Attic Insulation/Icicles


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Old 01-25-22, 09:43 AM
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Attic Insulation/Icicles

I insulated my attic with R30 batting. (10inches) There are 2 end vents as well as a end to end Peak vent.
Why am I still getting Icicles on the outside?
Should I add more Batting along where the roof meets the wall?
 
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Old 01-25-22, 11:08 AM
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Go outside and look at your roof. Where is the snow melting? If it is melting sorta uniformly from peak to gutters then your insulation is probably OK. If you notice the snow melting off over heated portions of the home then you might need some insulation work or improved attic ventilation.
 
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Old 01-25-22, 12:34 PM
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So there are no soffit vents - just gable and ridge?
 
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Old 01-25-22, 12:52 PM
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No Soffits at all. Roof edge is flush with the outside wall. Just Gutters from end to end.
 
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Old 01-25-22, 02:40 PM
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Ice dams, heat loss and poor ventilation.

Even with good insulation there is an area at the top of the wall where the double top plate exists that can leak a lot of heat. Poor coverage or minimal amount of insulation adds to the heat loss. No ventilation then the heat can only go up.


 
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Old 01-25-22, 03:03 PM
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My House Does Not have the Soffi overhang. The Roof meets the edge of the outside wall. Its Flush. The only thing beyond the roofs edge is the gutter.

Best picture I have. No Soffi or Over hang
 

Last edited by topcycle1; 01-25-22 at 03:24 PM. Reason: bad picture
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Old 01-25-22, 03:22 PM
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I found a better Picture. Side shot.

No overhang!
 
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Old 01-25-22, 03:45 PM
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Insulation does not prevent heat loss, it just slows it. Old houses were not built with modern ventilation standards in mind, nor were they concerned about energy loss. So the problem is that your rafters are too small and that makes the roof too close to your top plate and ceiling.

The lower you go on the roof, the closer (warmer) it gets because you have radiant heat loss. The distance between your warm ceiling and cold roof is just too close. Add to that, no room for baffles and no place for soffit ventilation. No room to have it all work correctly because it wasn't built with that in mind 75 yrs ago.
 
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Old 01-25-22, 03:52 PM
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I understand all that. There are 2 end vents as well as a Top Ridge Vent. House's the are identical to my home do not seem to have this issue.
 
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Old 01-26-22, 03:13 AM
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Yes you can have blown in insulation and not worry about clogging vents.

How big are the gable vents.
Also check that they are clear of debris.
Same goes with the ridge vent.

One way to check or at least compare attic insulation is to go out on a day when there is just frost on the roof.
Look at your roof and others that are aligned in the same direction.
See if they all melt approximately the same.
It should also melt fairly evenly over the roof surface.

Also check the attic access hatch.
A poor seal hear can allow a lot of hot air to get into the attic.
 
  #11  
Old 01-26-22, 09:34 AM
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Icicles on roof are not due to amount of insulation, but amount of insulation can impact it. Best to consider as separate subjects. Attic venting is also not a significant factor.

Best solution to icicles on and in gutters, lower roof and valleys is roof electric de-icing cables. When snow or ice comes turn them on. Day after weather clears turn them off.

DH been using heating cables for 20 years without issue. Does make cleaning screened gutters more difficult, but better than weight of icicles pulling them down. In some homes putting cables In down spouts to below frost line is worthwhile.

There are many types and lay outs.

https://www.google.com/search?client...UTF-8&oe=UTF-8
 

Last edited by doughess; 01-26-22 at 10:18 AM.
  #12  
Old 01-26-22, 10:58 AM
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Icicles on roof are not due to amount of insulation
Lets be clear, the amount of insulation is critical, so is the physical installation and air flow.

High insulation installed correctly, installed with batts folded and installed into the openings to the eves to minimize top plate heat loss with proper ventilation is the recipe for ice damn freedom.

High roofs help with access, low roofs make installation more difficult. I've never worked on a house without eve's but that probably doesn't help either!
 
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Old 01-26-22, 12:08 PM
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Icicles appear on things with no insulation like trees, etc.

Insulation is to reduce heat loss, costs, etc. so never considered it as factor in icicle build up.

When sun melts snow on roof, melt water flowed down to shady north side it froze into ice and icicles.

Maybe someone can provide cost/benefit analysis of insulation to deal with icicles.

DH considers the critical issue to be potential damage to property and humans from falling icicles. DH has well insulated home, low heating costs. In Post # 11 described how he deals icicles.



 

Last edited by doughess; 01-26-22 at 01:59 PM.
  #14  
Old 01-26-22, 02:26 PM
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You just aren't going to get away from ice dams when you have 2x4 rafters. No matter what you do.

But yes, electric cables zigzagged along the lower 2 feet of the roof and all down the gutter and downspouts and back would be a good idea... if you can afford it. They are quite expensive.
 
 

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