squeezing 3" insulation into 2x3 stud walls?

[Rogue Petunia]

hello, I've got an old house. It's brick with 2x3 studs, plaster and lath. While the kitchen is gutted down to the studs and brick right now, I'd like to add some insulation - you know, the "while you're in there" syndrome!

The minimum insulation I know of is 3". While it's R value isn't great, I figure it's better than nothing, right?

I am wondering if compressing it into a space that is only 2.5 inches deep will reduce its effectivness to a great degree

By the way, I do not want to go as far as building out the studs to 4 inches because I'd have to build out all the window jambs and rip down the cornice of the tin cieling and move it an inch too. Just not happening ;)

One last question, if I use the Kraft paper backed batting, do I need to also put up a polyethylene vapor barrier?

Thanks, in advance, for your thoughts on this.

-Rogue Petunia

[Joseph Meehan]

It will reduce the total overall R value, but it is not likely to be less effective that using thinner insulation which will start with a higher overall R value. It may even be better.

[Spud]

lath.

there"

search Foam insulation sprayed in place heres one to get you started

[Tom Baker]

Compressing the glass fiber insulation a bit should * increqase * its thermal resistance. This according to building researcher and Journal of Light Construction.

You might want to check the Building Science Corporation web site. It includes climate specific information on vapor barriers and so on.

My first reaction is to question how the separation of brick and insulation is to be done. Brick walls do let in water. You might check the BIA (Brick Industries of America) web site.

TB

[Randd01]

Shouldn't make a noticible difference. I would go with the batting with no paper and use the poly over it. You have wood over your brick right? If not you may want to put a barrier over the masonary first then batting then another barrier. But that may trap moisture hmmm!

[L. M. Rappaport]

On Sun, 02 Nov 2003 04:07:50 GMT, Rogue Petunia wrote (with possible editing):

Knaupf makes an R7 fiberglass insulation, 15" wide by nominally 2 1/4" thick which leaves room for venting off moisture. The model number is R-7U-MHR-15. Fiberglass itself is not what provides insulation, it's the trapped air, so I would not compress 3 1/2".

Where do you live - north or south? I.e., do you principally use heat or air conditioning?

[Art Todesco]

[Carolyn Marenger]

For the insulation... Go ahead and use fiberglass. Compressing it will lose a small amount of it's rated R value, but not much. Like you said, better than nothing.

Carolyn

[Tony Hwang]

Hi, And need vapor barrier. Tony

[CBHvac]

Depends..here in NC, there is talk of removing that part from the building code...

[L. M. Rappaport]

On Sun, 02 Nov 2003 17:43:00 GMT, Art Todesco wrote (with possible editing):

I think it would depend. Polystyrene foam has (or at least "had") an R value of 5 per inch and Polyurethane 6.5, so both are better insulators, but when last I checked (which was several years ago), polystyrene while not flammable gave off poison gas when burned, and polyurethane was flammable.

In addition, there was available a non-expanding foam based on urea formaldehyde. The "gotcha" there was that it apparently out-gassed fomaldehyde vapors for a long time and many folks had adverse reactions to it. I'm not up to date, but if that's been cured, it seemed like a very effective insulation. You'd want to know if it was open or closed cell however, and OP would still need to mention his location and whether his primary need was air conditioning or heating or some combination of both before water migration issues can be considered.

[Rogue Petunia]

[snipped to save space]

I'm not a guy. I may own as many tools as a guy, but I'm all woman :)

-Rogue Petunia

[Rogue Petunia]

Hi Larry, I'm in the North. Primary concern is heating and heat loss.

-Rogue Petunia

[L. M. Rappaport]

On Tue, 04 Nov 2003 03:49:21 GMT, Rogue Petunia wrote (with possible editing):

Unless foam has changed, then, I"d use the Knaupf I mentioned earlier and quoted below. I'd use foil backed. It's just a tad better than kraft in that it reflects radiant heat sources inwards, but with smaller studs, you really need all the help you can get. I don't think you need plastic over it.

Sorry about the guy/gal stuff.

[Rogue Petunia]

Hi Larry, I got a few repsonses in alt.building.construction about fiberglass and brick being very compatible. Specifically that the brick allows moisture through and if fiberglass was against it, it would become sodden. Perhaps even push out the drywall if it expands due to having been compressed (although I know you are recommending to NOT compress it).

