insulation Q'S

hunter41162February 21, 2009

Hello, hopefully someone can help me out.

Ok so I Put up 1inch extruded polstyrene and glued it to the wall. framed up my 2x3wall, not yet anchored down. Couple questions before I go any further.

1.What was supposed to be done at the top of a framed wall running parallel with the floor joists? as far as fire codes go. I have a two inch gap. I slid the xps up behind the floor joist to the subfloor. That covered 1 inch, the top plate will cover the other. is this going to be ok? Also do firebreaks absolutely have to be used inbetween studs extended to concrete?

2. What about the parallel joists? I am thinking of cutting smaller squares above the top plates and just gluing them in. Then when I cut the full sheets for the other wall notch around the joists to subfloor. ????essentially double insulating.

3. What, if anything, should be used on seams around the xps, like floor and in corners? would some caulk do anything? and is duct tape ok to use to tape the joints with?

4.I plan on adding 2 1'/2 inch xps for additional insulation in between studs and just sectioning to allow for running electrical. yes/no?

I have looked through every page and I am still a bit confused, never seems to be a defenite answer.

Thank you for reporting this comment. Undo

1)Re: fireblocking. See this thread and links. (Generally, it seems fireblocking the top alone is sufficient. But if a municipal inspection is required, you should ask what they require.)

2) No problem in doubling foam insulation.

3) Caulk or foam. There are some good pics on one of the recent threads. No duct tape! Use builder's tape, such as Tuck, Tyvek or 3M.

4) The more insulation, the better. But after the 1" XPS on the wall, you can economize by using other types--eg., fg, cellulose, mineral wool, EPS. Yes, you'll have to cut a slit for board type insulation if you're filling the entire cavity.

    Bookmark   February 21, 2009 at 9:13PM
Thank you for reporting this comment. Undo

What are you going to put in the rim joist area beside those two layers of 1" foam? Will there be fiberglass up against the rim joist with foam on the inside? I'd rather have the foam against the rim joist and the fiberglass on the inside, but I not totally sure on that.

I'm now 3/4 through putting foam boards in the rim joist area (so that it meets up with the wall foam) and it's VERY tedious and not cheap either. Maybe you could kind of come up the wall with the foam, make a right angle and cover the concrete and plate, and the go up to the floor above. Then stuff fiberglass in there. If the foam was 2" thick the vapor probably wouldn't condense on any cool areas.

You might be able to glue the blocks of foam as they make the turns with some kind of non-petroleum glue like polyurethane.

I was surprised at how much frost there was on the rim joist when I removed the unfaced insulation. I guess it would evaporate when it gets warmer, but still...

    Bookmark   February 22, 2009 at 12:26AM
Thank you for reporting this comment. Undo

I have decided to possibly do just 1 inch of xps cut in squares in rim joist area, and seal around it with spray foam insulation to seal them up. Cut the main wall xps flush with the block.I still havent decided on whether or not I am gonna change things up so my top plate extends to concrete for a little bit of a firebreak. If the wall is gonna go its gonna go...

    Bookmark   February 22, 2009 at 12:40PM
Thank you for reporting this comment. Undo

I was surprised at how much frost there was on the rim joist when I removed the unfaced insulation.

Illustrating perfectly the uselessness of putting fg in there as an air block or insulation. It only provides a home for mould.

    Bookmark   February 22, 2009 at 12:50PM
Sign Up to comment
More Discussions
Basement tile grout sweating
Hi Experts, We have a new house (1 year old, Hamilton,...
Joe Regular
want to finish basement but very humid...
Have an unfinished basement. House built 2012. During...
Replacing Steel Column With Stud Wall?
I am interested in replacing a steel column with a...
water in unfinished basement
Well its in the 50s here in NJ and the snow is melting....
Basement Renovation questions.
I need a basement renovation. It's dark and cold. Low...
Sponsored Products
Leucos | Star LED Recessed Lighting
$465.75 | YLighting
Leopard & Zebra Bottle/Sippy Cup Insulator Set
$8.99 | zulily
Quoizel Q1072FPN Archer Palladian Bronze Floor Lamp
Littman Bros Lighting
WAC Single Mini Spot Light LED Remodel Recessed Housing
Euro Style Lighting
DonnieAnn African Adventure AF6Q Animal Print Area Rug - AF6Q
$89.99 | Hayneedle
Quorum International White Two-Lights Flush Mount Light
$211.50 | LuxeDecor
Zaneen | Invisibili Adjustable 2 Light LED Recessed Lighting
$835.20 | YLighting
Cree Retrofit Trim 4" LED Recessed Light Fixture
$59.98 | Lamps Plus
People viewed this after searching for:
© 2015 Houzz Inc. Houzz® The new way to design your home™