8

Table 8-B.2.5 Fraction of Existing Masonry Chimney Installations

Venting Type North South

Masonry 71.8% 16.4%

Metal Vent 28.2% 83.6%

Table 8-B.2.5 provides the fraction of existing non-condensing installations that are 

commonly vented with gas water heaters, based on the 1991 GTI Water Heater Survey.9

Table 8-B.2.6 Fraction of Commonly Vented Furnace and Water Heater Installations

Common Venting Northeast Midwest South West

Common 78% 68% 22% 65%

Isolated 22% 32% 78% 35%

8-B.2.3.2.2Non-Condensing to Non-Condensing Furnace Installations

Many non-condensing to non-condensing furnace replacement installations require 

venting modifications to meet current safety requirements. There are two main issues that can 

arise when replacing a non-condensing furnace with a more efficient non-condensing furnace: 

relining an unlined chimney and resizing an existing venting system. 

Chimney Relining

There are two types of masonry chimney—interior and exterior. Exterior chimneys are 

usually exposed on three sides; they are less insulated by the structure, lowering the internal 

temperature and making it more likely that exhaust gases will condense inside. Interior 

chimneys are surrounded by the heated building; the temperature in the chimney tends to be 

higher, making flue gases less likely to condense. Because of these different insulating 

properties, the National Fuel Gas Code (NFGC)10 has different lining requirements for interior 

and exterior chimneys. These requirements are important, because the cost of chimney relining 

is a major component of a furnace installation cost.

Exterior Chimneys. In Table 13.11 of the Code,10 the minimum allowable input rating 

for appliances that are vented in exterior masonry chimneys is 150 kBtu/hour. This rating is the 
8-B-10

upper limit for input capacity for almost all residential furnaces sold today. Therefore, DOE’s

analysis assumes that all exterior lined chimneys will require a re-lining upon replacement.

Interior Chimneys. The NFGC mandates that all interior chimneys be relined when the 

furnace is isolated from the water heater (NFGC Tables 13.3 and 13.4).

10 When a furnace is 

vented in common with a water heater, the vertical vent upsizing / 7X rule applies. This rule 

specifies that the flow area of the vertical vent shall not exceed seven times (7X) the flow area of 

the smallest vent connector—the vent connector for the water heater, for example. Water heater 

vents are typically 3 inches in diameter, so an interior masonry chimney cannot exceed 49 square 

inches, corresponding to an 8 x 8 nominal chimney liner size. DOE assumed that all interior 

chimneys would need to be relined, if built before 1995 and if the existing furnace is a natural 

draft furnace.

DOE determined which furnace installations of the entire furnace sample would require 

chimney relining, based on RECS 2005 equipment age data and the fraction of chimney 

installations (see Table 8-B.2.3). Table 8-B.2.7 shows the equipment age bin data provided by 

RECS 2005. For each bin DOE assigned an equipment installation year using a uniform 

distribution with the ranges shown in the table. Finally, using the fraction of chimney 

installations shown in Table 8-B.2.3, DOE determined if the household had a chimney 

installation. To determine if a household had an unlined chimney, DOE used the following two 

criteria:

1) Furnace exhaust gases are vented through a chimney.

2) The existing furnace was installed before 1995 when building codes requiring the relining 

of chimneys were not yet in place.

Based on these criteria, DOE calculated that 26% of households in the RECS 2005

sample had an unlined chimney. DOE determined that half of these would be relined already by 

2016, based on furnace equipment retirements from 2005 to 2016. (By 2016 the existing furnaces 

that would require relining would be 26 years old or older). Therefore, the analysis resulted in 

13% of the stock needing to be relined in 2016. 
8-B-11

Table 8-B.2.7 RECS 2005 Furnace Equipment Age Data

RECS Age Bin Installation Year 

Uniform Distribution

Fraction of RECS Households

North South National

Less than 2 years old 2004-2005 13.3% 13.1% 13.2%

2 to 4 years old 2001-2003 13.0% 13.8% 13.3%

5 to 9 years old 1996-2000 22.5% 19.5% 21.3%

10 to 19 years old 1986-1995 26.8% 27.4% 27.0%

20 years or older 1965-1985 16.8% 19.3% 17.8%

Unknown 1965-2005 7.7% 6.9% 7.4%

Vent Resizing

Vent resizing occurs when the existing vent diameter is too large for the new gas furnace

or for the commonly vented furnace and gas water heater. Two solutions are possible: 1) vent 

connector resizing (most common) or 2) vent resizing (less common). There are three main 

types of vent connectors: Type B double wall, single-wall galvanized steel, and single-wall 

aluminum. A double-wall vent uses a galvanized steel outer tube to surround an aluminum inner 

tube and is sold in multiple section lengths. The air gap in between the tubes provides insulation, 

which reduces the likelihood of condensation in the vent connector. A single-wall galvanized 

steel vent is simply a zinc-coated steel tube vent. Aluminum single-wall vent connectors are 

similar to galvanized steel single-wall vents and are found in some regions. Condensing furnaces

do not require vent connectors.

The vent connector portion of the vent is the horizontal part of the masonry and metal 

vent systems shown in Figure 8-B.2.1 and Figure 8-B.2.2, respectively. In each figure there are 

two vent connectors shown: one for the water heater, and one for the furnace. As water heater 

capacity is typically less than furnace capacity, in many cases the water heater vent connector 

diameter will be less than the furnace vent connector diameter. DOE assumes that the furnace 

diameter is 4 inches on average, while the water heater vent connector is 3 inches on average.

For this analysis, DOE assumed that vent resizing occurs only when a non-condensing 

fan-assisted furnace (an AFUE of 80% or greater) replaces a natural draft non-condensing 

furnace (an AFUE of less than 75%). Although fan-assisted furnaces have been the only installed 

non-condensing designs since the early 1990s, there is still a fraction of the stock that includes 

natural draft non-condensing furnaces, based on RECS 2005 equipment age (see Table 8-B.2.7) 

and historical shipments by efficiency from GAMA and AHRI shown in 8-B.2.8.

11, 12 Using this 

data, DOE determined that natural draft furnaces will account for about 6% of the stock in 2016. 

Based on the consultant report (see section 8-B.6), DOE assumed that 75% of the venting 

systems with existing natural draft furnaces would need replacement of the vent connectors, 

while in an additional 10% of the installations the entire venting system would have to be 

resized.
8-B-12

Table 8-B.2.8 Fraction of Natural Draft Non-Condensing Non-Weatherized Gas 

Furnace for 2006 through 2010

Furnace Installation 

Year

North

%

South

%

National

%

1994-2005 0.0% 0.0% 0.0%

1993 0.8% 1.0% 0.9%

1992 2.2% 3.0% 2.6%

1991 39.2% 50.6% 43.8%

1990 44.4% 54.7% 48.5%

1989 54.1% 66.0% 58.9%

1988 51.6% 63.8% 56.5%

1987 55.1% 66.8% 59.8%

1986 68.6% 73.9% 70.7%

1985 64.7% 73.3% 68.2%

1984 62.6% 71.9% 66.4%

1983 68.4% 82.3% 74.0%

1982 71.6% 83.3% 76.3%

1981 74.8% 84.2% 78.6%

1980 78.0% 85.2% 80.9%

1979 88.9% 92.7% 90.5%

1978 97.3% 97.3% 97.3%

1977 98.2% 98.2% 98.2%

1976 99.1% 99.1% 99.1%

1965-1975 100.0% 100.0% 100.0%

Table 8-B.2.9 summarizes the three different venting issues associated with noncondensing furnaces including the frequency of installation requirements, the fraction of installed 

furnaces that could be impacted, the fraction impacted (Frequency * Fraction Possibly 

Impacted), and the average additional installation cost.

Table 8-B.2.9 Non-Condensing to Non-Condensing Venting Issues, Fraction Impacted,

and Average Installation Cost

Existing 

Furnace 

Replacement 

Furnace 

Installation 

Requirement

Frequency Fraction 

Possibly 

Impacted

Fraction 

Impacted 

Avg. 

Cost 

Chimney 

installed 

before 1990 

80% AFUE Relining all unlined 

chimneys 100% 13% 13% $681

Natural 

Draft 

80 % AFUE Installing New Vent 

Connectors 

(Converting from 

single-wall to Type B 

double-wall)

75% 6% 4% $199 

Natural 

Draft

80% AFUE Resizing Vent 

System 10% 6% 1% $576 
8-B-13

Table 8-B.2.10 shows the installation cost details for chimney relining or vent resizing.

Vent length is determined by taking into account the furnace installation location and the number 

of floors above the furnace. To determine the length of the vent, the number of floors is 

multiplied by the floor height, which varies from 8 to 10 feet. (For the example shown in Table 

8-B.2.10 the total vent length is 16 feet.)

