Strategies Workshop for 

RetrofitNY Awardees

Urban Futures Lab, Brooklyn

July 11, 2018

Lieko Earle, Paul Torcellini, Shanti Pless, and Michael Deru

NREL/PR-5500-72067
NREL | 2

Agenda

8:00 – 10:00 Opening & Introductions

10:00 – 11:00 Decision-making 

11:00 – 11:15 Break

11:15 – 12:15 Façade & Windows

12:15 – 1:15 Lunch break

1:15 – 2:15 HVAC & DHW systems

2:15 – 3:15 Appliances & Lighting

3:15 – 3:30 Break

3:30 – 4:30 PV & Metering

4:30 – 5:00 Closing
Opening & Introductions

Who are we and why are we here?
NREL | 4

Who are we?

Paul Torcellini

Commercial 

Buildings

Lieko Earle

Residential 

Buildings

Michael Deru

Building Energy 

Science

Shanti Pless

Commercial 

Buildings
NREL | 5

Awardee Round-Robin Introductions

In 10 minutes or less per project team:

 What is your project (describe building, 

overall scope)? (<3 min)

 What keeps you up at night related to 

achieving success?

 What are the biggest barriers in achieving 

the target EUI?

 What do you want to get out of today?

(<1 min)
Decision-making

Key elements for achieving integrated, 

state-of-the-art retrofit design
• RSF uses 50% less energy than if it 

were built to current commercial 

codes at no extra capital cost

• RSF increases space at NREL by 

60% but only increases energy use 

NREL/17825 by 6%
Many Pieces

• So many ways to 

assemble the pieces

• Design is about making 

decisions – need 

motivation to make 

the right decisions

• Who are the decision 

makers?

Used by permission: Paul Torcellini/NREL
Great Potential in Buildings

Clockwise from top: NREL/09202, 10884, 10140, 09249, 12637, 

11097 
Setting Goals

• Measurable goals are better

• From bad to good...

– I want a green building

– Design a LEED <rating> building

– Design a building to use 30% less energy than ASHRAE 90.1- 2013

– Design a building to use less than 25,000 BTU/sqft

– Design a ZERO ENERGY BUILDING

• Influencing purchasing decision—the owner
What are Zero Energy 

Buildings?

• Conceptually, a building that has no adverse energy [or 

environmental] impact [because of its operation]

• Energy consumption has been a long-term surrogate 

for environmental impact

• Boundaries and metrics

• What energy flows to measure
Zero Energy Building
Adding Renewables
Building on a Diet
ZEB Concept

Goal 1: 

Reduce Consumption

Goal 2: 

Apply On-site Renewable 

Energy

BALANCE!
Zero Energy Building (ZEB) Definition

An energy-efficient building, where on 

a source energy basis, the actual 

annual delivered energy is less than or 

equal to the on-site renewable 

exported energy.
Adding Value

II I

III IV

Value Added
NREL/17826

Photo credit: Paul Torcellini/NREL
Problem Definition: RFP Objectives

MISSION CRITICAL

Attain safe work performance/Safe Design Practices

LEED Platinum

Energy Star “Plus”

HIGHLY DESIRABLE

800 staff Capacity

25 kBTU/sf/year

Architectural integrity

Honor future staff needs

Measurable ASHRAE 90.1

Support culture and amenities

Expandable building

Ergonomics

Flexible workspace

Support future technologies

Documentation to produce a “How to” manual

“PR” campaign implemented in real-time

Allow secure collaboration with outsiders

Building information modeling

Substantial Completion by 2010

IF POSSIBLE

Zero energy design approach

Most energy efficient building in the 

world

LEED Platinum Plus

ASHRAE 90.1 + 50%

Visual displays of current energy efficiency

Support public tours

Achieve national and global recognition and 

awards

Support personnel turnover 

RFP also required maximum use of 

natural ventilation and 90% of floor 

space fully daylit
The Process

 Owner made tough decisions up-front

• Set budget

• Sought maximum value for that budget

• Prioritized goals

 Design-Build procurement process

• Managed the team to the RFP and its substantiation criteria

• Rewards

 Allowed design-build team to use creativity to maximize value--innovation

 Owner did not solve the problem (but knew the technical solution existed)
Innovation as a result of the process

Process drove creativity of solutions by providing appropriate 

constraints

Examples

• Datacenter – Is it in or out?

