Passive House: Bringing Passive Building into the 21st Century

Passive building aims to leverage natural resources such as sunlight, wind, and inherent material properties to achieve efficient and comfortable shelter.

In this post by Gert Guldentops and Autumn Dean we learn that for most of history, passive building strategies have been integral to the design and construction of all buildings.

Anasazi cliff dwellings were strategically oriented to maximize solar gains in the winter and minimize them in the summer, while ancient roman structures relied on mass masonry to maintain comfortable temperatures and on cupolas for natural ventilation.

Many of these passive methods have been pushed to the side as space-conditioning technology transitioned from windows and wood-burning stoves to electric air conditioning and gas furnaces. Architects, engineers, builders, and owners have come to increasingly rely on mechanical systems as they’ve become more accessible and efficient – pushing passive design to the back burner in mainstream construction. 

Passive House, a high-performance building standard, is leading the revival of passive building techniques. Passive House refines and enhances these ancient principles using today’s advanced materials, technology, and energy modeling tools to achieve ambitious energy conservation goals. Inspired by the expertise of our ancestors and modern advancements in construction, the core elements of successful Passive House projects include: 

• Compactness – Limit ratio of envelope surface area to volume of conditioned space. In turn, this limits heat loss via air leakage and thermal transmission, thereby also reducing space conditioning requirements. 
• Windows – Use high-performance windows to minimize energy loss. In cold climates, this often means installing triple-paned systems at modest to low window-to-wall ratios (< 30%). 
• Solar control – Strategically manage sunlight to lower energy requirements to heat and cool the building. In cold climates this is often achieved by design decisions such as finding optimal building orientation, large south-facing windows that capture low-angle winter sunlight with overhangs or shading devices blocking high-angle sunlight, limiting north-facing windows with few winter solar gains. Additionally, windows with different orientation do not require having the same solar heat gain coefficients (SHGC), finding the optimal SHGC for each orientation can further optimize the design.
• Airtightness – Design and install a continuous air barrier to reduce energy losses and moisture transport via air leakage. The air barrier should be designed to be as simple as possible and is typically positioned over the exterior sheathing.
• Thermal bridging – Avoid thermal bridges through strategic and continuous thermal insulation. Thermal bridging can have a large impact on the overall performance of highly-insulated buildings. 
• Insulation – Insulation should be continuous and thoughtfully selected to provide a specific U factor. Although many Passive Houses include significant amounts of insulation, optimizing the performance of the design per the above 5 bullet points can greatly limit the amount of thermal insulation required to meet the Passive House performance targets. 
• Ventilation – Use of heat recovery ventilation in hot and humid climates and energy recovery ventilation in cold climates is a necessity to meet the Passive House energy requirements. 
• Efficient space conditioning – Use efficient space conditioning systems.

Passive building is not a new concept. Passive House standards represent the honing of age-old strategies using today’s science and technology, as outlined above, to achieve unparalleled efficiency, durability, and comfort.

Join our growing tribe of building nerds and sign up for the best newsletter in AEC. Back of the Envelope delivers helpful info of immediate practical importance.