# Insulating double brick wall home. Via the inside.



## Ron6519 (Mar 28, 2007)

Is that wood sheathing behind the lath?
Ron


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## the punisher (May 29, 2008)

Ron6519 said:


> Is that wood sheathing behind the lath?
> Ron


The order of the materials are as follow:

Plaster-->Lathe-->3/4" Furring strips-->Nailed on the cement wall.


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## Wildie (Jul 23, 2008)

I had a house the same as yours in London, ON. Had the same problem!
In my case I removed the baseboards and built a 2X4 framed wall inside, tight against the plaster walls. Leaving the lathe and plaster in place! Installed in much the same manner as you would in a basement! 
After insulating with R12 f/g and installing new electrical outlets, I closed it in with 6 mil poly and drywalled.
Rather than rip off the window casings, which suited the period of the home, I built a cove around the outside of the casings! Not the most effective way of saving heat, but 90% of the surface was insulated and made a substantial difference in our heating costs!


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## the punisher (May 29, 2008)

Wildie said:


> I had a house the same as yours in London, ON. Had the same problem!
> In my case I removed the baseboards and built a 2X4 framed wall inside, tight against the plaster walls. Leaving the lathe and plaster in place! Installed in much the same manner as you would in a basement!
> After insulating with R12 f/g and installing new electrical outlets, I closed it in with 6 mil poly and drywalled.
> Rather than rip off the window casings, which suited the period of the home, I built a cove around the outside of the casings! Not the most effective way of saving heat, but 90% of the surface was insulated and made a substantial difference in our heating costs!


Yup I am in Toronto, ON so pretty much same weather as you. Building a 2x4 wall on top of the existing plaster is not an option, I just can't afford to loose those 4". My house is already pretty narrow as it is.

I have been researching and posting on other forums as well. Essentially what everyone is telling me is that the payback in energy savings that I will get from ripping out the plaster and framing a new insulated wall, is not worth the money it will cost for the job to be done.
Say it costs me 2000.00 to rip out the plaster and lathe and build new insulated wall, It would take me a few years to get that money back in energy savings.

What people have suggested, is to just throw drywall directly on the plaster and invest the extra money saved on better insulating my attic, since heat escapes upward that is where it should be best insulated.


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## Wildie (Jul 23, 2008)

the punisher said:


> Yup I am in Toronto, ON so pretty much same weather as you. Building a 2x4 wall on top of the existing plaster is not an option, I just can't afford to loose those 4". My house is already pretty narrow as it is.
> 
> I have been researching and posting on other forums as well. Essentially what everyone is telling me is that the payback in energy savings that I will get from ripping out the plaster and framing a new insulated wall, is not worth the money it will cost for the job to be done.
> Say it costs me 2000.00 to rip out the plaster and lathe and build new insulated wall, It would take me a few years to get that money back in energy savings.
> ...


 I did insulate the ceilings also! That's a given! 
I looked into having foam pumped into the void between the lath and the brick but I was told the payback wouldn't make it worthwhile!
Another option that you could consider is to fasten 2" of foam to the strapping, then drywall over this! 
I used this method in a stairwell and even R10 made a difference.
Most rooms can lose 2" on a wall without a problem.


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## the punisher (May 29, 2008)

Wildie said:


> I did insulate the ceilings also! That's a given!
> I looked into having foam pumped into the void between the lath and the brick but I was told the payback wouldn't make it worthwhile!
> Another option that you could consider is to fasten 2" of foam to the strapping, then drywall over this!
> I used this method in a stairwell and even R10 made a difference.
> Most rooms can lose 2" on a wall without a problem.


When you mean adding foam to the strapping you mean the lathe? Meaning just rip the plaster out and leave the little stips? add foam on top and then drywall? Or did you mean remove the plaster and strips and put foam insulation in between the 3/4 inch furing strips that are about 16" O/C

Or are you saying to throw the the insulation on top of the plaster and then drywall on top?

I'm a little confused.


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## Wildie (Jul 23, 2008)

the punisher said:


> When you mean adding foam to the strapping you mean the lathe? Meaning just rip the plaster out and leave the little stips? add foam on top and then drywall? Or did you mean remove the plaster and strips and put foam insulation in between the 3/4 inch furing strips that are about 16" O/C
> 
> Or are you saying to throw the the insulation on top of the plaster and then drywall on top?
> 
> I'm a little confused.


