Green Homes—Sealing & Insulation

Photo: newswatch.nationalgeographic.com

When your thoughts turn to energy efficiency and comfort, you may start thinking about new windows, a furnace, or an air conditioner. Experts suggest you take a step back. According to Energy Star, a national program from the federal Environmental Protection Agency and the Department of Energy, your most cost-effective move would be to first seal and insulate your home properly.

Assess the Problem
Start with a home energy audit, which can run from $200 to $400. While some homeowners may prefer to seek out leaks themselves, having a skilled set of eyes is almost more valuable than the specialized tests a professional auditor can perform.

Doug Maas, owner of A Closer Look Homes Inspections Inc. in Hortonville, WI, has audited hundreds of homes as a certified consultant under Wisconsin’s Focus on Energy program. He says each home has its unique problems. However, typically an audit might reveal homes that are leaky because energy conservation was not part of the construction process when fuel was cheaper. An audit might uncover a leaky home because improvement projects were incorrectly handled. Also, many homes were just not built to be as efficient as possible.

For Maas, a typical audit includes a blower door test, use of an infrared camera, a check for proper venting of combustion units such as a furnace or water heater, and inspection of insulation. His investigation also covers those areas that experience has taught him are likely to be typical air leak sites such as electrical outlets and where utility lines penetrate the house.

The blower door test involves a fan and measuring device in a doorway framework. The setup depressurizes the house and measures, in cubic feet per minute, the outside air drawn in through unsealed cracks and crevices.

An infrared camera reveals dark areas that identify where cold is penetrating the home envelope—typically basement walls and attic hatches, among other areas.

After homes have been sealed and insulated, an audit can also check to make sure mechanical equipment is venting properly. First the home is depressurized to a particular level by turning on all exhaust fans and shutting all doors and windows. Then a monitor is used to detect whether deadly carbon monoxide gas is being pulled into the home through any chimney backdrafts.

Follow Audit Advice
An auditor will list areas for potential improvements. Many homeowners can tackle the caulking, foaming and weatherstripping. However, depending on improvements needed, they may want to hire professionals for the insulation.

Sites to air seal are typically on the inside and will stop not only air infiltration but indoor humidity from getting into walls. Exterior sealing is more for keeping rain out of the walls than air leakage. Audit suggestions will be specific to your home. For example, one recent audit of an old home suggested that the owner seal: joints between outlet boxes and drywall; exterior wall penetrations such as the gas line, electrical entrance and dryer vents; and penetrations into the attic such as electrical boxes, wire and plumbing chases. Weatherstripping is suggested for attic hatches and doors.

An auditor will point out areas where insulation has been inappropriately installed or is insufficient. Getting the proper amounts in the right places will block heat loss in winter and heat gain in summer and keep a home envelope healthier. That same audit suggested that owners insulate an attic to an R-value of 40 to 44 with blown-in cellulose or fiberglass, secure rigid foam to the attic side of all attic hatches and insulate side wall cavities where infrared images revealed blown-in product had settled.

Air Leaks: What’s Your Number?
If you’re one of those homeowners who wants to get an idea of where you stand before hiring an auditor, the U.S. Department of Energy suggests this approach:

• Pick a cool, very windy day.
• Turn off your furnace.
• Shut all windows and doors.
• Turn on all exhaust fans that blow air outside, such as bathroom fans, to depressurize your home.
• Light an incense stick.
• Pass it around the edges of common leaks such as recessed lights, attic hatches, mail chutes, door frames, electrical outlets and switches.
• Watch the smoke trail. If it is sucked out of or blown into the room, there’s an air leak that may need caulking, sealing, or weatherstripping.

Here’s a rough rating of air “leakiness” for homes and typical amounts seen in the experiences of Maas. CFM numbers will vary greatly depending on the square footage of the home, he says.

CFM Ratings

• 500 cfm or less—Excellent
• 500-1000 cfm—Good
• 1000-1500 cfm—Fair
• 1500 or more cfm—Poor

Typical CFM data

• An old farmhouse: 4500 to 6500 cfm
• A three-bedroom ranch built in the 1980s: 1800-3500 cfm
• Average home today by builder not aiming for energy efficiency: 1500 cfm or more
• Homes built today for energy efficiency: less than 500 cfm