Table 8-B.2.10 Chimney Relining or Vent Resizing (Non-Condensing to NonCondensing)

Description Crew Labor

Hours Unit

Bare Costs (2009$)

Quantity

Total

incl.

Mat O&P erial Labor Total

Aluminum Flexible Vent (4” 

Diameter, includes vent kit) Q9 0.235 L.F. 10.53 6.85 17.38 16 366.67

Vent Connector (Furnace, 4” 

Diameter) Q9 0.706 Ea. 22.45 20.58 43.03 1 $152.24

Vent Connector (Water Heater, 3” 

Diameter) Q9 0.666 Ea. 18.60 19.41 38.01 1 $110.63

Total 0.71 59.70 31.10 90.80 $600.90

* 1 Q9 means a crew comprised of 1 sheet metal worker and 1 sheet metal worker apprentice.

Table 8-B.2.11 shows the installation cost details for installing a vent connector for a 

furnace. 

Table 8-B.2.11 Vent Connector Costs (Furnace): Replacement

Description Crew Labor

Hours Unit

Bare Costs (2009$)

Quantity

Total

incl.

Mat O&P erial Labor Total

Vent Connector (Vent chimney, 

double wall, type B, 4" Diameter) Q9* 0.235 L.F. 6.70 6.85 13.55 6 $112.20

Vent Connector (Type B Elbows, 

45 degree, 4" Diameter) Q9 0.471 Ea. 15.75 13.73 29.48 1 $40.03

Total 0.706 $152.24

* 1 Q9 means a crew comprised of 1 sheet metal worker and 1 sheet metal worker apprentice.

Table 8-B.2.12 shows the installation cost details for installing a vent connector for a 

water heater.
8-B-14

Table 8-B.2.12 Vent Connector Costs (Water Heater): Replacement

Description Crew Labor

Hours Unit

Bare Costs (2009$)

Quantity

Total

incl.

Mat O&P erial Labor Total

Vent Connector (Vent chimney, 

double wall, type B, 3" Diameter) Q9* 0.235 L.F. 5.35 6.47 11.82 6 $74.65

Vent Connector (Type B Elbows, 

45 degree, 3" Diameter) Q9 0.471 Ea. 13.25 12.94 26.19 1 $35.98

Total 0.706 $110.63

* 1 Q9 means a crew comprised of 1 sheet metal worker and 1 sheet metal worker apprentice.

8-B.2.3.2.3Non-Condensing to Condensing

The standard cases that DOE considered in the analysis represent condensing furnace 

designs at 90% AFUE or greater. DOE’s analysis assumes that, when replacing an existing 

condensing furnace with another condensing furnace, the venting requirements would be the 

same. 

DOE estimated that nationally in 2016 the majority of the replacement installations

would be from non-condensing to condensing furnaces. The next four sections explain the 

changes to the venting systems that would be required when installing condensing furnaces and 

provide information about the fractions of impacted installations. The sections address the 

following four installation issues:

• condensing flue vent (PVC);

• combustion air vent;

• concealing vents in indoor installations; and

• installation with orphaned water heaters.

Condensing Flue Vent (PVC)

When replacing an existing non-condensing furnace with a condensing furnace, the 

existing metal vent is replaced with a plastic (PVC) flue vent. The installation cost of the 

condensing furnace flue vent takes into account the following: 

• furnace location;

• house ceiling height and number of floors (determined for each furnace household in 

RECS 2005 sample);

• furnace distance from wall or roof, and whether to install a vertical vent (through the 

roof) or a horizontal vent (through the wall); and

• wall type, which determines the cost of penetrating the wall.

Table 8-B.2.13 shows the 5th percentile, average, and 95th percentile vent length results 

from the RECS 2005 household sample and the fraction of installations with vertical or 

horizontal vents.
8-B-15

Table 8-B.2.13 Condensing Non-Weatherized Gas Furnace Vent Length: Replacement

Vent Run Vent Length, ft Fraction of Installations

5th Pct Average 95th Pct

Horizontal 7 17 28 67%

Vertical 13 19 29 33%

Table 8-B.2.14 illustrates the development of installation cost components for plastic 

(PVC) venting for a condensing furnace in the replacement cases. The number of elbows 

required varies from 1 to 6 (presented as a uniform distribution). The vent termination is 

assumed to be the same cost as an elbow. The cost of drilling a hole through the building 

envelope is dependent on the type of outside wall material used for each household, as given in 

RECS 2005.

Table 8-B.2.14 Plastic (PVC) Venting Costs: Replacement Cost Example

Description Crew Labor

Hours Unit

Bare Costs (2009$) Quantity

Total

incl.

O&P

Mat. Labor Total

PVC, couplings 10' O.C., hangars 3 per 

10', schedule 40 (2" Diameter) Q1* 0.081 L.F. 3.25 2.50 5.75 16 $122.89

Elbow - PVC, schedule 40, socket joints, 

90" elbow, 1/2" (2" diameter) Q1 0.44 Ea. 2.47 13.61 16.08 1 $25.02

Termination - PVC, schedule 40, socket 

joints, 90" elbow, 1/2" (2" diameter) Q1 0.44 Ea. 2.47 13.61 16.08 1 $25.02

Knockouts to 8' high, metal boxes & 

enclosures (With hole saw, 2" pipe size)

1 

ELEC** 0.30 Ea. 35.35 14.43 14.43 1 $42.95

Total $330.57

* 1 Q1 means a crew comprised of 2 plumbers and 1 plumber apprentice.

** 1 ELEC means a crew of 1 electrician.

Combustion Air Vent (PVC)

A fraction of the condensing furnace installations are direct-vent installations, which uses 

combustion air supplied from the outdoor air. For each household in the RECS 2005 sample

DOE considered the following factors when calculating the installation cost of the combustion 

air vent for condensing furnaces in the replacement market:

• vent length, which is the same as flue pipe length; and

• vent installation fraction, which depends on the installation location.

Table 8-B.2.15 shows the fraction of direct vent installations by installation location, 

based on the consultant report in section 8-B.6. As shown in the table, nationally about 62.1% of 

the condensing furnace installations are direct vent. The fraction of direct-vent condensing

furnace installations for the North and South regions are also shown in the table.
8-B-16

Table 8-B.2.15 Fraction of Direct Vent Condensing Furnace Installations

ID Installation Location

Fraction of 

Direct Vent 

Installations 

Fraction of Installations

North South National

1 Basement (Conditioned) 67% 50.2% 14.6% 36.0%

2 Basement (Unconditioned) 33% 16.4% 6.5% 12.5%

3 Crawl Space 33% 10.1% 16.0% 12.4%

4 Garage 100% 5.5% 27.0% 14.1%

5 Indoor (Closet, Alcove, Utility Room) 67% 16.1% 29.2% 21.3%

6 Attic (Conditioned) 67% 0.3% 0.8% 0.5%

7 Attic (Unconditioned) 33% 1.4% 5.9% 3.2%

Total Fraction of Installations that are Direct Vent 59.3% 66.3% 62.1%

Table 8-B.2.16 illustrates the development of installation cost components for plastic 

(PVC) venting for a condensing furnace in the replacement cases. 

Table 8-B.2.16 Plastic (PVC) Venting Costs: Replacement Cost Example

Description Crew Labor

Hours Unit

Bare Costs (2009$) Quantity

Total

incl.

O&P

Mat. Labor Total

PVC, couplings 10' O.C., hangars 3 per 

10', schedule 40 (2" Diameter) Q1* 0.081 L.F. 3.25 2.50 5.75 16 $122.89

Elbow - PVC, schedule 40, socket joints, 

90" elbow, 1/2" (2" diameter) Q1 0.44 Ea. 2.47 13.61 16.08 1 $25.02

Termination - PVC, schedule 40, socket 

joints, 90" elbow, 1/2" (2" diameter) Q1 0.44 Ea. 2.47 13.61 16.08 1 $25.02

Knockouts to 8' high, metal boxes & 

enclosures (With hole saw, 2" pipe size)

1 

ELEC** 0.30 Ea. 35.35 14.43 14.43 1 $42.95

Total $330.57

* 1 Q1 means a crew comprised of 2 plumbers and 1 plumber apprentice.

** 1 ELEC means a crew of 1 electrician.

Concealing Vent Pipes

For a fraction of indoor installations, DOE added an installation cost to conceal the PVC 

vent pipes—putting in place structures to mask vents that pass through the living space. DOE 

assumed that half of the indoor horizontally vented condensing furnace installations would 

require such modifications. Table 8-B.2.17 illustrates the development of the installation cost 

components for concealing the vent piping in such cases.
8-B-17

Table 8-B.2.17 Concealing Ductwork Costs: Replacement Cost Example

Description Crew Labor

Hours Unit

Bare Costs (2009$)

Quantity

Total

incl.

