Re-Insulation: Interior or Exterior?

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Posted by: from Stony Plain
11/22/2012 at 9:11:28 PM

We just moved into a 40 year old house. We started to do some minor renovations and when we began to move some stuff into the reno'd rooms, we noticed that one of our quilts was frozen to the exterior wall. We then looked behind a bunch of moving boxes in an exterior corner and they were frozen to the wall and ice had formed between the boxes and the wall.

So my question is: Should I take the time to remove the drywall on the inside and re-insulate or should I wait till spring and insulate the outside?

Do you have any advice or other options we should consider?

Which is the most cost effective and/or best option? How much approx could this cost? (1200 sqft bungalow).

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Date/Time11/22/2012 at 10:13:04 PM

I have run into this before. You have two options

1. Pull drywall and re insulate, re drywall, paint. Either way vapor barrier is bad as well. If you go this way it's possible the cause of deteriorated insulation is in exterior sheeting of wall which would have to be addressed as well.

2. From the outside. This will be more expensive. Remove siding or brick. Remove exterior sheeting. Spray foam must be used existing vapor barrier is damaged. As foam drys it creates its own vapor barrier. Add new sheeting and house wrap and siding or brick.

By doing option 2 you get the best insulation money can buy and your interior can still be lived in while the work continues outside.

You can use the foam from the inside as well. Or batt and plastic vapor barrier.

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Andrew from AMB Construction in Vaughan
Date/Time11/22/2012 at 11:26:28 PM


Only one answer is proper- always and every time exterior re-insulation even if you have to spend more money.

I am contractor with 28 years experience (Canadian and European) and I think that interior insulation is some kind of sabotage for many reason. Funny things for me and completely incomprehensible is why the big builders doing this things with new houses?

It is very simple : perfect wall is that wall which is perfect heat conductor from inside and perfect insulator from outside - on condition that leave it to the heat exposure from the inside. I mean do not cover by drywall just put cement parging and and two finish coat.

The best insulation is EPS or common Styrofoam. My last building in Europe had 8" thick solid block from inside and 7" thick Styrofoam from outside except basement where I installed 5" thick EPS. Only that way guarantee you proper thermal work all the time. Another advantage this method is- you do not have to install vapour barrier in a basement.


Andrew Butylkin

AMB Construction

4800 Highway 7 unit #10

L4L 1H8 Woodbridge Vaughan ON

T(office) 416 800 2180

T(cell) 647 833 1775

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Richard from Ricklyn Renos in Penticton
Date/Time11/23/2012 at 7:47:22 AM

In my opinion it is better to install updated vapor barrier and foam insulation to the outside of the house. When you remove the drywall you open a big can of worms.

Also you can only install the same amount of insulation to 2X4 walls as originally existed. The cost varies greatly depending on the type of siding you will install over the new foam insulation.

A great time to give your home a face lift and increase the value.

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Antonio from Beccati Contracting in Toronto
Date/Time11/23/2012 at 8:43:16 AM

You should do it now and from the inside so you can do a proper job with insulation and vapore barrier.

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Date/Time11/23/2012 at 8:56:49 AM

If there is any decent size cavity in the walls, you might consider having the walls drilled and filled with cellulose fibre. I have seen this situation with older homes with paper backed batting in the walls and the 4" cavity is only filled with a 2" paper backed old fibreglass batt. You could drill a 1" hole minimum to determine what insulation is in there now and how it fills the cavity. If the there is no substantial cavity, then you may look to remove the walls from inside to re-insulate, just remember if you are going through the trouble of removing the walls inside, don't re-insulate with fibreglass, take the next step to use a better insulation product, cellulose, Roxul, spray foam, etc.

The most cost effective is to have the walls drilled and filled if possible, and then the costs increase from their. You also do have the option of re-insulating from the outside with a rigid foam board exterior insulation.

Brent Murray

Reitzel Brothers Insulation - Kingston, On


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Date/Time11/23/2012 at 11:49:23 AM

Hi Matthew,

Lots and of pros and cons to both options, you live in Stony Plain so temperatures of -20 aren't going to be uncommon this winter so it maybe something you want to address from the inside for now.

My advice though before you do anything is to have a thermal imaging report done on the house (perhaps you had one with a home inspection when you purchased?). The thermal report would identify areas of heat loss, moisture issues, insulation problems without having to do any distructive work. Perhaps this is an isolated problem and you just need to address that one area? Perhaps its an issue affecting all the exterior walls? The report will help you isolate the problem areas and give you a better idea of how you should tackle this.

Hope it goes well for you.


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Johnny from Avid Contracting in Oakville
Date/Time11/23/2012 at 7:13:52 PM

If your residence has that much cold air coming in I strongly suggest that you deal with this issue asap. The winter conditions will only deteriorate your home's cavity and could cause more extensive damage to support structures as well.

The temporary solution until you decide to renovate completely would be to remove an area of drywall and use some polymer spray foam or call an insulation specialist to spray that corner. Then replace and repair the area's finishes.

Avid Contracting

Johnny Bakai: (C) 905 599 2447

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Date/Time11/29/2012 at 9:37:37 PM

Fr om Ron Petrucci Drywall

Yes you should remove drywall and insulate.

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