Cut Carbon : Weatherize Your Home

Programs in addition to the town-sponsored Green Homes Brookline include:

• NSTAR at www.NstarOnline.com
• National Grid at www.nationalgridus.com/masselectric
• MassSAVE at www.masssave.com
• Visit the Department of Energy's web site at www.EERE.Energy.gov for additional tips
• Find a locally-based building professional to work with you

Some Background: Air Leaks VS. Insulation

Sealing air leaks with caulk, spray foam, or weather stripping will have a great impact on reducing utility bills – even as much as 30%. Many homeowners automatically assume that insulation is the answer to reduce heating costs. But in most homes air leakage is the biggest robber of heating dollars.

Houses leak air because of the difference between indoor and outdoor air pressure. The biggest pressure differences are high and low in a building – in attics and basements. Warm air rises and leaks out any unsealed areas at the top of the building. Leaks inward tend to be at the bottom of the structure, pulling in cool air.

Many air leaks and drafts are easy to find because they are easy to feel – like those around windows and doors. But holes hidden in attics, basements, and crawlspaces are usually bigger problems. If you added all the small leaks together, it might amount to a hole as big as a football – that would be worth fixing, wouldn't it?

THREE STEPS TO FIX AIR LEAKS

Step One: Finding Air Leaks

A blower door is used to both find and measure air leakage. The blower door test places a home under a known pressure and then measures how much airflow is required to maintain the pressure difference between indoors and outdoors. The tighter the house, the less air the blower door must move to maintain a given pressure. Besides measuring the airtightness of the house, it also helps to pinpoint specific air leaks.

To conduct a blower door test, technicians close all openings within the heated area of the house. They then seal a special, powerful fan within an exterior-door opening. The fan pulls air from the house. Gauges measure the difference between indoor and outdoor air pressures, as well as the air flow through the fan. The technicians adjust the fan to maintain a constant pressure differential and take readings, which they use to calculate the leakage rate.

During the test, outdoor pressure forces air through openings in the building envelope. It is easy to feel these leaks with bare hands. The technicians may also use squeeze bottles containing a chemical that combines with air to produce a puff of smoke. Leaks are unmistakable. The technicians record the exact locations of problem areas and give a report to the homeowner. This report will be very useful in the next stage of the process.

Step Two: Fixing Air Leaks

The homeowner or contractor seals the identified leaks with materials that include foam, acrylic adhesive tape commonly used to tape air barriers, acoustical sealant, polyurethane caulk, polyethylene sheet, and rigid foam.

Typical attic culprits include kneewalls, the attic access, soffits, bulkheads and dropped ceilings, chimneys and plumbing vent stacks.

Basement culprits are rim joists and utility penetrations, including dryer vents and utility pipes.

Step Three: Verifying the Fix

The final phase is verification. After leaks are sealed, the blower door test can be repeated to measure improvement on the airtightness of the home. It may point out an area or two that needs more sealing, or it may confirm that the job has been done well.

Homeowners are often concerned about sealing their house too tightly; however, this is very unlikely in most older homes. A certain amount of fresh air is needed for good indoor air quality and there are specifications that set the minimum amount of fresh air needed for a house. After any home sealing project, have a heating and cooling technician check to make sure that your furnace, water heater, and dryer are venting properly.