Damning Evidence

Home Inspector with JRV Home Inspection Services, LLC HOI 394

Ice damming occurring on a house in ConnecticutWith winter comes snow. The snow covered landscape is undeniably beautiful. Snow cover for  homeowners brings with it the potential for ice dams. Icicles are another one of winters beauties until they line the lower edge of your roof. Awe then turns to anxiety as a homeowner now must be vigilant for leaks. Fortunately not all snow fall will create ice dams that can cause leaks. By and large, the deeper the snow, the greater the likelihood for leaks.

In my experience the understanding of what creates ice dams is not always well understood. One theme I hear fairly often is the gutters are to blame. I have talked with several homeowners who have purchased new gutters after being advised they would solve their ice damming issue.  While gutters collect the melt water and eventually the ice that forms, they are not the cause for the formation of ice dams.

Bath vent or a snow melting device inside a Connecticut atticSimply, ice dams are formed by the accumulated snow on the roof melting and then refreezing at the edge. Of course all snow melts. The problem is when the snow melts too quickly, often exacerbated by a deep pack. The real problem is not the ice dams, for they are the result of other extremely common building practices. Yes, that's right, building practices. In other words it's the way houses are constructed that is usually the root cause for this problem. Furthering the issue, accessory components such as lighting also contribute.

The problem of ice dams begins inside the house at the ceiling plane common to the attic. Standard practice is to insulate the ceiling, for it is the area where the greatest heat loss occurs. Before the insulation is fitted, many components are first installed that make this surface holier than a piece of Swiss cheese. When all the work of putting in wires, lights, pipes and various ducts is completed, fiberglass insulation, usually in batt form, is finally laid over and around all of these irregularities. The fit, to say the least, is less than ideal.

Black smudges on fiberglass insulation show air by passes into this Connecticut atticAll of the holes through the ceiling plane are typically referred to as bypasses. The label is appropriate as each hole allows for warm conditioned air to "by pass" the ceiling into the attic. But wait you say, the insulation will halt the air movement. In actuality, usually not, especially when the insulation is fiberglass.

A common sight found on fiberglass insulation are black stains sometimes mistaken for mold. These dark smudges are dirt from air passing by the insulation from the conditioned space. Not convinced? Pull back the insulation at a stain. There will usually be an opening beneath. If not, the batt is poorly fit like in the photo.

The answer to the problem of fitting insulation into cavities and around irregularities has traditionally been to install loose insulation, again usually fiberglass, sometimes cellulose. Loose or blown fiberglass I have found to be marginally better than batt type fiberglass. The insulating ability (R value) of loose fiberglass (2.2/ inch) however is far less than batt type (3.7/ inch) or cellulose (3.8/ inch).  

Infrared image of blown fiberglass bleeding heat into an attic in Connecticut

There are two common problems I find regularly with blown fiberglass. First is cheating by installers. R - 38, the standard R value for attics in Connecticut, requires a depth of 15 inches. This assumes an R value of 2.5/ inch. I find with troubling regularity, attics with depths of 8 - 10 inches on newer construction or retro fits.

The second issue is blown fiberglass "insulation" does a very poor job of insulating. The infrared image shows heat leaking through about 8 inches of newer blown fiberglass. The installers cheated on the depth by bending the cardboard gauge used during installation at the 10 inch mark, thus putting in less than half the amount of insulation required by building code. The insulation was mounded near the attic entry to appear deeper.

An independent study done several years ago by the University of Colorado at Denver School of Architecture and Planning found that cellulose insulation significantly out performed fiberglass. Therefore using an insulation that doesn't insulate coupled with a ceiling that closely resembles a sieve is one of the major contributors to ice damming on most houses.

The lack of insulation above the wall assembly is a common cause for the creation of ice dams

As touched on several times earlier, attic by passes are just the beginning of the problem with heat loss that can cause ice damming. Some of the most common by passes are created by the very design of the house and can be difficult to remedy. The area where the wall and roof join is a known weak point in the thermal protection of the attic insulation. Often the insulation is not or simply can not cover the thermal bridge created by the wall framing. New houses can be built with roof assemblies that allow for insulation to be placed fully over the wall assembly and can accommodate the other important component in preventing ice damming, ventilation.

