How to deal with frost in the attic

When you see water stains on the ceiling of your second floor, and find frost in your attic, normally on the bottom of the roof board, the leaking is not from the roof, it is from inside of your house. Today we are going to find out how to fix this problem.


In winter, most of the time outside temperature is going down below zero, attic containing higher moisture will generate condensate water on the roofing nail point, which penetrates the roof board, then the bottom of the roof board also becomes wet, eventually frost generates on them.


So how can we fix this problem?

We must find out Where the moisture comes from? Basically moisture comes from the roof and inside of the house. so what can we do to stop or reduce moisture brought to the attic.

  1. Turn down the humidifier setting of your house

This method is quite straightforward. you can adjust the setting of the controller of the humidifier. While too low humidity will bring other issues to your health, such as itchy skin, dry eyes, nosebleeds, sore throats and more, you need to consider these issues when adjusting the humidity setting.

  1. Block the moisture leaking from outside and inside of house

It is highly unusual for there being enough moisture in ambient winter air to form condensation (frost) on the underside of the roof deck in winter.


1) outside leak

Moisture from leaks usually means that there is an ice-dam, with water entering the roof system under pressure. The short-term solution is to get rid of the ice-dam, and the proper solution is to ensure that the insulation and ventilation are sufficient to prevent the ice dam from forming in the first place.


2) air infiltration from the living spaces

Air infiltration from the living spaces is the more common cause of higher moisture levels in attic, and that needs to be solved by doing a good job sealing all the places where air can enter such as light fixture boxes, attic trap doors, etc.


3) incorrect venting of kitchen, bathroom, washer, drier or plumbing vents

Incorrectly vented outlet vents from appliances or rooms (kitchen, bathroom) or plumbing vents is unfortunately relatively common. The solution is usually to identify the source of the moisture, and connect an appropriate pipe to vent this outlet to the exterior. We see this when a renovation contractor "forgot" to connect the outlet to a vent on the roof.


If the air barrier is properly functioning, then the interior (living space) humidity should not have any appearance in the attic. Therefore, my suggestion is that If you find frost in the attic, one first has to identify which of the three causes is contributing to the problem. If it's due to air infiltration from the living space, then air-sealing should be the first thing you do, not the last. However, our experience is that most of the time we can trace the frost to moisture entering the attic through a poorly installed vent that either leaks moist air, or just vents directly into the attic space.

  1. Refill attic insulation to normal level, and Increase attic ventilation

Sometimes, you may not be able to find out where the moisture comes from, in this case, you need to increase the attic ventilation, meanwhile insulation needs to be refilled to normal height, otherwise condensate water may generate on the second floor ceiling. Before increasing the ventilation, must make sure the soffit vents tunnel is clear, not blocked by insulations.



Anyway, Gamma Roofing is always here to help you out. Call 416-848-5888.



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