The goal in a passive solar design is to have the sun supplement the heating of the house in the winter while rejecting the sun in the summer. This is primarily achieved by designing south facing overhangs over windows such that it would allow the lower sun to enter through the windows into the house during winter months, but as the sun rises higher in summer sky, it rises over the overhangs such that the direct sun is kept out of the windows.
Variables include the location and orientation of the house, how tall the windows are, and how far below the overhangs the windows are. In our case, we worked out to about a 28″ overhang (24″ + 4″ eavestrough), which would allow 90%+ of the sun in when the sun is at its lowest during winter solstice (where the sun is lowest in the sky), and would completely block the sun during the summer solstice (where the sun is highest in the sky). The picture on the right was taken in late July at about 3pm, and you can see the shadow line is not protruding into the house.
In addition, choice of materials inside is also important, as darker and denser materials are better at absorbing the sun rays than lighter materials. Slate or granite tiles, for example, would be perfect for this application, but in our case, we’ve chosen to use a medium dark stained cork flooring to gain some of the benefits of the passive solar design without giving up any comfort of the softer floor.
The windows that face south also has to be tuned to allow for greater solar gain, measured and represented by a solar heat gain coefficent (SHGC), usually at the expense of the R-value of the windows. In our case, our south facing windows had a SGHC of 0.44 compared to 0.26 for the rest of the house, at the expense of the R-value, decreasing from 5.5 to 3.8. However, the heat gain, even in the winter, will more than compensate for the relative increase in heat loss between the two different sets of windows.
Update- In real world observations during 2011, we have noticed that on winter solstice, the sun can reach as far as 15′ into the house from the window, heating the floor and its contents for free heat in the winter, while during summer solstice, the sun reaches just the window sill, reducing the cooling demand by having very little sun inside the house. Since our house is on a smart meter with hourly usage statistics provided by Powerstream, we have been able to correlate the time-of-day usage with Environment Canada hourly weather statistics, and the heating demand was reduced by an astonishing 25% when the sun was out. Our house is not the most aggressive design for passive solar, so much better gains can be achieved by simply orienting and sizing windows and soffits and choosing materials that can absorb heat in the winter.
Before the basement concrete slab was poured, a 2″ thick EPS (R7) was put in place to reduce the heat transfer to the soil beneath. In addition, PEX tubing was run in 90% of the basement floor space to allow for in-floor radiant heating. In-floor radiant heating allows for a more comfortable basement floor as it is no longer cold to walk on, and is efficient as heat rises throughout the house in the winter, as well as a reduction in the heating area that the fan coil has to service. The garage was insulated and roughed-in with the same system for the ability in the future of a heated garage.
The tubes are connected to the Daikin Altherma system, which provides radiant heating to the basement floor as well as the fan coil to heat the ground and second floors, as well as heating the hot water for the house.
In order to design an energy efficient house, one of the criteria is to build it as airtight as possible. However, the lack of fresh air can create health problems. Our Lifebreath Clean Air Furnace is a fan coil and a heat recovery ventilator (HRV) in one unit, and exhausts stale air out while drawing fresh air in as the furnace runs, while the heat exchanger portion recaptures a significant portion of the heat from the exit air and transfers it to the incoming air in the winter.
In addition, we have ducted all of the bathroom exhaust to an inline fan located near the furnace, which connects directly to the HRV, and having its mechanical operation is intertied to it, in order to recapture the heat from the exhausted bathroom air as well. The secondary benefit is that the fan location is away from the bathroom, and keeps the fan noise to a minimum in the bathroom. As well, because there are return air intakes in the bathroom to the air handler and HRV unit, there is consistent air flow in the bathroom, thereby keeping the moisture level to a minimum, greatly reducing the chance of mold growth in the bathrooms.
The process began with the architectural drawings, a specification of materials for insulation, and a designer that reviewed the materials to calculate a heat loss of house at design temperature (-20°C or -4°F in Markham, Ontario). Part of the problem was what R-Value and what air exchanges per hour (how leaky the house was) to use for the calculations, since much of this is unchartered territory, and we didn’t want to buy into the marketing hype from all the product manufacturers in terms of each product’s efficiency. In the end, we took a middle-of-the-road approach for each of the materials for R-Value, and assigned a low air exchange per hour knowing that the house was to be very well sealed. For the purposes of the building permit, we came up with an 80kBTU/h heat loss at design temperature, but in talking with our LEED certifier, he feels a house with the selected material will be far lower, perhaps as low as 50kBTU/h.
