Re: Furnace cold air return damper
I also live in Southwest Washington, and I'm reasonably familiar with construction practices here.
This is a fresh-air intake into the cold air return, and local building codes require it. Your furnace may have a timer that causes it to run the blower periodically. The purpose of this is to bring fresh outside air into the home to promote a healthy indoor environment. Some of these intakes are equipped with a motorized damper that opens only when the fresh-air timer calls for it.
In some parts of the country, these fresh air intakes are coupled with a "recovery heat exchanger" to prevent the loss of energy. Since this is a fairly moderate climate (typically 32-85 degrees F with rare extremes getting into the teens or just over 100), recovery heat exchangers are not common.
Feel free to contact the builder of your home or the furnace installer if you need help understanding it. Most of the major builders here would be happy to send someone out to your home at no charge (if they built it), even if you're not the first owner.
Last edited by Fencepost; 02-06-2013 at 01:46 PM.
The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.