The most common and natural way to ventilate older houses always has been with open windows and doors. But much of the time that isn't possible because the temperature is too warm or too cold outside -- and opening windows also will allow the heated or cooled air in the house to escape. In addition, there are security issues and concern about rain coming into the house. Dust, pollen, noise and insects (and larger creatures, such as mice) also can enter through open windows and doors. The new and optimal way to ventilate to create a modern, comfortable and healthy home is with a heat recovery ventilator (HRV) -- also known as an air-to-air heat exchanger -- or an energy recovery ventilator (ERV).
When new houses are built as tightly as recommended by the 2012 International Energy Conservation Code -- with a maximum of three air changes per hour at 50 Pascal (3ACH50) in most states -- there will be a shortage of fresh air in the house if the home is not ventilated properly. The results can include elevated carbon dioxide levels, diminished overall indoor air quality and potentially negative health consequences for the occupants.
How HRVs and ERVs Work
The HRV, or heat recovery ventilator, is an increasingly popular solution that can minimize energy loss and save on heating and cooling costs. The heated or cooled air already in the house is exchanged with fresh exterior air, while transferring some of the heat or coolness generated in the home to the incoming air.
An ERV, or energy recovery ventilator, functions in much the same way, but helps to control humidity. (ERVs are more often the ventilation choice in warm, humid climates.)