Our selection of a heating system had to be based on the 80kBTU/h value as we had to satisfy the building code requirements, but also allowed for flexibility to take advantage of a lower heat loss if it were the case. We considered 3 different types of heating system:
traditional natural gas fired furnace, for the lowest initial cost but the most energy inefficient,
geothermal, for the highest initial cost but also the most energy efficient, and
air-source heat pump, for a middle of the road approach in terms of cost and efficiency.
With traditional natural gas fired forced air furnace, we would achieve between 92-98% efficiency (1 BTU in, 0.92-0.98 BTU transferred into the house), but we would be dependent on fossil fuel. The price of natural gas, however, was (and still is) very attractive as it is at the lowest point in more than 5 years, and about 2/3 less than what it was at the peak. In terms of real costs, based on current Enbridge (local natural gas utility) prices as of October 1, 2010, inclusive of delivery and other charges, natural gas is supplied at $0.2666/m³, or $0.024/kWh as of January 2011.
With geothermal, we would be entirely on electricity, using a resistant heat backup. This would get us off fossil fuel (assuming the electricity isn’t coal or natural gas generated), and we would achieve a COP of 3.6 (1 BTU energy in, 3.6 BTU energy into the house), but the primary drawback was the cost of the geothermal system. Based on our location in suburban Toronto, we did not have enough of a lot size to bury the loops horizontally (trenching), but instead it will need to be drilled and installed vertically. The costs of the equipment and installation costs would have been in excess of $35,000 for a 6-ton (72kBTU) system, with the drilling alone representing over $10,000 of the $35,000 cost, and the rebates that were offered at the time only applied to retrofit homes, which we did not qualify. When we compared it to a typical natural gas system and air conditioner which would have cost well below $10,000, the $25,000 difference was hard to justify. Plus, at our 80kBTU/h, we would have required either a secondary system, or an additional electric resistant heat backup to satisfy the building department’s requirements based on our heat loss calculations, as the largest capacity for a mainstream geothermal system would have been 72kBTU/h. In terms of operating costs, the electricity costs vary between $0.08433/kWh to $0.13233/kWh depending on time of day (inclusive of all regulatory charges), so factoring in the COP of 3.6, we would have been barely break even during off-peak use and it would have been 50% more to operate during peak hours, at least given the current lows of natural gas pricing. To spend $25,000 extra with no cost recovery until (or if) natural gas prices rise, this option seems unpalatable.
With an air source heat pump, it works very similar to a ground source heat pump, except that it extracts energy from the air rather than from the ground. For the pump, heat exchanger, and air handler equipment, the costs were similar when compared to geothermal, but because there were no drilling costs involved, the cost of an air source heat pump would be far lower than a ground source. The primary drawback was that the efficiency of the air source heat pump tends to be lower than a ground source, and the output and efficiency of the air source heat pump declines as the temperature drops. In addition, for an air source heat pump, at least for the climate of Toronto, it was very unlikely to have enough output at design temperature unless it was for a small and highly energy efficient house, and as such the cost of the backup system needs to be factored in.
In the end, we chose a Daikin Altherma air source heat pump with a Navien tankless natural gas water heater as backup heat, fed into an in-floor radiant basement heating system and to a Lifebreath Clean Air Furnace with a built-in HRV which acts as the air handler to deliver warm forced air to the main and second floors. A Daikin domestic hot water tank was also installed so that the heat pump can be used for hot water for the house. This hybrid system approach allows us to adapt to a changing energy price market, by giving us the choice to select how low of an ambient temperature to run the heat pump to before switching over to natural gas. We also plan on adding the solar water kit that would allow us to use the sun to heat the domestic hot water to further increase efficiency.
In our case where the goal is net-zero energy, we would use the Altherma to as low an ambient temperature as possible. But, if our choice was for dollar efficiency, we could choose to run the Altherma when the ambient temperature was around 0°C, where the Altherma was more cost effective with the higher COP, and when the temperature falls below 0°C we would switch to the Navien tankless, with the logic being programmed into the Altherma Hydrobox, with no user invention required.
