Do I need ventilation for my finished basement? 

Building across Worcester County & Metrowest since 2016

So you are getting ready to make the big move and add more space for your family to enjoy but you don’t know the first thing about “meeting code”. Sure, you could wing it and hope for the best but hiring a professional that knows what is expected can really save you a lot of money and avoid costly surprises.

You also want to make sure your family is breathing clean air once the basement is finished. Basements are known for being moldy, damp and humid. Todays homes when not properly ventilated are 4 to 5x worse in air quality than the exterior. Finishing them without the proper ventilation can be asking for trouble and worse, poor breathing air for yourself, friends or family. 

When it comes time to finishing your basement, ask your contractor “what does my basement need for ventilation”? Chances are, if your basement is below grade,(like many are here in New England)those small Hopper windows are just not enough to make sure you are breathing clean air.

Chapter 3 of the IRC (International Residential Code) and M1505 (Mechanical code) states that your window openings need to equal 4% of your finished floor space.

So for simple math….

100 sq foot room x 4%= 4 square feet of net opening for ventilation.


1000 square foot basement x 4%= 40 square feet of net opening

Quite often, this can’t be achieved in a below grade basement and some walk out basements. Mechanical ventilation may be a good idea if this is the case. A product we use quite often is, Panasonic’s Whisper ERV. Operating at a 20/40 cfm (barely audible) this fan is designed to exhaust old air out while bringing fresh air in ensuring that you are always having fresh air to breath. The Panasonic also does a fair job decreasing the humidity of air that is brought in by about 40%. That means when it’s muggy out you aren’t bringing a lot of that in as a result of running it.

Typical installation cost will range between 2000-3500 to have installed depending on your area.

If you need more information please reference the video above. Please be sure to check out these resources for your next basement remodel!


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