1. Cleaning the Air in an R-2000 Home
The Need for Mechanical Ventilation
Cleaning the Air in an R-2000 Home
R-2000 homes are built to be extremely airtight. This limits the uncontrolled flow of air in and out of the home and greatly reduces heat loss and moisture damage to the building structure.
To complement this airtightness and ensure a healthy living environment, R- 2000 homes use a mechanical ventilation system to remove pollutants from the home by replacing stale indoor air with fresh outdoor air. These pollutants come from a wide range of sources – household contents and materials, people and their activities as well as family pets (see “Some Typical Household Pollutants”).
In most R-2000 homes, the preferred mechanical ventilation system is an HRV. This system allows fresh air to be distributed throughout the house. A properly installed, operated and maintained HRV exhausts indoor air pollutants and excess humidity to the outdoors while distributing fresh air throughout the house. During the heating season, the HRV captures heat from the outgoing air and uses it to preheat the incoming fresh air. During the air-conditioning season, an HRV can reverse this heat-exchange process, removing some of the heat from the incoming air and transferring it to the outgoing air.
Cleaning the Air in a Conventional Home
In recent years, more and more existing homes have undergone energy-efficiency improvements such as upgraded insulation, improved air sealing, the installation of energy-efficient windows, doors and heating systems, etc. As well, improved practices in new home construction have resulted in more energy-efficient and airtight conventional homes.
In many of these homes, air infiltration through doors, windows and other openings in the building shell is too random and does not always provide adequate ventilation, which is just as important in a conventional home as in an R-2000 home. Even when there is an acceptable rate of air exchange, the fresh air may not be getting to the rooms where it is needed. As a result, mechanical ventilation is needed in many conventional homes in order to evenly distribute fresh air throughout the home and maintain a healthy living environment. An added benefit of mechanical ventilation systems is their capability to filter the incoming fresh outdoor air.
What is an R-2000 home?R-2000 homes are the most energy-efficient and environmentally friendly homes on the market today. Built, tested and certified to exacting technical standards, R-2000 homes use up to 50 percent less energy than conventional homes. They feature
See "Need more information" to find out how to obtain information on R-2000 homes. |
Some Typical Household Pollutants
You can eliminate or reduce certain sources of indoor air pollution by understanding where household pollutants come from. However, no matter how careful you are, there will always be some pollutants in your home and, therefore, a need for ventilation.
Table 1 identifies the most common pollutants and their sources. Additional information on indoor air quality is available from the Canada Mortgage and Housing Corporation's Canadian Housing Information Centre at the address provided in the "Need more information" section.
Table 1
Common pollutants and their sources
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| Pollutant | Source |
| Excess moisture (humidity) and moulds | A crawl space with an exposed earth floor, people,clothes drying indoors, cooking and washing, plants, firewood stored indoors, etc. |
| Urea-formaldehyde | Some types of particle board, panelling, carpeting, furniture, textiles, etc. |
| Radon | Soil and ground water |
| Tobacco smoke | Smoking |
| Household chemicals | Cleaning products, certain hobby supplies, paints and solvents, aerosols, etc. |
| Odours, viruses, bacteria and dandruff | People and pets |
| Combustion by-products (including carbon monoxide, nitrogenoxides, carbon dioxide and particulates) | Fuel-burning appliances, including furnaces, heaters, range/ovens, gas clothes-dryers, fireplaces, wood stoves, etc.* |
| * CAUTION: Do not rely on an HRV to remove combustion by-products from your home or to supply the combustion air requirements of fuel-burning appliances. If combustion by-products are escaping into your home, either an appliance or its venting system are not operating properly and must be repaired immediately. Fuel-burning appliances should be installed to vent to the outdoors. Unvented fuel-burning appliances, such as barbecues, portable gas-fired or kerosene space heaters, unvented gas fireplaces, etc., are not recommended for use indoors. |
How Much Ventilation Does Your Home Need?
The capacity of a home's ventilation system is usually based on the number of rooms in the house. HRV capacity is measured in litres per second (L/s) or cubic feet per minute (cfm) of fresh air provided to the home.
Using the information in Table 2, you can calculate how much fresh air is needed under normal circumstances to maintain good air quality in your home.
Table 2
Fresh air requirements per room
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| Room | Ventilation Air Supply |
| Master bedroom | 10 L/s (20 cfm) |
| Unfinished basement | 10 L/s (20 cfm) |
| Other rooms | 5 L/s (10 cfm) each |
Based on these figures, a ten-room home (unfinished basement, living room, dining room, family room, kitchen, two bathrooms, a master bedroom, and two bedrooms) would require an HRV with a rated capacity of 60 L/s (120 cfm). To ensure adequate ventilation, the total ventilation capacity of the HRV at high speed should be close to this total (see “High-Speed Operation”). The suggested low speed HRV ventilation rate should be 40–60 percent of the high speed.
According to the standards used in Canada, a minimum ventilation rate of 7.5 L/s (15 cfm) is required for each person in the home in order to provide a level of indoor air quality that most people would find acceptable.
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Source: Natural Resources Canada (NRCan) - Office of Energy Efficiency