blowing in wall insulation


Old 10-13-10, 08:02 PM
Thread Starter
Join Date: Oct 2010
Location: canada
Posts: 11
Red face blowing in wall insulation

Hi all. Hoping someone might be able to offer some advice. I have an older home built,I believe, in the 30's or 40's, and has zero insulation in the walls. Getting tired of microwaving my coffee cup in the winter before I can pour a hot coffee into it so I started to consider adding some insulation. I had pretty much decided to blow in cellulose from inside but in doing my research, have found some info that has me worried. I read that these types of homes,(brick veneer outside, lathe & plaster inside) were designed to dissipate any moisture behind the walls to the outside and therefore, blowing in insulation especially without being able to add a vapour barrier is asking for trouble. Can anyone shed any light on this? I would like to think that if my local Home Depot advertises the insulation ,and machine to apply it ,is applicable to walls as well as attics ,than it should be safe right? Anybody heard of any problems with moisture with this application? I would love the benefits of the added insulation but don't want to risk causing a much more serious problem. I am also a little concerned with the fact that the mortar between my bricks is far from pristeen. Will moisture work its way in from outside and soak the insulation as well? Sorry this is so long, but I am really concerned about doing more harm than good and hope someone out ther might have experience with this. I guess I could always live with the cold coffee cup. Thanks for any help.
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Old 10-14-10, 04:28 AM
Join Date: Oct 2008
Location: New England
Posts: 9,995
Hi Martin and welcome.
What you have heard is pretty much correct. Brick requires a drainage plane on tthe inside to promote drying. I will attach a link that has some reference to this. I've driven through parts of CA and brick is very popular up there so sure wish they would come up with a solution. I know the foam guys are constantly trying to fill that gap with foam and I have to keep saying no.

There are three ways to insulate a wall, inside the wall, on the inside surface, and on the outside. If we rule out the interior and the outside, you are left with insulating it on the inside surface. That can mean removing the plaster, building a new wall to depth, and then insulating and drywall. The other approach is to cover the inside surface with rigid foam insulation and drywall over that, screwing into the lathe.

Given the age of the home, it is probably rather leaky, and sealing air leaks is often easier and more productive. Check your walls to see if any are open top to bottom, called balloon construction. I will also add a link on air sealing as there is often much to gain.

BSD-106: Understanding Vapor Barriers — Building Science Information

Old 10-14-10, 05:57 AM
kolias's Avatar
Join Date: Jul 2004
Location: Canada
Posts: 1,227
My opinion on “blowing in wall insulation” is no good. A few years back I did a kitchen / bath reno and when I opened the walls to do the plumbing / electrical all the blown insulation had sag at the bottom of the wall in a wet ball. When I pointed to the owner he said that the job was only done 5 years ago!

I would say that blowing insulation should be applied only to horizontal surfaces like attics and nothing more.
Old 10-14-10, 12:19 PM
Join Date: Oct 2004
Location: PA
Posts: 1,838
get a blower door test then follow him around and see where everything is leaking. You will be amazed. it's worth the $ to find the leaks. I'm unsure if infrared would be appropriate in your circumstance since you cant easily insulate your walls. Maybe someone else can chime in.

you didnt say anything about your attic. If you can, i'd put more insulation up there. I recently discovered there's so little insulation in mine and ill be adding more soon.
Old 10-14-10, 01:03 PM
Otown's Avatar
Join Date: Sep 2010
Location: USA
Posts: 53
I worked for a company in Ohio where we used a cellulose based material.We would actually from the outside drill two holes between each stud, one upper and one lower. we would start at the lower hole and fill until flow becam restricted, and then the same for the top. The material we used was a ground up newspaper with a fire retardent added. The stuff worked great in the walls and attics.

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