Importance of Makeup Air System

First of all, this has nothing to do with cosmetics or romantic relations. Having said that, you’ll notice that I include the word romantic with relationships because it does very much have to do with a particular type of relationship.

Most notably, between that of combustion within a furnace (particularly), the forced air type is found in most homes as opposed to hot water or steam heat, as found in many homes in the United States. In my handyman experience, I have done a few maintenance tasks to furnaces within the scope of minor home repair issues.

Why am I writing about something called “Makeup Air,” and why should you care. The primary reason for caring about “makeup air” is to eliminate drafts of cold air coming into your home uncontrolled. You may have a handyman service like mine to do weatherstripping of doors and windows. I have put plastic on windows and applied caulking to close gaps in the outside structure of a home.

One thing that is overlooked is whether the furnace is getting enough combustion air because if it isn’t, it’s going to pull it from your doors and windows, even your fireplace (if you have one), causing drafts. This kind of uncontrolled cold air flow contributes to making your home uncomfortable.

In terms of makeup air for your furnace, this is accomplished by using a duct that comes in from a basement wall or window (easiest) to just in front or to the side of the furnace a few inches above the floor. This is to supply the furnace combustion chamber with all the fresh air it needs so that it doesn’t draw it from the rest of the house, creating uncomfortable drafts.

This combustion air supply is usually provided by most high-efficiency furnaces. However, it is still important to make sure that it is not blocked by snow outside or anything else. With most high-efficiency furnaces use a large PVC pipe. If you don’t have a high-efficiency furnace, you mostly don’t have this makeup air inlet.

Check this pipe on the outside of your home where it may penetrate your basement wall. I have seen (while doing other handyman work) where this pipe is not effectively sealed into the surrounding wall creating a passageway for critters to enter your home.

There is another part to this “makeup air” scenario, and that is mainly high-power kitchen range hoods that draw 400 cubic feet per minute of your homes inside air to the outside. Some can draw. I’ve learned as much as 1,200 cfm.

Building code M.1503.4 requires that a range hood that draws out more than 4oo cfm must have a Makeup Air inlet synchronized with the operation of the exhaust hood. In other words, additional ductwork must open to supply fresh air whenever the exhaust hood is switched on.

Don’t forget you also have bathroom vent fans –which should be on a timer–the switch can also contribute to this vacuum condition, especially if the range hood or furnace or both are on at the same time.  

As a handyman service, I will install a timer switch for the bathroom vent fan, service the bathroom vent fan, and check any wall penetrations in the basement to make sure they are properly sealed. I don’t install a makeup air inlet to work together with a range hood–which would require a heating and cooling contractor.

My business model and the law keeps my work generally within the range of carpentry, drywall, concrete patching, some types of cleaning, and very minor plumbing and electrical work. Feel free to contact me at any time for these services.

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About the author
Ben White has written thousands of articles on everything home improvement. He has had the privilege of writing for such websites as the Huffington Post, DeWalt,, HGTV, and many others.

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