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Old 09-12-2020, 12:57 PM   #1
ekb
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Attic Interim Insulation Step


Hi,

This is my first post, and I'm a first time homeowner, so please bare with me.

Background: The attic in my 1.5 story bungalow (or maybe you would call it a cape cod) is lacking in the insulation and ventilation department. The attic has knee walls and ceiling to define the conditioned living space (with 2 side attics and 1 small top attic). Currently, there is no venting at the eaves (my home doesn't have soffits for vents), but in the top attic above the living space there are 2 gable vents and 4 or 5 box vents - safe to say there is no air flow from the eaves to the top attic. I get some serious snow melt above where the slanted walls are since there is no venting, and this is causing ice damns and creating havoc on my roof, gutters and brick exterior. There is 2" of old aluminum faced cotton insulation along the rafters, r-13 fiberglass batts in the knee walls, and some insulation packed into the slanted wall rafter space - I imagine there is maybe a foot of loose fill in the ceiling. The rafters are 2x6, so there is only 5.5" to work with for insulation on the interior. Also, the insulation was not installed very well, and some is falling loose.

My ultimate plan (maybe 2 or 3 years down the road), is to totally rip out all of the insulation and do an unvented attic at the same time as installing a new metal roof. I would use closed cell spray foam to fill the 5.5" rafters, completely seal any air leaks, remove the air vents, and add an extra inch or two of continuous rigid foam board under the roof rafters, and also add rigid foam board insulation under the metal roof (I figure that would get me close to the recommended r-value in region 5).

While I save up for the new roof should I:
(a.) buy more fiberglass batts to patch the crappy insulation job now, or
(b.) should I demo the interior, remove all insulation and get the foam spraying done now?

I'm a little wary of option b because I don't know if the roof deck is in poor condition (i.e. don't want to demo to find I have to replace the roof before I can spray the insulation), and not sure if option a will fix anything.

Hope that wasn't too much information. Thanks for any help!

Rick
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Old 09-12-2020, 01:27 PM   #2
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Re: Attic Interim Insulation Step


You have some good ideas but I think the roof should be done at the same time with a master plan for the job.

Maybe just a heat tape for the ice dams until you can do the whole job.
https://www.icedamcompany.com/2015/1...am-heat-cable/
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Old 09-12-2020, 05:21 PM   #3
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Re: Attic Interim Insulation Step


I think you have wrong ideas about insulation and ice dam. I will be using some definitive words. I welcome any correction.


BTW, is your attic heated in winter? Have a plan to make it into a living space?


The ONLY (definitive word) fix for ice dam is a cold roof. There is no other passive fix. As such, it is actually better not to insulate and to keep downstairs heat, esp along the eave, away from the roof. If you're heating the attic, then you must leave at least 1.5" space between insulation and the roof deck and fill that space with cold air. Passive or active, that cold air must keep itself cold. Some sort of cycling. There is a vent that can be incorporated with roof shingles but i've no experience there and the vent opening size makes me feel doubtful. Maybe you could ask about roof venting in the roof section or try other forums. How effective it is.



You can insulate the attic floor or rafters with amazing insulation but it will not help with ice dam. Insulation, no matter the kind or amount, will not keep the roof cold because insulation does NOT stop heat (energy) from moving from heated space to unheated places. Insulation slows it down and saves the heating fuel, but does not stop the heat loss. This is same thing in summer with air conditioning, except without the ice dam.



Heating cable zigzag along the eave is actually a good idea. Cheap (by electrician cost) and least intrusive. Scraping snow off the roof is another.


One idea may be to install intake vent and exhaust fan in the crawl space behind the knee wall and spray foam the floor space and the knee wall. Small 200 cfm inline fan probably will be enough for a small crawl space. Large enough vent covers maybe. Floor to r60 and the wall to r40? Super insulating the crawl space would allow you to keep the space cold during winter without encroaching into the living space. Lots of insulation also helps with keeping the space as cold as possible. So cold crawl space, cold roof along the eave. Ice will stay on the roof without melting from undeaneath and becoming a dam. With a metal roof, but with a gutter, same ice dam problem can happen.



