As we transition from winter to spring, our thoughts turn to opening up the house to fresh air. But air sealing and proper ventilation are important year ‘round. We'll cover the basics, some common issues, and methods to make your home more comfortable and efficient.
Air sealing and ventilation – the movement of air through your home – are intimately connected. Ventilation can be either controlled or “natural.” Natural ventilation is called infiltration. This is the air that comes through a drafty window, under the door, or through a receptacle or light switch on an exterior wall. Unless you are building a super-efficient new house, there will always be gaps and cracks for infiltration.
While for decades builders thought infiltration was beneficial, numerous studies have demonstrated that the more air-tight a house is the more durable and comfortable it is.
Why? As air is pushed out of your house by your vent hood, clothes dryer, or bathroom fan, outside air seeps in to replace it. If you have a leaky basement window, that will be one source of this “make-up” air. So if it's winter, you are bringing in very cold and dry air. When it meets the warm and humid air in your basement it could lead to condensation around the windows, on the wall, or inside your wall – a common source of mold. Plus your furnace uses energy to heat it.
Likewise in the summer you are replacing cooler and less humid air with warm and more humid air. This will again lead to condensation and increased energy use.
You can address many infiltration issues with air sealing. Many of the most common gaps are accessible: around windows, doors, and such places as where your foundation meets the first floor exterior walls if your basement ceiling is unfinished (the “rim joist.”) In these places you can use high quality sealants, weather stripping, and insulation.
Insulating the rim joist costs only a few dollars at a home improvement store: a roll of batt insulation (unfaced fiberglass), a can of spray foam, and a piece of rigid insulation (usually pink or green). Using gloves and eye protection, simply cut a piece of the rigid insulation to fit between your joists, seal around it with the spray foam, and then cut a piece of the fiberglass to fit snugly in the space (don’t compress it, that actually lessens the effectiveness), then cut a piece of the rigid insulation to fit between your joists snugly to close off where you just put the insulation. Use the spray foam around the edges to fill the gaps and glue the rigid insulation in place. This easy and inexpensive method is very effective and you can do it in a weekend afternoon. Alternatively you can have an insulation contractor do this work, including using closed-cell spray foam on your rim joist for an even better seal.
Bathroom fans are another area that can be easy to overlook but play an important part in the health of your home. Every bathroom (even powder rooms) should have a fan – and that fan MUST exhaust to the outside. Go up to your attic (or have your heating technician do it) and make sure the bathroom fans have a duct that goes either out the roof or out an exterior side wall. If the fan simply vents into your attic, have the heating technician correct this. You are dumping warm moist air into a cold dry (in the winter) environment, which can lead to condensation, mold, and rot.
The other important role a bath fan can play is to meet the code minimum ventilation requirements. This standard has a minimum ventilation rate (expressed in cubic feet per minute or cfm) based on the number of bedrooms and square feet of the home. For example, a house that is 2,000 square feet and three bedrooms requires a minimum constant ventilation rate of 120 cfm. A typical bath fan ranges from less than 80 cfm to more than 130 cfm, so this means you should have at least one fan running continuously. The idea is that contaminants, such as CO2 and the gasses from carpets, glues, and products you bring into your home, should be expelled and replaced with fresh outside air.
Of course if you have an older home without any bath fans, you should seriously consider having a heating/air conditioning company install them. However, there is a modern alternative that’s even better: a small box known as an ERV, or Energy Recovery Ventilator.
Used for decades in commercial buildings, the growing popularity of the Passive House building standard has brought the ERV to homes. Any house will benefit from an ERV as it brings in controlled ventilation and captures the heat from the air being exhausted. This makes them energy-efficient while supplying your home with filtered fresh air 24/7.
While an ERV with dedicated ductwork is the best solution, that’s not always possible in an older home. However, you can add one to your existing forced-air furnace or ducted air conditioning system. If you have a boiler and radiators and no air conditioning, you can add one along with a small duct air conditioning system that most heating/air conditioning companies that service Shaker Heights are experts in installing.