What is Infiltration?
According to
ENERGY STAR, air leaks in your home account for between 25% and 40% of your heating and cooling costs. Uncontrolled outside air entering into your home through holes and cracks in the building structure is known as infiltration. Positive air pressure generated from wind and other environmental factors coupled with negative air pressure generated from mechanical systems in the home such as ventilation fans, chimney and exhaust flues promote infiltration. Not only does infiltration substantially increase your heating and cooling bill, it may be responsible for moisture damage, insect incursion, and dirt entering your home.
All homes require some ventilation. Controlled ventilation is necessary to prevent moisture build up in attics and to remove odors and air pollutants from the living spaces of your home. Exhaust fans are a feature of well designed bathrooms and kitchens that provide for the removal of excessive moisture, unwanted odors and dangerous combustion gasses. Too little ventilation of a home can result in furnace and water heater backdrafting issues, illness and possibly even death. Professionals quantify ventilation in terms of Air Changes per Hour (ACH), or the number of times the volume of air inside your home exchanges with outside air.
Healthy homes should have no less than 1/3 of an ACH.Most of the older housing stock in western Pennsylvania is excessively leaky. Based on the hundreds of audits conducted throughout the years, CCI’s auditors say that they frequently encounter homes exchanging inside air with outside air
1 to 1-½ times every hour! All those holes in your home are sucking out more than air, they're sucking out dollars too! Clearly, there are immense opportunities in our housing stock to reduce infiltration and save energy and money, but the question is where and how?
Where is Infiltration Occurring and What Do I Do About It?
By far, the easiest and most effective time to address infiltration is while a home is being constructed. Proper air sealing during construction pays for itself year after year in energy savings and improved comfort.
Unfortunately, for most of us this is not an option. We need to seal the home we're in. The following are a few of the most common areas where air leakage occurs in most homes:
- Around windows and doors
- Attic hatches and doorways
- Fireplaces
- Foundation to building framing attachment
- Recessed ceiling lights that penetrate into your attic
- Unsealed access to coal cellars
- Wiring and plumbing penetrations
If you can see daylight or feel a draft around the areas identified above, you've found a source of infiltration. Spider webs can also offer a clue to infiltration sources. Spiders know that where there is a draft, there is a hole and where there is a hole, there is a bug entering your home.
Energy auditors use a device called a blower door to assess the tightness of a home. While in operation, the blower door creates a partial vacuum which is used to scientifically measure the level of infiltration in your home. Since the home is under a higher vacuum than would ever occur naturally, the blower door affords the auditor opportunities to seek out and identify the most concerning sources of infiltration specific to your home. A blower door can also identify when your home is too tight and requires supplemental ventilation for combustion appliances to work properly.
How Do I Stop Infiltration?
For small cracks and holes around windows and doors, use long-lasting caulk. Although somewhat more expensive, silicone caulk remains flexible and stays intact over time. A downsize of most silicone caulks is that they cannot be painted.
For larger holes typically present around plumbing and electrical penetrations, use expandable spray foam. Remember, that a little foam goes a long way and that it expands before hardening.
Install thresholds and door sweeps to slow the drafts that occur below doors. For the sides and top of doors, install vinyl covered weatherstripping. Vinyl weatherstripping tends to be a bit more expensive, but it holds up well in regular use and is resistant to moisture damage.
Two-inch thick rigid foamboard pressed into the band joists above your foundation and caulked in place provide an excellent air sealing solution to prevent air seeping into your basement.
When your fireplace is not in use, make certain that your damper is closed tightly. Inflatable chimney balloons are available that fit beneath your damper during periods of non-use. They are made from durable plastic and can be easily deflated and removed when you want to use the fireplace then re-inflated after the fireplace has cooled down.