One other major by pass can be HVAC duct leakage and or uninsulated duct work. Installing HVAC equipment in the attic is in my opinion a very bad idea, but quite often the only option.

An ideal installation of insulation and ventilation in an attic

Attic ventilation I have found in my experience is too often misunderstood. Ventilation alone is not the cure for ice dams and or moisture issues found in attics. Those issues very often begin at the ceiling. Properly installed ridge and soffit venting has been proven to be a superior attic venting method. However any system, especially a passive one, can be overwhelmed. When attic by passes allow for large quantities of conditioned air, sometimes laden with extra humidity by the homeowners, to enter the attic, the venting is not able to keep up. The result can be moisture issues inside the attic, typically on the roof sheathing and ice dams outside when conditions are right.

Condensation, mold and moisture damage on roof sheathing

To try and neatly wrap all this up, ice dams are created mostly by preventable and often repairable building issues. Solutions should be looked for beginning inside the house, specifically the ceiling common to the attic. Sealing and better insulating the ceiling paired with adequate and properly installed ventilation can significantly reduce or even eliminate ice dams from forming. Lastly the best benefit from having a well sealed and insulated attic is increased energy efficiency. The energy savings should help off set the cost of repairing / upgrading the attic space.

In the end while the evidence may be damning, there is great hope for a reprieve from the winter snows.


Posted by

James Quarello
Connecticut Home Inspector
Former SNEC-ASHI President
JRV Home Inspection Services, LLC

 ASHI Certified Inspector

To find out more about our other high tech services we offer in Connecticut click on the links below:

Learn more about our Infrared Thermal Imaging & Diagnostics services.

Serving the Connecticut Counties of Fairfield, Hartford, Middlesex, New Haven, Southern Litchfield and Western New London.


Re-Blogged 1 time:

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  1. Joe Jackson 01/12/2013 05:04 AM
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James Quarello
JRV Home Inspection Services, LLC - Wallingford, CT
Connecticut Home Inspector

Joe, Yes ventilation is important, but you may be missing the real issue.

David, I have noticed that trend in some newer construction.

Jay, It seems at times more effort goes into scamming that into doing the job correctly. 

Clint. Its shameful what we find at times. 

Jan 09, 2013 10:20 PM #5
Tom Arstingstall, General Contractor, Dry Rot, Water Damage Sacramento, El Dorado County - (916) 765-5366
Dry Rot and Water Damage www.tromlerconstruction.com Mobile - 916-765-5366 - Placerville, CA
General Contractor, Dry Rot and Water Damage

Ice damning can be eliminated by moving to a warmer climate James.  :)

We don't get much of that here, but I enjoyed learning about the topic.

Jan 09, 2013 10:38 PM #6
Charles Buell
Charles Buell Inspections Inc. - Seattle, WA
Seattle Home Inspector

Jim, when exactly is the world going to wake up to the fact that fiberglass is a sham?

Jan 10, 2013 04:25 AM #7
Steven Cook
No Longer Processing Mortgages. - Tacoma, WA

Jim -- thank you for a very enlightening explanation of the issue of ice dams on rooves in the winter.

Jan 10, 2013 05:56 AM #8
James Quarello
JRV Home Inspection Services, LLC - Wallingford, CT
Connecticut Home Inspector

Tom, I like that idea best of all :)

Charlie, Good question. I'm doing my best to educate the public against the evils of fiberglass :)

Steven, My pleasure. 

Jan 10, 2013 06:49 AM #9
Ginger Harper
Coldwell Banker Sea Coast Advantage - Southport, NC
Your Southport~Oak Island Agent~Brunswick County!

Jim..Thanks for the post regarding the fiberglass problems that occur with ice on our roofs..Glad we are in the south and we hardly ever have snow..  I learned something from you.  Thanks again..

Jan 10, 2013 07:46 AM #10
Rosalie Evans
Meritus Group Real Estate - Sioux Falls, SD
The Evans Group, Sioux Falls, SD Homes For Sale

We had some major issues with ice dams a few years back in this area. Since that time I have noticed that there has been an increase in ice dam heaters on the edges of roofs. Do you recommend these? 

