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Passive House Principles
For a building to be considered for Passive House certification, these five principles must be met.
Thermal Insulation
A variety of insulation types were used to achieve international Passive House EnerPHit Plus certification. Graphite-enhanced expanded polystyrene foam board insulation (GPS) was installed on the basement ceiling (lower envelope), below interior concrete, and on the building front and rear exterior. A total of 8 inches of GPS was used on the exterior applications. Johns Manville Climate Pro fiberglass blowing wool insulation was used to fill floor and ceiling joist cavities. Rockwool Comfort Board 80 was used to insulate interior wall surfaces. A total of 8 inches of polyisocyanurate board insulation was used on the roof.
Passive House Windows
The high performance windows are Passive House certified and manufactured in Pennsylvania. The Ventana Select Series 86 Thermal Performance made in Export, PA are all triple-glazed with various low-e coatings tuned to the orientation. Each window is held into place on the outside of the building by structural foam that acts as a thermal break minimizing any loss of heating or cooling. The rear façades are clad with ribbed steel siding attached with a thermally broken clip system.
Adequate Ventilation Strategy
The mechanical system consists of a single Ventacity RS3000 Energy Recovery Ventilator (ERV) serving the entire building. ERVs are equipped with two fans, one that draws fresh air into the building and one that pulls stale air out. When these two airstreams pass through the ERV, a heat exchanger within the system transfers heat and moisture from one airstream to the other. ERVs provide improved indoor air quality, better HVAC efficiency and improved moisture and odor control.
Airtightness
A major focus of the design and construction was airtightness with mechanical ventilation. The airtightness of the building was measured throughout the interior building rebuild. Air sealing involved the masonry infill of mortar joints and joist pocket cavities. Infrared cameras where used in conjunction with blower door testing to identify air leakage. After the masonry infill of mortar joints, a Visconn liquid-applied air barrier was applied to the interior masonry surfaces. Prosoco R-Guard was used on the exterior masonry walls to prevent air and water leakage. Adhero Visto tape was used to seal envelope surfaces and seams, and whenever dissimilar material surfaces were encountered (repaired joist pockets).
Thermal Bridge Reduced Design
Thermal bridges are weak points in the building envelope where outdoor temperatures can move in, or indoor temperatures move out in an uncontrolled manner. Thermal breaks can reduce the thermal bridge by up to 75%. The façade clip system in the building front (stone) and rear (metal cladding) incorporated thermal breaks and were coupled with staggered graphite-enhanced expanded polystyrene (GPS) rigid foam insulation whose seams were taped and caulked. Windows were thermally broken in their design (frames) and installation.