Attic Frost in Saskatchewan and Alberta: Facts You Need to Know

We have had a long stretch of bitterly cold weather in Saskatchewan & Alberta in the past few weeks and with it comes the risk of attic frost. When it warms up and we hit temperatures above freezing, you may be thinking that your roof is leaking. We have been receiving lots of calls and doing lots of inspections due to people thinking they have a roof leak.

Chances are, your roof is not leaking. When warm, humid air from the built environment accumulates and condenses, frost will typically appear in your attic on the underside of your roof sheathing. When the temperatures warm, and the frost starts to melt, improperly sealed pot lights, attic hatches and other areas of ceilings where penetrations in, or no vapour barrier is present will start to drip through. Small amounts of frost developing is not abnormal during low overnight temperatures. When small amounts of frost have a chance to melt, it should evaporate and allow the sheathing to dry, without a major concern.

When a large amount of frost accumulates and does not evaporate prior to more accumulation, a more serious problem occurs. The longer this goes on, the greater volume of ice you will have and the greater volume of water you will have leaking down when it warms up enough to melt. 

In some cases, frost will form on the North side of the attic sheathing and not the South. During the day, as the sun is out, in certain circumstances it will produce enough heat to warm the south side and allow it to thaw and evaporate moisture, but the north side will still have frost as it does not get warm enough to cause evaporation.

The worst cases of attic frost that we have encountered are when a bathroom fan or dryer vent is vented into the attic as opposed to the outside environment. When warm, humid air is blown into a cold attic space it will wreak havoc with frost and the aftermath of the melt could become very costly as the water drips into the drywall of your ceiling and your wall cavities. 

Other scenarios that cause issues in your attic are where people have additional insulation blown in with no insulation stops in place and they think the more the merrier. Insulation being blown in without attic stops typically restricts the air flow from the soffits.

When air flow from the soffits is restricted an attic will not stay ambient to the outdoor temperature and frost will most likely occur. Another common problem occurs when there is inadequate ventilation at the roofs peak. When this occurs the ventilation through roof vents or continuous ridge vents is inadequate and frost will also appear. ends up clogging up the soffits. When the soffits are clogged air flow is restricted and without airflow an attic will not stay ambient to the outdoor temperature and frost will most likely occur.

Relative humidity (RH) levels in your home & attic and ways to control it:

Anytime the RH goes above 50%, it becomes a concern in the built environment; 35-45% RH is an acceptable level of humidity in the built environment. The more humid it is in your home or office, the worse it will be for accumulations of condensation in the attic. 

Using fans in your bathroom while showering and in your kitchen when cooking will help reduce humidity as long was they are NOT vented into your attic. If your basement is humid you should consider purchasing a good dehumidifier that has a drain line, so you don't have to worry about draining it regularly.

If you are running an energy efficient furnace and don't have an air to air exchange system connected, I highly recommend looking into installing one. Air to Air exchange systems are a great way to control humidity in your home. If you are in need of an air to air exchange system and are in Saskatoon and area, we recommend 306 Plumbing & Heating

Ventilation in your attic:

Proper ventilation is a major factor in a healthy frost-free attic. In lots of cases, insulation baffles weren't installed, and the insulation gets packed into the soffits to the facia and restricts the flow of air throughout the attic.

Even when your soffits are free from insulation clogging the air flow and you have baffles in place, the air from the soffits must have somewhere to flow through too. Your roof should have vents and either a ridge cap vent, or other that creates a draw of air from the soffits.

Air barriers in your ceiling:

Air leakage through electrical fixtures such as pot lights, bathroom ceiling fans and other electrical components are sometimes not sealed properly to the vapour barrier. When this happens warm and, in most cases, humid air leaks through from the home into the attic.

In some cases, no air barriers will even exist, and it is very important to put the barriers in place to prevent energy loss and frost from forming in the attic on the roof sheathing. If you have no vapour barrier installed in your attic, there are still options such as spray foam, removing insulation and placing a new vapour is also an option. Once insulation gets wet, the R value is reduced and it must be replaced, not dried.

If you do not have any vapour barrier and your truss system is such that it won't allow for install of a vapour barrier from above, spray foam will most likely be your only option.

We can eliminate frost in your attic quickly and mitigate the damages that would occur to ceilings and wall cavities in the event you just let the frost melt. Fill out the form on this page or call now 1-888-909-6653.