Monitoring Results for the Factor 9 Home
Canadian building scientists and a family of four set out to build a home that uses nine times less energy than the average - and half the water.
September 03, 2010
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A version of this article appears in the September/October 2010 issue of Home Energy Magazine.
The Factor 9 Home is a single-family residence located in Regina, Saskatchewan, Canada. It was built in 2007 as a demonstration home through the sponsorship of the Canada Mortgage and Housing Corporation (CMHC), Natural Resources Canada (NRCan), the Saskatchewan Research Council, and other stakeholders. Regina is located in a cold climate at 50° latitude, just north of North Dakota. It has about 10,200 heating degree-days per year.
The Factor 9 Home was designed to use 90% less energy per square meter of floor area than the average existing home in Saskatchewan (circa 1970), and to use 50% less water than a conventional home. The resulting energy target was 2.79 kWh/ft2 (30 kWh/m2) per year of total purchased-energy consumption, and the water use target was about 8,830 cubic feet (250 cubic meters) of water per year. Both targets assume a house with four occupants.
The homeowners, who paid for the construction, wanted to live in an energy-efficient, water-efficient, and very durable home. The energy and water efficiency features are described below. For durability, the family chose upgraded asphalt shingles, brick exterior siding, and a concrete-piling foundation—instead of traditional strip footings—for the highly expansive clay soils under the house, and wood-frame windows with exterior metal cladding. There are four people in the family: two adults and two children under ten years. One of the adults runs a company in Regina—Pan-Brick—that produces an R-12.9 insulating brick siding that is marketed in Canada and Japan. Pan-Brick was used for cladding on the Factor 9 home, which was completed in April 2007.
To see if our performance goals were met, NRCan and CMHC funded the monitoring of the energy and water use in the Factor 9 Home for a one-year period ending in May 2008. A number of indoor air quality (IAQ) indicators were also measured.
We installed a low-cost whole-house electrical monitoring device called The Energy Detective to provide instantaneous feedback to the occupants on their electrical use and to help them use energy wisely. The readout device was placed in the kitchen, where family members could easily read it.
Energy and Water Efficiency Features
The house features a very energy-conserving envelope, with an insulation level of R-80 in the attic, R-41 on the above-grade walls, and R-44 on the basement walls. All of the walls are made of structural insulated panels (SIPs). The R-value in the above-grade walls is a combination of R-28 for the SIPs and R-12.9 from Pan-Brick insulating brick siding for the R-41 total. At the rim joist, the insulation level is R-27. The building is well sealed, with a measured airtightness level of 1.2 ACH50, which is tighter than the Canadian R-2000 standard of 1.5 ACH50.
Most of the windows in the house face south, capturing the sun’s energy in the winter to help heat the interior. In the summer, the few east- and west-facing windows limit heat gain. The roof overhangs on the south side of the house limit the amount of solar energy that strikes the south windows in the summer.
On the south wall of the house, 220 square feet (20.4 square meters) of solar panels provide space heating and water heating for the Factor 9 Home. The heat is transferred from the solar panels to a 621-gallon (2,350-liter) hot-water storage tank in the basement that is a recycled unit from a former brewery. A mixture of propylene glycol and water is used to transfer the heat from the solar panels to the storage tank. A fan coil with a brushless DC motor is used to distribute the space heating.
The house was designed so that the passive-solar heating would provide more than 40% of the total annual space-heating requirement. The solar panels provide part of the domestic water heating and a good portion of the space heating requirement. The Factor 9 Home features a drainwater heat exchanger to preheat domestic hot water before it enters the solar storage tank. An instantaneous electric heater provides the auxiliary energy needed for domestic water heating.
To provide mechanical cooling in the summer, a network of plastic pipes was installed in 22 of the 33 concrete pilings supporting the foundation, in order to extract cooling from the ground; the approximate annual ground temperature at the base of the pilings is about 41°F (5°C). The water in the plastic pipes can provide space cooling for the house. The same fan coil used for space heating is also used for space cooling. Manually operated valves switch from the space-heating to the space-cooling mode.
A heat recovery ventilator (HRV) recovers heat from the air exhausted from the bathrooms, kitchen, and laundry room. The incoming fresh air is preheated by the HRV before it enters the return side of the fan coil that distributes heat from the large water storage tank. The special unit has DC fan motors with low electric consumption. Two different heat-exchange cores are used, one with plastic plates and one with treated paper plates. The latter will allow moisture in the exhaust air to be recycled back into the home in the winter, when the indoor air tends to be too dry.
Energy-efficient CFLs and an Energy Star refrigerator, freezer, clothes washer, and dishwasher are installed in the house.
Rainwater and melted snow water runoff from the roof are stored in two 9,500-liter tanks in the crawl space beneath the basement floor. This nonpotable water is used for ultra low-flow toilets and landscaping. Landscaping was designed to reduce the need for water. Faucets are aerated, showerheads are low flow, and the dishwasher and clothes washers are low-flow models.
Over the one-year period of occupied monitoring, the measured purchased-energy consumption of the house was 3 kWh/ft2 (33 kWh/m2) of floor area. In comparison, a typical home of the same size built in 1970 would have a consumption of 31 kWh/ft2 (331 kWh/m2) or 10 times as much. A graphical comparison of the purchased-energy consumption of the two houses is shown in Figure 1.
