How Low Can We Go?
Well, just like any project, things come up and adaptions have to be made with new information.
East side of the house overlooking the future off-grid solar system forms being prepared for concrete (right side).
We had a few challenges along the way (which will be addressed in a later blog post "Lessons on Lessons on Lessons"). Some of these challenges resulted in adjustments in the models we ran in the Passive House Planning Package (PHPP) software and Hot2000. Some of these challenges were related to inexperience in building a home (it's our first, and last!), and some were in relation to limitations in materials and contractor experience in this type of project.
As an example, we initially calculated for wall insulation thickness of a full 12" on the main exterior walls. What actually happened was we had a 10.5" of insulation and a 2" air gap (with it's own insulation value) on the main floor. The basement floor was a bit different with no air gap. A reduction in slab insulation also resulted in altered calculations. However, some of this can be made up with increased insulation in the ceiling which will be completed in the coming weeks. Lastly, identifying the specific performance of our windows more accurately in Hot2000 software made a big improvement in internal heat gains and overall performance.
So, accounting for these differences, we're currently sitting at 22 in the PHPP. In Hot200, we made an improvement down to 46 GJ/Year from 78, our very first initial model. Since this home is Net Zero through solar energy, our actual numbers will sit at 0 GJ/Year and should even run Net Positive! In comparison, a comparative code built house sits at 117 GJ/Year. So even without the solar energy, this house would run at 40% the total energy consumption of a regular house, which includes energy for both electricity baseloads and heat.
Construction still in progress. South side (passive solar side!)
More information on Alberta's energy mix and the transition toward solar energy can be found below:
Total energy consumption for the Thomas House without on-site renewables included in the model.
Can you imagine if all builders built to this standard? Homeowners would save all of their annual energy costs, not to mention reduce their total greenhouse gas emissions drastically. An interesting note on GHG emissions in Alberta: Choosing the source of your energy for your home is important. For heat, conventional homes are usually powered by natural gas, which is considered an renewable but alternative energy source and does have environmental impact through emissions. Electricity in Alberta is currently generated form 41% coal (down from 50% in 2015), 40% natural gas (up from 39% in 2015), 2% hydro and 5% wind. However, the electricity landscape is changing in Alberta. By 2030, Alberta plans to increase it's renewable energy production to 30%, and this will include energy from biomass, geothermal, hydro, solar and wind.
Thomas House including renewables - Net Zero, potentially net-positive
The point is: If you are building a home, or have the opportunity to renovate and update your appliances, think carefully about the impact you will be making with regards to sourcing your energy. If you transition your appliances & mechanical equipment now, not only are you able to take advantage of rebates offered through Energy Efficiency Alberta, but you can preemptively take advantage of transitioning from natural gas, to electric in preparation for Alberta's transition toward renewable energy sources. Further, as solar energy becomes more cost effective and accessible, your electric appliances and equipment (and vehicles!) can be directly powered from sun energy. It's a win/win!