PASSIVE HOUSE | BEYOND EFFICIENCY

By: Paul Thompson AIA, CPHC

Passive house sets the standard for efficiency by taking a conservation approach to reduce energy use in homes and other buildings. The ‘passive’ part is the super-insulated and airtight thermal envelope. More importantly - health, durability, and resilience inherent in passive houses add value well beyond the 70-80% energy reduction compared to standard construction.

Like passive solar buildings, passive houses use free sun energy for heat during the winter, but they do not rely on the sun as a primary heat source.  Unlike passive solar design, the indoor climate in a passive house is consistent due to the superior building envelope. Comfort is a passive house requirement, along with the following: 

▪    Airtight construction (no drafts or uncontrolled air infiltration)

▪    Continuous insulation (thermal bridge-free construction)

▪    Superior windows and doors (triple-pane glass in our area)

▪    Balanced ventilation with energy recovery (fresh MERV-filtered air with an ERV or HRV)

▪    High-efficiency, right-sized mechanical systems.

Building performance is predicted with an energy model calibrated to low-energy use buildings. The energy model uses local climate data to optimize the building design by analyzing assemblies and glazing, equipment, heating and cooling loads, shading and siting, overall energy use, and renewable energy. In our climate (Zone 4A), humidification control is becoming increasingly important. The quality of construction is proved with a blower door test, which measures the air tightness of the building envelope, and certification adds quality control and verification.

Isn’t passive house design and construction radical, expensive, and unachievable? No – I’m writing this article while sitting in a historic passive rowhouse in Philly. Consider that the building codes have requirements for all these issues – climate-based design (IRC R301.2), energy conservation (IRC N1102), continuous insulation and airtight construction (IRC N1102.4), and mechanical ventilation (IRC R303.4), in addition to durability requirements for water and vapor resistant construction.

Well-designed buildings are less expensive to heat and cool and have reduced maintenance costs. Durable buildings reduce mold growth and other hazards to people and pets. Passive House is the bedrock of a zero-carbon future – and is achievable today. 

By the way, Passive Houses can be any building type – homes, row homes, apartments, fire stations, high rises, offices, churches, new construction, retrofit, modern, and historic. 

Resources: Phius, Passive House Network, Passive House Accelerator, Green Building United Passive House Community, Passive Rowhouse Manual