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Old 05-16-2013, 08:34 PM   #1
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Expanded cape ˝ finished ˝ unfinished


I have an upstairs bedroom that I need to insulate but I’m not sure what the right approach is.


There are 2 issues I have to this problem. 1. Insulating the attic and 2. Insulating the bedroom. Currently there is minimal insulation up there now. I also have soffit vents, 2 gable vents and a ridge vent. (I know having a mixing gable and ridge vents is a whole other topic).
First, I’m pretty sure I need to insulate the unfinished attic portion. Because it is all open I plan to use un-faced bats R38 or higher. I Plan on insulating the underside of the roof and soffits. I’m concerned about venting when I do this. How much of the soffits do I cover? Do I run the insulation from the roof bays down to the soffits? Do I stop at some point to allow for airflow?


Second issue, how to insulate the adjacent bedroom? I have access through the attic to either side of the knee walls. I can use the same R38 for the soffits and the knee walls. But I’m not sure how to insulate the space between the ceiling and the roof. There is not a lot of space so I’m thinking about renting a machine to blow-in insulation but how much? Do I fill that void completely with insulating or do I have to be concerned with air flow again.
Any thoughts or suggestions would be greatly appreciated
Thank you in advance

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Old 05-18-2013, 12:55 AM   #2
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Expanded cape ˝ finished ˝ unfinished


Welcome to the forums! Where are you located?

Gary

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Old 05-18-2013, 07:21 AM   #3
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North New Jersey
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Old 05-18-2013, 11:51 PM   #4
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Yes, that is why I asked location, thanks; http://publicecodes.cyberregs.com/ic..._11_par002.htm
http://publicecodes.cyberregs.com/ic..._11_sec002.htm

Either way, just leave room for ventilation: http://oikos.com/esb/51/sideattics.html

If possible, cover the knee wall attic side air-permeable insulation with housewrap or rigid foam board (check local AHJ for ignition barrier requirements) to prevent wind-washing degrading the R-value.

You require air-flow or enough rigid foamboard on complete roof to prevent condensation without air-flow, pp.71; http://www.buildingscience.com/docum...n-roof-venting

IMHO, the exhaust vents are fine; http://en.allexperts.com/q/Roofing-1...able-Vents.htm

http://www.finehomebuilding.com/desi...ble-vents.aspx

Soffit usually is not insulated.

Gary
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Old 05-22-2013, 08:26 AM   #5
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Thanks Gary,

You provided lots of great info that i didn't find in my searches.

You mention how to insulate the knee walls, but didn't mention if i should try and insulate the void between the roof an the ceiling of the bedroom. do you think that would be necessary? if so, should i rent a blower to blow in insulation on the top and slopes on either side of the room?

after reading your info and doing more research I'm thinking about adding a gable fan to the attic. what is your opinion about adding the fan.
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Old 05-22-2013, 05:14 PM   #6
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Went through the same research you are doing now when I insulated my Cape.
You want to leave a space for air flow between that ceiling and roof. If you fill that gap with insulation you close off the side attic to air flow & set-up for moisture & mold problems. Also may hurt your roof longevity a bit in the spot where insulation touches the decking.
That said you also want to insulate that gap as best you can, or you loose a LOT of heat through that small area. What I did was pull out the existing 1"-thick crappy batts & cut strips of rigid foam insulation to fit as close as possible between the joist bays (2" XPS stacked 2 layers thick = R-20).
You could do more or less XPS to get the most R-value while still keeping a 1-2" air gap below the roof decking in each bay.
Most important is proper air-sealing before you add insulation. Capes are notoriously leaky. Research where the big leaks are common & seal them up or your insulation won't do much good.
Biggest leak I found were all my floor joists running straight into the side-attics with nothing to stop attic air infiltrating btwn the 1'st flr ceiling & 2'nd flr floors. This is common depending on age of the house.
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Old 05-22-2013, 06:51 PM   #7
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Just found another issue. my bays are only 5.25" deep. R30 bats are 9.5 thick. not sure what to do now. Bays are inconsistent too range from 12.5" - 15.25" wide. on avg 15" wide.
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Old 05-31-2013, 09:15 AM   #8
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Update

I got sick of reading all the contradictory science out there. Figure, I should stop over-thinking or this project would never get done.
– one consistent theme in all my research was AIRFLOW. Which I think I achieved.


Below is a list of activities that I completed.
Note: I was not able to achieve desired or necessary R-value due to space limitations – but it’s better than what I had, which was nothing.

-Installed 1x2x8 in-between rafter
-Installed 2” thick foam board in rafter (R-10) – used spray foam to seal
-Cut and installed “air dams” at the bottom of rafter, along the soffit – used spray foam to seal
-at this point I have created a 2” channel of air from the soffits to the “ceiling”
-installed r-13 fiber glass over foam board
-total r- vale of roof deck r-23
-Repeated for other side of the roof

-Studded out the ceiling of the attic and placed r-19 on the ceiling
Note: had to use r-19 on the ceiling instead of r-30. The r-30 would have partially covered my gable vent.

-installed r-19 on gable wall

As mention previously the other ˝ of the second floor is a finished bedroom
so to prevent air leaking from behind the knee wall into the unfinished attic I covered those opening with r-30.

If I do not notice a considerable difference in controlling the temperature on the second floor
– I will pay someone to create access panel on either side of the finished room and insulate. (too much back breaking for me to get behind the those knee walls)

All told it took 2 weekends and about $600
I received a quote awhile back to for about $1,900


Please comment if you feel I made any error, or if you feel my approach was right.

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