The purchased electrical energy consumption for the house amounted to 8,969 kWh for the period from June 1, 2007, to May 31, 2008. The peak daily electricity consumption for the house was 86.3 kWh per day (3.6 kW) for the one-week period ending December 25, 2007. This peak consumption is much smaller than the design heat loss for the house as calculated by the HOT-2000 computer program (10.5 kW at -29°F, or -34°C). This is because the HOT-2000 program calculation assumes
- no passive-solar contribution;
- no active-solar contribution; and
- no internal heat gain from people.
The outside temperature for the week ending December 25, 2007, was warmer than -29°F (-34°C). In addition to the electrical consumption in the house, a modest amount of wood was burned in an airtight wood fireplace. Over the monitoring period, the useful-heat output from the wood consumption was calculated at 994 kWh.
The reduction in purchased-water use was also quite dramatic (see Figure 2). For a family of four, the average water consumption in Canada is 132,000 gallons (501 cubic meters) per year. For the one-year monitoring period, the measured water consumption of the Factor 9 Home was 45,100 gallons (171 cubic meters), a reduction in purchased-water use of 66%. In the monitored year, the total precipitation was less than half of the average annual precipitation of 15 inches (388 mm) for Regina, reducing the amount of water available to the roof collection system. The exterior landscaping for the home was not completed during the one year of monitoring. Water collected from the roof is directed to two membrane tanks with a combined volume of 5,800 gallons (22 cubic meters) located in the crawl space beneath the basement floor. Based on the annual average precipitation in Regina, annual precipitation on the roof of the house should average 10,000 gallons (38 cubic meters).
Incremental Cost of Efficiency Measures
The homeowners did a substantial amount of the work on the house and were able to get discounts on materials through their professional contacts. Thus it is difficult to put a precise figure on the incremental cost of the efficiency measures. The incremental construction cost for the energy and water efficiency measures was roughly CAN$37,000 (US$36,000 at time of printing), or 12% more than the cost of conventional construction.
The water savings are CAN$488 (US$470), per year, based on current water prices in Regina. The house does not use any natural gas. The energy savings compared to a new home of similar size located in Regina (that is heated with natural gas) are estimated at CAN$952 (US$920) per year. This estimate is based on reference data in the Canadian Residential Energy End-use Data and Analysis Centre database of homes built between 1998 and 2000. The combined energy and water savings amount to CAN$1,440 (US$1,390), a year, based on current energy prices in Regina. The rate of return on the incremental cost of the energy and water efficiency features of the home is 3.9% per year, based on current energy prices. This is equivalent to a simple payback period of 26 years. In a number of Canadian provinces, substantial cash grants are now available to help reduce the incremental cost of the energy-efficiency measures. These cash grants improve the economics even more.
Indoor Air Quality
Well-sealed residences cannot rely on natural ventilation to dilute the pollutants generated indoors. The Factor 9 Home has an HRV to provide mechanical ventilation. To assess IAQ, we made short-term measurements of volatile organic compounds and radon gas in the home.
The total volatile organic compound (TVOC) reading over a two-day interval was 5.4 mg/m3 of air.
Canada does not currently have a residential guideline for indoor TVOC values. However, the European guideline is 0.3 mg/m3 of air. The relatively high reading for TVOC in the Factor 9 Home was probably attributable to the extensive painting that was done in the basement just before the measurements were taken.
Radon values were measured using a factory-calibrated digital readout device—the Safety Siren Pro 3 Radon Detector. Over the period from April 6, 2008, to June 22, 2008, the weekly radon readings measured on the main floor of the house varied from a low of 1.1 picocuries per liter to a high of 1.9 picocuries per liter. The current Canadian guideline for radon is 5.4 picocuries per liter ( 200 Bq/m3).
A Little Room for Improvements
The Factor 9 Home demonstrated the technical feasibility of measures that can significantly reduce household energy and water consumption, and the incremental costs were not overwhelming. The semipassive cooling system, which rejects heat into the concrete pilings beneath the house without the use of a refrigeration cycle, proved to be technically viable in this climate zone.
The energy and water efficiency measures on the Factor 9 Home, such as the R-80 attic insulation and the energy-efficient HRV, have been used in a number of net zero energy homes built since the Factor 9 Home was monitored.
Two additional energy conservation measures could improve the energy performance of the Factor 9 Home: more R-10 insulation in the wood truss basement floor, and more insulation on the thermal storage tank for the active-solar heating system. (Because it was insufficiently insulated, this tank took a very long time to heat up when the water was cold.) With these measures, the annual energy consumption for the house could meet the 2.79 kWh/ft2 (30 kWh/m2) purchased-energy target.
Rob Dumont is a former building scientist with the Saskatchewan Research Council (SRC). Don Fugler of the Canada Mortgage and Housing Corporation assisted with the drafting of this article. This article was based on research managed by John Gusdorf of Natural Resources Canada and funded by NRCan and CMHC.
Many thanks are extended to the homeowners, who cheerfully took many manual readings during the monitoring period and graciously allowed the monitoring to take place.
For more information:
A CMHC Innovative Buildings case study entitled Factor 9 Home: A New Prairie Approach (CMHC 2007) provides information on the design of the home and photos of the construction. To download a PDF of the case study, go to www.cmhc-schl.gc.ca/en/inpr/bude/himu/inbu/ and click on the link to Energy Efficiency.
For a YouTube video of author Rob Dumont discussing the Factor 9 home, go to www.youtube.com/watch?v=oRpy-G3-qOo
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