Jan 10, 2013 08:04 AM #11
Chuck Mixon
The Keyes Company - Cutler Bay, FL
Cutler Bay Specialist, GRI, CDPE, BPOR

One job I hate is insulation work on my house. After reading your post, I think still is a bad day worth of work but all the more required.

Jan 10, 2013 08:10 AM #12
Steven L. Smith
King of the House Home Inspection, Inc. - Bellingham, WA
Bellingham WA Home Inspector

Mr Quintarillo,

Frankly, my problem with the stuff is it gets into my coveralls and unders and it really itches me. Your friend,


Jan 10, 2013 08:11 AM #13
Joel Weihe
Realty World Alliance - Wichita, KS
Helping you to use your VA home loan benefits

Cellulose is the way to go, yes. When I was a construction manager I preached it's qualities to no end. 


As to attic ventilation it's one of the things I paid a lot of attention to and to this day will factor that in when showing homes to clients.

Jan 10, 2013 08:34 AM #14
Pat & Wayne Harriman
Harriman Real Estate, LLC (203) 672-4499 - Wallingford, CT
Broker/Owners, Wallingford CT Real Estate

I always damning the ice at my house, Jim! Man, you should hear...

What? You didn't mean it that way? Oh.

Never mind.

Jan 10, 2013 08:42 AM #15
Christina Sanchez Hood
Palo Alto, CA
#SiliconValleyHOODS | Inspired Living
James, congrats on the feature and thanks for the great insight and lesson.
Jan 10, 2013 10:36 AM #16
Charles Buell
Charles Buell Inspections Inc. - Seattle, WA
Seattle Home Inspector

Ruh roh nutso is back!  Time to break out the grill again

Jan 10, 2013 01:36 PM #17
James Quarello
JRV Home Inspection Services, LLC - Wallingford, CT
Connecticut Home Inspector

Ginger,  As Tom suggested living in a warmer climate is probably the best cure :) Seriously, fiberglass is poor insulation and I do not suggest using it.

Rosalie, I see them here as well. They seem to work, but are not an actual solution. All though they might be the only way to solve ice damming in some instances. 

Chuck, The most important part of re-insulating is sealing all the by passes, then putting down the insulation. 

Nutsy, Have you been on "vacation" at the gray bar motel?  Again.

Joel, Glad to hear you appreciate cellulose. The Pink Panther has brain washed many, many people.

Wayne, I damn the snow, does that count? :)

Christina, Thanks for reading. Glad you found it informative.

Charlie, I'll have to find it. It's been a while since I need it.  

Jan 10, 2013 09:09 PM #18
Donald Hester
NCW Home Inspections, LLC - Wenatchee, WA
NCW Home Inspections, LLC

Jim, I try to sell the evils of fiberglass also. We have some perfect weather that last few weeks for ice damming. See a lot of ice on homes of late.

Jan 10, 2013 10:25 PM #19
Jill Sackler
Charles Rutenberg Realty Inc. 516-575-7500 - Long Beach, NY
LI South Shore Real Estate - Broker Associate

Thanks for the in-depth lesson. Worthy of a feature for sure.

Jan 11, 2013 04:45 AM #20
James Quarello
JRV Home Inspection Services, LLC - Wallingford, CT
Connecticut Home Inspector

Don, We have not had very much snow so far this year. Haven't seen any monster icicles yet. 

Jill, Thanks for reading it. 

Jan 11, 2013 08:51 PM #21
Jason Sardi
Auto & Home & Life Insurance throughout North Carolina - Charlotte, NC
Your Agent for Life

I loathe fiberglass and ice.

That written, I have a special place in my heart for snow.

Hope you are off to a nice 2013, Jim!

Jan 12, 2013 11:32 AM #22
James Quarello
JRV Home Inspection Services, LLC - Wallingford, CT
Connecticut Home Inspector

Jason, Same to you. As for the snow, I have a special place for it too, but its a bit further south ;)

Jan 12, 2013 08:22 PM #23
Dagny Eason
Dagny's Real Estate - Wilton, CT
Fairfield County CT, CDPE Homes For Sale and Condo
Jim- what a thorough post!!
Feb 19, 2014 10:33 PM #24
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