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Discussion Starter · #1 ·
HAd a remodel last years where we changed the pitch on a roof and added another 4000 square foot onto the house. The HVAC contractor decided to install the furnace in the attic after we changed the pitch from 2/12 to a 6/12. now when it gets cold the rafters ice up. We made sure to cut holes in the old roof above the soffits to make sure of proper ventilation. so I believe the furnance could be bringing in extra moisture. should the furnace itself be insulated? Should I insulate the new rafters inclosing the attic? The home owner has complained of water running out of the soffits need to figure this out. My first thought is that having the furnace in the attic was a bad idea. just need confirmation on my thoughts.
 

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Just a guess but,

Furnace is causing the snow on the roof to melt, as it runs off the roof it re-freezes when it rolls down over the soffits (where the roof is not getting heated from the furnace). Classic ice dam.

Make sure you have a ridge vent, then run popper vents all the way from the soffit to the ridge in each bay. Popper vents are just styrofoam spacers that let air flow between the insulation and the sheathing. After the popper vents.... insulate.

Problem solved if I guessed right.

Never seen a furnace in the attic... new one on me...
 

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Norm, its becoming more popular in my area anyway, to put furnaces in attics. Especially on remodels and additions.
 

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Wow R, Haven't seen it here yet, but we are kinda backwoods here.

July, I'm not sure if the ridge vent and soffit vents will do it alone. The heat is still going to make it to the sheathing. Insulation will stop the heat from hitting the sheathing. The popper vents (they're cheap) will allow cold air to run against the sheathing keeping it dry and cold. Cold will keep the snow from melting.

You may want to look at the edge of the roof and see if you have an ice dam, in the first place. That should let you know if that's the case. On a 6/12 the dam probably won't have to be too big to cause problems.

How high up on the rafters is the ice, inside the attic, forming? By the ridge, eaves, or in the middle? I understand some is coming out the soffits.
 

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Do you have pics? If the ice is forming on all the rafters regardless of their distance to the peak, you have a moisture problem. If it's only near the exterior top plates, you potentially have an ice dam which is being made worse by too much heat in the attic from the furnace.

My 2 cents.

The HVAC guys, framers, insulators, and other GC's may have more ideas for you too.

In any case more information or pictures are needed.
 

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My furnace is also in the attic. Maybe I should get up there when the temp is low and check things out.
 

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mines up in the attic too, i have natural gas with a forced hot air system. works great, never had a moisture problem though.
 

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Discussion Starter · #14 · (Edited)
I was there today and the roof for the most part is free of snow and ice the homeowner install heat wire on the over hang ice builds up every where except where the furnace is located. maybe I should put some gable fans in.
 

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KemoSabe
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HAd a remodel last years where we changed the pitch on a roof and added another 4000 square foot onto the house. The HVAC contractor decided to install the furnace in the attic after we changed the pitch from 2/12 to a 6/12. now when it gets cold the rafters ice up. We made sure to cut holes in the old roof above the soffits to make sure of proper ventilation. so I believe the furnance could be bringing in extra moisture. should the furnace itself be insulated? Should I insulate the new rafters inclosing the attic? The home owner has complained of water running out of the soffits need to figure this out. My first thought is that having the furnace in the attic was a bad idea. just need confirmation on my thoughts.
First, where does the condensate drain run to? Could be the water running out of the soffits. If the drain freezes, the overflow pan could be filling with water, adding to your moisture problem. My furnace is 90+ and dumps quite a bit of condensate. I've had the drain freeze also.:furious:
 

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I was there today and the roof for the most part is free of snow and ice the homeowner install heat wire on the over hang ice builds up every where except where the furnace is located. maybe I should put some gable fans in.
This may be obvious, but do you have soffit vents (that are unobstructed)?
 

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Loneframer came up with a good point. I honestly don't know squat about furnaces.

But if ice is forming everywhere except where the furnace is located, leads me to believe an ice dam is still forming. Maybe after the dam forms, there is enough heat in the attic to eventually melt the dam after its caused the problem.

Whatever the problem, sounds like once you know what it is, it should be straightforward to fix.

Welcome to CT, by the way... Leaky roofs tend to push formalities aside...:laughing:
 

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Based on all the extra moisture up there, it sounds to me like the duct work isn't sealed correctly, and if it's a gas furnace it isn't vented properly and/or as already mentioned something wrong with the condensation drain. Time to get the HVAC guy back to check things out.
 

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is ductwork insulated,80 or 90 percent furnace? if its an 80plus where is combustion air coming from?if ductwork is not insulated it could basically be same result as a cold tank on a toilet in hot bathroom,temp differance is making the roof sweat. :blink:
 

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Discussion Starter · #20 ·
First, where does the condensate drain run to? Could be the water running out of the soffits. If the drain freezes, the overflow pan could be filling with water, adding to your moisture problem. My furnace is 90+ and dumps quite a bit of condensate. I've had the drain freeze also.:furious:
When I get some time to check the attic out I will check out the condensate drain have to get a hold of the hvac guy find out what he did. he is a tough guy to get back on the job to fix things.
 
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