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