Mat O&P erials Labor Total

Trip Charge 1 

CARP* 0.5 Ea. 0.00 15.12 15.12 1 24.47

Knockouts to 8' high, metal boxes 

& enclosures (With hole saw, 2" 

pipe size)

1 Elec 2.222 Ea. 35.35 72.99 108.34 1 157.64

Wallboard repair 8"-12" (cut 

square, patch san and repair finish) 1 CARP 0.5 C.L.F. 3.04 20.72 23.76 8 222.54

Total $404.65

* 1 CARP means a crew of 1 carpenter.

Orphaned Water Heaters–Chimney Relining and Vent Resizing

When a condensing furnace replaces an existing non-condensing gas furnace that is 

commonly vented with a gas water heater, the water heater after the installation becomes

“orphaned”. Many of these “orphaned water heaters” require venting modifications to meet 

safety requirements. Such requirements include upgrading the vent connector, resizing metal 

vents, or masonry chimney relining. Based on the consultant report (see section 8-B.6), DOE 

assumed that 100% of the venting systems with existing natural draft furnaces would need to 

have the vent connectors replaced for the orphaned water heater, while an additional 40% would 

need to have the entire venting system of the orphaned water heater resized or upgraded. DOE 

assumed that all orphaned water heater chimneys would need to be relined if built before 1990 

and if the existing furnace is a natural draft furnace. Based on the consultant report (see section 

8-B.6), DOE also assumed that 20% of the venting systems with existing fan assisted noncondensing furnaces would need to have the entire vent of the orphaned water heater resized or 

upgraded.

Table 8-B.2.18 summarizes the four different scenarios that might be encountered in such 

replacement installations. The table shows the scenario description and the analysis results about 

the frequency of applying these requirements, fraction of installed furnaces that could be 

impacted, the fraction impacted (Frequency * Fraction Possibly Impacted), and the average 

additional installation cost.
8-B-18

Table 8-B.2.18 Non-Condensing to Condensing Venting Issues, Fraction Impacted and 

Average Installation Cost

Existing NonCondensing 

Furnace 

Replacement 

Furnace 

Installation 

Requirement

Frequency of 

applying 

requirements

Fraction 

Possibly 

Impacted

Fraction 

Impacted 

Avg. 

Cost 

Natural Draft Condensing 

Furnace

Convert Water 

Heater from single 

wall to B Type vent 

Connector

100% 2% 2% $114

Natural Draft Condensing 

Furnace

Resizing Orphaned 

Water Heater 

Chimney or 

upgrading Metal 

Vent

40% 3% 1% $531

Natural Draft Condensing 

Furnace

Reline all unlined 

chimneys for 

Orphaned Water 

Heater 

100% 7% 7% $555

Fan Assisted Condensing 

Furnace

Resizing Orphaned 

Water Heater 

Chimney or 

upgrading Metal 

Vent

20% 38% 8% $540

Table 8-B.2.19 shows the installation cost details for chimney relining or vent resizing

for an orphaned water heater. 

Table 8-B.2.19 Chimney Relining or Vent Resizing (Orphaned Water Heater)

Description Crew Labor

Hours Unit

Bare Costs (2009$)

Quantity

Total

incl.

Mat O&P erial Labor Total

Aluminum Flexible Vent (4” 

Diameter, includes vent kit) Q9 0.235 L.F. 10.53 6.85 17.38 16 366.67

Vent Connector (Furnace, 4” 

Diameter) Q9 0.706 Ea. 22.45 20.58 43.03 1 $152.24

Vent Connector (Water Heater, 3” 

Diameter) Q9 0.666 Ea. 18.60 19.41 38.01 1 $110.63

Total 0.71 59.70 31.10 90.80 $600.90

* 1 Q9 means a crew comprised of 1 sheet metal worker and 1 sheet metal worker apprentice.

Table 8-B.2.20 shows the installation cost details for installing a vent connector for a 

furnace.
8-B-19

Table 8-B.2.20 Vent Connector Costs (Furnace): Replacement

Description Crew Labor

Hours Unit

Bare Costs (2009$)

Quantity

Total

incl.

Mat O&P erial Labor Total

Vent Connector (Vent chimney, 

double wall, type B, 4" Diameter) Q9* 0.235 L.F. 6.70 6.85 13.55 6 $112.20

Vent Connector (Type B Elbows, 

45 degree, 4" Diameter) Q9 0.471 Ea. 15.75 13.73 29.48 1 $40.03

Total 0.706 $152.24

* 1 Q9 means a crew comprised of 1 sheet metal worker and 1 sheet metal worker apprentice.

Table 8-B.2.21 shows the installation cost details for installing a vent connector for a 

water heater.

Table 8-B.2.21 Vent Connector Costs (Water Heater): Replacement

Description Crew Labor

Hours Unit

Bare Costs (2009$)

Quantity

Total

incl.

Mat O&P erial Labor Total

Vent Connector (Vent chimney, 

double wall, type B, 3" Diameter) Q9* 0.235 L.F. 5.35 6.47 11.82 6 $74.65

Vent Connector (Type B Elbows, 

45 degree, 3" Diameter) Q9 0.471 Ea. 13.25 12.94 26.19 1 $35.98

Total 0.706 $110.63

* 1 Q9 means a crew comprised of 1 sheet metal worker and 1 sheet metal worker apprentice.

8-B.2.3.3 New Construction Installations

For furnace installations in new construction, DOE accounted for the installation cost of a 

new venting system for both non-condensing furnaces (80% AFUE, baseline) and condensing 

furnaces (AFUE of 90% and greater, standard cases).

Table 8-B.2.14 illustrates the typical installation cost for venting a non-condensing 

furnace in new construction. As in the replacement case, vent length is determined by taking into 

account the furnace installation location and the number of floors above the furnace. 
8-B-20

Table 8-B.2.22 Non-condensing Venting Costs (Typical 2-Story House): New 

Construction

Description Crew Labor

Hours Unit

Bare Costs (2009$) Total

incl.

Mat. O&P Labor Total

Vent chimney, double wall, galvanized 

steel (4" Diameter) Q9* 0.24 L.F. 5.95 10.35 16.30 $346.52

Double Wall, Galvanized Steel 

Adjustable Length piece, to 12" Q9 0.47 Ea. 11.45 20.75 32.20 $44.53

Type B Wall Thimble, 4" to 7" 

Adjustable(4" Diameter) Q9 0.47 Ea. 13.90 20.75 34.65 $94.46

Vent Connector (Type B Elbows, 45 

degree, 4" Diameter) Q9 0.47 Ea. 13.95 20.75 34.70 $47.28

Roof Flashing (4" Diameter) Q9 0.47 Ea. 8.05 20.75 28.80 $40.79

Tee (4" Diameter) Q9 0.62 Ea. 30.00 27.10 57.10 $149.40

Tee Cap (4" Diameter) Q9 0.38 Ea. 2.34 16.79 19.13 $28.41

Top (4" Diameter) Q9 0.36 Ea. 11.45 16.04 27.49 $37.28

Total 334.09 186.43 520.52 $788.67

* 1 Q9 means a crew comprised of 1 sheet metal worker and 1 sheet metal worker apprentice.

** 1 CARP means a crew of 1 carpenter.

Table 8-B.2.14 illustrates the typical installation cost for venting a condensing furnace in 

new construction. DOE accounted for the installation of the plastic PVC flue vent, as well as for 

the combustion air vent in direct-vent systems. 

Table 8-B.2.23 Plastic Venting Costs: New Construction

Description Crew Labor

Hours Unit

Bare Costs (2009$) Total

incl.

Mat. O&P Labor Total

PVC, couplings 10' O.C., hangars 3 per 

10', schedule 40 (2" Diameter) Q1* 0.08 L.F. 1.21 3.69 4.90 $128.52

PVC, schedule 40, socket joints, 90" 

elbow, 1/2" (2" diameter) Q1 0.44 Ea. 2.18 20.03 22.21 $64.91

Total 0.52 3.39 23.72 27.11 $193.43

* 1 Q1 means a crew comprised of 2 plumbers and 1 plumber apprentice.

In the new construction cases, DOE also accounted for the installation costs of commonly 

vented furnaces (together with a water heater). When installing a condensing furnace in new 

construction, 100% of the cost of the venting system is assigned to the orphaned water heater 

installation. When a commonly vented non-condensing furnace and water heater are installed, 

then the venting cost is equally divided between the two appliances. Therefore, for commonly 

vented non-condensing furnace installations, DOE subtracted half of the venting system 

installation cost, while in the condensing furnace installations with orphaned water heaters DOE 

added half of the venting system installation cost of the orphaned water heater.
8-B-21

8-B.2.4 Condensate Removal for Condensing Furnaces

Condensate removal is required for all condensing furnace installations in both 

replacement and new construction cases. DOE considered the following when assessing the cost 

of condensate removal:

• Condensate Pipe: For condensing furnaces, excess condensate must be deposited in a 

drain. Therefore, for all installations DOE applied the cost of adding condensate pipe (on 

average 15 feet).