The roof over the living space also must have min 1.5" (but more probably is better - more cold air, more time it takes to warm) passive/active cold air. The space also keeps the lumber and the sheathing dry.
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Old 09-13-2020, 07:56 AM   #4
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Re: Attic Interim Insulation Step


Thanks for that, Nealtw. Kind of thinking doing it all at once is the best approach as well. Maybe waiting a couple years isn't such a big deal? I will check out the heat tape!

[QUOTE=Nealtw;6296433]You have some good ideas but I think the roof should be done at the same time with a master plan for the job.

Maybe just a heat tape for the ice dams until you can do the whole job.
https://www.icedamcompany.com/2015/1...am-heat-cable/
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Old 09-13-2020, 08:31 AM   #5
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Re: Attic Interim Insulation Step


Hi carpdad - yes the attic is heated in the winter (we use it as our master bedroom). I've read that spraying closed cell foam directly on the underside of the roof between the rafters is acceptable and doesn't require an air gap since it adheres directly with the wood surface. So you're saying I will still have ice melt in that scenario? Seems like if I slow the heat transfer enough (high enough r-value), the cold outside air would be able to keep the roof cold. The reason I like that approach is because the rafters are only 5.5" thick, closed cell foam has highest r-value per inch, I don't loose 1-2" to air gap (baffles), and venting at the eaves may have issues. I've looked into those roof shingle vents - some seem to think they are prone to problems. Also there are fascia vents (gap between roof trim and home), but I'd have to look at those more. Good idea asking the roofing forum. Thanks.

Quote:
Originally Posted by carpdad View Post
I think you have wrong ideas about insulation and ice dam. I will be using some definitive words. I welcome any correction.


BTW, is your attic heated in winter? Have a plan to make it into a living space?


The ONLY (definitive word) fix for ice dam is a cold roof. There is no other passive fix. As such, it is actually better not to insulate and to keep downstairs heat, esp along the eave, away from the roof. If you're heating the attic, then you must leave at least 1.5" space between insulation and the roof deck and fill that space with cold air. Passive or active, that cold air must keep itself cold. Some sort of cycling. There is a vent that can be incorporated with roof shingles but i've no experience there and the vent opening size makes me feel doubtful. Maybe you could ask about roof venting in the roof section or try other forums. How effective it is.



You can insulate the attic floor or rafters with amazing insulation but it will not help with ice dam. Insulation, no matter the kind or amount, will not keep the roof cold because insulation does NOT stop heat (energy) from moving from heated space to unheated places. Insulation slows it down and saves the heating fuel, but does not stop the heat loss. This is same thing in summer with air conditioning, except without the ice dam.



Heating cable zigzag along the eave is actually a good idea. Cheap (by electrician cost) and least intrusive. Scraping snow off the roof is another.


One idea may be to install intake vent and exhaust fan in the crawl space behind the knee wall and spray foam the floor space and the knee wall. Small 200 cfm inline fan probably will be enough for a small crawl space. Large enough vent covers maybe. Floor to r60 and the wall to r40? Super insulating the crawl space would allow you to keep the space cold during winter without encroaching into the living space. Lots of insulation also helps with keeping the space as cold as possible. So cold crawl space, cold roof along the eave. Ice will stay on the roof without melting from undeaneath and becoming a dam. With a metal roof, but with a gutter, same ice dam problem can happen.



The roof over the living space also must have min 1.5" (but more probably is better - more cold air, more time it takes to warm) passive/active cold air. The space also keeps the lumber and the sheathing dry.
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Old 09-13-2020, 08:51 AM   #6
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Re: Attic Interim Insulation Step


Hi ekb and welcome to the forum. I'm a retired energy auditor now energy consultant and I live in a cape and they are a challenge. From what you have described your cape in Michigan is in trouble and fixing it isn't going to be easy. Also, winter is approaching so outside work, if any, needs to be done quickly. Contractors usually are very busy this time of year.

