Three Interlinked Systems Power Peak Performance

Effectively designing and assembling air, vapor, and thermal control layer systems is a key factor in creating a high-performing building.

Imagine living inside of a balloon. Actually, living inside of an airtight space. Cooking, bathing, petting your dog or cat, heating… breathing. No way for all that funky air to move out. Just sitting in your living room, in a balloon filled with… that. I am guessing you would like to poke a hole in that balloon to get some of that air out and replace it with some clean, fresh air. But wait, don’t let all the heat out or allow the balloon to deflate. We better build a frame to wrap around the balloon too, so it doesn’t blow away; we call that frame the building envelope.

The balloon (air and vapor control)

One of the principle systems of a high-performance building is having an airtight building envelope. We are effectively attempting to wrap the building in a balloon skin. Every single hole we poke in the balloon (yes, every single one, even the nail holes) are sealed so that air flow and vapor drive are controlled. Windows and door must be airtight and seamlessly integrated into the building wrap or weather resistant barrier (think Gore-Tex). The balloon is also acting as a base layer of subsequent systems. Once complete, no matter the size of building, we aim for a collection of holes in the entire building envelope that is no larger than a business card. This space could be a large collection of pin holes or just a few small holes in the balloon that were not sealed in the building process.

The only way to properly achieve air tightness is by having clear direction from our designers and architects about how this system is assembled. What products are we using? How does one product or material connect to another? For example, the air control layer under the concrete slab is a different material than what is applied to the walls. It is like connecting Gore-Tex to DryVent. How do we connect the two? How does the air control layer transition from roof to wall? Without careful collaboration between the architect and builder and then between the builder and the tradespeople performing the work, and precise drawings detailing all these assemblies, achieving the air tightness standard for high performance buildings would be impossible. No airtight Gore-Tex balloon for you.

The fan: continuous ventilation

An airtight building envelope demands that a second principle system be introduced: continuous ventilation. This requires more than your run-of-the-mill bath fan; I am talking a super-whammy, run-all-day, every day, wicked-energy-efficient fan that endlessly ventilates the air in the building. The HRV (heat recovery ventilator) system that we use in high performance homes does triple duty. It constantly pushes warm vapor-laden air out, and pulls fresh, clean filtered air in. While ventilating, it extracts the heat from the exhaust air and uses this heat to warm up the incoming fresh air… all the time — leaving you with some of the best indoor air quality you could imagine. Remember, you are living in a balloon. All that dank air from living is constantly being exhausted and replaced with fresh air.

The sweater (thermal control)

Ok, so now you are living in your balloon, the air is moving great, and it is January and there is a northeaster blowing. You have your base layer on, but now you need a sweater… for your balloon. This is another principle system of a high-performance home. That balloon needs to be super insulated with a nice sweater. But not a puffy coat. Puffy coats have seams. Those seams act as pathways (thermal bridges) for heat to escape. Even if you have a super thick puffy, it does not much matter if you have those pathways for heat to escape. Homes that are being built to simply meet the code standards are built with thermal bridging. Every single 2x6 wall stud acts as a thermal pathway unless you put something over the path. Constructing the building envelope in a way to prevent thermal bridges is crucial to meet the standards of a high-performance home. Wrapping the building in a continuous layer of insulation is one method of removing thermal bridges. The thermal control layer that wraps the balloon must be very well planned, and collaboration between builder and designer is critical for proper execution.

Focusing attention on these three systems in the design and build process significantly reduces the amount of energy consumed by the systems themselves while creating comfort for the people living in the building.