Q: This past year, I have made my house more airtight, but the indoor air often feels and smells stale. What are my best options for bringing in some fresh outdoor air?
A: When tightening up a house to save energy, pollutants can build up and create unpleasant and sometimes unhealthy stale air issues. A warm spring day is a great time to open the windows to let fresh air indoors. But it is smart to plan for the upcoming summer when opening windows is not an efficient way to ventilate your house — especially when you are running your air conditioner.
There are four basic mechanical methods to introduce fresh air into your house. The simplest is an exhaust-only system. This often uses a central ducted vent fan to depressurize the house. This draws fresh air in through gaps and leaks in the house exterior. Passive inlet vents can be installed in an airtight house. This is the least expensive system to install. This works well in arid Colorado, especially during summer. Its drawback is the fresh air may not be distributed evenly throughout the house. It will increase utility bills slightly and may cause chilly drafts during winter.
A supply-only system uses ducted fresh air fans to create a positive pressure indoors. This forces the stale air out through cracks in the exterior. It is simple and inexpensive to install like an exhaust-only system. Its primary advantage is the incoming air can be filtered, and it provides better control over the fresh air flow.
A balanced system uses a combination of ducted supply- and exhaust-only systems. This provides better control of the ventilation because it does not rely on just cracks or leaks in the house exterior. It costs more to install because it requires two ducted systems. It uses more electricity because it runs two sets of fans.
A heat recovery ventilation system is the most efficient and expensive balanced system, typically costing $1,000 to $2,000. During winter, heat from the stale outgoing warm air is transferred to the incoming cold, fresh air. During summer, the stale outgoing cold air precools the incoming hot outdoor fresh air. Up to 75% of the energy in the air can be saved.
An HRV system is simple and has a heat exchanger inside a cabinet and two separate blowers, one for incoming air and one for outgoing air. The HRV has its own duct system, usually drawing stale indoor air from bathrooms and the kitchen. The incoming fresh air ducts often lead to the main living spaces and hallways.
Consult a professional HVAC company for any of these options.
If adding one of these mechanical systems is not in your budget, open the windows on nice days and air out the house.
James Dulley is a freelance writer and a DIY enthusiast who helps homeowners and businesses save money on their utility bills.
