framing for insulation under frozen bathroom


Old 01-18-05, 06:21 PM
Thread Starter
Join Date: Mar 2003
Location: NE Pennsylvania
Posts: 293
framing for insulation under frozen bathroom

A few weeks back I wrote that pipes burst in bathroom built on main floor with nothing underneath (was a porch at one time).

At that time I was sure there was no insulation in walls, because even the fixtures froze. Long story short - I was wrong there is insulation in walls.

Next idea is that I'll enclose the space underneath and insulate it - I'm thinking of using 2x8 on corners of walls so I can get a higher "R" factor. Okay here's the dumb question. Since the wall won't be supporting anything except insulation is there any reason to use 2x8 through out or can I throw 2 x 4 every 18" and set them back 4" to allow for the depth of insulation? will I lose any insulating benefit by doing it this way?

I'm thinking this is a dumb question - but I'd like som opinions ....thanks
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Old 01-18-05, 09:54 PM
robby521's Avatar
Join Date: Dec 2004
Location: Alabama
Posts: 152
as far as useing a 2x8 i would think it is a over kill,maybe a 2x6 or just 2x4s.if you use them i dont see what would hurt to use some 2x4.
Old 01-18-05, 11:25 PM
Join Date: Sep 2004
Location: Canada
Posts: 71
What insulation types have you considered. Do you know the condition of the insulation in the wall? Is it fiberglass? Is it moisture laden? Keep in mind that 2% moisture content in fiberglass insulation reduces R19 grade to R12.
You may wish to spend some time researching the various insulating materials you have to choose from. Not one single insualtion material is suitable for all situations. The three methods of heat transfer are radiation, convection and conduction. The standard and more popular insulations such as fiberglass only addresses conduction. When you take the other two forms of heat transfer the effectiveness of fiberglass can change dramatically.

"Air movement also greatly affects the R-value of fiberglass, as heated air moving through the fiberglass drastically reduces itís conductive value. ( see "Attic Insulation Problems In Cold Climates" March 1992, pp. 42-43 Nisson, J.D. Ned, JLC, in the R Value Fairy Tale )"

To better understand these concepts one needs to refer to the basics of "thermal dynamics and insulating" I am providing a link which should help understand how heat behaves and how insulations perform and fall short.

Old 01-19-05, 04:58 AM
Thread Starter
Join Date: Mar 2003
Location: NE Pennsylvania
Posts: 293
framing/insulation under bath

The existing insulation (in exterior walls) is fiberglass (rolls) I pulled siding off and it appears dry - I'm considering using fiberglass under the bathroom and yes there is a LOT of air movement in the wall between bath and kitchen - I'm going to use blown in in this particular wall - I know that usually there's no insulation between two heated rooms - but I'm hoping that once the cold air is reduced or eliminated in this wall the radiator in bathroom will be sufficeint to heat the room - I still need to address the open area underneath...I'll check the link you sent- thanks for response.

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