Built Green™ vs. LEED®: Energy Impacts of Residential Green Building Programs

Jonathan Heller P.E.March 6, 2009

Program Analysis

WSEC 2006

Prototype Development: Single Family

1850 SF 2800 SF 1400 SF

Mandatory Energy Measures:Single Family

Silver:

Gold:

+ Low Flow Faucets

+ Low Flow Faucets, Prescriptive Envelope, & Lighting Measures

4-Star:

5-Star:

Space Heat52%

Water Heat22%

Lighting8%

Appliances + Plugs18%

Typical Single Family Energy End Use Breakdown (KWH/Yr)

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

40,000

45,000

1400SF 1850SF 2850SF

KW

H/Y

ear Appliances + Plugs

Lighting

Water Heat

Space Heat

Size Matters:Prototype Annual Energy Use

Single Family % Savings over WSEC (Gas Heat)

Source Energy CO2 Emissions: 1850SF Single Family

0

2000

4000

6000

8000

10000

12000

14000

WS E CB as eC as e

4-S tarB uilt

G reen

5-S tarB uilt

G reen

L E E DS ilver

L E E DG old

WS E CB as eC as e

4-S tarB uilt

G reen

5-S tarB uilt

G reen

L E E DS ilver

L E E DG old

G as Heat and Water E lec tric Heat and Water

CO

2 lb

s / y

ear A pplianc es

+ Plugs

L ighting

Water Heat

S pac e Cool

S pac eHeat

Single Family Results

EnergyStar guarantees ~12% savings over WSEC (more savings likely for higher levels of certification)

Size matters Glazing area matters Programs address all loads except MELs Mostly prescriptive

Prototype Development: Multifamily

60 Units 190 Units

Mandatory Energy Measures:Multifamily

+ 15% Modeled Savings

+ 30% Modeled Savings

4-Star:

5-Star:WSEC 2006

Silver:

Gold: 90.1 2004

+ 14% Modeled COST Savings

+ 14% Modeled COST Savings

Multifamily Energy Savings

LEED Multifamily Modeling: ASHRAE 90.1-2004 Appx. G LEED requires 14% savings in Energy COST

Baseline was developed for office buildings

Well below residential WSEC (e.g.. window U-Value=0.62)

Must model cooling even if none installed

Must use typical commercial HVAC systems

“Regulated Loads” only (HVAC, hot water)

Built Green Multifamily Modeling

“Building modeled to have 15% better performance than energy code”

Any program? Hand Calculations?

No base case definition (electric resistance vs. heat pump)

No definition of how to determine base loads

Modeled Site Energy Use:Mid-Rise 890SF Apartment

High-Rise Electric Heat:Built Green Energy Savings

Measure Savings Notes

--- 0.00% WSEC 2006

1KW Solar PV (1150 kwh/190 units) 0.00% Prerequisite

Low Flow Plumbing (77% water use) 5.40%

Lighting (1.75>0.6W/sf) 11.00%

Energy Star Appliances (1800>1500kwh/yr/unit) 11.80%

High Eff Airside Centrifugal Chiller (COP 3.1) 12.70%

Wastewater Heat Exchanger (HX) 15.10% 4-Star

Corridor HX (65% recovery efficiency) 22.20%

Glass 0.40/0.36 > 0.36/0.32 (U/SHGC) 24.20%

Triple Glass (0.25/.28) 28.60%

Quad Glass (0.16/0.25) 32.20% 5-Star

High-Rise Gas Heat:LEED Cost Savings

Measure Savings Notes

--- 0.00% ASHRAE 90.1 2004

Envelope Improvements to WSEC 8.80% WSEC 2006

Low Flow plumbing (77% water use) 13.60%

Chiller COP from 2.8>3.1 14.70% 2 Points – Silver/Gold

Multifamily Results

Modeling based rather than prescriptive – more questionable results

No reliable savings with LEED Size matters Glazing area matters LEED does not address lighting or appliances Large variation in building type, size,

configuration, systems.

Comparison to Multifamily billing data

Recent study from Vancouver BC indicates higher energy use than predicted.

69% of heating energy associated with corridor pressurization.

43% of electricity use outside of apartments. Brings into question the common assumption

that Multifamily is significantly more energy efficient than Single Family.

Where do we go from here?

Code council currently working toward WSEC 2010 that would improve efficiency 30%.

Need to develop Prescriptive options for Multifamily. Need to address unregulated loads (Lighting, MELs,

glazing area, size, corridor ventilation). Need more research on common area energy

consumption in Multifamily. Need more research on MELs.

Questions/Comments: Jonathan Heller (206)322-3753

JHeller@ecotope.com