• Insulation, radiant tubing, and air based systems

– Worked with subcontractors, vendors, manufacturers

• Domestic hot water

• Creating scale—the façade treatment

• Think about what scaling can be done to overcome barriers
Goals for this effort

 Criteria specified in NYSERDA RFP

• Ventilation rates

• Thermal comfort criteria

 Low Cost and Replication

 Zero Energy and Zero Energy Ready

 20 kBtu/ft2 annually

• 11 kBtu/ft2 for heating and cooling

• Note: these are consistent with the K-12 and office goals.

• www.ashrae.org/aedg
Site EUI 

(kBtu/ft2/yr)

Assumptions:

• 75% of Roof 

area available 

for PV

• 2 stories

44

41

37

34

31

28

24

21

18

Site energy use intensity targets to meet the available rooftop PV annual 

energy production (75% roof PV, 2 floors)

NYC

68 kBtu/ft2/story

Upstate

56 kBtu/ft2/story

4 story

17/14
LEGEND:

NOT RATED

LEED CERTIFIED

LEED GOLD

LEED SILVER

LEED PLATINUM

SOURCES:

www.fayobserver.com

www.dbia.com

www.nasa.gov

www.eomega.org

www.oregonsustainabilitycenter.org

www.americas.rlb.com

http://greensource.construction.com

www.1800larimer.com

www.usgbc.org

www.smithgroup.com

www.cronkite.asu.edu

PROJECTS AND LEED CERTIFICATION

COMMERCIAL BUILDING CONSTRUCTION COST

PER SQUARE FOOT COST

RSF II

$246

Platinum

RSF 

$259

Platinum

Average 

$355
Measured Versus Modeled Monthly and Cumulative EUI Credit: Chad Lobato/NREL

0

4

8

12

16

20

24

28

32

36

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

Model

RSF

PV

Model

RSF

PV

Model

RSF

PV

Model

RSF

PV

Model

RSF

PV

Model

RSF

PV

Model

RSF

PV

Model

RSF

PV

Model

RSF

PV

Model

RSF

PV

Model

RSF

PV

Model

RSF

PV

October

2010

November

2010

December

2010

January

2011

February

2011

March

2011

April

2011

May

2011

June

2011

July

2011

August

2011

September

2011

Annual EUI (kBtu/ft2)

Monthly EUI (kBtu/ft2)

PV

Data Center

Mechanical

Systems

Plug Loads

Lighting

The PV system is sized 

for an annual EUI of 

35.1 kBtu/ft2.

Note: The annual EUI values 

are demand side values
Advanced Energy Design Guidance

• K-12 Publication Date: 

January 2018

• Office Guide

– 60% draft for peer 

review September 

2018

– Publication June 2019

• Multi-family underway

Credit: Advanced Energy Design Guide for K-12 School 

Buildings- Achieving Zero Energy (2018)
Pathway

 Set energy goal

 Reduce plug loads

 Reduce lighting loads

o Daylighting: massing, orientation, amount of glazing 

o Daylighting only works if you can reduce the electric 

lighting load

o Low LPD for lighting + lighting controls

 Thermal and water envelope

o Tight and tested 0.10 cfm/ft2 at 75 Pa

o View glass is important! (but it is quadrant 2)

o Frames are the weak point

o Natural ventilation

 HVAC system type-selection and sizing
Key Questions

 What to look for: Where is the cutting edge of the 

technology?

 How do you scale up the technology?

 What are the strategies (bulk purchase, etc.) for 

managing cost?
Façade and Windows

What is achievable that is cost effective?

