Raider Bill
Registered Users
Posts:69
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| 10/07/2008 5:15 PM |
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I'm to the point that I have to insulate on top and close the gables.
I'm getting conflicting sides on where to insulate [ on top of ceiling or under roof deck]
Wheather or not to vent the attic.
There will be no duct work up there. It will be closed off.
I was thinking of having spray foam applied to the top of the ceiling sheet rock thus sealing the living space completely like a igloo cooler.
HAve been reading about not venting the attic area but am concerned with condensation. Metal roof installed.
I have not covered the gables yet so gable vents will not be a problem.
So the questions are
1] where do I insulate?
2] vent or no vent
3]should this be in the ICF forum?
I hope to get back up the middle of this month. Will take me about 5-10 days work then I can get living in this baby! |
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PanelCrafters
Registered Users
Posts:1329
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| 10/07/2008 7:39 PM |
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Important! Where are you building?
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....jc
If you're not building with OSB SIPS(or ICF's), why are you building? |
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Raider Bill
Registered Users
Posts:69
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| 10/07/2008 7:59 PM |
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South east Tenn near Athens.
Mixed humid |
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PanelCrafters
Registered Users
Posts:1329
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| 10/08/2008 9:09 AM |
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Posted By Raider Bill on 10/07/2008 7:59 PM
South east Tenn near Athens.
Mixed humid
You can go either way. Take your pick here. I do prefer the foam sealing the ceiling as opposed to foaming the roof though.
Good Luck! |
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....jc
If you're not building with OSB SIPS(or ICF's), why are you building? |
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Raider Bill
Registered Users
Posts:69
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| 10/08/2008 9:27 AM |
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Seems to me foaming the ceiling WOULD be the best way to control the living space. Smaller area to condition. Smaller unit, smaller bills.
I have a full size drive in basement so any duct work will be run under the living space floors once I get to that part of the project. The majority of heat will be with a wood stove. |
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sprayseal
Registered Users
Posts:1
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| 10/21/2008 9:20 AM |
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yeah i would definately go with the spray foam method. Its probably the most effective hassle free form of insulating a home. It can also be done quickly and easily. I currently install foam spray home insulation for numerous clients and our research shows us that it works well in almost any situation.
Thanks
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wes
Registered Users
Posts:376
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| 10/22/2008 7:19 AM |
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Bill,
I don't want to start an argument, but I would recommend insulating the underside of your roof area in lieu of the ceiling.
First, in our climate zone, you should not ventilate the attic. This introduces way too much humidity into this space during our hot, humid summers, not good. However, even a vented attic will become very hot during the warmer months, and an unvented even more so. And in our cold, humid winters you don't want icicles hanging off the underside of your rafters. And if you intent to use the attic space for storage, as any man with a wife will do, anything stored there will be exposed to these temperature shifts.
However, if the roof plane is insulated, the attic space is tempered to near the indoor conditions. This space doesn't have to be maintained at the same temps as the living space, just introduce a little air movement to keep the space from becoming stagnant. The added costs for construction and maintanence will be minor compared to the increased usability of the space, and the long term stability of your roof structure. |
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Wes Shelby
Design Systems Group
Murray KY
wandr@ainweb.net |
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Raider Bill
Registered Users
Posts:69
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| 10/22/2008 8:58 AM |
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Wes,
I've got to say this is confusing the heck out of me!
I suppose the very best way would be to insulate both the roof plane and the ceiling but $$$ prevents that right now. Although,if that is the best way in the long run I could make arrangements to do this I suppose.
It seems to make sense to limit the amount of conditioned space as in insulating the ceiling but then condensation could be a problem as you say. Insulating the roof plane increases the amount of heat a/c needed to a point.
The way the trusses are there is really no place up there for storage. I have a full drive out basement for storage plus no wife to argue about it.
Because this is a ICF house I'd think that keeping the conditioned space to a minunim would be better?
I have noticed that the area is just as humid as here in Florida during the summer and very damp in winter. |
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johncarl
Registered Users
Posts:5
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| 10/22/2008 12:47 PM |
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| You ever thought about using the attic space as a return plentum? Just another thought |
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Raider Bill
Registered Users
Posts:69
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| 10/22/2008 12:58 PM |
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No ductwork, will be using a split ductless mini system when needed.
