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:

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

Size Matters: Prototype Annual Energy Use

Single Family % Savings over WSEC (Gas Heat)

Source Energy CO2 Emissions: 1850SF Single Family

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: % Modeled COST Savings

Multifamily Energy Savings

LEED Multifamily Modeling: ASHRAE 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 MeasureSavingsNotes % WSEC KW 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 MeasureSavings Notes %ASHRAE Envelope Improvements to WSEC8.80%WSEC 2006 Low Flow plumbing (77% water use)13.60% Chiller COP from 2.8> %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)