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).
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).
Our ceiling insulation material is from Nudura, the same manufacturer as our Insulated Concrete Blocks in the exterior walls. The Nudura Ceiling Technology is a 2.5″ or 3.5″ sheets of EPS with built-in wood strappings for simple installation of drywall. These were delivered onsite as 4’x8′ sheets with ship lap edges, which provides a tight fit at the seams.
Our installation consisted of, from top to bottom, the roof truss, a 1/2″ sheet of drywall, a 3.5″ sheet of the Ceiling Technology, followed by another 3.5″ sheet running in perpendicular direction, and finally a finish sheet of 1/2″ sheet of drywall. The ceiling insulation “sandwich” assembly hangs on the underside of the roof truss system, which completely eliminates any thermal bridging of wood.
In total, we have 7″ of EPS, which would in theory only net an R27 based on the EPS alone, and below what the Ontario Building Code requires. However, because of the reduced thermal bridging and the greatly reduced air leakage, Nudura has tested the product in the field and have shown for the product to perform at an equal or greater than an R60 fiberglass batt or loose fill type insulation.
For our project, there was a cost increase of approximately $7,500 compared to a 12″ loose fill sprayed in cellulose, but with far better performance in heat loss as well as air infiltration.
CaGBC LEED for Homes – Points can be acheived in Energy and Atmosphere, in Insulation (EA 2), or exceptional energy performance (EA 1.2) via the ERS/HERS method.
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.
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.
This entire project began with the announcement of the renewal energy program that the province of Ontario had plan to implement in April of 2009, and the feed-in tariff that was to be offered. In looking at what the best method to take advantage of the program was from a small scale perspective, we quickly realized that it would be cash flow positive from the solar panel investment, and that it would help pay for some (if not all) of the additional energy efficiency upgrades for the house. This became the lynch pin in this entire project from an energy perspective as well as from a financial perspective.
We began by looking at lots that were on streets with an east-west direction fronting on the south side of the street that were as wide as possible within our budget, while still fitting our personal requirements for area amenities. We were fortunate enough that, within a very short period of time, we were able to locate and secure the purchase of a 100′ wide lot in a suburban area of Toronto. Our next step was to design the house to maximize the roof space available for the solar panels, and in doing so we included four design aspects for this purpose:
The first was to specify that the roof pitch for the south facing portion of the roof to be an 8/12 rise (33.7° pitch), which was within a couple of degrees of optimal for our geographic location.
The second was to set back the 2nd floor rear wall so that the south facing roof could extend from the top of the first floor all the way to the ridge (see architectural drawings).
The third was to use two gable ends instead of a hip roof to maximize the south facing roof.
The fourth was to incorporate a tandem garage; this allowed us to add roof space and storage space without increasing the conditioned area of the house.
By incorporating the above design aspects, we were able to design a roof with over 2,300 sqft of area to mount the solar panels, which allows us to mount a 30kW PV system, very likely to be the largest roof mounted residential system in the province. In comparison, most approved systems for residential mounting in this region has been in the 6kW-8kW range, with many being as small as 2kW-3kW.
We chose to work with Honeybee Solar based on their knowledge, and their willingness to look at source different solutions, and in our case, panels and inverters that will allow us for the greatest payback. The panels are from CEEG and from Eclipsall, about 15% panel efficiency, while the inverters will be from Aim Energy (local Ontario content) through Honeybee Solar, which provides some of the highest yielding inverters on the market. In their test site in Southern Ontario, they were able to generate over the course of a year 70% more power on a flat-straight-to-the-sky panel installation than a typical DC installation. In real world use, we are expecting about 1.3kWh/W of panel, a 25-30% than a traditional string inverter installation.
Our system of about 30kW will cost somewhere in the neighbourhood of $200,000, but the 20 year contract that the Ontario Power Authority offers for a system of this size will pay back $0.713/kWh, and we anticipate we will generate more than $30,000/year. In a pre-tax calculation, on an annualized basis, this would offset close to a $450,000 mortgage based on a 20 year amortization and a 2.99% interest rate (as of July 2012).
Total production is anticipated to be around 40,000kW/h per year, of which we anticipate about half will be used by the house for daily electrical uses as well as for cooling, and the other half will be used for heating in the winter using a combination of our Daikin Altherma heat pump as well as natural gas. Our calculation includes the BTU used by burning the natural gas, converted to kWh.
CaGBC LEED for Homes – Points can be acheived in Energy and Atmosphere, in the renewable energy section (EA 10.1), or exceptional energy performance (EA 1.2) via the ERS/HERS method.