We chose their ERLQ split system that was rated at 54kBTU, but for our purposes of heating in a Toronto winter, it would only be capable of generating about 25kBTU/h at design temperature of -20°C, and about 37kBTU/h at freezing, which would allow us to be on the heat pump until the temperature dropped well below freezing. Even at -20°C, the Altherma would deliver a COP of 2.5, and at 0°C it would deliver a COP of about 3.0, so while it doesn’t deliver quite the efficiency of a ground source heat pump, the lower initial costs far outweights the reduced efficiency, and it contributes significantly to our goal of becoming a net-zero energy house. In the summer, the Altherma would deliver chilled water to the system for cooling.
When the heat loss of the house becomes greater than the Altherma can handle, the Navien tankless water heater would kick in, supplying up to 160kBTU/h, more than sufficient for any Toronto weather, and also satisfies the building department in terms of meeting the design heat loss. The Navien tankless unit offers efficiency of up to 98%, which is one of the highest (if not the highest) efficiency available on the market today.
The Lifebreath Clean Air Furnace is a water coiled based air handler that would take the warm water from the Altherma or the Navien tankless, and blows air over the coil to extract the heat into the house. A built-in HRV is part of the Clean Air Furnace, which we needed because of the air tightness of the house.
Total system cost is estimated to be about $10,000 to $15,000 above a traditional forced air natural gas and an air conditioner, perhaps less as we had an in-floor radiant heating installed for the basement. Cost recovery as compared to current natural gas rates would be fairly long, but in temperatures of above freezing, the higher COP would be more cost efficient than natural gas, and in the summer the system should be more efficient than a standard air conditioner. In operating costs, it would be cheaper to operate the Altherma over natural gas when the ambient temperature is above freezing, and would cost slightly more when the temperature drops below freezing, based on the current utility rates. But the balance point would change should natural gas prices begins to rise from these very low levels.
CaGBC LEED for Homes – Points can be acheived in Energy and Atmosphere, in HVAC (EA 6), or exceptional energy performance (EA 1.2) via the ERS/HERS method.
Update (March 2012) – Through the 2011-2012 winter, we have observed that we were able to continue to run the ASHP and maintain house temperature to as low as an outdoor temperature of -10°C, consistent with the 50kBTU heat loss projection as opposed to the 80kBTU design calculation.
Update (July 2012) – The continuing decline in natural gas pricing has skewed the economic benefits towards natural gas over ASHP or GSHP, so please bear this in mind in considering the cost efficiencies of ASHP or GSHP.
In the summer of 2005, a rain storm ripped through southern Ontario. In Thornhill where our site is located, up to 8″ of rain fell in 45 minutes, causing some of the most severe flooding the area has seen. Since then, newly constructed buildings in the area were mandated by the Town of Markham to have on site rain storage, the volume to be determined through a formula and based on the additional land coverage of the new building. The purpose was to alleviate the load on the storm sewer system as it was at capacity.
In our case, we were required to store 2000L of water. We ruled out a leach pit (i.e. an underground “cistern” that allows water to seep slowly into the ground) because of the costs involved, and decided at at grade storage was the most practical choice. As we went on to investigate on certifying the house under the LEED for Homes program, we did some calculations and decided to store on site 6000L of rain water.
We acquired 6 of the 1000L slimline Handytanks, which were not barrels at all, but marine grade PVC supported by a steel frame, all of which is neatly packed in a flat box for transport. We were able to fit all 6 of them in my Prius, to give an idea how compact they were to transport.
The 6 “tanks” are connected together to make an intertied system, and we have the entire rear half of the roof’s rain flowing to the tank via an 80′ long eavestrough. Tanks were placed at the edge of the building, which also simplifies the plumbing when compared to an underground storage system.
In the spring, we will be installing a sprinkler system, and our hopes is to contstruct a system so that it would priority on using the rainwater before using the municipal water for irrigation.
CaGBC LEED for Homes – Points can be acheived in Water Efficiency, in Rainwater Harvesting System (WE 1.1).
Typical sod from a sod farm in Ontario consists of a 90% Kentucky blue grass and a 10% fescue mix. As part of our goal for LEED Platinum certification, we sought out drought-tolerant turf, and was able to find a 60% Kentucky blue grass and 40% fine fescue mix from Green Horizons, one of a few local farms that grows specialty sod.
The benefit of such a mix is that during the summer season, there are lower watering demands. In exchange, however, the shade of grass isn’t as green, and the blades not as fine. However, this was an acceptable trade-off for us, and will also help us be more reliant on the rainwater collected by the rain barrels (see our 6000L rain storage). As a side benefit, the thicker blades of grass gave us a more lush lawn, one that the kids loved to roll in.
