Since I am very interested in efficient home building techniques, as addressed in episode 8 of the Talkbots podcast and numerous blog posts in my White Noise blog, I took notice of a new house going up in my neighbourhood that appeared to be built using other than typical wood framing construction. I noted the owner/builder's contact info and checked to see if I could get a glimpse into how they were building their new house. Much to my delight, they said yes, and I met with Gerry onsite, on a snowy, windy Sunday morning in March 2022.
The house was still under construction with kitchen cabinetry, countertops and fixtures still in the process of being installed. Even though there was no furnace running and only a very small space heater operating on the main floor, the interior temperature was a pleasant 13C and would likely rise more with each passing minute. The house felt so warm and cozy that I had to take my coat off. I proceeded to ask Gerry all about the decision process and the materials and techniques used in building the house.
Although he sent for the Passivhaus design documents, he didn't quite build the house to Passivhaus standards, but they did build with a very efficient 8 inch thick exterior wall made using SIP (structural insulated panels). SIP panels are a sandwich of outer layers of magnesium oxide board with a core of thick polystyrene foam, like Styrofoam, but in this case the foam is infused with graphite to increase insulating qualities. The windows were German made wood framed triple pane windows that are built for Passivhaus construction, and the patio doors were a massive lift & slide design, which makes for a much more durable and efficient air seal when closed.
He chose to use thermal solar panels on the roof to preheat city water, making it much easier for the electric tankless water heater to get the water to the temperature needed for showers and baths, and was also using this hot water to heat the basement and main floors with hydronic radiant heating. There were also separate electric solar panels on the roof to supplement his electricity needs including an agreement with the utility company to sell excess power back to the grid. No furnace required. Because the house is so airtight, it is equipped with an efficient ERV unit (energy recovery ventilator), which exchanges stale indoor air with fresh air from outside on a constant basis. The ERV has an 85% efficiency rating, which means that 85% of the heat in the exhausted air is being recovered to pre-heat the incoming fresh air. The system also includes an air pre-heater, to assist with warming the incoming air on colder days. The constant air movement from the ERV helps distribute the heat all around the house and even takes heat that is collecting at the top of the regular and high vaulted ceilings to redistribute into the house-wide system.
The thermal solar panels are potentially capable of generating so much heat, especially in the summer, that he is considering the possibility of building an underground seasonal heat storage system, which would capture excess heat all summer long and then slowly release it back into the system in winter.
Building a house like this definitely comes with challenges, as there are a limited number of developers and builders who can do it, many of whom are only focused on their particular methods and materials. You can't ask a typical developer to install a different brand or style of window or flooring material from what they normally use, or tell the builder that you want Passivhaus grade doors made in Germany, and specific custom windows and walls. It's almost impossible to direct a builder to make the exact kind of efficient house you may have in your mind or plan. So Gerry had to apply to be registered as an owner/builder, which the government has to approve on a case by case basis. Needless to say, you can only do this if the house is for you, not something you'll sell once it's finished.
Gerry said that a huge challenge was dealing with HVAC companies. They use a standard rule-of-thumb formula to determine the size of the furnace you’ll need. Based on the energy calculations Gerry came up with considering the increased insulation and the tight envelope, his resulting equipment size and capacity did not even come close to what the HVAC companies were recommending. When Gerry disputed their conclusions, they said they can’t just give him whatever size he wants, he has to pay for a professional analysis. Gerry feels that HVAC companies want to sell you the biggest and best unit they can. In the end, because he chose an in-floor heating solution, the house didn’t need a furnace after all.
Gerry’s entire house SIP envelope was built in a factory, then delivered and installed quickly onsite. Ideal factory work conditions, a stable workforce, computer guided laser cutting of pieces, all improve the tightness of the envelope due to increased accuracy and as perfect a fit as you can get. This saves a ton of time for any worker that has to interface with the walls, such as drywallers, cabinet makers, etc. Because unlike your average home, in this case, the factory built walls create perfect square corners and all lines are perfectly straight. Plus you save money on site because the people putting the envelope together don’t have to be there as long.
Based on my conversation with Gerry, there are a lot of choices in both construction techniques and materials that even the average Canadian efficient home builder might not be familiar with. So he had to do a lot of research. He made decisions based on value add and reliability, he didn't choose things on a whim and was not reckless with the spending. But he made selections that many wouldn't even know were a thing or they had obsolete information based on data that might have been valid decades ago, but not now. For example, the German made windows he chose are Sitka spruce wood frames, which most folks would think is a horrible idea for a place like Canada. But these particular wood frames were designed for cold climates, with special exterior coatings that make them very hardy and good insulators too. Very few builders would think to offer these modern wood frame windows as a choice to their customers, even though they exist and are far superior to their predecessors.
This house is environmentally friendly, as it doesn’t burn any natural gas as it doesn’t have a furnace or fireplace. Even the hot water is heated by solar or grid power. There are no exhaust fans, as the ERV unit does a great job of exchanging all indoor air with pre-conditioned (and filtered) fresh air many times per day. Because it doesn’t use OSB, there is no off-gassing from the glues. The materials used make for a clean, comfortable, efficient, and sustainable home.
The audio file of our talk can be found here.
No comments:
Post a Comment