The key to an energy efficient home is a well insulated and air tight building envelope. I will not go into any construction details, but just list the key building elements and products we used.
- Building exterior wall footings using the Fab-Form Fastfoot system reduces moisture seepage through footings.
- 4" concrete basement slab insulated with 4" of Type II EPS panels, effective insulation value of R16.
- All interior point and strip footings insulated with 4" EPS foam to reduce thermal bridging.
- Basement walls: Logix Platinum ICF blocks with 6" concrete. These graphene infused blocks provide an insulation value of R27 (while the more common "regular" blocks offer R23). We also used the Logix ICF window and door buck material to minimize thermal bridging.
- Subfloor with 11 7/8" TGI joists, insulated with Roxul safe-and-sound for thermal and sound insulation. Drywall on basement ceiling is installed on resilient channels to further reduce sound transfer.
- Main level walls are 8 1/4" SIP panels from Insulspan with nominal insulation value of R36 resulting in effective insulation value of R29. The wall panels sit directly on top of the ICF walls and the subfloor sits within the SIP panels. This reduces chances of air leakage and results in reduced thermal bridging around the subfloor.
- The roof is made of 10 1/4" SIP panels with nominal insulation of R45 (R37 effective).
- Roof finish is Prolok standing seam metal panels from Westform.
- Windows are a very important part of an energy efficient design. The best windows on the market are European Passivehouse certified windows. These windows come with a big price tag, and we went for some "middle ground" by selecting triple pane windows from Westeck's 4000 series. Compared to insulation values of R3 to R4 for "standard" double pane windows mostly used in our area, these windows have insulation values of around R7].
- Our exterior doors are insulated fibreglass on the main floor, and insulated steel doors in the walk-out basement. These doors have insulation values of about R5. You can get some really high performance doors with insulation values of R7 or higher, but again, the cost difference was prohibitive for us to go that route.
- During construction, we put a lot of attention to air sealing. All SIP panel joints had 2 thick beads of caulking. All transitions between different building elements and building envelope penetrations were carefully sealed. This effort paid off during the air tightness test (blower door test) at the end of construction. We achieved an amazing air tightness of 0.98 ACH (air changes per hour at 50 pascals).
One important aspect of an energy efficient house design I learned in my Passivehouse training, is to maximize passive solar heat gain in the winter. The location and orientation of our house is ideal for this. Therefore, I planned the size and height of the overhang of the south facing wall to take advantage of the low sun in the winter - while providing full shade from the high sun in the summer. To further strengthen this effect, our windows (and patio door) on the south and west walls have a very low "solar heat gain coefficient", which collects more energy from the sun during the cold time of the year.
Every energy efficient house needs mechnical ventilation to minimize heat losses when bringing fresh air into the home. In our case, this is done through a Venmar HRV (heat recovery ventilation system). This approach is very common now and all heating/ventilation contractors are familiar with these systems.
Space Heating / Hot Water
Growing up in Germany where most homes are heated with hydronic baseboard heaters, I never got used to the forced-air heating systems which are commonly used in North America. I just don't like the noise of the furnace and ducts, and the inability to control the temperature separately for different areas of the house. After reading a lot about different methods of heat distribution, I decided to go with hydronic radiant floor heating for both the basement and the main floor.
After the decision for a "water based" heating distribution system was made, I had to decide what heating source to use. While we have access to natural gas in our neighbourhood, I didn't want to use any fossil fuel based heating system, and the next obvious solution was a heat pump.
Heat pumps are very common in our mild Vancouver Island climate, and they operate with very high efficiency. But most commonly used heat pumps are "air to air" heat pumps, which can be easily added to furnace based forced air heating systems.
Searching for the most efficient air to water heat pumps, I came across a lot of European manufacturers, but hardly any of them were available (and CSA certified) in Canada. I finally found Chiltrix, a North American manufacturer who claims to use highest quaity components resulting in an efficient and flexible heat pump system. Their heat pump can provide space heating and cooling, as well as domestic hot water. Due to the low heating load of our home, we only needed a single unit to cover the whole house. Our system includes the Chiltrix 19 gallon storage tank for the in-floor heating and a 70 gallon tank for domestic hot water. Both tanks are well insulated and made of stainless steel, so they should hopefully last us a life time.
