The Thermal Envelope and energy efficiency

Posted by Woodrow Aames ~ September 23, 2011

No matter where you live, one of the best ways to improve energy efficiency in your home is to secure or re-enforce your Thermal Envelope. The Thermal Envelope is the combined effect of your existing windows and doors, wall and roof assembly, weather-stripping, insulation and air retarders.

In short, every component of your home interior and exterior builds an envelope that separates your living space from the elements. Skimp on any of these factors or allow them to fall into disrepair, and you're adding to your year-round utility bills.

The Federal Citizen Information Center (FCIC) contends that insulation is a critical factor in securing the thermal envelope. You should strive, where possible, to install products with higher insulation R-values than those required to suit local building codes.

Consider that the insulation of foundations and slabs is also critical in putting a seal at the bottom of the residential envelope. Insulation beneath your heavily used appliances (washing machines, water heaters, HVAC) can bounce needed heat up into your home in the winter months.

There are simple home improvements to help you stay warm, and securing your windows is one of them. The FCIC reports that a typical home loses 25% of its heat through its windows. You can have an atypical home: install Energy Star-rated windows.

Create an air-tight envelope

Seal the air leaks in your home. Leak sealing alone can cut 50% of your utility costs. Planet Green recommends sealing your chimney, your attic, windows, doors and light fixtures.

Most homeowners ignore the gaps where lighting, electrical or plumbing passes into living spaces. If you can see a candle flicker in one of these gaps, you've got trouble. Get out the caulking gun or putty. Think of it this way: if you were to tally up the total square footage comprised of small leaks in the home, the gap can be tantamount to leaving an outside door open. Or, if you need a better description, imagine leaving a window open on a submarine.

A poorly sealed chimney can allow 14 percent of your warm air to escape routinely. In hot climates, an un-insulated attic can be a killer, especially in places like Tucson where roof temperatures can top 150 degrees.

For techies only

Want to better understand the thermodynamic aspects of the home protection envelope? Oberlin College has devoted an entire chapter of a textbook on solar energy to the subject. Learn how to calculate thermal resistances, heat flow and u-values, infiltration and energy loss. Take good notes!

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