What is Passive House?

Passive House is the world’s most rigorous home energy performance standard.  What does this mean? Compared to conventional homes built today, Passive House-certified homes use 80-90% less energy, with only modest cost premium.

The standard is fixated around three main performance goals:

• Less than < 4.75 kBTU/ft²/year towards heating and cooling (each)
• Air infiltration of less than or equal to 0.6 Air Changes/Hour at a pressure of 50 pascals
• Total source energy use < 38kbtu/ft²/year

Because these are performance goals, there exist any number of combinations of wall sections, design features, window packages, and active systems that could achieve these goals.

Passive House criteria are not only based in energy performance.  They also account for occupant comfort and health; for example, interior temperatures should not vary by more than 4-5 degrees between perimeter areas (i.e. next to a window) and more central spaces. Minimizing the temperature differences greatly reduces convective movement, which eliminates drafts. Furthermore, healthy indoor air quality is maintained by providing at least 18 cubic feet per minute (cfm) per person of continuous fresh air ventilation, which exhausting the kitchens and bathrooms at a prescriptive rate (35 and 25 cfm continuously, respectively). In total, all of the air in the house will be completely replaced every 3 hours.

Homes are certified by the Passive House Institute via Certified Passive House Consultants, who must pass rigorous training and certification exams and subsequently work with project teams during the design process and verify compliance upon construction completion.

We are proud to pursue the Passive House criteria on the Little Compton project and hope the project inspires others like it.

How does a Passive House achieve such high levels of performance?

Passive Houses achieve their rigorous performance level through careful engineering and design.  Because the standard is so stringent, one cannot simply “use their gut” to assemble the parts; rather, a trained designer must run multiple iterations of a complex energy model to assess the home’s performance.  In this sense, Passive Houses require a great deal more of upfront planning and design prior to construction.

In a northern climate such as Little Compton, the hardest criteria to achieve is the heating energy per square foot requirement.  The Passive House Planning Package (PHPP) is the model that is used to predict performance of the home.  No amount of heat loss is unimportant in the Passive House paradigm—every thermal bridge, window, window location, shading device, etc is calculated.