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Don’t put a V-8 in your Vespa

Would anyone think it’s wise to put a V-8 engine in a Vespa scooter? Well, I can think of some suicidal television talent that might think that was cool. With the famous last words -- “Watch this!” -- they would ride into oblivion. But, most of us aren’t showing off for the camera. 

We’re more or less rational, so applying unnecessary power to a problem seems wasteful. But that’s standard practice for most new homes built with forced air systems. With today’s modern energy standards, a forced air furnace is typically oversized. For example, a new, 2200 sq. ft. home built to the current Northwest ENERGY STAR (2008) standard would have a design heat load of about 28,000 btu/hr. That’s the amount of heating capacity needed to keep the house comfortable in the coldest expected conditions for western Oregon and east of the Cascades. 

Here’s the interesting part. The smallest gas furnace currently made has a heating capacity of 40,000 btu/hr. So, it’s impossible to buy a properly sized gas furnace.

The heating load of modern homes in the Pacific Northwest has been dropping rapidly, because builders are installing more insulation and more efficient equipment. They are also sealing homes against drafts. And the newest trend is to install all heating and cooling equipment, including all ductwork, inside the buildings conditioned space. In addition, the size of new homes is dropping.

The result is lower heating and cooling needs, which should translate into smaller heating and cooling equipment. Smaller equipment should cost less and save home buyers money, although it may not be a lot. Manufacturers of heating equipment could recognize this emerging market and develop products with lower output capacity.

To get a better match between heating system size and heating need, some builders are moving away from central, forced air systems altogether. Instead, they are installing furnace-rated fireplaces and gas unit heaters or ductless heat pumps. Both these approaches have proven themselves to keep modern homes comfortable with smaller equipment and less energy waste. 

About the Author

Bruce Sullivan

Bruce Sullivan is the New Homes Outreach Program Manager and Green Building Consultant in Central Oregon for Earth Advantage Institute. He has been involved in energy efficient construction since 1983. He has worked for the Oregon State University Extension Service, Eugene Water & Electric Board and Iris Communications, Inc. In 1996, he established Oikos.com one of the world’s first web sites dedicated to green building. In 2006, Bruce’s personal high-performance residence, built by SunTerra Homes, was honored with the NAHB Research Center’s EnergyValue Housing Award and the NAHB Green Building Award. Bruce is based in Earth Advantage’s Bend office.