Title 24 requirements pave the way towards net zero energy home designs
BY XAVIER GAUCHER
A few years after finishing building our house, I discovered the Passive House standard and became very frustrated. Why? Because neither my architect nor my contractor told me about this fast growing construction standard! Why not? Because they too did not know it. Later, I took the Passive House certified training, at which point, I did not understand why every single construction was not built that way. It increases significantly the comfort level and the durability of the building, and results in almost no energy bill. I then made two decisions: 1) I wanted everybody to know about the Passive House standard and 2) my next house was going to be a Passive House.
So, when we moved to Los Angeles from France in the summer of 2015, we found a house to renovate in the location we wanted (because Passive House also works for retrofit). Even though there was no Passive House yet in Southern California, I knew that it was possible. There are more than 40,000 Passive House buildings all around the globe, in almost every climate zone. Because of the mild Southern California climate, it is actually easier to implement here than anywhere else.
Moving to California, I also discovered the California Net Zero Energy goals starting in 2020 for all new residential construction, just a few years from now (Net Zero Energy (NZE): a building which generates through renewable energies, mostly solar, as much energy in one year as it will consume). I was surprised that most of the trade professionals I was meeting did not even know about the CA NZE goals; and for those who, adding solar panels on the roof of the buildings was their simple solution. Was this true? I then started working on the design of the house (with the Passive House energy modeling & design tool – PHPP) using the standard Title 24 construction code requirements. My conclusion was that the roof of the house, built to the current construction code, would not be big enough to fit enough solar panels for the house to be Net Zero Energy.
This was a very concrete example of why solar panels are not enough to meet the oncoming requirement; the house had to be more energy efficient to be able to reach Net Zero Energy. I then started to include the 5 Passive House principles to lower our future energy consumption: 1) High level of Insulation: we almost doubled the Title 24 insulation requirements for the walls; filled the 11” roof rafters with R38 insulation and the 6” floor joists with R21 insulation. 2) Thermal bridge free design: we insulated all the building connections, making sure that insulation was continuous everywhere. 3) High performance windows: we selected high-performance windows, doors, and sliding glass doors, making sure they were also airtight. We also made sure that the windows were shaded by awnings or by adding shades for the ones which were not shaded. 4) Very airtight envelope: Installing an airtight barrier in the walls, roof, and floor and taping it to eliminate any air leaks and avoid drafts and energy loss, and we tested it with a blower door before closing the walls. 5) Continuous ventilation: since the house is airtight you need continuous ventilation to ensure the high level of air quality required, so we installed a continuous ventilation system which runs 24/7.
Those 5 basic principles allowed us to reduce the heating and cooling requirements by 63 percent (it is up to 90 percent reduction in cooler climates).
The house will be fossil-fuel free and will run only on electricity: a small 1-ton heat-pump HVAC system will heat and cool the entire house; a heat-pump water heater; an electric clothes dryer; an induction cooktop for cooking, which was already a great switch we made with our previous house… and I am French, so you can trust me with cooking! The annual electricity consumption will be less than the annual production with only using 12 solar panels on the roof of our 2,000 sq. ft. house, reaching the Net Zero goal.
What about the cost? The additional cost from regular construction was less than 5 percent. So even in Southern California, every new construction or retrofit should be done according to the Passive House standard.