• Condensate Pump: If a drain is not near, then the condensate must be pumped to a remote 

drain. If a central air-conditioner is present, then DOE assumes that already there is 

either a drain nearby or a pump already exists to remove the condensate from the air

conditioner during the cooling season. DOE assumes that a condensate pump is required 

for half of the installations without a central air conditioner.

• Condensate Freeze Protection: If the condensate is exposed to freezing temperatures,

then heat tape and pipe insulation is required. DOE assumes that heat protection is 

required in all unconditioned attics.

• Drip Pan: Some codes require a drip pan. DOE assumed that a drip is required for all 

attic installations or furnaces installed in a 2nd floor or above.

• Additional Electrical Outlet: DOE assumed that half of installations requiring a 

condensate pump or heat tape would also require an additional electricity outlet. DOE 

included this additional cost

Table 8-B.2.24 summarizes the condensate removal adders associated with condensing 

furnaces. The table shows the criteria, the frequency of applying these criteria, the fraction of 

installed furnaces that could be possibly impacted, the fraction impacted (Frequency * Fraction 

Possibly Impacted), and the average additional installation cost.

Table 8-B.2.24 Installation Fractions and Average Costs for Condensate Removal

Installation Cost 

Description

Criteria Frequency of 

applying 

criteria

Fraction 

Possibly 

Impacted

Fraction 

Impacted

Averag

e Cost

Pipe All installations 100% 100% 100% $13

Drip Pans Attics or higher floor 

installations

100% 7% 7% $45

Pump Installations without AC 50% 11% 6% $208

Heat Tape and 

Insulation

Installations in 

Unconditioned Attic

100% 5% 5% $98

Electrical Outlet 

(additional) 

Installations requiring a 

Pump or Heat Tape

50% 8% 4% $136
8-B-22

In addition to the installation costs, the electricity use of the pump and heat tape is taken 

into account (45 watts for Heat Tape and 60 watts for the condensate pump) in the energy use 

calculations (see chapter 7).

8-B.2.5 Advanced Controls

DOE assumed that the more advanced controls found in two-stage and modulating 

furnaces will require additional labor hours to install the more complex thermostat and related 

components. DOE applied an average cost of $19 to all furnaces with two-stage or modulating 

controls.

8-B.2.6 Summary of NWGF Installation Costs

Table 8-B.2.25 (for replacements) and Table 8-B.2.26 (for new construction) show the 

fraction of the impacted installations, the average cost of each installation, and the resulting 

average total cost for all furnace installations.

Table 8-B.2.25 Replacement Installations: Average Installation Costs for NonWeatherized Gas Furnaces

Installation Cost Adder Criteria Installations 

Impacted

%

Average 

Cost

2009$

Total 

Cost 

2009$

Non-Condensing Furnaces

Basic Installation All Installations 100 690 690

Flue Vent Connectors 75% of natural draft vent systems 4 199 8

Chimney Relining 100% of unlined chimneys 13 681 87

Vent Resizing 10% of natural draft vent systems 1 576 4

TOTAL $789

Condensing Furnaces

Basic Installations 100% of installations 100 690 690

New Flue Venting (PVC) All Installations 100 306 306

Combustion Air Venting (PVC) 62% of installations 62 301 186

Concealing Vent Pipes 50% of indoor horizontal vented 5 302 15

Orphaned Water Heater Chimney Relining & Resizing 18 501 89

Condensate Removal 100% of installations 100 71 71

TOTAL $1,357
8-B-23

Table 8-B.2.26 New Construction Installations: Average Installation Costs for NonWeatherized Gas Furnaces

Installation Cost Adder Criteria

Installations 

Impacted

%

Average 

Cost

2009$

Total 

Cost 

2009$

Non-Condensing Furnaces

Basic Installation All Installations 100 509 509

New Flue Vent All Installations 100 1,036 1036

Common Venting credit 1⁄2 common venting cost is credited 48 -405 -195

TOTAL $1,350

Condensing Furnaces

Basic Installations 100% of installations 100 509 509

New Flue Venting (PVC) All Installations 100 247 247

Combustion Air Venting (PVC) 60% of installations 60 239 144

Common Venting Adder 1⁄2 of common venting cost is added 48 405 195

Condensate Removal 100% of installations 100 13 13

TOTAL $1,108

8-B.3 MANUFACTURED HOME GAS FURNACES

DOE developed installation costs for manufactured home gas furnaces using RS Means 

cost data, information for industry experts, and a consultant report (see section 8-B.6). DOE 

developed separate costs for new construction and replacement markets. Based on the shipments

model (see chapter 9), DOE assumed a 50% new construction fraction in 2016. 2, 3, 4, 5, 62, 3, 4, 5, 6

8-B.3.1 Basic Installation Costs

Basic installation costs were developed using the same approach as was used for nonweatherized gas furnaces (see 8-B.2.2). The average basic installation cost for replacements is

$597 and for new construction is $376.

8-B.3.2 Venting

HUD code requires sealed combustion (Direct-Vent) for all installations of manufactured 

home furnaces. According to industry experts and product literature, PVC piping for condensing

furnaces is usually combined with a metal vent system.

DOE determined that the average cost for adding PVC venting in the replacement market

is $279. For new construction market, DOE determined that installing the metal vent for noncondensing applications would cost $302, while the PVC venting cost on average would be 

$364.
8-B-24

8-B.3.3 Condensate removal

DOE assumed that all condensing furnaces require condensate piping and freeze 

protection (heat tape and pipe insulation). These costs are applied to both replacement and new 

construction markets. For half of the installations, DOE assumed an additional electrical outlet 

was required for the condensate heat tape. Condensate piping, freeze protection (heat tape and 

pipe insulation), and electrical outlet costs were developed using the same approach as was used 

for non-weatherized gas furnaces. The average installation cost adder for replacements is $185

and for new construction is $141.

8-B.3.4 Additional Costs Associated with Space Constraints

Mobile home furnaces are usually installed in very tight spaces and often require space

modifications if the furnace dimensions are larger than the existing furnace. Manufacturer 

literature shows that many condensing furnaces are much larger than existing non-condensing 

furnaces.

Table 8-B.3.1 shows the approximate fraction of condensing furnaces that have larger 

dimensions compared to non-condensing mobile home furnaces. DOE grouped the available 

condensing models listed in the 2010 AHRI Directory by efficiency (90%, 92%, and 96% 

AFUE). All 90% AFUE models are manufactured by Nordyne, and their dimensions are the 

same as existing non-condensing furnaces. Only half of the 92% AFUE models are manufactured 

by Nordyne, and the remaining half have larger dimensions than the existing non-condensing 

furnaces. At the 96% AFUE level, all models listed in the 2010 AHRI Directory have larger 

dimensions than the existing non-condensing furnaces

Table 8-B.3.1 Installation Fractions for Condensing Furnaces that Encounter Space 

Constraints

Efficiency Criteria Installations 

impacted

90% AFUE Nordyne models only 0%

92% AFUE All manufacturers except Nordyne are larger 50%

96% AFUE All listed models are larger 100%

For condensing mobile furnace replacements with space constraints DOE applied a 

$200-$600 space constraint adder.

For the condensing mobile furnace new construction market, DOE assumed that the 

decreased living space has a net cost. To calculate this effect, DOE used July 2010 U.S. census 

data on the average cost of a mobile home in July 2010 ($64,000) and average square footage 

(800 sq. ft.). DOE then assumed that the extra space required for a larger condensing furnace is 2 

sq. ft. based on available model data. This resulted in an average cost adder of $160 ($64,000 * 

2 sq ft / 800 sq ft).
8-B-25

8-B.4 OIL-FIRED FURNACES

DOE developed installation cost data for oil-fired furnaces using RS Means data, industry 

experts, and a consultant report. DOE developed separate costs for the new construction and 

replacement markets. Based on the shipments model (see chapter 9), DOE assumed a 10% new 

construction fraction in 2016.

2, 3, 4, 5, 62, 3, 4, 5, 6

8-B.4.1 Basic Installation

Basic installation costs were developed using the same approach as was used for nonweatherized gas furnaces. The average basic installation cost for replacements is $475 and for 

new construction is $350.

8-B.4.2 Venting

DOE considered the additional venting cost associated with stainless steel venting for a 

fraction of installations between 83% AFUE and 85% AFUE based on the fractions shown in 

Table 8-B.4.1. For the fraction of installations at 82% to 85% AFUE that are already part of the 

base case, DOE assumed that no stainless steel vent is required. 

