Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Insulation

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 08-31-2011, 07:19 AM   #16
Exterior Construction
 
Windows on Wash's Avatar
 
Join Date: Aug 2011
Location: VA, MD, DC
Posts: 6,219
Rewards Points: 16
Share |
Default

Faced or unfaced?


Quote:
Originally Posted by heybales View Post
No, you still need the vapor barrier on the warm side. The radiant barrier will just help keep some heat out of the resolution, and since you plan on having these exposed edges of insulation above the studs, will keep the air flow from making it less effective.

You should really just put in thick enough to reach the edge of the studs, and put some rigid foam up across the the whole length. Adds something to the studs, which don't have much R-value really.

In theory with your plan, during the evening summer hours where it's slightly cooler and more humid, if the upstairs room is nice and cool, the edges of those studs could get water condensation. Even if it's not dripping to some surface below, constant moisture is how you get mold growth.
+1

Well said. R-value of wood is less than 1 per inch. To properly insulate that wall, you really need to put a good thermal break across those studs.

Your climate region will dictate the necessity of a vapor retarder or not.

Windows on Wash is offline   Reply With Quote
Old 08-31-2011, 12:28 PM   #17
Member
 
msaeger's Avatar
 
Join Date: Mar 2011
Location: Minnesota
Posts: 262
Rewards Points: 0
Default

Faced or unfaced?


Aside from the knee wall I can't really do anything about the studs being not being insulated though right.
msaeger is offline   Reply With Quote
Old 08-31-2011, 04:14 PM   #18
Registered User
 
Join Date: Mar 2009
Posts: 9,968
Rewards Points: 0
Default

Faced or unfaced?


I would put rigid foam board on the attic side of the knee wall, blocking the floor joist bays from air inbound, and run a baffle up to protect the bottom edge of the sloped ceiling batts from air-- fig.#4 here: http://www.buildingscience.com/docum...ty-insulation/

You will need to drywall the foamboard since the attics are connected. If out of budget, just furr-out the studs with foam strips to flush with the f.g. batts and cover with a housewrap to stop wind-washing; http://www.simplesavings.coop/simple...ee%20walls.pdf Study both pages.

With faced f.g.inside, I would not use foil facing anything on the attic side because of it's low permeability rating, possibly stopping moist air from inside heading to the attic (due to pressure/temperature difference), condensing on it's backside. Granted, there may not be much due to the vented sloped ceiling, but why risk it...

ADA the drywall, caulk/canned foam the floor blocks, air seal the electrical outlet plugs, and use required insulation R-value in the walls and ceiling, not just whatever fits the ceiling joists/rafters/studs. The attic should be close to outside air temperature in the winter, money is better spent on insulation than radiant barrier in your location. You want radiant heat during the winter.... with minimal AC in the summer.

Gary
__________________
If any ads are present in my answer above, I do not condone/support/use the product or services listed, they are there against my permission.
Gary in WA is offline   Reply With Quote
Old 08-31-2011, 10:42 PM   #19
Newbie
 
Join Date: Aug 2011
Location: Kansas City metro
Posts: 10
Rewards Points: 0
Default

Faced or unfaced?


Your other option is to skip the insulation against the wall, and do the ceiling deck. Usually cheaper, and may get thicker batts in there.

In the following page, you are attempting house A. But if you do house B, don't even have to worry as much about the floor joist air movement, though air blocks would help.

http://www.inspectapedia.com/Energy/...n_Location.htm

But as long as your local building codes allow, and more are recognizing the validity of an insulated roof deck, then it would be much easier to install those faced bats to the roof joists. If deep enough, may even be able to keep an air pathway on top of it from bottom to top of the bays.
heybales is offline   Reply With Quote
Old 09-01-2011, 07:40 AM   #20
Exterior Construction
 
Windows on Wash's Avatar
 
Join Date: Aug 2011
Location: VA, MD, DC
Posts: 6,219
Rewards Points: 16
Default

Faced or unfaced?


Quote:
Originally Posted by GBR in WA View Post
I would put rigid foam board on the attic side of the knee wall, blocking the floor joist bays from air inbound, and run a baffle up to protect the bottom edge of the sloped ceiling batts from air-- fig.#4 here: http://www.buildingscience.com/docum...ty-insulation/

You will need to drywall the foamboard since the attics are connected. If out of budget, just furr-out the studs with foam strips to flush with the f.g. batts and cover with a housewrap to stop wind-washing; http://www.simplesavings.coop/simple...ee%20walls.pdf Study both pages.

+1. We normally fur it out to get the added depth and throw a sealed radiant barrier or housewrap across it. We don't have vapor barriers on the bathroom side when we do it. You do run the risk of trapping moisture if you are not careful to leave a drying pathway.

You would be amazed how many guys are throwing up foam boards that are not flame spread rated and leaving them exposed. We see it all the time. Scary if there is ever a fire.

With faced f.g.inside, I would not use foil facing anything on the attic side because of it's low permeability rating, possibly stopping moist air from inside heading to the attic (due to pressure/temperature difference), condensing on it's backside. Granted, there may not be much due to the vented sloped ceiling, but why risk it...

ADA the drywall, caulk/canned foam the floor blocks, air seal the electrical outlet plugs, and use required insulation R-value in the walls and ceiling, not just whatever fits the ceiling joists/rafters/studs. The attic should be close to outside air temperature in the winter, money is better spent on insulation than radiant barrier in your location. You want radiant heat during the winter.... with minimal AC in the summer.

+1

Radiant barriers are far better suited, if at all, for more cooling degree dominated climates. We do use them when we have narrow wall spaces and have radiant heat gain issues (garage kneewalls, etc).


Gary
All good advice again.
Windows on Wash is offline   Reply With Quote
Old 09-09-2011, 10:04 AM   #21
Member
 
msaeger's Avatar
 
Join Date: Mar 2011
Location: Minnesota
Posts: 262
Rewards Points: 0
Default

Faced or unfaced?


I think I am pretty much stuck putting plastic up for the vapor barrier. After talking to the places selling insulation they say no one carries faced R21 because the inspectors here won't accept that for a vapor barrier.

I was planning on using adhesive with the screws on the drywall but that won't really be much good with the plastic up there would it?

msaeger is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Insulation - Faced vs. Unfaced + Plastic Sheet WaldenL Building & Construction 4 07-06-2011 11:41 AM
insulation - faced or unfaced and which direction neil buckner Insulation 0 05-23-2011 10:22 AM
Faced vs unfaced insulation in basement? mathias400 General DIY Discussions 0 05-19-2010 10:01 PM
Faced or Unfaced Insulation ? - Room below porch buchmana Building & Construction 2 02-01-2010 09:29 PM
Faced or Unfaced Insulation in Attic??? capenpeck Building & Construction 13 11-06-2009 07:23 AM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.