How to Get the Fresh Air Exchange You Need in Your Home
Air exchange in Canadian homes has been a growing issue as codes require building tighter envelopes to prevent unwanted air leakage and save energy. Homes built in Ottawa prior to 1985 had relatively little resistance to air leakage. As a result, these homes were drafty with high, uncontrolled air exchange rates that made them uncomfortable and often very dry in winter. In our pursuit for energy efficiency, housing standards have led to home being built much tighter, restricting unintended air exchange through more effective air barriers and insulation. The new reality is that new homes built in Ottawa, as well as many older upgraded homes are so airtight that air exchange rates are less than what is considered healthy. Since 1990, the National and Ontario Building Codes require some method of mechanical ventilation, such as exhaust fans, an HRV or ERV to ensure an adequate air exchange rate to control levels of unhealthy contaminants. This is generally measured by Air Changes per Hour, or ACH.
What Does This Mean to You?
Signs of poor air exchange rates include a stale smell, odors tend linger a long time, and humidity tends to be higher than desired in fall and winter. Humidity can lead to problems with condensation on windows and in the structure of the home. In Ottawa, where we spend many hour indoors, ensuring you are getting the enough fresh air exchange in your home is even more important If you, or anyone in your family suffer from respiratory conditions, like asthma, bronchitis or chronic colds. Given the high cost of energy to heat a home in Ottawa, most of us are understandably reluctant to open windows or use exhaust fans to maintain an air exchange in the winter. Even opening windows or using exhaust fans may not provide sufficient air exchange to improve indoor air quality under all circumstances.
The use of a balances mechanical air exchanger, such a heat recovery ventilator (HRV), or an Energy Recovery Ventilator (ERV) will be much more effective. It is important to note that bath fans will exhaust air, creating a negative pressure on the home, which causes outside air to be pulled through small openings. This is a common method used in tract homes, and does meet older minimum codes. This method exhausts a great deal of heat energy, and is less than ideal in circulating fresh air throughout the home. Recently, there has been a trend in Ottawa where builders are more often opting to install heat recovery air exchange systems.
Recent changes in the Ontario Building Code (OBC) put more restrictions on energy efficiency, while increasing the incentives to installing heat recovery air exchange systems, like Heat Recovery Ventilators (HRV) and Energy Recovery Ventilators (ERV). These heat recovery air exchange systems recover as much as 95% of the heat in exhausted air, and transfers it to the incoming fresh air. HRV’s and ERV’s are balanced so the exact amount of air exhausted is also supplied to the home from outside, creating a balanced air exchange. This balanced air exchange ensures that there is neither a positive or negative pressure created in the home, resulting in a comfortable controlled home environment and a sound structure for years to come.
Below Zero Heating & Air Conditioning has been installing Heat Recovery Air Exchange Systems in Ottawa and surrounding communities since 1999. Whether a new home or a retrofit of an existing home around Ottawa, we have the expertise to provide the right advice and follow through with expert design, installation and service.
See here for a PDF publication from NRC Canada about Heat Recovery Ventilators