Home>Discussions>INSULATION & HVAC>How to insulate inside wooden walls
3 posts / 0 new
Last post
How to insulate inside wooden walls

We live in a 1913 farmhouse in Georgia that was built with large windows, high ceilings and hollow walls. Central air and heat were added to the house and we have added attic insulation, but it is expensive to heat or cool because of its uninsulated walls. We have beaded board Tongue & groove heart pine interior walls and exterior pine siding on the house, with a 4" gap between them. We want to insulate them without dismanteling our entire house. We have seen articles and blogs discussing different types of insulation and it looks like we could use the open cell foam insulation by having an installer drill holes in our exterior siding (or perhaps removing & then replacing one piece of siding). However, we are concerned because we do not think there is any way to add a vapor barrier to our house and are worried about moisture getting trapped in our walls if we insulate without one. Georgia has a hot, humid climate that is also sometimes very cold.
We have considered the cellulose insulation that can be blown in but Georgia is has a high termite risk and with wood interior and exterior walls, we are concerned. Is there any insulation we can add to the hollow walls of this old house without running the chance of getting moisture trapped between the walls? Or will we have to remove all siding to add vapor barrier and get it right? (see picture of one wall we removed to replace 9’ sliding glass doors with 6’ French doors).

Re: How to insulate inside wooden walls

Hello, Very touchy situation. Since you are finished on the inside only way to solve is from exterior. Use fiberglass blown in if you choose to blow in. Its a bit more expensive than cellulose but mold wont grow on the fiberglass like it will on cellulose. Looks like the is no sheathing on house? I would say to do it correctly, remove siding, use rolled/batt fiberglass insulation, add some house wrap, this will allow walls to breath some to release some moisture if it is trapped inside. You can then re-side, or install some foam polystyrene board then side. This will boost your R value.People have to remember, a tight house is not the best. The house has to breathe just like we do, if not it start to get sick, mold etc. Hope this helps.;)GregC

Re: How to insulate inside wooden walls

I agree with GregC --- touchy situation.

However , I disagree with GregC in that cellulose is treated with a Borax solution to prevent mold and inhibits termites.

Also with fiberglass there still is a chance with mold occurring --- while the fiberglass itself is not food for mold it's organic material and moisture that is trapped within the fibers or contact with the wood structure and drywall which promotes mold.

The touchy part of this situation is the acceptable method of vapour control.

Depending on regions some practices are to allow pass through breathing. In other words the home will breathe to the outside and to the inside depending on weather . If the primary concern for conditioning is cooling then breathing will occur to the inside since the dehumidification is done by the A/C. When heating is secondary the breathing will occur to the outside.

In hot and humid areas where cooling is the main conditioning and little to no heating requirements then vapour control is done to the exterior and the breathing occurs to the inside with the A/C dehumidifying.

Generally --- in northern winter climates where heating is a primary conditioning and cooling is secondary --- vapour control is done to the interior.

If you are unsure as to what method is appropriate to your area contact your municipal building department for their advice.

Sponsored Stories

TV Listings

Find TV listings for This Old House and Ask This Old House in your area.