I first thought that a highly insulated house like ours would not require any cooling. But in some discussions, my energy advisor voiced some concerns - that the building could get too hot in the summer due to our design to capture passive heat in the winter. As our heat pump supports cooling through "fan coil units", I asked our heating contractor to prepare 2 spots in the house for future installation of such fan coil units.
Our first summer is just getting started, and we actually feel that the interior temparature in living room and bedroom gets higher than we like it. We decided to add one FCU for cooling in the master bedroom and one in the living room. We will install a Chilltrix CXI34 in the bedroom and a CXI65 in the livingroom.
The south facing roof with a 3:12 pitch (14 degrees) provides enough space for up to 35 standard size PV solar panels. Depending on the power of the panels, this would be enough space for a 13-15 KW solar system. BC Hydro offers a program called "Net Metering" where customers get credits for feeding power back to the grid. This allows customers to treat the hydro grid like a "big battery". Most customers generate excess power when it's sunny, and collect credits which can then be used on cloudy days and over the winter. Ideally, a solar system for this program would generate just enough energy (averaged over a year) to cover the need of the household. BC Hydro will pay customers only a very small amount (4-5 cents per KWh) for energy sent to the grid and not used up by credits. Therefore, it doesn't make economic sense to size a solar system bigger than what is used by the house.
As part of our house design, I created an energy model (using the Hot2000 software from Natiional Resouces Canada) to predict the energy requirements for heating, cooling, appliances, etc. This energy model was also the basis to size our solar system. The model predicted that our house would use about 11,000 KWh of energy per year (excluding our electric car, which needs up to another 2,500 KWh). I didn't know how realistic these numbers were and wanted to start our solar system on the small side to avoid excess production.
We ended up installing 11 KW of solar panels with an option to add another 7 panels if necessary, for a maximum of 13.5 KW. These are the components we used for our solar system:
- 28 PV panels, Canadian Solar 390 watt each
- Panel frames clamped to roof panels to avoid penetration of panels
- 7 Micro Inverters, each supporting 4 PV panels, installed under solar panels
- APS ECU communication/data logger to monitor and control the system
SIP panel walls are a challenge for electrical installations if you don't want to strap all walls to provide an extra space to run cables and install electrical boxes. We wanted to avoid such strapping for most walls, so we ran electrical cables inside the SIP walls. During SIP panel construction, the factory can cut 1" channels through the panels using a laser. This requires detailed planning of all electrical runs in SIP panel walls at a very early construction phase. We tried to design our electrical layout as detailed as possible. While our electrical contractor team never worked with SIP panels before, they did a great job in getting the job done.
Another challenge was light fixtures in the ceiling on the main floor. Our ceiling finish is white-washed 1x6" T&G spruce boards, and for most light fixtures we wanted to use in-ceiling LED lights. While these lights have a fairly small installation depth (about 2"), we didn't want to cut lots of wholes into the SIP wall panels. Therefore, we strapped the ceiling with 2x4" on flat, and that provided enough space for lots of light.
As a "nerd", I'm a big fan of Home Automation systems and, of course, I wanted to equip our home with as much technology as possible. This is more a hobby then a "building feature" for me and I may write a separate blog post about this system. For the construction process, this just meant to prepare the wiring in a way that installation of things (like smart switches) was possible.
Years ago, people would install phone and cable antenna jacks all over the house to have the ability to install phones and TVs where needed. Now most of that is replaced by using Wifi or Cat-5 cables. I like to have cable based network connections available in some key locations:
- living room TV to connect streaming devices by cable
- several cat-5 outlets in the office to connect computers and other central devices
- one cat-5 cable high on the wall of the office to install a Wifi access point - to provide good Wifi coverage for the main floor
I also asked our electricians to install speaker cables in the living room to allow the connection of a 5.1 surround sound system, and we ran all the cables required for the TV in the living room inside the SIP panel wall.