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The Larkspur Remodel: A Phased Approach to the Passive House Standard
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The Larkspur Remodel: A Phased Approach to the Passive House Standard

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An example of a recent (2009) renovation designed to meet the Passive House energy standard, using a phased approach. (And yes, the air-tightness standard is possible on a retrofit!)

An example of a recent (2009) renovation designed to meet the Passive House energy standard, using a phased approach. (And yes, the air-tightness standard is possible on a retrofit!)

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  • Roxul Top Rock MD rigid mineral wool was used on the exterior walls. We also wrapped the insulation at the jambs and headers of the windows to improve the window performance.
  • We elected to cover the existing T&G roof sheathing with an additional skin of OSB as this was easier to air-seal. 30lb Roofing felt was then placed over the OSB and API Kingspan metal SIPS insulation and roofing panels were used as both insulation and roofing finish surface.
  • Perimeter insulation product: Energy Edge. (Plastic cover over 2” Expanded Polystyerene.) The taped seam on the corner is part of the Sto Gold mastic we used for our wall sheathing air-tightness layer, under the Mineral Wool exterior insulation.
  • Three weeks of continuous air-testing and envelope tightening yielded results! We waiting to finish our air-sealing before we installed the exterior insulation and siding.
  • Note: The projected energy consumption is based on final Passive House Certification compliance. Since we did not install the basement above-floor insulation, the actual number is expected to be higher than the projected numbers shown. The projected number does not take the solar PV credits into account either, so it could potentially be lower.
  • Client has a pool and a hot-tub!!
  • Biggest surprise for us here was the Thermal Bridge losses at both the roof to wall junction and the foundation to wall junction: 30% overall! These are two details that can be completely designed OUT of new construction. Seems like a no-brainer to do so…
  • Cost numbers were around $110/sf for this remodel. We still haven’t parsed out what percentage of that was to get it to meet the PH standard. We’re estimating that a new roof, new windows and new siding would have cost this client around $90/sf. We have buried 4 data loggers inside this project and will be retrieving them after a year. We placed one inside the house, one outside directly near the interior sensor, and two are buried within the walls on the interior and exterior sides of the old exterior siding.

The Larkspur Remodel: A Phased Approach to the Passive House Standard The Larkspur Remodel: A Phased Approach to the Passive House Standard Presentation Transcript

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  • Who we are: A DESIGN BUILD COMPANY + PRODUCT DISTRIBUTOR, PERFORMANCE TESTER and ENERGY ANALYST
  • What do we do? We DESIGN + BUILD Q+ homes that can PRODUCE MORE ENERGY than they consume. We have committed to build all our NEW PROJECTS so that their building ENVELOPE meets the PASSIVE HOUSE STANDARD
  • Larkspur Remodel
  • Overview:
    • The existing house: what it needed
    • Our approach to the remodel
    • Building materials & details
    • Testing & Energy comparisons
    • Some preliminary conclusions!
  • Our Process:
    • Review the existing structure: what had to be replaced, what could be saved?
    • Analyze the process for energy efficiency, least waste and disruptive install process, lowest toxicity.
    • Review the cost/benefit: what should be done now, what could be saved for later?
  • The existing home:
    • Cabin style
    • Simple shape
    • Needed new roof
    • Needed new windows
  • Positives:
    • Existing sealed crawlspace
    • Existing ventilation system with HRV
    • Existing Solar HW and PV
    • Simple shape
  • Negatives:
    • No roof insulation
    • Minimal wall insulation
    • Un-insulated foundation
    • Aluminum frame single-pane windows
  • Client’s goals:
    • Improve indoor comfort
    • See what it would take to meet PH standard
    • Build for her children’s future
  • The Passive House approach:
    • Super-insulated building envelope with no thermal bridges
    • Airtight to 0.6 ACH @ 50pa
    • Mechanical Ventilation with > 80% Energy Recovery
    • 4.75 kBTU/sf 2 yr max energy demand, 38 kBTU/sf 2 y Primary Energy Demand
  • The Wall & Window system:
    • BEFORE:
    • Redwood faced plywood siding
    • 2x4 stud walls
    • Fiberglass batt insulation (poorly installed)
    • Wood panel interior on furring strips
    (hr.ft 2 .F/BTU) 11.1 R-Value:
  • The Wall & Window system:
    • AFTER:
    • Rainscreen siding w/ Hardi siding
    • Building paper
    • 3” Mineral wool insulation
    • Airtight barrier: (Redwood faced plywood siding
    • Existing wall remains
    (hr.ft 2 .F/BTU) 22.3 R-Value:
  • Window details: (hr.ft 2 .F/BTU) 8 R-Value: (hr.ft 2 .F/BTU) 1 R-Value:
  • Exterior Insulation:
  • Roof system:
    • BEFORE:
    • Asphalt shingle roofing
    • T & G sheathing exposed to the interior
    • 6x8 rafters @ 4’-0” oc.
    • No insulation
    (hr.ft 2 .F/BTU) 2.2 R-Value:
  • Roof system:
    • AFTER:
    • 6” metal-clad foam prefab panel roofing
    • Same roof system with wall insulation wrapping up to the roof insulation.
    (hr.ft 2 .F/BTU) 50.2 R-Value:
  • Roof installation:
  • Foundation & Perimeter:
    • BEFORE:
    • 4” Concrete slab
    • Conventional spread footing
    • No insulation
    (hr.ft 2 .F/BTU) 1.4 R-Value:
  • Foundation & Perimeter:
    • AFTER:
    • 3” interior foam/mineral wool insulation ‘installed’ above the interior slab
    • 2” foam insulation at the perimeter
    Note: We didn’t install the above-slab insulation at this time. Cost and complexity were the limiting factors. However, we do see this as possible for a future renovation and know that the rest of the structure will allow final PH Certification at that time. (hr.ft 2 .F/BTU) 10.2 R-Value:
  • Foundation details:
  • Foundation details:
  • AIRTIGHTNESS!
  • Testing, testing… Source: Sustainable Spaces GreenUP report for client, 2007, & PHPP 0.54 8.20 PHPP (ach/hr n50) 22 196 Equiv. Hole (sq inches) 227 3469 CFM50 After Before   AIR LEAKAGE
  • Previous energy cost: Source: Sustainable Spaces GreenUP report for client, 2007 EXISTING (kWh/sf,yr) Elec: 4.46 Gas: 8.08 Total: 12.54
  • Where the losses were: Source: Sustainable Spaces GreenUP report for client, 2007
  • Projected energy use: Source: Sustainable Spaces GreenUP report for client, 2007 Note: The projected energy use assumes final PH compliance. It has been modified for variance between PHPP TFA and typical overall sf energy use calculations. Benefit of the Solar PV system is not included. However, since we did not install the slab insulation, it will likely be higher.
  • Compared to others: Source: PG&E & Sustainable Spaces GreenUP report for client, 2007, & PHPP
  • Projected leaks: Source: PHPP file for this project
  • Bug screens…
  • Exterior shade screen…
  •  
  • Early conclusions:
    • The PH air-tightness can be achieved on retrofits with careful planning and testing
    • The economic case is challenging for this particular project (but makes solid sense for new construction.) Cost: $85/sf.
    • The improvement in occupant comfort is already being enjoyed by our client
    • Energy analysis… Watch this space!
  • Thank you from the Team: Architect: Josh Moore Project Manager : Carlos Velasquez Crew: Attu Fave Paea Favaleaki Peter Soruco Testing: Stefan Carpentier Energy Analysis: Mary Graham Bronwyn Barry