Photo credit: Karla Butterfield/Steven Winter Associates
Factory Built, Modular Apartment -in-the-Loop 

Integration Research Platform

Shanti Pless, Ron Judkoff NREL Commercial Buildings

Brice Leconte, Developer and www.iUnit.co founder

January 2017

Photo credit: Brice Leconte/iUnit
https://www.nrel.gov/esif/partnerships-iunit.html
“Parts of the industry could move toward a manufacturing-inspired mass-production 

system, in which the bulk of a construction project is built from prefabricated 

standardized components off-site in a factory. Adoption of this approach has been limited 

thus far, although it’s increasing. Examples of firms that are moving in this direction 

suggest that a productivity boost of five to ten times is possible.”

http://www.mckinsey.com/industries/capital-projects-and-infrastructure/our-insights/reinventing-construction-through-a-productivity- revolution

The report calls for a global effort to 

modernize and upgrade the construction 

industry across seven broad areas:

• Reshape regulation and raise 

transparency

• Rewire the contractual framework

• Rethink design and engineering 

processes

• Improve procurement and supplychain management

• Improve on-site execution

• Infuse digital technology, new 

materials, and advanced automation

• Reskill the workforce

“America’s construction industry productivity 

is lower today than it was in 1968.”

http://ternercenter.berkeley.edu/uploads/offsite_construction.pdf

“Off-site construction of 

housing, which leverages the 

efficiencies of factory 

production to achieve 

significant cost savings, 

represents a much needed 

solution to this problem. It has 

the potential to revolutionize 

the way homes and 

apartments are built.”

“Inefficiencies in traditional 

construction have hampered 

productivity and driven costs up for 

decades, resulting in increasingly costly 

development. Today, in many regions in 

the United States, the production of 

housing - especially infill multifamily 

housing – has become so costly to 

produce it demands rents or sale prices 

that are unaffordable for most people.”
Pre Fab is catching on...

“No one would question how we 

build cars today. It would be comical 

to have all the parts delivered to 

your driveway with a dozen workers 

to build it,”

“Yet we build our homes, schools 

and offices in this inefficient and 

wasteful manner every day.”

https://www.forbes.com/sites/bisnow/2017/08/02/the-riseof-the-prefabricated-building/amp/
Energy-Efficient Prefabricated Housing

NREL iUnit

iUnit Denver Delivery Eliot Flats, Denver

iUnit Interior

NREL/48961

Photo credit: Brice Leconte/iUnit Photo credit: Brice Leconte/iUnit

Photo credit: Brice Leconte/iUnit
NREL/16763

NREL/17833
Window Design

A light redirecting 

device reflects 

sunlight to the 

ceiling, creating 

an indirect 

lighting effect.

Fixed sunshades 

limit excess light 

and glare.

NREL/17900 Credit: RNL
Windows

• Evaluate the SHGC and the U-factor (tradeoff between solar

gains and heat transfer

• Consider the tightness of the window system

– Casement

– Double hung

– Sliders (harder to make tight)

• Installation sealing is critical (lots of great windows, poorly

installed)
• Super windows with U-factors less than 0.1

– Film layers, trip/quad glazing systems, low-E coatings

• Low-E rejects certain spectrums (your cat won’t like it)

• Noble gases (do leak out)

• Operable windows

• Screens (reduce solar gains, if that is important)

• Ability to create volume and price reductions

Windows
Key Questions

 What to look for: Where is the cutting edge of the 

technology?

 How do you scale up the technology?

 What are the strategies (bulk purchase, etc.) for 

managing cost?

