Home>Discussions>INSULATION & HVAC>Replacing insulation from the inside - vapor barrier?
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blarson
Replacing insulation from the inside - vapor barrier?

Hi!

I'm redoing a small utility room in my 1950s house. After removing the drywall, I found 1.5" fiberglass insulation stapled between studs on the external wall. I'm tempted to tear it out and replace it with modern 3.5" insulation. A couple quick questions:

1. Is this a good idea?
2. Do I need to worry about a vapor barrier?

The house has wood siding and is located in Kansas City, so we see a wide range of climate.

Sten
Re: Replacing insulation from the inside - vapor barrier?

Any time you add more insulation it's a plus so long as you don't pack it in tight which will defeat it's purpose. Vapor barriers are usually done on exterior walls to help keep out moisture or dampness which could cause mold. You can get two different types of insulation, paper back or bare, the paper on the insulation is the vapor barrier and that's what I would use. Just make sure the paper is on the living space side. Good Luck!!! :)

JLMCDANIEL
Re: Replacing insulation from the inside - vapor barrier?

Because of all the complaints about mold I would go with plain bates then apply plastic sheeting. The plastic will act as a moisture bearer and block air infiltration. And yes going to 3½" will give you better insulation providing you have walls built with 2 X 4 studs.
Jack

canuk
Re: Replacing insulation from the inside - vapor barrier?

Make sure to use housewrap tape on all seams of the plastic vapor barrier.
The idea of a vapor barrier is to be a sealed envelope to be effective.

What about the ceiling ... is this being done as well?
If so overlap the ceiling vapor barrier 6 - 12 inches over the plastic on the walls and tape the seams.

Ohio Paul
Re: Replacing insulation from the inside - vapor barrier?

I have a similar project as blarson. I'm remodeling a bedroom in my older home built in 1912. Adding insulation from the inside is my only reasonable option. It has wood exterior siding. I'm totaling gutting walls and ceiling to the studs. I did the same thing to another bedroom in the house a few years ago and used faced insulation without a plastic vapor barrier and did not get the results I was hoping for. The room temperature fluctuated a lot even after putting in the faced wall & ceiling insulation. I am hoping to remedy this in my new project by using unfaced insulation along w/plastic vapor barrier.

1) Has unfaced insulation w/plastic vapor barrier worked satisfactorily for anyone?

2) I located some clear 6-mil polyethylene sheeting at my local home supply store. Would this work well as a plastic vapor barrier?

jkirk
Re: Replacing insulation from the inside - vapor barrier?

the key thing to remember with vapor barrier is that it has to be on the warm side of the wall, this varies by region
in warm southern regions it has to go on the outside of the wall, in northern cold weather prone areas it is on the inside of the wall. this is so that any moisture in the air cant get to the cold side and condensate which causes mold and rot

as for which grade, 6 mil is the standard but make sure it is the rated plastic, there is 6 mil which is simply used for masking off areas for dust or for putting down on floors before additional protection goes down

canuk uses 8 mil but thats for packing his lunch, his meatloaf is like a brick, regular plastic wrap isnt strong enough

canuk
Re: Replacing insulation from the inside - vapor barrier?
jkirk wrote:

canuk uses 8 mil but thats for packing his lunch, his meatloaf is like a brick, regular plastic wrap isnt strong enough

LOL --- funny boy :D:D

jkirk
Re: Replacing insulation from the inside - vapor barrier?

you learned that from sprucey didnt you?

canuk
Re: Replacing insulation from the inside - vapor barrier?

If you mean the meatloaf brick --- yep -- got the receipe from Sprucey.;)

1 pound lean burger
1 cup portland cement
2 cups sand
mix in tomatoe sauce as much as desired
bake at 375 until firm --- let cool then wrap in 6 mil poly to keep fresh for next day

yum yum

jkirk
Re: Replacing insulation from the inside - vapor barrier?

no accelerants?

canuk
Re: Replacing insulation from the inside - vapor barrier?

The accelerant is what you happen to be sipping while waiting for the meatloaf to cook --- at least that's what Sprucey taught me.;)

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