Heat is woodstove only. Possible small electic heater in bedroom the need arises.
Attic space is huge but pretty much useless for storage. |
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Farmboy
Registered Users
Posts:157
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| 10/24/2008 12:14 AM |
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Based on previous discussions on this topic, I recall a few sensible conclusions:
1. Stratification. At some steady state, the air in the living space will straify into layers of warmer temps starting from the floor. So it will be a few degrees warmer at at the ceiling and even warmer above the ceiling. But by insulating under the roof deck (non ventilated attic) the attic should only be 10 degrees or so above the room temp and certainly less than not insulating the roof.
2. Reducing Infiltration. If the foam works as advertized, it will reduce/eliminate drafts and humidity issues in the attic.
3. I've been in a 100% SIP house and the attic space was actually very comfortable, about the same temp as the living space. Now you may not get the same R-value with a foamed truss roof, but it should be relatively comfortable.
I'm planning on foaming under my roof deck. Will run insulated HVAC duct in the attic. As long as my thermostat isn't at the ceiling level, I expect my HVAC system to keep our living area comfortable. Got any pics of your progress so far, Bill?
Cheers, Dave |
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Raider Bill
Registered Users
Posts:69
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| 10/24/2008 9:12 AM |
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| If you just insulate the roof deck then wouldn't you be wasting a/c and heat due to infiltration through the ceiling? |
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GWhittleAL
Registered Users
Posts:20
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| 10/27/2008 3:58 PM |
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I have to agree with Wes Shelby on this one. When you build in a high humidity environment, controlling humidity is your biggest energy consumption. 50% of your cooling loads can be from de-humidification. Not adequately controlling the humidity can lead to mold, mildew, and structural damage to your home.
Tightly seal the envelope of the house and prevent humidity from entering therein and you will cut your energy consumption by as much as half. This has a much larger energy efficiency effect than worrying about the relatively small added conditioned space.
With such tight construction, however, make sure you have adequate air exchange with an energy recovery ventilator with humidity controls. If you get your required air exchanges by merely feeding "fresh air" into the system, then you will still be spending the energy to remove humidty from the house over and over again.
The goal is to get the temperature and humidity of the house to a comfortable level and then use minimal energy to maintain a steady state. To do this, everything within the envelope of the house needs to be conditioned and sealed from the outside. |
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malibud
Registered Users
Posts:30
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| 11/10/2008 1:05 PM |
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I am in the same location Western carolina and have the same problem ..Foam on the roof deck = 4300$ insulation blown on flat r50 and batts on cathdrel r38 = 1300$ Big price difference. I plan to go w/ the vented. Question how do you make sure vented air from the soffits do not get in to the living spaces |
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PanelCrafters
Registered Users
Posts:1329
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| 11/10/2008 4:57 PM |
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Posted By malibud on 11/10/2008 1:05 PMI am in the same location Western carolina and have the same problem ..Foam on the roof deck = 4300$ insulation blown on flat r50 and batts on cathdrel r38 = 1300$ Big price difference. I plan to go w/ the vented. Question how do you make sure vented air from the soffits do not get in to the living spaces
I've always liked putting down 1" to 1.5" of foam to seal everything up. You've got to consider any penetrations, which range from holes from electricians and plumbers to sealing around anything embedded in the actual ceiling. The foam would do this well.
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....jc
If you're not building with OSB SIPS(or ICF's), why are you building? |
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cmkavala
Registered Users
Posts:818
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| 11/10/2008 5:09 PM |
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Bill;
I agree with Wes as well, and the AC ducts if run overhaed, will be more efficient in conditioned space |
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Chris Kavala
chris@southernsips.com
1-877-321-SIPS |
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malibud
Registered Users
Posts:30
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| 11/10/2008 6:57 PM |
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| The insulation guy said since the foam goes on Hot they do not like to spray it on dry wall...?? |
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PanelCrafters
Registered Users
Posts:1329
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| 11/11/2008 6:43 AM |
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Posted By malibud on 11/10/2008 6:57 PM
The insulation guy said since the foam goes on Hot they do not like to spray it on dry wall...??
Fine. Just go out and buy a couple of Froth Paks and DIY.
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....jc
If you're not building with OSB SIPS(or ICF's), why are you building? |
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