May 2011
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Complications with cathedral ceilings

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Guidelines for minimizing ice dams with cathedral ceilings

by Joan P. Crowe, AIA
4 people have posted comments


Homeowners and designers often desire cathedral or vaulted ceilings because of their aesthetic appeal and added height to a given space. But if a home is located in a heating climate zone—where a building's interior generally is heated for a longer portion of the year than it is cooled—problems such as ice damming may arise because cathedral ceiling roof systems are difficult to ventilate.

However, there are ways to achieve proper ventilation and minimize ice dams' effects.

Ventilation

A cathedral ceiling is considered a compact, or "warm," roof assembly, which means each roof system component is in direct contact with the preceding component; therefore, there is no attic space between the ceiling and roof deck. These types of roof assemblies present particular ventilation problems, especially in heating climate zones. The problem most associated with unventilated, improperly insulated cathedral ceilings in cold...



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Comments (4) Login to post a comment or rating

Posted by howard on 5/12/2011, User rating 
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Joan, Good Article! Check www.structeavent.com for the only complete intake product line on the market. Howard hayers@acs-reps.com
Posted by djeffwhite@yahoo.com on 5/11/2011, User rating 
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Joan. Have you considered using Polyurethane Spray Foam Insulation applied directly to the underside of the roof deck creating an unvented roof assembly. We are seeing the complexity of vented roof assemblies and energy efficient design causing ice dam problems in zone 5 and 6. The warm air in the home or building moves through air permeable insulation and causes the snow to cycle through freeze thaw. Insulating the roof deck tends to eliminate ice dams. The tricks are: 1. Use a quality contractor 2. Make sure the truss "top cord" is sprayed with foam as well as every member that comes in contact with the roof. 3. Make sure you install a sufficient amount to prevent the heat from see the roof deck. Zone 5 R806.4 recommends R-20.
Posted by Ventalot on 5/11/2011, User rating 
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Good article. We have been finding in the midwest that flat roofs subject to snow build up over 10 inches result in severe ice damming if the roofs are not vented. The cold roof is essential to avoid this from happening. Interior moisture is as much a problem in the newer homes as the vapor barrier is often incorrectly installed and without a safety precaution that venting brings, a prematurely rotted out roof is often the end result
Posted by robbsmith on 5/8/2011, User rating 
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Good detail

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