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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Why is that window wet or foggy looking?

When house-hunting in Silicon Valley, it’s good to take note of how clear the windows are. Sometimes when a dual pane window appears wet or foggy, it’s not just a matter of the sprinklers hitting it, but instead could be a failure of the vacuum seal. If that’s the case, the window will not be as attractive as intended.

There are some window repair professionals who claim that they can de-fog windows with condensation (the common belief is that foggy windows must always be replaced).  What many consumers do not know when purchasing dual pane windows is that many of them will fail, unlike the single pane windows they are replacing. (The Old House Authority site says 30% of the time, a replacement window will be replaced within 10 years. It also advises that “More heat is typically lost though your roof and un-insulated walls than through your windows. Adding just 3 and 1/2 inches of insulation in your attic can save more energy than replacing your windows.”)

 

Seal failure of dual pane window

Seal failure of dual pane window

 

Many of my home buyer clients for Los Gatos, Almaden, Cambrian and San Jose insist upon having dual pane windows in their future house or townhouse.  Before assuming that any brand is OK, though, do some research to learn about the windows’ failure rate and how long the warranty on them will be.  Dual pane windows look great and do save a little energy, but if you have to replace one third of them within ten years, it won’t be a bargain at all.

Further reading on insulation and windows

What Can You Learn from a Silicon Valley Roof on a Frosty Morning?

Closed curtains or blinds in an open house? What is the seller trying to hide?

Why does it matter if the bedroom windows are small or high?

Creating pleasant window views