Table 8-B.4.1 Stainless Steel Venting Installation Fractions by AFUE level

Efficiency, 

AFUE

Faction Requiring 

Stainless Steel Vent

82% 0%

83% 25%

84% 50%

85% 75%

The average installation cost for stainless steel venting is $1,285. For condensing oil-fired 

furnaces, 100% of installations are assumed to require direct-vent PVC piping, with an average 

cost of $512. In addition, all condensing oil-fired furnace installations that include an oil-fired 

water heater were assumed to incur the cost for redoing the venting system for the orphaned 

water heater. This resulted in an average additional cost of $1,081 for 15% of the installations.

8-B.4.3 Condensate Removal

Condensate removal installation costs (pipe, pump, heat tape, and insulation) were also 

incuded, as was done for the non-weatherized gas furnaces. The average cost was $180.
8-B-26

8-B.4.4 Additional Labor for Condensing Furnaces

DOE assumed that additional labor would be needed to install a condensing furnace, 

because of the additional labor hours required to tune up its combustion system; on average two 

additional hours would be needed at a cost of $104).

8-B.5 RS MEANS 2010 REGIONAL LABOR COSTS

DOE used regional labor costs to more accurately estimate installation costs by region. 

RS Means provides average national installation costs for different trade groups as shown in 

Table 8-B.5.1. Bare costs are given in RS Means, while labor costs including overhead and

profit (O&P) are the bare costs multiplied by the RS Means markups by trade shown in Table 8-

B.5.2.

Table 8-B.5.1 RS Means 2010 National Average Labor Costs by Crew (Standard 

Union)

Crew Type Crew Description Laborers 

per Crew

Cost per Labor-Hour

Bare Costs Incl. O&P*

2 Plum (Crew L-1) 2 Plumbers 2 $46.70 $70.24

1 Elec 1 Electrician 1 $47.00 $69.94

Q1 1 Plumber, 1 Plumber Apprentice 2 $42.03 $63.21

1 Carp 1 Carpenter 1 $38.10 $59.28

* Q&P includes markups in Table 8-A.8.2

Table 8-B.5.2 RS Means Labor Costs Markups by Trade (Standard Union)

Trade Workers 

Comp.

Aver 

Fixed 

Overhead

Overhead Profit Total

Plumber 8.1% 16.3% 16.0% 10.0% 50.4%

Electrician 6.5% 16.3% 16.0% 10.0% 48.8%

Carpenter 18.3% 16.3% 11.0% 10.0% 55.6%

RS Means also provides labor cost factors for 295 cities and towns in the U.S. To derive 

average labor cost values by state, DOE weighted the price factors by city or town population 

size using 2008 census data. Since RECS 2005 household location is identified by the nine 

census divisions and 4 large States, DOE then population weighted the State data using 2008 

Census data into the appropriate nine census divisions and 4 large States. Table 8-B.5.3 shows 

the final regional price factors used in the analysis.
8-B-27

Table 8-B.5.3 Final Labor Cost Factors by Census Division and Four Large States

Census Division 

and 4 large states Census Division Name States Labor Cost Factor

1 New England Connecticut, Maine, Massachusetts, New 

Hampshire, Rhode Island, Vermont 1.18

2 Middle Atlantic* New Jersey, Pennsylvania 1.27

3 East North Central Indiana, Illinois, Michigan, Ohio, Wisconsin 1.12

4 West North Central Iowa, Kansas, Minnesota, Missouri, Nebraska, 

North Dakota, South Dakota 0.97

5 South Atlantic**

Delaware, District of Columbia, Georgia, 

Maryland, North Carolina, South Carolina, 

Virginia, West Virginia

0.73

6 East South Central Alabama, Kentucky, Mississippi, Tennessee 0.75

7 West South Central*** Arkansas, Louisiana, Oklahoma 0.66

8 Mountain Arizona, Colorado, Idaho, New Mexico, 

Montana, Utah, Nevada, Wyoming 0.82

9 Pacific**** Alaska, Hawaii, Oregon, Washington 1.06

10 New York 1.66

11 California 1.25

12 Texas 0.66

13 Florida 0.72

* Includes New York, which is separated out as a large state.

** Includes Florida, which is separated out as a large state.

*** Includes Texas, which is separated out as a large state.

**** Includes California, which is separated out as a large state.

The distribution of each RECS 2005 product class sample is different, so the average 

labor cost weighted by RECS 2005 sample weights is different from the RS Means national 

average (i.e., labor cost factor of 1.00). Table 8-A.5.4 shows the fraction of households in each 

division and four large states for each product class sample and the resulting average labor cost. 
8-B-28

Table 8-B.5.4 Final Labor Cost Factors and Fraction of Households in RECS 2005 

Sample

Census Division

and

4 large states

Labor 

Cost 

Factor

Fraction of Households in RECS 2005 

Sample

NWGF MHGF OF

1 1.19 3.6% 2.9% 44%

2 1.28 8.3% 4.7% 24%

3 1.12 20.2% 12.0% 0%

4 0.99 9.1% 5.4% 0%

5 0.73 7.9% 22.4% 2%

6 0.75 3.7% 11.5% 0%

7 0.66 4.1% 4.3% 0%

8 0.82 9.4% 4.6% 0%

9 1.08 2.7% 6.6% 0%

10 1.66 4.8% 1.3% 31%

11 1.23 17.4% 2.0% 0%

12 0.66 7.6% 7.7% 0%

13 0.73 1.3% 14.8% 0%

Average Labor Cost Factor 1.04 0.87 1.34

8-B.6 CONSULTANT REPORT (EER CONSULTING)

The following is the furnace installation report prepared by EER Consulting, LLC., for 

Lawrence Berkeley National Laboratory (LBNL) on October 1, 2010.

8-B.6.1 FURNACE Installation Requirements

In general, furnaces must be installed within the scope of their approvals as listed in the 

installation instructions and applicable local and/or national installation codes such as The 

National Fuel Gas Code, Z223.

The following tables are a summary of the major tasks required to install a furnace in a 

new construction and replacement application. 

Additionally, many installations will include a humidifier for winter use. A small portion 

of installations will have zoning systems with separate temperature control of specific areas of 

the home or business. Many commercial applications of weatherized equipment will have 

accessory parts added to the unit for ventilation, power saver (outdoor air) cooling, and building 

pressure relief. Ventilation systems are commonly tied to non-weatherized equipment and are 

becoming more prevalent in residential installations.

Most incorporated areas require a permit and inspection process for both new 

construction and furnace replacement. The inspections are based on provisions of the 

manufacturer’s instructions, the Fuel Gas code, ANSI Z223/NFPA 54, and local building code. 

Unincorporated areas may or may not require permits and inspection, generally depending on 

state law.
8-B-29

 

Manufactured (mobile) homes have their furnaces, ductwork, and venting installed in the 

factory as the home is being assembled and, as such, are not covered in typical new permitting 

and inspection programs. The installation requirements for these units are a combination of 

HUD, UL, or ANSI Z21.47 codes.

All states are required to have an energy code for new construction; however, many 

smaller states have not complied at this point in time. Generally, the energy code is adopted, 

sometimes with exceptions, from the Residential Building Code. California and Florida are 

notable exceptions with individual state codes. The codes must contain provisions to use 

standard efficiency equipment for construction and specify additional system factors such as 

insulation value on ductwork. Texas sets and allows preapproved tradeoffs in construction 

packages, generally including duct insulation thickness, window characteristics, equipment 

efficiency, etc. The California code, Title 24, requires system proof of nominal performance 

with such requirements as airflow testing of installations and duct leakage testing, both on new 

construction and replacements.
8-B-30

Table 8-B.6.1 Furnace Installation Requirements (New Construction)

Gas Oil

non-weatherized Weatherized Manufactured

nonweatherized

<+80 

AFUE

>=90 

AFUE Home

New Construction

Load calculation, equipment selection, 

duct and vent/air intake design x x x X x

Bid and sell the job x x x X x

Procure equipment, supplies and permit x x x X x

Deliver materials for rough-in to the 

jobsite x x x X x

install supply air duct system-plenum, 

trunk, runs, boots and registers x x x X x

install return air duct system-plenum or 

duct, panning, runs, registers x x x x

install air filtration x x x x

install vent system and terminal x x X x

install intake air system and terminal o

install combustion air supply x o X x

install fuel supply and shutoff x x x X

install fuel supply line and tank x

connect to line voltage electrical supply x x x X x

install room thermostat and wire x x x X x

install condensate drain and/or pump x x

rough in code installation inspection (if 

permits were pulled) x x x x

install hanger system for horizontal 

installations x x

install mounting frame, above grade 

applications o

install combustible base for downflow if 

required o o o

install secondary drain pan for AC and 90% 

upflow and horizontal x x x

install furnace cabinet x x x X x

install AC coil x x X x

Startup and checkout x x x X x

Perform Title 24 or equivalent tests x x x ? x

final code inspection (if permits were 

pulled) x x x x

x= applicable to most installations

o= optional with circumstances
8-B-31

Table 8-B.6.2 Furnace Installation Requirements (Replacement)

