Anatomy Of An Ice Dam

[Jay Markanich]

When deep snows happen, ice dams often happen too.

Notice two words in the diagram:

Convection and Conduction.

An easy way to remember what they do is this:

Conduction is THROUGH and convection is TO.

Cooking heat is conducted through a frying pan into the food, which heat also convects to the upper level and the upstairs feels warmer.

Deep snow on a roof creates a condition ripe for ice dams.  There are a lot of battles going on between heat and cold.

Since Friday I have gotten lots of calls because of ice damming.  And it is a huge problem.  And some of the icicles I have seen are enormous!  They could skewer a woolly mammoth!

The first photo shows literally what the diagram is teaching above.

This is a box window on a house I visited on Saturday.  To the right is the garage and the left a box window.  The other side of the box window looks just like this side.

Trapped water is being forced through the siding, soaking into the garage wall and onto the garage floor.

Trapped water is also being forced up into and under the cedar shakes and into the box window ceiling and framing.

The first thermal image is what my thermal camera saw in that box window.

This is immediately under those shakes you see in the digital photo.

The pattern of water intrusion is clearly visible as lavenders and purples.

The darkest purple is 38 degrees F.

The other thermal image is of the other side of this same box window, about 6' wide.

This moisture is clearly getting into the wood framing of the window as well.

Ice damming is a real problem and happens around here every time we get deep snows.  Fortunately the snow is melting slowly and saving foundations.  Too much water pressure around the house and, well, other problems begin there too!

My recommendation: Pay attention to your house!  If possible, try to eliminate some of the build up at the bottom of the roof.  Your house will appreciate it.

I bet your gutters will too!

[Marcel R. Cyr]

Good graphic Jay.

Was there any visual signs without using the IR camera?

Those pictures came out real good.
Wish I had the money to have one. 

[Jay Markanich]

No Marcel.  I found problems all over the house that they did not know they had.  The only indication was the puddle in front of the bathroom door (yesterday's post) and the dripping from the kitchen light (yesterday's post).  But no staining or wet spots elsewhere.

[Marcel R. Cyr]

Nice find Jay. 

[Casey Patten]

I spent yesterday afternoon on my roof shoveling.  There was some ice build up, but most of it did melt off with the sun, hoping for some more today.  But it was deep, I was up to my knees in some spots!  I look across the street at my neighbor's place; ice dam that's probably 18-20 inches up the roof and a good 4 inches thick!

[Jay Markanich]

Not a good place to be Casey.

[David Macy]

The causes of ice dams are many and complex.

On my own house I have one due the outside air temperature increasing and the sun causing radiant heating. Then it refreezes when the temperatures drop. It is only on one area of my house.

My neighbor had numerous roofers out last year that wanted to replace his roof. He had ventilation added but he still get really bad ice dams due to lack of insulation and what I stated about the temperature and sun.

I have been thinking about the IR camera for a few years now, failing the RESNET course last spring kinda put a damper in my thinking...

I have a hard enough time getting clients to pay for a home inspection, but if I purchase the right IR camera and have the proper training and market properly I could pay off the camera in one year.

[Jay Markanich]

Get training, then get training, then play with it, after training, and play some more.  After that, it is part science, part art, and part interpretation.

Training, good training, is essential.

IR is a great arrow to have in your quiver Dave.