CaGBC LEED for Homes – Points can be acheived in Sustainable Sites, in Basic Landscape Design (SS 2.2).
All of our drains in the house is tied into a single drain stack in the basement of the house, and a drain stack heat recovery coil was installed in the drain stack. A 6 foot section of 4″ copper pipe sits in the center to handle the waste water, and as the copper picks up the residual heat in the water, the heat transfers to the copper tubing that the incoming water flowing to the hot water tank, thereby preheating the cold municipal water as it enters the tank.
When hot water is being used in the house and drawn out of the hot water tank, replacement cold water effectively flows around the drain stack and picks up the heat from the returning waste hot water.
Cork flooring was chosen for about 70% of the floor space, except for bathrooms (where we used tiles and/or stone), and the living/dining/office, which we went with a traditional hardwood.
The cork flooring has a very unique pattern that doesn’t resemble traditional hardwood, one that you either love or hate. In our case, we chose function and comfort over esthetics (not that we mind the look), as the cork floor is a softer, warmer, and overall more comfortable floor to stand and walk on. The randomness of the pattern allows scratches and scuffs to be less visible. A side benefit is the sound absorbancy of cork, which should help dampen the sound travelling throughout the house.
We had considered a slate floor for the family room, kitchen, and dining room areas, where it would have benefitted from the thermal mass effect of the winter sun shining on the floors as these rooms were south facing, but in the end comfort won out, and cork it was.
Our flooring was sourced from Jelinek Cork Group in Oakville, one of the oldest cork companies around. We chose their Sierra Brown in a floating style floor, with a further 2.5mm cork underlayment.
Installed costs were about $7.50/sqft (at list price), similar to hardwood flooring.
CaGBC LEED for Homes – Points can be acheived in Material and Resources, in Environmentally Preferable products (MR 2.2).
A concept that never made sense to me was the concept of a dryer that used energy to heat the air, and exhausted that hot air out of the house. Thing about it… On a cold February Canadian day, you’re first paying to heat the air inside the dryer, and when it gets exhausted, replacement air has to enter the house to balance the air pressure, and you’re paying a second time to heat the frigid outside air that ultimately winds its way into the house.
In many parts of the world, a combination washer and condensing dryer was very common, but yet the selection in the US and Canada can be counted with two hands. Since our choice was limited, and based on prior good experience with an earlier LG model, we chose to purchase two LG WM3987HW for the house, one to put in the laundry room, and a second to put in the upstairs semi-ensuite.
The LG combination washer/dryer unit has several benefits. For one, you don’t need an exhaust, simplifying the installation and most importantly, much more energy efficient. All it requires is a water supply, a drain, and a standard 15A 110V receptacle, instead of the 30A 220V that a typical dryer requires. That’s 1/4 the maximum potential draw of electricity. Sure, the machine takes longer to dry the clothes, and as such the energy savings might not be 75%, but it is much more efficient nonetheless.
The lack of exhaust allowed us to install one in the upstairs bathroom by tying into existing plumbing, and allowed us to have a second floor laundry within the common washroom, a major convenience as we did not need to carry the laundry up and down the stairs.
The general common complaint on these all-in-one washer/dryer is that it takes a very long time to complete a cycle (3 hours 30 minutes average from start of wash to completion of dry), but we have adapted our laundry washing to be done overnight by setting the delay function on the unit to start around 4am, and in the morning we have clean clothes ready to go or ready to be folded. The other common complaint is that the clothes coming out has a very slight smidgen of dampness as a result of the condensing drying method, but usually it evaporates by the time we are done folding the clothes.
A pet peeve: LG is proverbially raping the Canadian public on this unit. When we bought this unit in 2011, the Canadian MSRP was CAD$2600, and the US MSRP was USD$1679, and we ended up purchasing two units in Buffalo for USD$1300 each, so even after the NY state tax and the trailer rental, we were WAY WAY ahead than buying in Toronto. I understand the Canadian market is a smaller market, but the price difference was just outrageous with the exchange rate factored in. I contacted LG Canada in 2011 regarding their price discrepancy in the two markets, and their reply was:
“Thanks for contacting LG customer service. The reason why prices are lower in the U.S is because of the bigger market. That is the same for almost every product sold their. Have a great day.”
LG, this is SHAMEFUL. You have a great product, but the way you treat your Canadian customers is atrocious.