Windows are inherently a weak point in the building envelope in terms of its insulative properties. Wall assemblies, to the Ontario Building Code, requires it to be insulated to R-19. Compared that to windows, the minimum requirements for an Energy Star window is R3.2 for our region (Southern Ontario, Zone B). However, while windows can be a source of heat loss, they can also be a source of heat gain as well, which is bad in the summer, but advanteageous in the winter. Our choice involved a combination of strategies to take a balanced approach to the problem.
We looked at windows from various manufacturers, and compared the R-values of the windows. What we found was that triple pane windows in general offer a higher R-value compared to double panes, but at a price premium. To complicate matters, our design called for large casement windows, which when combined with the weight of the triple pane glass, caused us to look at fiberglass framed windows exclusively.
Fiberglass frames have several benefits. They are far stronger than vinyl frames, and would withstand the test of time much better in our case of triple pane casements, the largest of which would be 30″ wide by 60″ tall. Each of the casements weighed in excess of 100 pounds, and one can imagine the stress of the weight while the window is opened with little support. The other major benefit is that in differing temperature extremes, fiberglass expands and contracts at a rate very similar to glass, while vinyl expands and contracts much differently, giving the potential of an increased air infiltration compared to the ideal test environment of which the standardized testings are based.
When selecting coatings for the windows, we tuned it based on the exposures of the windows. For north, east, and west facing windows where the sun shines rarely on it, we selected windows that offered us the best R-value. For the south facing windows, however, we chose windows that had coatings that allowed for a higher solar gain heat coefficient (SGHC) for heating benefits in the winter, by giving up some R-value for the windows. We countered the effect of the gains in the summer by calculating sun angles and designing the overhangs above the windows to block sun in the summer, but at a lower sun angle in the winter, the sulight would enter the house.
Our Fibertec Windows offered an R-value of 7.7 for the fixed panes, and 5.5 for the operable casements, far exceeding the energy star requirements. The south facing windows offered an R-value of about R4 for the operables, but the SGHC was increased from 0.26 to 0.44 to allow for more heat gain in the winter. Our other reason for selecting Fibertec windows was for their hinge design, as it sat closer to the bottom of the frame for better support of the heavy triple pane casements. Their custom brickmould that are channel locked to the window also allowed for an easy installation that reduced on-site installation time. We estimated a total cost increase of about 25% from a traditional double pane vinyl windows.
CaGBC LEED for Homes – Points can be acheived in Energy and Atmosphere, either via the air leakage tests (EA 3.3) and the exceptional windows (EA 4.3), or exceptional energy performance (EA 1.2) via the ERS/HERS method.
For floor joists, we chose an open web joist design.
These joists are a premium from an engineered I-joist (which are the standard choice for floor joists), but offers more flexibility in ducting and plumbing design. It also uses less than 1/2 the amount of wood than dimensional lumber, and can be made of wood harvested from a young growth tree.
The main retangular chase is an 8 1/2″ x 21″ opening, which allowed us to fit both the supply and return air trunks through, with the rest of the ducting and piping running through the triangles of the joist. A traditional I-joist would have required significantly more labour to cut openings through the joist, if there were enough space to do so, or limit the trunk and duct runs to be parallel to the joists, or would require bulkheads and frame-outs to hide the ducting.
Open Web Joist - Chase Opening
The joists allowed us to reduce the boxes and bulkhead to hide ducting to almost zero, with the exception of inside a main floor closet and the main floor powder room. It also allowed us to create a basement ceiling with minimal bulkheads, except where load bearing beams are installed.
We estimated an upcharge of about $1.25-$1.50/sq.ft. floor space for an open web design from I-joists. However, we were able to offset this cost by building an 8′ basement height instead of a 9′ basement and still be able to get 8′ clear, as the bulkheads are no longer an issue.
Our joists were engineered, manufactured, and supplied by Kent Trusses of Sundridge, ON. These joists are sold in 2′ increments in length, and the ends of these joists are trimable by up to 1′ on each end, therefore not requiring exact measurements when ordering, and flexibility of install on the job site.
CaGBC LEED for Homes – Points can be acheived in Material and Resources 1.4 for open web floor trusses, and in our case, MR 2.2 for local production.
Part of our exterior wall system were constructed with structured insulated panels (SIP). We used these panels in two areas: in areas where we could not use ICF because of a lack of a supporting wall underneath to bear the weight of the concrete in the ICF, and in wall areas that faced into an unconditioned area, such as the wall separating the garage and the living space, and a section of walls that faced into the lower attic.
