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high performance

09   /   06   /   2022

Have you ever wondered what exactly it means for a structure to be labeled as "high performance?" Well, we have some insights into what this measure of efficiency entails and how it is achieved.

To put it very simply, the idea of high performance is that you have a structure that is so efficient that it uses very little energy to operate. There are a variety of standards that measure efficiency such as LEED, Energy Star, and the Cadilac of them all is Passive House. BONSAI is a certified Passive House designer and builder through the Passive House Institute of Germany (PHI). PHI is "an independent research institute that has played an especially crucial role in the development of the Passive House concept - the only internationally recognised, performance-based energy standard in construction," (Passivhaus Institut)

Passive House is based around 5 building principles: 1. Airtight Building Envelope, 2. High Insulation, 3. Reducing or Eliminating Thermal Bridging, 4. High Performance Fenestrations, and 5. Whole Building Air Circulation. In some instances, depending on the climate, insulation can be lowered while still maintaining a high level of energy efficiency. However, creating a thermally unbridged home with minimal leakage is top priority for us. It is extremely difficult to attain zero thermal bridge, and Passive House standard requires fully unbridged.

If you were to take a look inside the walls of a structure, you would see that every building has two barriers; a vapor barrier on the warm side of the wall (in this climate), and a weather barrier on the outside. When installed and sealed correctly, they serve as an air barrier. Building Code allows for a maximum of 3 Air Changes per Hour (ACH), while Passive House requires less than 0.6 ACH. Ultimately, every building is going to leak some amount, so we aim to hit 1 ACH for our builds and measure this with a blower door test.

Another key passive house principle that cannot be overlooked is high performance fenestrations, aka windows and doors. Quality windows and doors are a critical path to high performance building because they are the weakest point of a wall. Code requires a resistance value of R20 (for walls), and a typical code window would be around an R4/R5. A high-performance window has the potential to yield an R10. That is a huge bang for your buck if you can make the investment and is the largest contributor toward a high-performance building envelope.

The other principle we place huge importance on for our building practices is whole building air circulation, which we attain through the use of an Energy Recovery Ventilator (ERV). The vast majority of living organisms use lungs to breathe, so why shouldn't buildings do so as well? Buildings aren't salamanders, they shouldn't breathe through their skin. An ERV is a buildings' lungs, constantly providing fresh air from outside and exhausting the stale air. It crosses the energy paths and reduces the amount of energy loss by up to 70%. All of these measures combined make it so a building requires very little energy input and puts less of a demand on the grid and natural resources. 

All of these principles can be applied to both new builds and restorations/remodels. In our opinion, there's really nothing more sustainable than working with an existing structure. Sustainability can even be taken a step further by looking at ways to produce energy on site, but, that's a topic for another day! We truly believe in the benefit of using high-performance and Passive House standards to design and build homes and hope you do as well. Reach out to us if you'd like to learn more about high-performance or Passive House.

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