As homes have gotten tighter and tighter to conserve energy, we have created indoor air quality issues. Stale air can carry all kinds of particulate as well as allow for elevated carbon dioxide levels. Furnishings, pets, molds, dust mites and hundreds of other elements in the home can make for poor indoor air quality and affect the way we breathe and thus our over all health.
This post is about whole house ventilation and how we use it to improve indoor air quality in new and remodeled homes—often required in many jurisdictions and certainly in Washington State.
In some homes the whole house ventilation is achieved by integrating it with the furnace operation. With this approach air is pulled into the duct work by the furnace fan and distributed to the home through the duct-work the same way heat is distributed. This is a good way to do it because it results in fresh air being distributed evenly throughout the home.
Other homes have exhaust fans (perhaps laundry or bathroom exhaust fans) that pull the air into the home. In these homes there may be little vents in the window units that create an actual opening in the wall to pull air in. This picture shows the air intake at the top of the outside of the window.
There are other means of doing this as well, including HRV’s (Heat Recovery Ventilation units). These units have the ability to pull fresh air into the home while the outgoing air passes over the incoming air. The heat of the outgoing air transfers to the cooler incoming air reducing heat loss dramatically. These units are very effective and even required in some jurisdictions.
But back to this story.
I did a one year warranty inspection next door to a home that I had done a purchase inspection on. On the home of the one year warranty inspection I found the same defect that was on the other house—and the whole development may have been this way.
This first picture shows the duct-work of the air intake coming off the side of the furnace return air duct and the location of the electronic damper that shuts off the duct-work when the furnace is in heating mode.
This next picture shows the intake pipe termination at the roof. What is wrong in the picture? Note that the cap has a back draft damper in it.
This is not the correct cap. When the furnace is trying to pull in fresh air it is just pulling the damper tighter—-no fresh air is drawn in. A simple enough fix—-but not functional the way that it is.
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