Gas Oil

non-weatherized Weatherized Manufactured

nonweatherized<+80 

AFUE

Replacement >=90 

AFUE Home

Load calculation, equipment selection, 

duct and vent/air intake design x x x X x

Bid and sell the job x x x X x

Procure equipment, supplies and permit x x x X x

Deliver materials to the jobsite x x x X x

modify or replace supply plenum and AC 

coil mount if necessary x x x X x

modify return duct or plenum if necessary x x x x

modify air filtration if necessary x x x x

reuse or modify vent system and terminal 

or reinstall as required x x X x

reuse or modify intake air system and 

terminal or reinstall as required o

review, and if necessary, install 

combustion air supply x o X x

disconnect and reconnect fuel supply and 

shutoff x x x X

disconnect and reconnect fuel supply line 

and tank x

disconnect and reconnect line voltage 

electrical supply x x x X x

disconnect and reconnect or replace room 

thermostat as required x x x X x

reconnect or install condensate drain 

and/or pump x

modify hanger system for horizontal 

installations if necessary x x

install mounting frame, above grade 

applications o

install combustible base for downflow if 

required o o o

install secondary drain pan for AC and 90% 

upflow and horizontal if needed x x x

install furnace cabinet x x x X x

Startup and checkout x x x X x

Perform Title 24 or equivalent tests o o o ? o

Educate owner on equipment and 

operation x x x X x

final installation inspection o o o O o

x= applicable to most installations

o= optional with circumstances
8-B-32

8-B.6.1.2 Furnace Installation Issues

The following table lists installation issues and occurrence frequencies.

Table 8-B.6.3 Additional Installation Issues and Frequencies

Original 

furnace

New 

Furnace

New 

Plastic 

vent 

New Plastic 

combustion 

air pipe

Water 

Heater 

Oversize 

Common 

Vent

Furnace 

Oversized 

vent or 

chimney

Heating 

condensate 

disposal

Condensate 

freeze-up

Modify 

existing 

combustion 

air supply

65 AFUE 78 AFUE Some Some

65 AFUE 90 AFUE Yes Some Some Some Some Some

78 AFUE 90 AFUE Yes Some Some Some Some Some

8-B.6.1.2.2Plastic vent length for condensing equipment

Currently, the majority of condensing furnaces are being installed in basements, with a 

smaller number in crawl spaces, garages, and attics in the northern parts of the United States. 

Typically, the furnace is installed near the center of the basement or crawl space. 

In new construction, the venting can be vertical or horizontal. On vertical installations, 

the exhaust pipe (and air intake pipe when used) are easily framed into the structure walls and 

terminated above the roof, leaving a more attractive sidewall appearance and reducing the 

chances of blockage due to snowdrifts. A reasonable estimate is 60% of installations are 

vertical. The remainder is horizontal, with the vent generally running through the floor joists to a 

termination on the outside of the sill plate. Two-story homes that have an upstairs and 

downstairs furnace generally have them both located in the basement; however, mounting the 

upstairs unit in the attic is becoming more common.

The average length of run for vertical and horizontal installations in new construction is 

around 20 feet. An example is a 4-foot rise off the furnace and a 12- to 15-foot horizontal run to 

the sidewall of the house. In many instances a foot or two of pipe is required on the outside of 

the home for clearance to normal snowfall. A typical single-story vertical vent is 4 feet to the 

first floor, 8 feet through the first floor ,7 feet in the attic, and one foot above the roof. A twostory vertical vent would be another 9 feet longer than the average single story, and in a 

multifamily building it would typically be 5 to 10 feet shorter.

About 75% to 80% of replacement furnaces in the current market are condensing units 

that are sidewall vented, with the intake and exhaust pipes running horizontally through the 

ceiling joists and exiting the sill plate. In some instances, a PVC vent and intake may be 

installed in the dormant vertical vent or chimney.

Pipe material is generally PVC, Schedule 40, or other grades as specified by the furnace 

manufacturer, with diameters of 2, 2.5, or 3 inches depending on the manufacturer’s instructions 

for pressure drop, input (flow), and physical layout.
8-B-33

If an increasing number of States adopt the requirement to install condensing furnaces, as 

proposed in the joint agreement, homes in more southern areas will fall under this requirement, 

providing an estimated 10%-20% increase in the number of horizontal or downflow furnaces, as 

opposed to upflow, in the total condensing market balance. Horizontal furnaces in attics and 

downflow furnaces in closets or garages in single-story homes generally will be vented vertically 

rather than horizontally.

8-B.6.1.2.3Combustion air piping for condensing equipment (new plastic pipe and 

modifying existing combustion air supply)

Many of the most common “standard” models of condensing furnaces today are certified 

to be installed as either a Central Furnace with only an exhaust pipe and predefined termination, 

or as a Direct-Vent (sometimes called separated combustion) central furnace with an intake air 

pipe and predefined termination in addition to the exhaust requirements of the central furnace. 

The “better” tier of furnace offerings has the same venting flexibility, and the “best” generally 

are direct vent. 

The standard and better units installed as Central Furnaces must meet the code 

requirements for combustion and dilution air. Specific requirements are found in local codes, a 

manufacturer’s instructions, or the National/International Fuel Gas codes. 

Basically, the codes require no specific combustion air supply if the furnace is installed in 

a large volume room and the house is not unusually “tight” in terms of leakage of outdoor air 

into the house. If the home and furnace room do not meet the volume and tightness 

requirements, a combustion air supply must be installed in order for the furnace to be installed as 

a Central Furnace (exhaust pipe only) or it must be installed as a Direct Vent (intake air and 

exhaust pipes). Direct vent is often also selected where the combustion air supply may contain 

contaminants that would add to the corrosiveness of the condensate, such as home shops used for 

finishing furniture or commercial cleaning operations. 

To meet the combustion air volume requirement, a 75,000-Btuh-furnace and 35,000-

Btuh-water heater installation would require a room about 25 ft x 25 ft x 8 ft. To satisfy the 

combustion air requirement totally by a duct (or ducts) to the outside for combustion air delivery 

to the furnace and water heater requires a 7-inch-diameter duct located at the top of the closet. 

Some jurisdictions will allow a combination of the volume method and combustion air duct for 

compliance. Hopefully this gives a feel for the typical code requirements, and more information 

can be developed as needed.

Nationwide from 50% to 60% of all condensing furnace installations are estimated to be

direct vent, with the rest being central furnace installations. The adoption of regional standards 

may shift this ratio slightly toward more central furnace installations.
8-B-34

Table 8-B.6.4 Differences of Direct Vent fractions by location

Installation Location Fraction of Installations Requiring 

Direct Vent

Basement Heated 67

Basement Unheated 33

Crawlspace 33

Indoor (Closet, Alcove, Utility Room, etc.) 67

Attic Conditioned 67

Attic Unconditioned 33

Garage 100

Current generation “good” and “better” furnaces are certified to be installed as either 

direct vent or central furnaces. The installation selection is typically Central Furnace except 

where special situations exist such as: 1) the additional cost of direct vent versus providing a 

combustion air supply; 2) the presence of corrosive materials in the indoor air supply; and 3) the 

acoustics, or the indoor combustion air noise, of the installation. “Best” models are generally 

certified only as Direct Vent.

8-B.6.1.2.4 Chimney Relining & Water heater oversizing in common vent situations 

(Orphaned water heater)

When a condensing furnace is installed as a replacement for a Category I (natural draft or 

induced draft) furnace that is commonly vented with a gas water heater, the common vent may 

be oversized for the remaining (orphaned) water heater. 

A past estimate of commonly vented furnaces and water heaters was about half of all 

Category I installations. The common vent is traditionally either a metal “B” vent or a masonry 

chimney. Across the United States, metal B vents are used about three to four times more often 

than are masonry chimneys. The ratio is lower, perhaps 2:1 or 3:1 in areas with older homes, 

particularly in the northeastern parts of the United States. The introduction of induced draft 

furnaces and boilers in the 1980s led to extensive research on common vents and new code 

provisions to prevent oversizing of the vents for orphaned water heaters, while severely limiting 

the use of external masonry chimneys and vents. Vent connectors from the appliances also 

generally necessitate a change from a single-wall pipe requirement to a double-wall (B vent) 

specification. (See Appendix A for examples of vent and chimney sizing based on the National 

Fuel Gas Code table.)

