We recently did some duct testing for some clients on a house built in the mid 60’s. As was normal for the time the house used the framing members to form HVAC chases for air supply and returns to the furnace. In 2000 the owners decided to update their old furnace with a new 90% efficiency one to increase comfort and live-ability along with reduce their heating costs. During our initial inspection we were unable to pressurize the houses ductwork to even 5pa using our high output fans.(5pa is about the force of a slow exhale).
Upon inspecting the crawlspace we were able to determine that along with having a 8” supply that was originally capped off with duct tape that had long ago failed and now vented directly into the crawlspace. There were multiple penetrations of plumbing and electrical through their pan ducts that when the system was turned on and we were in the crawlspace we could actually feel the air flow in the crawlspace through entire area.
While access is very limited and difficult for this type of work, the furnace is reduced to maybe 40% of its output going into conditioned space. The air return picking up any dust and insulation from the crawlspace and returning it back to the confines of the house. Imagine the dust and health concerns this would raise.

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We are premier builders for additions, remodeling and new construction for Corvallis and the Willamette Valley. We specialize in unique and challenging projects and apply sustainable building principles.

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644 NW 4th St. Corvallis, OR

Greg Christianson

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