• Trade-offs with other systems

• Economies of scale

• Industrialization & automation
HVAC and Domestic Hot 

Water (DHW) Systems

Scalable solutions for all-electric retrofits
NREL | 43

Resident Cooling Solutions

NREL/23650

NREL/23651
NREL | 44

Better HVAC Technologies

• Heat pumps

– Ducted or ductless

– Single-zone or multi-zone

• Mini-split/ductless mini-split/multi-split/VRF

– Very high-efficiency up to 42 SEER and 15 HSPF

– Don’t forget the EER (95F)

• Ground-source heat pump (GSHP)

NREL/18327

NREL/18328
NREL | 45

Heat Pump Water Heaters 

(HPWH)

• Extract heat from one place to make hot 

water

• Ideal if you need cooling and 

dehumidification (multifunction), but 

cools in the winter

Photo credit: Paul Torcellini/NREL

NREL/18671
NREL | 46

Small scale multi-function devices

• Heating, cooling, ventilation with heat exchange capabilities

• Small size suitable for an energy efficient dwelling unit

• Example: https://www.minotair.com/minotair-pentacarev12_us/
NREL | 47

Multi-function Heating, Cooling, Water Heating
NREL | 48

Sewer Energy Recovery

http://www.sharcenergy.com/what-we-do
NREL | 49

Energy/Heat Recovery Ventilation

• Ducted

• Ductless

NREL/20185
NREL | 50

Other Ideas

• Sewer heat recovery

• Equipment with demand response capabilities

• Minimizing ductwork

• All ductwork in thermal envelope

• Insulating and sealing ductwork

• Pipe insulation (first 4 feet on inlet/outlet)

• Variable refrigerant flow and mini-splits

• Ground-source heat pumps

• Thermal zoning (spaces that need minimal conditioning)

• Ability to maintain systems (filters, strainers, equipment swaps, etc.)
Key Questions

 What to look for: Where is the cutting edge of the 

technology?

 What is the “magic box” that you really want?

 How do you scale up the technology?

 What are the strategies (bulk purchase, etc.) for 

managing cost?
Appliances and Lighting

Low-hanging fruit?
NREL | 53

Lighting

• LEDs have come a long way and the 

technology is rapidly changing

– Can retrofit into Edison base fixtures

– Dimming has to be done right

• Efficiency gained with directionality

• Color temperature matters

• Bi-level control

• Fluorescent retrofits

Photo credit: Paul Torcellini/NREL

Photo credit: Paul Torcellini/NREL

Photo credit: Paul Torcellini/NREL
NREL | 54

Exterior lighting and common areas

• LED is very directional (which is part of the reason for the 

efficiency)

• Design the lighting for the space

• Put the Lighting Power Density on the plans

– Target less than 0.5 W/ft2 for common areas; 0.2 W/ft2 for 

hallways

• Vacancy-sensor based controls (vs. motion sensor)
NREL | 55

Appliances

EPA most efficient appliance list for 2018

Bulk purchase across RxNY program? 

In particular, there’s no reason not to replace 

dated refrigerators and washing machines.

Also consider:

• Ventless dryers

• Clothes lines

• Smart appliances: Responding to grid signals?

NREL/48439
NREL | 56

Miscellaneous Electric Loads / Plug loads

• Reducing the plug, lighting, and appliance loads will reduce 

the cooling loads

– Computers should be Energy Star and on energy-efficient 

settings

– Home entertainment center (TV and peripherals) should 

have some type of load management (either via advanced 

power strips, or built-in smart TV capabilities, etc.)

• Pay attention to Xboxes, gaming computers, aquariums, 

reptile heaters, etc.

• Metering plug loads—rewarding tenants that meet plug load goals?
NREL | 57

Other ideas

• Capitalize on IoT devices

• Regenerative elevators

• Minimize elevator usage (attractive stairs, slower elevators)

• Low-light security cameras (and then less night lighting)

• Filtered water systems (rather than bottle water systems)

• Minimize vending machines (and required Energy Star units)

• Thermostatically controlled ceiling fans
Key Questions

 What to look for: Where is the cutting edge of the 

technology?

 How do you scale up the technology?