Our SIPs are made of two sheets of oriented strand boards (OSB), with expanded polystyrene (EPS, aka Styrofoam) sandwiched in between. Various sizes and thickness are available, and for the majority of the SIPs we used had either 4’x9′ or 4’x10′ sheets that were 8 1/4″ thick in total (7 1/4″ EPS). Channels at the edge are carved out for installation of splines using 2×8 lumber as well as for the plates. Every 4′ a spline was installed, and glued and nailed together to the OSB. In our case, we had ordered the panels with built-in channels for electrical wiring. What surprised us was how rigid the wall system as we were installing even without the nails in place; the tight fit of the spline to the OSB and the rigidness of the SIP allowed it to stand on the base plate with no flex whatsoever.
Benefits include an air tight structure, and reduced thermal bridging compared to traditional timber frame, as “studs” are every 48″ instead of every 16″. The fit between the OSB and the spline/plates are also very tight and glued together to minimize potential air leakages.
In costs, we estimated this to be about a $3/sq.ft. wall space upcharge for material and labour from traditional timber framing, and about $6/sq.ft. less than the ICF.
Our SIPs are from Insulspan, sourced through Kent Trusses (who also supplied our floor and roof trusses). The SIPs were ordered in 6 1/2″ and 8 1/4″ thicknesses, in 4’x9′ and 4’x10′ sheets, with wiring channels put in at 14″ and 44″ from floor.
CaGBC LEED for Homes – Points can be achieved in Energy and Atmosphere, either via the air leakage tests (EA 3.3) or exceptional energy performance (EA 1.2) via the ERS/HERS method. Points is also available in Material and Resources (MR 1.4) for SIP and MR 2.2 for local content.
For our house, we have chosen to use insulated concrete forms (ICF) as the primary wall system for the exterior walls of the house, with sections that are structural insulated panels (SIP).
ICFs are made of 2 sheets of expanded polystyrene (EPS, aka Styrofoam) with concrete poured in between. The materials comes in blocks, and is assembled on-site in a similar fashion to Lego blocks. The blocks act as the form work for the concrete as it is poured into the cavities between the two sheets of EPS, and is a stay-in-place form work, as the blocks of EPS are not removed after the curing of the concrete. The EPS acts as the insulation for the wall, and the concrete provides the strength, and a total air and thermal break between the inside and outside of the walls.
On the inside, drywall is directly fastened to the ICF, as the ICF have built-in plastic strappings that act both as a structural component for strength and for holding the EPS together, as well as for screwing the drywall into the straps. For electrical, the EPS is thick enough to accomodate the mounting of the electrical boxes, with the wires being embedded into the EPS. No penetrations through the concrete is required, except for venting purposes.
This method of building provides a much stronger structure, which may be an advantage if you are in an natural disaster prone area. Other benefits include a much tighter building envelope, as the concrete wall system is a monolithic system and no possible penetrations for air leakage. This translates into a significant reduction of heat loss, as up to 1/2 of the heat loss of a house can be attributed to air leakage. If you live near a noisy environment, another benefit is the significant noise reduction from the outside.
In using the ICF, we decided to go from basement to the roof, except in areas on the second floor where there was nothing underneath to bear the weight of the concrete. For the basement walls, this is fairly cost competitive with traditional poured concrete walls or cement blocks. Once we went above ground, however, it becomes a significant cost upgrade to use ICF. For this reason, there are some builders that will choose to use ICF for the basement, and either traditional timber frame (cheapest) or SIPs (more expensive than traditional, less expensive than ICF) for above grade exterior walls. Expect an upcharge of $8-10/sq.ft. wall space material and labour from traditional timber frame, and an upcharge of $5-7/sq.ft. wall space from SIP, depending on complexity of project.
In our house, we have chosen to use blocks manufacturered by Nudura, supplied through our contractor for the exterior “framing” (Stevens Construction). The blocks consists of 2 5/8″ sheets of EPS on the outsides, with a 6″ cavity for the concrete. Other cavity thicknesses are available, starting at 4″ and increasing in 2″ increments.
CaGBC LEED for Homes – Points can be acheived in Energy and Atmosphere, either via the air leakage tests (EA 3.3) or exceptional energy performance (EA 1.2) via the ERS/HERS method. In our case, it would qualify for Material and Resources (MR 2.2) for local content, as the concrete and the ICF are both manufactured within 800km.