The most likely homes to require a new vent for an orphaned water heater originally had a large 

capacity natural draft furnace and in many cases a masonry common vent. Over time, the heat 

load of the home was reduced with insulation, sealing, new windows, and other measures, 

permitting the furnace input size to be reduced. When the older furnace is removed, the existing 

common vent is oversized for the water heater. 

The “fixes” that are applied for an orphaned water heater are usually selected for the 

economics of completing the installation, and some will be influenced by future operating costs. 
8-B-35

The most common fix is to install a new, smaller B vent in the existing common metal vent or 

masonry chimney chase. However, some relining of masonry chimneys with cast-in-place liners 

may also be done. Power-vent water heaters or tankless water heaters with sidewall venting are 

another more costly option employed when the customer is energy conscious and willing to pay 

also for a new, more expensive water heater. In 5% to 10% of these instances, a new, electric 

water heater is installed to replace the gas unit, because this is a less expensive alternate to a 

separately vented water heater. A reasonable estimate would be that from 20% to 25% of 

common vents result in orphaned water heaters. The following table shows the scenarios for 

venting systems and frequencies.

Table 8-B.6.5 Scenarios for Venting Systems and Frequencies

Existing 

Equipment

Replacement 

Equipment

Installation Requirement Frequency

65% AFUE 80 % AFUE Convert from single wall to B Type 

vent Connectors

75%

65% AFUE 80% AFUE Resizing Vent System 10% 

65% AFUE 90% AFUE Convert Water Heater from single 

wall to B Type vent Connector

100%

65% AFUE 90% AFUE Resizing Orphaned Water Heater 

Chimney or upgrading Metal Vent

40%

80% AFUE 90% AFUE Resizing Orphaned Water Heater 

Chimney or upgrading Metal Vent

20%

As mentioned above, the weatherization of homes can create a reduction in furnace input 

size when replacements are installed. 

8-B.6.1.2.5Condensate 

Condensate Removal from Condensing Furnace. If there is no drain close to a newly installed 

condensing furnace (about 20% of installations) through which condensate can be removed, then 

adding a pump is common. However, if an evaporator coil exists that has already a condensate 

pump, then that pump is usually used to remove the furnace condensate too. In most basement 

installations the furnace will be close to a drain. In new construction, adding a pump is less 

likely to be needed, because the builders generally plan in advance how to handle the 

condensate. Neutralizer filters are not that common any longer; they have problems with 

plugging up. 

Condensate Freezup. Based on a review of Lennox and Carrier installation instructions, it is 

necessary to apply insulation and electric heat tapes to condensate traps, condensate pumps, and 

drain lines in unconditioned spaces that may be subject to freezing in order to prevent condensate 

from freezing and potential nuisance shutdowns or breakage of plastic parts. The heat tape is to 

be self-regulating—limiting its own temperature by varying resistance—or its temperature must 

be externally regulated with specific limits on watts per unit of drain area.
8-B-36

Whether or not to apply insulation and heat tape on units in unconditioned spaces is 

mostly based on the installers’ judgment. Personal experience with an attic installation that had 

an insulated condensate line, but no heat tape, in Dallas indicates some freezing can be expected 

during night setback and when the ambient temperature is in the 10 °F-20 °F range. If this 

system had an external condensate trap, or condensate pump, it would need heat tape to prevent 

damage.

The majority of installations in unconditioned spaces that are subject to prolonged 

freezing temperatures should include insulating condensate handling parts and the application of 

a regulated heat tape. Examples of such unconditioned spaces include unconditioned attics, 

crawl spaces, and exterior closets.

8-B.6.1.2.6Special considerations for manufactured home furnaces

Traditionally, furnaces installed in manufactured housing (mobile homes) have a special 

design, such as a direct-vent, downflow configuration unit of a natural draft design (sometimes 

called a balanced flue) or more recently an induced draft, 75%-80% AFUE direct-vent furnace. 

Physical size and design are particular to a standard-size closet with return air through the front 

of the cabinet. Two manufacturers, Coleman and Nordyne supply more than 90% of the market. 

Standards for mobile homes construction and approvals are specified by HUD. 

Replacements usually are the current version of the 75%-80% AFUE OEM mobile home 

furnace, although, where codes permit, traditional condensing furnaces from all manufacturers 

have been installed in a direct-vent configuration for increased energy savings. A quick search 

does not indicate a condensing furnace option in new homes.

Modular homes, another subset of manufactured housing, are commonly available with 

minimum efficiency furnaces or, as an upgrade option, a condensing furnace. In a limited 

number of homes observed in the Midwest, the furnace had been installed at the jobsite, usually 

in a basement that was constructed as the foundation for the modular home.

8-B.6.2 Furnace Installation Costs

There are nearly an infinite number of variables inherent in the installation or 

replacement of a furnace, thus making it impossible to estimate an average installation cost with 

any degree of certainty. Depending on the specific job, some or all of the basic tasks listed 

above are performed. The installer’s labor, material, and overhead costs also vary widely, 

compounding the difficulty in estimating average installation costs. Some state requirements,

such as California’s Title 24, include duct and airflow performance measurements and minimum 

performance standards, again adding to the variability of the cost. And how is the installation 

cost apportioned when both the furnace and air conditioner are installed or changed out? Or 

filtration and control upgrades such as night setback thermostats or zone controls are added? 

Also, how should the benefits of weatherization programs or rebate programs, such as federal tax 

credits or state, municipal, and utility rebates, be assigned?
8-B-37

A study to estimate “typical” costs could be performed through surveys of installers in 

multiple geographic regions, or by specifying a limited set of “typical installations” and 

estimating their costs based on geographic differences in equipment requirements, labor, and 

overhead. Such a study would be far larger than the scope of this project allows. 

However, based on experience, some guidance can be provided on the range of costs 

today. A non-weatherized furnace replacement could be expected to be in the range of $1,500 to 

$40,00 for basic 80% or 90% AFUE equipment depending on the degree of difficulty in the 

change-out and local rates. Replacement of the air conditioning system at the same time as the 

furnace adds $2,000 to $5,000 for lower SEER equipment with standard controls. Top-of-theline furnaces and air conditioners with advanced controls, enhanced filtration, and other features

can top $10,000 per system.

New construction will also vary widely for the reasons mentioned previously, as well as 

geographic differences in construction, such as location, rigid or flex duct, length of vents, ease 

of condensate disposal, high volume tract housing vs. a single custom home, and more. 

Minimum efficiency systems could be expected to range from $5,000 to $8,000 per system.

8-B.6.2.1 Additional Installation Costs

The cost of relining a chimney in general is around $300-$700. In about 10% of 

installations that require chimney relining the cost could be as high as $1,000-$1,200.

8-B.6.3 Regional Differences

In addition to the regional items noted elsewhere in this report, the following regional 

considerations may also affect the cost of furnace installations.

Predominantly Heating Climates (Northern) 

This area tends to have a higher proportion of condensing furnace installations rather than 

non-condensing units. In replacement situations, this requires some additional installation work 

and cost. A new plastic vent (and perhaps air intake) and termination must be installed, along 

with a means of condensate disposal. Because many of these homes originally had metal or 

masonry common vents for the furnace and water heater, it is not uncommon for a new vent to 

be required for the water heater to operate properly.

Supply and return ductwork tends to be in the basement, consisting of rigid metal with 

rigid takeoffs and, in some cases, a short flex duct run to the register boot. These systems 

generally require more labor than average for installation in new construction. 

Predominantly Cooling Climates (Southern)
8-B-38

HVAC equipment and ductwork tend to be installed in the attic space, requiring 

additional secondary drain pans for condensing furnaces and air conditioner coils. Condensate is 

generally gravity piped to the home drainage system. In the portion of this area subject to 

freezing attic temperatures, heat tapes may be necessary to insure condensate drainage from 

condensing furnaces located in non-conditioned locations.

Supply and return ductwork generally consists of rigid plenums with flex duct supply and 

return runs. Building cavities are often used as a part of the return air system.

8-B.6.4 Furnace Installation Locations

The following table is an estimate of a snapshot of the currently installed furnace 

population.

Table 8-B.6.6 Estimated Furnace Installations, 2009

gas non-weatherized, 

80% interior

% % by closet exterior

Position basement attic

except

basement crawlspace garage closet

Indoor upflow 58 40 3 10 4 1

horizontal 35 24 11

downflow 7 3 4

gas non-weatherized, 

90% interior

closet exterior

basement attic

except

basement crawlspace garage closet

Indoor upflow 77 67 2 4 3 1

horizontal 16 6 10

downflow 7 5 2

oil non-weatherized Garage or

basement crawlspace closet

Indoor upflow 90 90

horizontal 5 5

downflow 5 5

gas weatherized sidewall

rooftop or on grade

outdoor horizontal 40 30 10

downflow 60 55 5

No definitive statistics are available regarding installations, and the following discussion 

will present some of the thought behind the estimates listed above. Furnaces are now commonly 
8-B-39

built in horizontal upflow , horizontal downflow, or true multi-position configurations, thereby 

eliminating the information on configuration previously available in GAMA statistics.

