built green™ vs. leed ® : energy impacts of residential green building programs jonathan heller...
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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