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:

Frosty roofs in winter


A tree blocks part of the view, but it’s still apparent that the home on the left is losing heat to the attic and roof.  The house on the right has a frosty roof nearly everywhere. There are some vent pipes with darker areas nearby, so warm air may have been coming up from a bathroom (warm moisture from a shower would do it) or laundry area or kitchen could warm up spots. But overall, it’s well blanketed in frost.

Frosty roof summary

When it comes to frost on a roof in a cold winter morning, more is better.

The homes where there’s little or no frost are essentially “defrosting” their roofs with escaping heat. Homes that hold in the heat better do not have warm roofs and thus have a good amount of frost on top.

Of course, places where air or gas is meant to escape, such as at the vent pipes, are going to warm up the area immediately around them.  If there are just patches of melted ice with no such pipes nearby, perhaps your insulation has been disturbed and it’s worth a visit to the attic.

Buying a home? Drive by early on these cold winter mornings to see how frosty the roof is. Assuming that the home is occupied and heated, this can provide good insight as to how well the insulation is functioning to keep the heat in and the cold out.

Also, check the home inspection report to see what is said about the insulation (if any is present, how much, any rating?).

Selling a home? Make sure your insulation is good – it is a selling point that cost-conscious homebuyers will appreciate! It’s wise to make sure that you aren’t loosing heat whether selling or not.

If you have never stepped outside to check your roof on the super cold mornings, it’s important that you do do.  If insulation is needed, added it is a great way to go green and lower your power bills.


Related reading:

Concrete tile roofs: pros and cons (on this site)

Fanciful roof art (on the Live in Los Gatos blog)

Vaulted or open beam ceilings (on this site)

Asbestos in homes (on this site)