What are your thoughts on fiberglass and brick? Perhaps I should use furring strips on the brick to keep the fiberglass from directly touching the brick?

oh, and don't worry about the guy/gal stuff - I've got a good sense of humor and it didn't bug me! And besides, "Rogue Petunia" is just a posting nickname, so how could anyone tell based on that, right?

Thanks, Rogue Petunia

[Trent©]

You can read almost ANYTHING on the Net. lol

Funny...I took it as being your first and last name...and that you were of a nationality with a unique, unusual first and last name. And Rogue sounds masculine...or at least neutral.

Have a nice week...

Trent

Fighting for peace is like screwing for virginity!

[L. M. Rappaport]

On Tue, 04 Nov 2003 13:02:24 GMT, Rogue Petunia wrote (with possible editing):

I think it's important to note that proper installation of any fiberglass insulation leaves the external surface NOT in contact with anything else, brick, wood, whatever. There is always supposed to be an air space and it should be vented. I am guessing that this applies even more so to brick since, as you say, it does provide a cool surface upon which water can condense at some point in the year. Fiberglass will not expand when wet, but it will lose substantial R value.

Hopefully, this explains the problem: In the winter, you have cold dry air outside and warm, relatively (to the outside) moist air inside. At some point, the moisture in that moist air would condense. What you are trying to achieve is twofold: most important is to keep the moisture out of the insulation and keep the dewpoint within the dry area. Since there is no moisture there to condense, there is no problem. This is one of the best reasons for using a closed cell foam

- you guarantee that the dewpoint will occur within the medium and there will be no moisture to condense there. If only it weren't poisonous when burned (in the case of polyurethane) or outgassing (urea-formaldehyde). You keep moisture out of the wall with kraft or foil facing. Obviously you might want to be extra careful around outlet boxes. There you might want to wrap the outside of the box in plastic and tape the plastic to the foil or kraft facing.

So, the long and the short of it is this - if you use Knaupf or similar insulation, it will not touch the brick and you'll be fine.

That said, I am a bit confused. Normally, brick is applied as a veneer against sheathing (nominally 5/8" plywood). I think you're saying you have masonry walls of some substantial thickness with 2 x 3 studding directly against it. Those 2 x 3's provide structure for the sheetrock only - is that correct? If that's the case, you won't be able to vent the insulation without some major surgery. That would make me be especially careful about keeping moisture out of the cavity between the studs.

Ok.

[Chris Lewis]

According to L. M. Rappaport :

Both are flammable, and both give off toxic fumes. Which is why you MUST provide fire protection to foamboard insulation by code. Drywall qualifies.

While the hazard was rather greatly overblown, it _did_ occasionally cause problems. These days installed UFFI insulation is a severe house value decrement.

I wouldn't consider it.

[L. M. Rappaport]

On 6 Nov 2003 03:47:36 GMT, Chris Lewis wrote (with possible editing):

...snip

Just curious, Chris, are you opposed to it because of the negative impact on the value of your home due to the perceived problem, or because there are other technical problems with the stuff? We never used it because of a possible sensitivity to formaldehyde, but it did look appealing. No expansion and a possible shrinkage of under 1% at least at the time.

[Chris Lewis]

According to L. M. Rappaport :

Taken in isolation, UFFI application and insulation characteristics are extremely good.

In the past, MOST UFFI problems were probably due to poor mixture control and perhaps even poor QC on the production of the stuff.

Ie: if it didn't mix completely, you wouldn't get 100% chemical reaction completion, and you'd be left with localized hotspots of (toxic) volatiles.

Secondly, there are "treatments" for problematic UFFI - air-to-air heat exchangers and there are apparently ways to "force" uncombined volatiles out or to reaction completion (expensive, but a whole lot cheaper than a whole house tearout).

And thirdly, "problems" usually only arose with the unduly sensitive. But formaldehyde and related chemistry are nasty beasts, and long term dosages too low to cause problems themselves can trigger more generalized chemical sensitivity.

Its troubled past, plus uncertainties about whether my contractor might goofup and leave me with unmixed bits, plus the remote possibility of the kid becoming chemically sensitized makes me say no, entirely aside from house value.

And even now, a UFFI installation can be a real-estate deal or mortgage killer.

My aunt and uncle bought a beautiful century home with UFFI. We didn't tell them to run away as soon as they possibly could - they didn't have kids. Just pointed out that they will probably have difficulties selling later.

There are apparently new foam technologies that don't have anywhere near as much trouble, but I've never been tempted to research them.