Heat wire on roof

[sfalvey]

Pros and cons for heat wire on roof at eaves where gutters are located?

Thanks all.

[dfogleman]

Scott, I assume you are referring to the wire used to create heat to melt ice dams. My opinion is that they are helpful if you have an ice dam problem however it has always been a signal to look closer at the attic ventilation and insulation and gutter systems. I would also look closely at the installation of the wire where it attaches to the roof and how it is supplied with power. These are the issues I have come across while climbing around of roofs.

If the roof is getting ice dams and the ventilation, insulation and gutter is correct then you might live in NH certainly not here in balmy PA...

[mthomas2]

Never seen one installed except to correct a problem, as noted above when you see them, ask yourself: why?

[phinsperger]

I suppose it depends on your local climate. I see them here quite often and even when there is no insulation or venting issue of the attic. Some house designs (ie, long overhangs over porches on the south side) just lend themselves to be more prone to ice damming than other designs. Also the weather patterns (freeze thaw cycle) is worse in some years than others.

Nick said he had 44" of snow Here I am a hours drive north of Toronto Canada without so much as a flake of snow at present.


I wouldn't assume that there is a insulation or vent problem based on the presence of cables in my area but yes, you may wish to look a little closer.

I disclaim the cable installation itself. Many of these have been spliced (which you are not allowed to do) or have other installation issues. I will however recommend them to a client that needs a quick fix for insulation/venting issues until such corrections can be made and also to people concerned about protecting that new finished room.

I have not seen any problems of heat declining the life of the shingles. Most damage (2nd to damaged caused by homeowner installation) is from avalanches ripping the wire off the roof and the clip taking part of the shingle with it. A relatively rare occurrence based of what I have seen.

[Joe Funderburk, CMI]

What's an ice dam?

[Larry D. Kage]

Originally Posted by jfunderburk

What's an ice dam?

Actually, Joe, it's called "damn ice" up here but we haven't had much of it lately...It's a balmy 45 degrees in northern Michigan.

[Roy D. Cooke, Sr]

Originally Posted by jfunderburk

What's an ice dam?

Joe
Here is a good explanation .
http://www.extension.umn.edu/distrib...ng/DK1068.html


Roy Cooke
</IMG>

[David P. Valley]

Originally Posted by phinsperger

I suppose it depends on your local climate. I see them here quite often and even when there is no insulation or venting issue of the attic. Some house designs (ie, long overhangs over porches on the south side) just lend themselves to be more prone to ice damming than other designs. Also the weather patterns (freeze thaw cycle) is worse in some years than others.

I wouldn't assume that there is a insulation or vent problem based on the presence of cables in my area but yes, you may wish to look a little closer.

My thoughts exactly.

99% of the time, when I spot heat wires or that 3 foot metal sheeting at the roof edges, I know there's bound to be an issue with insulation and ventilation in the attic or cathedral cavity. The heat wires are installed due to excessive ice forming along the roof eaves, above the plate-line of the exterior walls. Heat lost from homes at this point aggravates snow melting and ice-dam development.

There are two reasons for increased heat loss at this point: Rafters on most homes sit directly on top of exterior walls leaving a shallow space for insulation between the top of the wall and underside of the roof sheathing: Low R-value = heat loss! And secondly, home builders are not particularly fussy when it comes to air-sealing this point to prevent any movement of warm indoor air up to the underside of the roof surface. Air can leak through wiring and plumbing penetrations here. Also, the warm indoor air can leak from the wall cavities rising upward and passing between the small cracks that exist between the wall top-plate and drywall.

I'll always update my clients on how to resolve ice damming, depending upon the situation at hand.