Can you add some pictures of your home, dormers and slope need to be considered.

Low gable end vents along with roof vents over those side attics can help with air exchange and help keep the roof cooler as @carpdad was explaining. Since a metal roof will be added in the future any holes added now can be easily repaired.

Knee wall and side attic floor need to be well insulated and look for your vent stack as it often uses the knee wall as a path to the roof. And often it is NOT well air sealed.

You have a lot of work ahead of you and it is important to get it sequenced so nothing you do is in conflict with what needs to be done.

Get those pictures
Bud
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Old 09-13-2020, 04:08 PM   #7
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Re: Attic Interim Insulation Step


If you read, eg, 100 home owner reviews, probably half will say no problem and half problems. Manufacturers and the sellers are likely to list the benefits and conveniently forget the problems. I'm diy like you and have not studied or even built like you want. Interested in at least couple of issues, insulation and moisture control. Problem is they are opposite sides of a same coin. Unvented insulation can add to house's moisture problem.


Installers do not make the problems public. Even the honest installers are not likely to go back to the same work site or remove the work and review the performance. Joe Listiburek is one of the few who can. Search and see who he is. His accumulated experiences have made him a believer in vented spaces and i'm a believer.


I sympathize with your problem. You want most insulation but have limited space for it. You're not the only one. Because of divided reviews, i can't condemn all installers. What i'd do is what i believe.


Spray foam has its problem as well. Search for spray foam fume problems. Spray foam is a product of chemical reactions. It is especially sensitive to ambient and chemicals temperature. I think the fixes are easy enough. Spray in correct ambient temps and in thinner layers. Filling 2x6 space in one shot may cause chemical problems.


You make a point about outside temps keeping the roof cold. Makes sense. But ice dam starts with snow and snow is a good insulator. Snow may keep the roof from losing the heat radiated from below. Not dismissing your idea. Just showing there are many sides to an issue.
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Old 09-14-2020, 02:30 PM   #8
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Re: Attic Interim Insulation Step


Hi Bud- here are some pics showing the front and back of the house. The side view I drew lines to indicate where the conditioned space is. The front dormer is currently in the unconditioned space (side attic). What kind of temporary roof vent do you recommend for the side attics? Thanks!

Quote:
Originally Posted by Bud9051 View Post
Hi ekb and welcome to the forum. I'm a retired energy auditor now energy consultant and I live in a cape and they are a challenge. From what you have described your cape in Michigan is in trouble and fixing it isn't going to be easy. Also, winter is approaching so outside work, if any, needs to be done quickly. Contractors usually are very busy this time of year.

Can you add some pictures of your home, dormers and slope need to be considered.

Low gable end vents along with roof vents over those side attics can help with air exchange and help keep the roof cooler as @carpdad was explaining. Since a metal roof will be added in the future any holes added now can be easily repaired.

Knee wall and side attic floor need to be well insulated and look for your vent stack as it often uses the knee wall as a path to the roof. And often it is NOT well air sealed.

You have a lot of work ahead of you and it is important to get it sequenced so nothing you do is in conflict with what needs to be done.

Get those pictures
Bud
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Attic Interim Insulation Step-img_1948.jpg   Attic Interim Insulation Step-img_1952.jpg   Attic Interim Insulation Step-img_drawing-conditioned-space.jpg  
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Old 09-14-2020, 02:35 PM   #9
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Re: Attic Interim Insulation Step


Thanks carpidad - the mixed opinions are definitely difficult to wade through. I appreciate the feedback and will definitely reconsider going with a vented roof. Trying my best to fix everything right, and not unintentionally create more problems down the road.
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Old 09-14-2020, 02:55 PM   #10
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Re: Attic Interim Insulation Step


Rectangular vents like you would see on the gable end of a home only installed down low.

Bud
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