An energy audit can determine the best place to seal your home, so that there is no warm air leaking out during winters, or in during summers. This is also called sealing the building’s thermal boundary or thermal envelope (Harley, 2012). Locations within the boundary are called ‘conditioned’ and any parts of the house outside the boundary are ‘unconditioned’. In addition to reducing fuel and electric bills, sealing your home envelope can also reduce cold or hot spots, drafts, noise, and moisture on windows, and discover health issues related to mold and excessive dust.
An energy audit process uses a blower door to blow air out of the home; then any air leaking in is found as a source of wind you can feel. In addition, a thermal camera can show hot and cold spots in your home, which may indicate where additional insulation is required. The audit leaves you with a report, indicating useful fixes. Auditors are expert advisors for evaluating home energy changes, such as recommending ways to ensure condensation does not form on colder surfaces in a home (exterior walls or protrusions), which may enable mold to develop. One good place to find an expert for home performance assessment is through Energy Star.
Heat rising in a house is due to the ‘stack effect’ (Amann et al. 2012). Generally cooler air leaks into a house at lower levels of the house and rises as it heats to higher levels of the home, also concentrating to higher pressures. This high pressure warmer air then tries to escape to the cooler, low pressure air outside air, at the top of the house. So leaks at the bottom of the house let cold air in and leaks at the top of the house let warm air out.
In addition to the temperature gains or losses, humidity is a concern for homes. Moisture can cause mold and mildew can aggravate allergies and asthma. Moisture can in addition rust metals, age wood products and increase off-gassing of toxins in furniture and carpeting (Amann et al., 2012). When sealing a home envelope, it is important to monitor and control humidity levels in the home, by using exhaust fans in bathroom and kitchens to whisk away excess steam from showers and cooking, as well as by controlling basement leaks and rain penetration. It is easier to eliminate or reduce humidity and toxic gases at their source, rather than after they have been dispersed throughout the home.
Older homes were built to allow fresh air into the attic to discourage mold; it also made heating these homes an expensive effort. Insulation is like a warm sweater, but does not serve as a wind break. Therefore, cold air blows directly through simple insulation. Two solutions include:
- Sealing below an attic or within the attic: This allows air to penetrate the attic but not the rest of the home.
- Sealing the attic roof. We sealed the house by filling plastic bags with loose insulation and stuffing the bags into the uninsulated rafters. Then we covered the lower, missing ceiling with pink insulation board, as shown below. Now, to cool the house, we open windows and ensure that any moisture in the air is whisked away using bathroom or kitchen fans.
Insulating Pipes or Ducts: Often radiator pipes or HVAC (i.e., heating, ventilation and air conditioning) ducts go through uninsulated or crawl-space storage attics. This is a waste of heating/cooling and is dangerous when radiator pipes are exposed to freezing temperatures! Experts (Harley, 2012)(Amann et al., 2012) recommend using insulation to cover pipes (shown above) or ducts (shown below). Radiator pipes can be covered in foam (1/2 inch thick) or fiberglass (3/4 inch) pipe insulation. For the radiator pipes above, the pipe insulation did not hold well over time (particularly as we periodically accessed our storage) so we taped over the slit with silver duct tape. Know that if your pipes already have insulation coverage, it may be asbestos – do not touch (Harley, 2012).
For HVAC air ducts, be sure to seal accessible ducts first. Duct seams are estimated to lose up to 20% of air flow (Amann et al., 2012), which may allow dust and other allergens to enter your home. Seams should be sealed from the outside using mastic compound (preferably) or UL-181b duct tape (shown below). Other duct tapes will dry out and not last. Mastic can be applied with a paint brush, caulk gun, or cotton gloves. Aeroseal is a product professionals can use to clean and seal ducts from inside the duct system.
After sealing ducts, insulate any in unconditioned space. Experts (Harley, 2012) (Amann, 2012) recommend insulating with a foil- or vinyl-faced fiberglass wrap at R-6 or better. In attics, increase the R-value to R-8 or R-10.
Benefits: Colder or drafty rooms become more comfortable and reduce energy costs. Other benefits:
- Lower heating costs!
- Radiator gets HOT water
- Reduced risk of radiator pipes freezing
- Sealing of house envelope
- No cold air flowing through attic in winter
- More comfortable attic in winter
Sealing Basement: In an older home, sometimes there is a space between the brick or outer wall, and the inner walls. This can be observed in the basement, looking up, where the basement ceiling meets the edge of the wall. We would not have found this or our attic issues without an energy inspection. To fix, we again filled plastic bags with insulation and stuck them up the holes to both seal (plastic) and insulate (using insulation).
Benefits: a warmer basement in winter; a cooler basement in summer!
Checking Recessed Lights: Recessed lights can also be a significant leak. In our case, wind came through outdoor vents directly through the recessed lights. Using the advice of an energy auditor, we sealed the outdoor vents, insulated that part of the attic roof and the upstairs temperature became much more stable. Of course, using well-working bathroom fans for at least 20 minutes after baths and showers is very important to reduce moisture!
References
- Harley, Bruce (2012) Insulate and Weatherize for Energy Efficiency at Home. The Taunton Press, Newtown CT.
- Amann, Jennifer Thorne, Wilson, Alex, and Ackerly, Katie (2012) Consumer Guide to Home Energy Savings, 10th edition. New Society Publishers, Gabriola Island, BC Canada.