Insulation, Radiant and Vapor Barriers - What insulation for between-room interior walls? R13vs15?

Couple questions, I have a couple rooms I'm redoing where I have to completely tear out the drywall and start over. I noticed that currently I have R11 on the exterior walls, and nothing on the interior walls.

Will it be worth the money to take out the R11 and put in R13 or R15? I have no problem doing this if it's worth the money. Also, what should I use for between rooms? I would think that no vapor barrier is needed, so I wouldn't need the Kraft-Faced paper. Reasons being privacy and sound deadening. I don't know if it helps with much else, does it?

So how's it go for interior walls? How does it stay in place?

You only have to insulate exterior walls of a house. You want to insulate so you make a "Box" to isolate the inside from the outside. Think of an oven, eventually everything inside gets to the same temperature if it's isolated enough from the outside.

Unless you're trying to do something eccentric like independently control the temperature of each one of your rooms, then you could insulate interior walls, and add a complex heating system, and install air tight interior doors, and.... well you get the picture.

-Mark

You will save no money because of the insulation unless each room has its own thermostat.

It could be a problem if you had a roof leak and got the insulation wet. That would require the iterior drywall and insulation to be removed because of mold. I saw this on a 5500 sf house near New Orleans, where all the 2x6 insulated interior walls had to be stripped and replaced.

Insulation will provide a minor decrease in sound transmission.

Dick

Thermostats and heat won't be a problem because s/he doesn't want it for that, but for sound.

You can put in whatever size will fit in there but like Concretemasonry said, it won't help too much with sound. Do a search for sound insulation and see what you can find for sound products.

keep the R-11 and focus on noise through/under the doorways.

Like Dick said, insulation alone in a wall does very little for sound control. If you want to control sound between rooms with no doors, then you can get a pretty good increase by attaching resilient furring channels horizontally to the studs AND add sound insulation in the wall. Be sure to caulk any type of penetration such as electrical boxes.

The weakest point in any wall, besides penetrations, is a door. To improve a door, use a solid core wood door or insulated metal door. Weatherstrip all around the door, including the bottom, just like you would an outside door.

Bruce

Well, if you want to up your current exterior insulation, I carefully remove your R-11 and put it into your interior walls. Then buy new R-15 for your exterior walls. That way the minimal deadining effect from adding insulation will at least be free! I plan to insulate between my bathroom and bedrooms... unless there is a reason I shouldn't, like moisture.