The primary functions of your home’s attic are to reinforce your roof and to help regulate the interior temperature of your home. In most cases, a home’s attic is out of sight, thereby causing it to be out of mind. However, this mentality is problematic when it comes to attic frost. While frost in itself isn’t hazardous, the eventual thawing of the frost can cause significant damage to your home’s insulation and lead to mold formation, water stained ceilings and compromised roof sheathing.
Working with a reliable contractor that understands your home’s building envelope is critical step to preventing attic frost. Humidity is the biggest contributor to attic frost formation and there are several ways a home’s level of humidity can unknowingly become too high.
Kitchen Exhaust Fan Issues: Kitchen exhaust fans that recirculate the air throughout a room instead of expelling it outdoors can cause a home’s level of humidity to be higher than it should be. The same is true of failure to turn on a fan while a home’s range is in use.
Inadequate Attic Air Sealing: Lack of attic air sealing also allows frost to form, as warm air penetrating into the attic causes moisture to condense on chilly surfaces.
Full Home Humidity Systems: Houses with full home humidity systems are at risk for attic frost if the home’s level of humidity is excessive.
Missing or Incorrectly Installed Bath Fans: Fans that vent to a roof vent or into the attic itself introduce excess humidity into the space. Failing to run a bath fan for an extended period after a shower can also elevate home humidity levels too high, leading to frost formation. When the humidity meets cold air within the attic, frost is formed. Construction code does not dictate the installation of a bath fan in a bathroom with a working exterior window. However, failure to have one installed can raise your home’s humidity to an unhealthy level.
Basement Vapor Barrier Issues: Homes built without sheeting to curtail the manifestation of moisture intrusion in basement walls will not only make a basement or crawl space colder, but it will also allow excess moisture to be introduced into the interior of the home.
The Stack Effect & Attic Frost Formation
In the winter months, the stack effect causes outside air to be drawn in through gaps in your basement and then redirected up your home’s walls to the attic. It exits the attic through areas that have not been fully sealed off, but not before causing frost to form due to the temperature disparity. Attic air sealing in conjunction with proper levels of insulation will prevent air from escaping the home. When this happens, moisture condenses on cold surfaces, ultimately resulting in attic frost formation.
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