Mar 20, 2022 |
Ed Fryday, ACI, CMI® | TREC License: #6932

Are Exhaust Fans Really Important?

Yes, exhaust fans are important! Whether located in a bath, laundry area or at the cook top you really should use them. Exhaust fans are needed to remove warm moist air from the house. I the south Texas area we already have enough humidity!

We’ve almost all had the experience of getting out of a shower and finding the mirrors all fogged up. If you will notice, there will be water from condensation on many surfaces in the room at the same time. If your bath exhaust fan was operating properly most of that humid air would have been removed from the room and your mirror not so foggy or not foggy at all.

It is important that the exhaust fan actually vents to the exterior. You don’t want to put that warm moist air into the attic. There are other things in the attic that don’t like it also. The main one is you’re A/C system. When the A/C is running the air handler and ducts get cool and the moisture from the vented air can condense leaving wet areas in the attic. This is especially true where flexible A/C ducting is in contact with other ducts and or at supply air plenums that leak cold air or are not well insulated on the inside. Note: putting insulation between A/C duct does not stop the condensation. Air space between the ducts is what works.

According to Vince Hoechten of who is a Texas licensed mold assessor & consultant, when you allow condensation to form in your attic, you create an environment where mold begins to grow and can flourish. If your house does not have exhaust fans in wet areas, you will not have as big a problem. However, if you do have exhaust vans be sure they vent to the exterior.

Many homes have exhaust fan vents that terminate over soffit vents. This used to be standard procedure, but standards change for a reason. In this case it should be noted that soffit vents are intake vents, So, air from fan vents that terminate at soffit vents is just drawn back into the attic. Unfortunately, many homes have exhaust fans that just blow into the attic.

Exhaust fans in laundry and kitchen areas are important as well, though slightly less so than bathrooms.  Top load washers do not seal when the lid is closed so warm moist air get into the laundry room and should be exhausted out. Boiling water on the stove creates steam which should be exhausted to the outside.

Many older homes just don’t have any exhaust fans. They are not required by building standards in laundry areas or in bathrooms with openable windows. Range hood fans are not required to vent out. Many of them just recirculate through a filter.

If warm moist air is not exhausted to the exterior, it gets drawn into your A/C system through the return air. This introduces it directly to the A/C’s evaporator coil. Most of it turns into water as condensation in the coil but some of it will pass through the coil causing moisture buildup inside you’re A/C ducts which provides more opportunity for mildew or mold to grow.



Posted: Mar 20, 2022
Posted by: Ed Fryday, ACI, CMI® | TREC# 6932
ASHI# 250764 | InterNACHI# NACHI07031703
Space City Inspections, LLC
(281) 636-9419


Ed Fryday, ACI, CPI, CMI®

Ed Fryday, ACI, CPI, CMI®

Email: Contact Ed Fryday
Phone: (281) 636-9419
TREC License: #6932

ASHI Member ID# 250764
InterNACHI ID: NACHI07031703

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