By Tim Gould
When you first think about conserving energy and making the place you live more comfortable, it may be best to start by identifying your home's thermal boundary.
The thermal boundary, sometimes referred to as the thermal envelope, which restricts or slows the flow of heat, is a catch-all term for the parts of the home that separate the indoor areas that are heated and cooled (conditioned space) from the outdoors or any areas in your residence that are not heated or cooled (unconditioned space). Conditioned spaces are the living room, bedrooms, bathrooms, kitchen, etc. Besides the great outdoors, other unconditioned spaces are usually the attic, crawl spaces, unfinished basement and the garage.
Defining the thermal boundary seems easy at first, but when you begin to look at the many points where the boundary may be breached, it can become a challenge. Add to this that a home's air barrier—which is made up of any material that restricts air flow, such as sheathing, house wrap, and drywall—should be in alignment with the thermal barrier. Remember, most insulation such as fiberglass does not stop air movement. Without an aligned air barrier, fiberglass insulation provides little thermal benefit. An ideally insulated home will have fully aligned thermal and air barriers that are contiguous and continuous over the entire building—encapsulating the conditioned space, thus creating a good thermal envelope around your living area.
There are too many points to list here where breaks in the thermal and air barriers may be found. However a detailed guide and list can be found at www.energystar.gov by searching for "Thermal Bypass Checklist Guide" (look for a large 10.9 MB file, not just the smaller checklist). While the guide's intended use is to qualify Energy Star homes, it is a valuable resource that lists all potential problem areas and includes photos and diagrams clearly showing how to make improvements by sealing and insulating homes. It can be a useful tool for the homeowner to understand basic approaches to saving energy so that they can make improvements themselves or hire a contractor to do it for them.
Tim Gould is director of Energy Egghead, an Amesbury-based company that can be found at www.ENERGYEGGHEAD.COM and provides professional energy audit and conservation services.