 What are the strategies (bulk purchase, etc.) for 

managing cost?
PV and Metering

Important questions for optimization 
Current Multifamily Metering Barriers...

iStock/174637491

iStock/470985289
Example: Factory-Built Apartment-in-the-Loop

Metering considerations

Individual apartment utility metering

• Residential rate with high fixed meter 

charge

– Blended rate up to $0.16/kWh

• Limits large PV systems on Multifamily 

buildings

– Need to tie small PV system into each 

apartment meter

• Expensive hardware and install

– Up to $1000/apartment

• Split incentive

– Owner doesn’t pay bill

– Tenant doesn’t control building design

Move to Single Building Utility Meter

• Single commercial building rate

– $0.04/kWh, and $20/ peak kW

– Software metered at $60/apartment

– Allows for large PV install

• Software feedback to tenant to overcome 

split incentive

• Develop “effective” real time rate to apply 

to each unit in software

– Provide real time feedback

– Provide $ energy budget of solar provided 

energy

– Pay additional bill if over energy budget, 

bank if under

• Investigating application of behavior change 

of “Bill Avoidance” and monthly solar 

budgets

• Investigate “Tenant in the loop” solutions vs 

hardware control solutions
NREL | 62

Metering

• Establish a metering plan

• Verify the energy goals

• Low-cost metering solutions

• Stand alone servers with multiple channels

• Dashboards for occupants?

What do you plan on accomplishing with metering?
NREL | 63

Photovoltaic Systems

• “Best” orientation is latitude facing south based on the 

maximum power output for a fixed panel—HOWEVER,

• PV is so cheap—

– Mounting Structure is a major cost. Wind loading, etc. 

• Flat roofs: ballasted system with minimal penetrations 

(which causes a thermal bridging issue)

• East/West panels have an advantage on smoothing out the 

daily load (rather than a high noon peak)
Photo credit: Advanced Energy Design Guide for K-12 

School Buildings- Achieving Zero Energy (2018)

Photo credit: Advanced Energy Design Guide for K-12 School Buildings- Achieving Zero Energy (2018)
Credit: Paul Torcellinii/NREL
NREL | 66

Photovoltaic Systems

• Can add to facades, parking areas, etc.

• In reality, the maximum area that “belongs” to the building is the 

site footprint.

– If you cover a façade on a tall building, then that “resource” is 

taken from another building—or think of it as someone else 

shading your PV array

• Size estimation: pvwatts.nrel.gov

– Warning: tends to slightly over-estimate

– Does not account for snow cover

– A PV system should generate at least 1.1 kWh/Wdc installed
NREL | 67

Photovoltaic Systems

• Needs a structural analysis

– Can the weight support the PV system including the wind 

loading (if adding a “sail” to the building)?

– Example:

• Built up roof could not support structurally a PV system

• Replace roof at 90% of useful life with EDPM membrane

• Created enough weight capacity to add PV system and 

added appropriate amount of insulation
Credit: Paul Torcellinii/NREL
PV Interconnections

Credit: Advanced Energy Design Guide for K-12 School Buildings- Achieving Zero Energy (2018)
Key Questions

 What to look for: Where is the cutting edge of the 

technology?

 How do you scale up the technology?

 What are the strategies (bulk purchase, etc.) for 

managing cost?

 What key information/data are crucial to inform future 

retrofit projects?
www.nrel.gov

Thank you

This work was authored in part by the National Renewable Energy Laboratory, operated by Alliance for Sustainable 

Energy, LLC, for the U.S. Department of Energy (DOE) under Contract No. DE-AC36-08GO28308. Funding provided 

by U.S. Department of Energy Office of Energy Efficiency and Renewable Energy Building Technologies Office. The 

views expressed in the article do not necessarily represent the views of the DOE or the U.S. Government. The U.S. 

Government retains and the publisher, by accepting the article for publication, acknowledges that the U.S. 

Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published 

form of this work, or allow others to do so, for U.S. Government purposes.

Our contact information:

paul.torcellini@nrel.gov

303-384-7528

michael.deru@nrel.gov

303-384-7503

shanti.pless@nrel.gov

303-384-6365

lieko.earle@nrel.gov

303-275-4355