Some clues to furnace type and location can be gleaned from foundation type. 

Residences with basements represent one of the largest segments of the existing foundation 

types. According to Census statistics, currently about 30% of homes are built with basements, 

50% on slabs, and 20% with crawlspace foundations. Thirty years ago, the equivalent statistics 

were 40%, 40%, and 20% respectively, showing the trend to a larger percentage of US 

construction in the south and west. 

The foundation type is important because, when a basement is present, generally an 

upflow furnace and basement or first-floor ductwork are located therein. Two-story homes with 

basements may be served by one furnace, or the second floor may be served by a second upflow 

furnace located in a closet on the second floor, or a horizontal in the attic. In a limited number of 

applications, a weatherized unit may be mounted on or next to the foundation wall and connected 

to ductwork through this wall. 

Basement construction tends to be standard in about two thirds of the United States, 

primarily the Northeast and Midwest portions. States such as Washington, Oregon, California, 

Nevada, Arizona, New Mexico, Texas, Oklahoma, Arkansas, Louisiana, Mississippi, Alabama, 

Georgia, Florida, South and North Carolina, and Hawaii are predominately slab or crawl space 

construction.

Slab foundations generally have the furnace and duct system in the attic in primarily 

cooling climates. The use of a closet and an upflow furnace in the conditioned space is declining 

in single-story slab homes. Homes in climates with significant heating demand may have the 

duct system buried in the slab foundation (Oklahoma, for example). Two-story slab homes 

generally have one or two furnaces with upper-story ductwork and one or two furnaces located in 

the attic.

Single-story crawl space homes generally have a horizontal furnace and duct work 

located in the crawl space. Some have weatherized furnaces located next to the foundation.

Parts of California and Arizona have concentrations of existing roof-mounted non-weatherized 

furnaces and air conditioners on residences. Tennessee and the surrounding states also make use 

of non-weatherized packages on grade in new and replacement for applications.

Commercial applications of non-weatherized furnaces are generally in basements or utility 

closets or rooms, although some will also be in attic spaces. The majority of weatherized units 

for this application will be roof mounted. 

Condensing furnaces tend to be concentrated in states requiring the most heating, and 

non-condensing furnaces tend to be in those states with less heating and greater cooling needs. 

Oil furnaces are primarily found in the northeastern states, with a few in the Midwest and 

Northwest. Gas manufactured (mobile) home furnaces tend to have a special direct-vent, 

downflow design that is suited to a standardized closet-size application.
8-B-40

8-B.6.5 Fraction of Common Vents

There is no data available to reference for determining how many furnaces and water 

heaters are common vented. In the mid 1980s, as condensing furnace installations became more 

common, industry opinion held that a good estimate of common vents in all homes was in the 

50%-70% range, with more in the basement in heating climates. The growth of condensing 

furnace sales, code requirements that limit common venting with induced draft non-condensing 

furnaces, the issues with condensation in masonry chimneys, and the shift of new construction to 

the South and West have caused a significant decline in the percentage of common vents. A 

reasonable estimate of today’s installed base might be in the 20%-30% range.

8-B.6.6 Additional Information about Weatherized Furnaces

Most states have some installations of weatherized furnaces in residences. The largest 

concentrations are found in three or four states. California and Arizona have a significant 

replacement market for roof-mounted units. Tennessee and the surrounding areas have many 

units mounted on grade, in both the new construction and replacement market. Florida may also 

have a significant number of installations.

Commercial use of non-weatherized units is universal in all states for small offices, retail, 

and other uses. Most are mounted on the roof, although a small percentage are on exterior wallsupported platforms or on grade.

Residential use is probably driven by ease of replacement, freeing up floor or yard space 

for other uses, cost effectiveness, as well as some because “that’s the way we’ve always done it 

around here”.

Air conditioning condensate is either piped into a drain, or dumped on the roof depending 

on local codes and conventions. Currently there are no, or very few, condensing heat sections in 

these units. Condensate disposal issues primarily associated with freeze-up are the major 

impediment to the satisfactory mass application of condensing technology to condensing 

furnaces.

8-B.6.7 Appendix A: Examples of vent and chimney sizing based on the National Fuel 

Gas Code table

I pulled down a copy of the GAMA venting tables that is probably close, if not identical 

to the current code tables and ran a couple examples similar to our conversation last night.

Let's assume a home originally had a 125Kbtuh furnace and 35 kbtuh water heater, both 

atmospheric, cat 1. Also assume the common vent is metal B vent and was 15 ft high, and the 

connectors for the two appliances were single wall. Connector length is 5 feet with a one foot 

rise.
8-B-41

Originally, the common vent would have been 6" dia B vent (or larger) at the installers 

option. For starters, let's assume 6".

Let's say the first replacement was a 125kbtuh fan assisted. The venting tables would say 

the fan assist appliance must be 144k minimum and the installer would be faced with a choice of 

going to 5" common vent or double wall vent connector. Undoubtedly they would choose to use 

the double wall vent connectors.

Next, let's assume the original equipment was oversized and the home had been 

weatherized, and a heat loss analysis yielded a 75kbtuh fan assist furnace as the replacement. As 

long as he uses a double wall vent connector, 4 or 5", the installation is ok. However, had the 

original common vent been 7", it would need to be relined with 5 or 6".

Next, let's assume the furnace is removed from the common vent (condensing installed 

with separate vent system). The venting tables have no minimum for atmospheric, and allow the 

water heater with typical 3 inch draft hood outlet on the 6" common vent. However to be 

compliant, it must meet the 7 times oversize rule. The 3" dia draft hood outlet is 7.1 square 

inches, and the 6 in common vent is 28 sq in, therefore it passes the 7* test. However, if the

common vent were 8", it would not and the vent would have to be relined.

There are millions of combinations of variables making it difficult to generalize about 

when resizing is needed and when not. However, larger vents from older atmospheric 

installations are more likely to require upgrading the vent connector and/or downsizing the 

common vent.

A couple observations to remember on masonry common vent (chimney). First as I 

recall, the vent tables apply to internal, not external chimneys. External automatically need 

upgrading, at least in colder climates. Masonry were generally a minimum 8x8 or 8x12 tile (non 

tile lined, brick only, are not usable without lining) and as such are more apt to be oversized for 

both the change to a fan assist furnace, or orphaned water heater. 
8-B-42

REFERENCES

1. RS Means Company Inc., RS Means Residential Cost Data. 29th Annual Edition ed. 

2010: Kingston, MA

2. U.S. Department of Energy - Energy Efficiency & Renewable Energy, Technical Support 

Document: Energy Efficiency Standards for Consumer Products: Residential Furnaces 

and Boilers, 2007. Washington, DC. 

3. RS Means Company, Facilities Maintenance & Repair Cost Data 2010. Kingston, MA.

4. U.S. Department of Energy - Energy Efficiency & Renewable Energy, Technical Support 

Document: Energy Efficiency Standards for Consumer Products: Residential Water 

Heaters, 2001. Washington, DC. 

5. Smith, D. C., Consultant Report - Water Heater Installation Costs, 2008. Florence, SC. 

6. RS Means Company Inc., 2010 Mechanical Cost Data. 2010. Kingston, MA.

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Consumption Survey: 2005 Public Use Data Files. 2008: Washington, DC. 

http://www.eia.doe.gov/emeu/recs/recspubuse05/pubuse05.html

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J. C. Cross, G. R. Whitacre, J. G. Murray, W. J. Sheppard, D. W. DeWirth, and W. H. 

Thrasher, Assessment of Technology for Improving the Efficiency of Residential Gas 

Furnaces and Boilers, Volume I and II - Appendices, September, 1994. Gas Research 

Institute. AGA Laboratories, Chicago, IL. Report No. GRI-94/0175. 

9. D.D. Paul et al., Assessment of Technology for Improving the Efficiency of Residential 

Gas Water Heaters, December, 1991. Battelle. Columbus. Report No. GRI-91/0298. 

GRI/GATC Water Heater NAECA Analysis. 

10. National Fire Protection Association, National Fuel Gas Code -2002 Edition, 2002. 1 

Batterymarch Park, P.O. Box 9101, Quincy MA. 

11. Gas Appliance Manufacturers Association (GAMA), Updated Shipment Data for 

Residential Furnaces and Boilers, personal communication. April 25, 2005.

12. Air-Conditioning Heating and Refrigeration Institute, AHRI Regional Furnace Shipments 

Data, 2010. (Posted Submitted to DOE on July 20, 2010) 

<http://www.ahrinet.org/Content/Furnaces_609.aspx>