What Can You Learn from a Frosty Roof?

Viewing a frosty roof, or a one without frost on an icy morning, can provide useful information about the home’s insulation.

Frosty roof photos (and why it matters)

Here are some homes in Los Gatos viewed early one winter morning when the sun had barely risen.   The home on the left shows some ice over and near the eaves, but not higher up on that roof.  The house on the right  has frost all nearly all of its roof except over the garage where it connects to the 2nd story.   What is happening?

 

Two homes on an icy morning - one with more frost than the other

 

In the left house, the roof is warm and the frost is melting or gone, while on the right the roof is not warm except in one spot.

Frost is a good indicator that the insulation in the attic is keeping the heat in the home and that it’s not being lost to the attic and roof. The house on the right is very well insulated. The one warm spot may be close to the furnace, water heater, washer, or dryer – something in the garage is heating up that corner of the roof.

This has nothing to do with the roof type, by the way. The one on the left is metal and the one next to it is composition shingle. In the photos below, at the left is another comp shingle and to the right of it has a concrete tile roof.

Let’s look at another example:

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