The construction of a Net Zero home is a lot more comprehensive than a typical house.
Everything must be meticulously measured and executed with perfect accuracy, or else the house will use energy that might not be able to be made back in energy collection strategies like PV solar panels. In a perfect world, if a house uses tons of energy, one could simply pop a few more solar panels on the surrounding property, and voila — the house is still Net Zero. But in the real world, solar panels, though amazing, are pricey and cumbersome. And the less energy used, the fewer solar panels needed, and the easier it is to maintain a relaxed and affordable Net Zero life.
Designing and building a home’s structure is where the meticulous, Net-Zero-conscious planning begins. Even before taking into account energy used by residents (like the number of appliances and electronics used), the building’s structure needs to be able to minimize constant background energy like heating and cooling loads. And for a passive, net zero house, it is usually the home’s insulation and leak-free air barrier that are responsible for keeping the house efficient and comfortable. In a nutshell, this is why Kawartha Highlands was designed to be extremely well-insulated and air-tight.
Kawartha Highlands’ structure begins as conventional.
After digging a 4 feet deep trench, we poured our concrete footings and erected poured concrete foundation walls 6 inches thick. Then on our foundation walls, we put up our 2×6 stud walls, with oriented strand board (OSB) sheathing. These stud walls are load-bearing, and support the home’s engineered truss roof, which is topped with plywood sheathing.
After these conventional building elements is where things get interesting. Instead of the usual drywall, we clad the ceiling with OSB, in order to support the mountain of insulation we planned on blowing into the attic. Had we only used drywall, the ceiling would surely have collapsed under the weight!
After our 2×6 stud wall structure, we build a second wall, of 2×4 wood studs, offset to the interior of the first wall by 7.5 inches. This inner wall sits on the slab on grade and runs right to the underside of the ceiling. This two-wall system, aptly called a “double-stud” wall assembly, would be filled to the brim with insulation – but more on that in a later blog post!
Something very important to remember about beginning structural work is that constructing a perfect house doesn’t only need a perfect design — it needs a perfect execution.
Sometimes during construction, the particularities of a design can get lost in the fray, be carried out improperly, or be stalled or defeated by external forces like weather, finances, or time (or lack thereof!). These problems are normally resolved quite easily, yet with such an ambitious goal like this one’s, the stakes are that much higher. A house is either Net Zero or it isn’t, and even the smallest hiccup can seriously affect its goal.
We would have to wait and see whether our careful design could be carried through without any complications. And should any problems occur, we would have to be willing think radically outside the box.