Posted on

Attic Frost! Insulate or ventilate

Picture shows gap around electical conduit that allows lighter-than air water vapor to rise up into attic
Picture shows gap around electical conduit that allows lighter-than air water vapor to rise up into attic
Gaps in top-plate of home’s walls allow vapor into the attic from the home’s humidifiers, cooking showers, and even the dog breathing.
Gap around electrical conduit pipe is caulked
I used silicone caulk to stop vapor from rising up into the attic

Why is there attic frost on my roof wood?

Take a quick look in your attic and you may find attic frost on the wood of your roof, especially on the north side where it’s colder. Humidity indoors is essential in the winter. For example, your house will feel warmer when the humidity is higher. In addition, you may find relief from a dry scratchy throat or avoid a common cold by having the right amount of humidity in the air of your home. Even your wood floors and furniture need humidity to prevent cracking.
Unfortunately, there is a hidden danger when the humidity is too high. Humidity or invisible water in gas form is lighter than air so it’s always trying to rise and get into your attic space. That’s why I have been jumping up and down about sealing your ceiling. I don’t know if that’s why they call them ceilings but here is pictures of what I’m talking about.That’s where humidity can start to cause a problem and why attic ventilation is so important. During the winter, the attic should be cold and ventilated for several reasons. If your attic is warmer than outside air, ice dams and leaking may occur. In addition, dangerous and damaging mold may grow as a result of ice dams and leaks in the attic or water vapor condensing forming wetness and attic frost. This may eventually cause structural damage to your home’s framing and feed dangerous mold.

Tip: Don’t  insulate or add more insulation until you stop up these gaps. Always add more ventilation with insulation because now your attic will be colder that ever and the same amount of rising water-vapor that may not have been a problem before can now condense and form frost. Added ventilation will keep your attic dryer by letting vapor escape. Sealing gaps will stop the source of the attic vapor. Bath fans that blow into the attic should be vented out through the roof using 4 inch round insulated duct and a roof damper with a screen  and flashing so all that hot humid air goes up and out and away from your house. (Not out through the soffit vents because the hot humid air just rises back up into the attic even if through other vents).

Attic Fan with humidistat helps, but there’s other problems that need attention first. I sell humidistats for attic fans but, don’t run out and buy a humidistat (even from me) until you have talked to me first.

Jeff Tideman,“Jet Fan Man”. FREE Consultation.
Phone 630-834-9165

You can buy my humidistat, but only if you promise to read the instructions first: