Passive House in California:Overkill or Appropriate?
Bronwyn Barry, Assoc.AIA
Certified Passive House ConsultantDirector, One Sky Homes
COPYRIGHT ONE SKY HOMES 2013
Agenda:T-24 Comparisons
Assemblies that workWhat really matters?
Glazing over the details
Nominal vs Actual
24’-0” wall = 288” (100%)2x6 @ 16” o.c. (18) = 27” ( 10%)Batt Insulation = 261” ( 90%)
Nominal Actual
R-Value/inch Whole Wall 85/15% 75/25%Studs 1.3 7.0 1.1 1.8Batts 3.5 19.3 16.4 14.4Total Wall 17.4 16.2
The Sunnyvale Retrofit
Windows Walls Roof Floor Total0
10
20
30
40
50
60
70
80
90
100
Typical T-24 Project R-value (hr.ft2F/BTU.in)
PH Project R-value (hr.ft2F/BTU.in)
Windows: AlpenWalls: 2x4, cellulose w/ 2” PolyisoRoof: 6” PolyisoFloor: 4” Polyiso
Sunnyvale Retrofit Assembly Details
FOUNDATION & BARGE RAFTER
ROOF: R-40
WALLS: R- 23
WINDOWS: R-5
FLOOR: R-40
COPYRIGHT ONE SKY HOMES 2013
The SIPS New Build
Windows Walls Roof Floor Total0
10
20
30
40
50
60
70
80
Typical T-24 Project R-value (hr.ft2°F/BTU.in)
PH Project R-value (hr.ft2°F/BTU.in)
Windows: EnerSignWalls: 8” SIPSRoof: 10” SIPSFloor: Slab with 2”EPS
Stick Frame Net Zero
Windows Walls Roof Floor Total0
10
20
30
40
50
60
70
80
90
100
Typical T-24 Project R-value (hr.ft2F/BTU.in)
PH Project R-value (hr.ft2F/BTU.in)
Windows: Alpen + SorpetalerWalls: 2x6, cellulose w/ 1” EPSRoof: 13” Truss, CelluloseFloor: Slab, 4” EPS
Cottle ZEH - Assembly Details
Foundation - R-23 ICF Stem Wall R-15 Slab Floor
Walls – R23
Ceiling - R-50 Loose-fill Cellulose
1. Super-Insulate2. Avoid Thermal Bridges3. Air Seal ( tight! )4. Windows/Doors – high-performance5. Heat Recovery Ventilation (HRV) in most
Climates6. Solar aware design7. Use PHPP
Passive House Recipe" Buildings heated with hair dryers"
Envelope Results kBTU/ft2.yr heating energy
Preliminary Aug 3, 2009 Max. allowed = 4.75 kBTU/ft2.yr
SIP wall system** Prefab Stud wall Site built
5.5" 7.25" 5.5"5.5" w/ rigid
insul. 7.25"7.25" w/
rigid insul.9.5" TJI studs
Window Est. Cost ($K) 49 52 47 53 49 55 79
Sierra Pacific* 4.52 4.01 5.11 4.58 4.54 4.19 3.91
37 86 89 84 90 86 92 116
**assuming $4k for interior furring
using Recoup 200DX HRV w/ 3' OA duct runs
4" EPS under slab
11-7/8" TJI roof
4" EPS slab edge
Challenging walls
Source: Performance analysis from Dan Johnson, Arkin Tilt Architects and cost estimates from Quantum Builders
A dozen ways to build a wall
Floor to floor assembly with open web hanging floor truss
Complicated junctionsHundreds of ways to mess them up!
Which details really matter?
Air-sealing?Insulation?
Ventilation?Thermal Bridges?
orWindows?
SILL & JAMB (CASEMENT)
The Sunnyvale Losses
Exterior Walls21%
Roof17%
Floors21%
Windows30%
Exterior Door2%
Ventilation9%
Total Heat Losses = 15,170 kBTU/yr
Windows: AlpenWalls: 2x4, cellulose w/ 2” PolyisoRoof: 6” PolyisoFloor: 4” Polyiso
The Sunnyvale Gains
Windows: AlpenWalls: 2x4, cellulose w/ 2” PolyisoRoof: 6” PolyisoFloor: 4” Polyiso
Windows (So-lar gains)
50%
Internal Heat Gains50%
Total Heat Gains = 7,748 kBTU/yr
Losses66%
Gains34%
Annual Heat Demand = 7,556 kBTU/yr
= 4.85 kBTU/sf.yr
The Cottle Losses
Exterior Walls31%
Roof9%
Floors12%
Fndn Stem wall1%
Attached Garage7%
Windows26%
Ventilation13%
Total Heat Losses = 28,986 kBTU/yr
Windows: Alpen + SorpetalerWalls: 2x6, cellulose w/ 1” EPSRoof: 13” Truss, CelluloseFloor: Slab, 4” EPS
The Cottle Gains
Windows: Alpen + SorpetalerWalls: 2x6, cellulose w/ 1” EPSRoof: 13” Truss, CelluloseFloor: Slab, 4” EPS
Total Heat Gains = 19,853 kBTU/yr
Windows (Solar gains)
Internal Heat Gains
Losses59%
Gains41%
Annual Heat Demand = 9,133 kBTU/yr
= 3.67 kBTU/sf.yr
Image: Lorna Fear IR images
The Camera Never Lies!
Upcoming
Wednesday, March 20th
Pacific Energy CenterSan Francisco
www.co2zeroca.org
More from Mark….
Questions?
Thank YouBronwyn Barry
Resources:
www.passivehousecal.orgwww.aphnetwork.orgwww.passivehouse.com
