I really enjoy and benefit from reading posts about maintaining a property. This home inspector does a fine job of discussing the importance of allowing a home to have some balance and not be air tight.
Modern houses are "tighter" than older ones. There are vapor "wraps," like Tyvek, Amoco, and those with builder logos on them, that is a plastic that allows vapor and moisture out of the house, but wind and moisture cannot easily get in. There are better windows now, far tighter than they used to be. Doors have great seals. There is more insulation in the walls and attic space. All this combines to prevent air movement into and out of a house.
Overall houses are "tighter." And BALANCE is important. A balanced air-flow into and out of a house leads to one that is more healthful, has less indoor air pollution and creates a good positive/negative balance of air pressure.
Over the years I have contacted Dr. Max H. Sherman when I have had questions. He works for the Lawrence Berkeley Labs and helps develops the standards from which ASHRAE (American Society of Heating, Refrigeration and Air Conditioning Engineers) creates its recommendations for everything from appliance manufacture, efficiencies and installation, to the eventual codes on such. He has always been gracious in getting back to me with answers to my questions. He did a lot for me when I was researching information for this blog.
Dr. Sherman has an excellent article about how and why houses need to breathe, published on the web here:
It is instructive and informative and well worth the read. Home inspectors might want to bookmark it.
So, when I see something like the photo on the right, I know what it is for.
It is the builder's attempt to create balance. That is an air intake for the furnace.
It has its downfalls. It can introduce as much as 2 gallons of water into the house just from outdoor humidity! In humid climates this much humidity needs to be tempered mechanically. Dr. Sherman discusses that above.
It can also introduce temperature extremes, obviously, which need to be handled as well.
But it is a valid attempt to balance the house! However, I always check these intakes.
Why? Because they are drawing in air. This house is 15 years old. That means this intake has been drawing in air for a long time.
Air is dusty! The intake can clog! That blocks air flow.
Wasps are famous for building nests in protected spots. I have seen huge wasp nests inside these. That can also block air flow.
Wanting to demonstrate this potential in photo I negotiated rose bushes and a small cypress to get my ladder into position for this shot! Stretching I almost centered the clogged vent cover in the picture, and this was my third attempt!
So, at risk of suggesting YET ANOTHER THING TO PAY ATTENTION TO ON YOUR HOUSE, may I suggest that you check annually to insure that your air intake, should you even have one, is not blocked.
My recommendation: this all seems like a minor point to make. It is not! Balance is important when houses are tight. It is best to have healthful conditions inside in terms of fresh air, humidity and air pollution. Also there should be positive/negative air pressure differences that are tempered when bath and kitchen vents are run! Check on it! You will be glad you did.
Jay Markanich Real Estate Inspections, LLC
Based in Bristow, serving all of Northern Virginia