 The wooden, horizontal strips called lath are nailed to vertical strips that are, in turn fastened to the brick work!
The lathing provides a tooth for the plaster to adhere to.
In your case, as space is important, I would remove all the plaster and the lath. This combination will be be anywhere from 3/4" to 1" thick! 
Once the plaster and lath are cleared away, nail 2" styrofoam board to the vertical strapping. ( make a mark on the floor and ceiling to indicate where the strapping is located)
It would be a good idea to use construction adhesive to fasten the foam, as well as nailing.
Then apply 1/2" drywall over top of the foam, again using liberal amounts of adhesive, and screw this to the vertical strapping using long drywall screws!


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## the punisher (May 29, 2008)

Great advice. Thanx a million.


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## DougDobbs (Mar 18, 2009)

Glad to read this thread. I'm new here and my problem is similar so I thought I'd piggyback on this thread.

I've got a house with a concrete block perimeter wall and tried to find a way to insulate on the outside and take advantage of that thermal mass. However, nothing I could find in the way of an exterior finish seemed durable enough or looked "ok" for our neighborhood. So I've decided to insulate on the interior. I'm almost through with the gutting, one or two ceilings left and we'll be there. (They're coming down to put PEX in the first floor ceilings and get rid of really bad odors in the house.) 

I looked long and hard and can't see where anyone has done what I'm about to do, so all thoughts are more than welcomed.

We've stripped off two (!) layers of strapping and plywood paneling. The plan is to put a layer of 2" styrofoam "blue board" on the interior of the perimeter walls, then frame a 2x4 wall inside of that. More 2" foam is cut to fit inside the stud pockets, then a light layer of spray foam to finish filling the cavity and provide a vapor barrier. The rooms are big and won't feel the loss of floor space too much. The tough part will be framing around the windows and doors.

I'm going to run some 2" pipe inside the wall, from basement to attic as conduit for future electrical wires, etc. The goal is to build something that will be super-insulated but not have moisture problems. I'm in S. Pa., 6000 degree day zone, and I want to use as much passive solar energy as I can. An air-to-air heat exchanger and beefed up attic insulation are part of the plan.

With the thick walls and some stone veneer, we're hoping to take a 1940's house back to 1750's look to fit the vernacular of the area, but with high insulation standards to benefit the current day. 

I've thought this through many ways, and I think I've got all the angles covered, but I've never seen anyone do things this way. Any suggestions or insights?

Thanks,

Doug


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## jcalvin (Feb 6, 2008)

Let me get this straight. Starting from the outside working in you have approx. 4" brick, 1/2" gap, 4" brick?, 1/2" gap, concrete wall, 3/4" furring strips, lathe, ans 1/2" of plaster. If that is correct, you have approximately 10 1/4" of wall thickness, and that is assuming that the concrete wall is only a skim coating of concrete. I know this isn't exactly the nice pink panther insulation, but it counts for something. I don't think it is worth the time to insulate this. If that is a solid concrete wall, you will have to build out another wall and retrim all the windows. Gonna take a long time to recoup enough money to afford this.


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## Wildie (Jul 23, 2008)

DougDobbs said:


> Glad to read this thread. I'm new here and my problem is similar so I thought I'd piggyback on this thread.
> 
> I've got a house with a concrete block perimeter wall and tried to find a way to insulate on the outside and take advantage of that thermal mass. However, nothing I could find in the way of an exterior finish seemed durable enough or looked "ok" for our neighborhood. So I've decided to insulate on the interior. I'm almost through with the gutting, one or two ceilings left and we'll be there. (They're coming down to put PEX in the first floor ceilings and get rid of really bad odors in the house.)
> 
> ...


 I would wonder about your method of filling the stud cavities! Cutting foam would be time consuming and would have to be caulked around the whole perimeter!
If your going to get prepared to spray a 'light' layer of foam over top, why not just spray the stud cavities and be done with it!


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## DougDobbs (Mar 18, 2009)

The time issue isn't so big a deal, I can cut the foam pretty quickly with a table saw. A loose fit would be enough, doesn't have to be caulked, the spray foam will seal the gaps pretty well. Foam board is 1/3 the price of spray foam, it's a cost savings to fill the void this way. I have more time than money. 

I'm more concerned about moisture being trapped between the block and the first layer of blue board. I've considered putting shallow spacers in there to allow some air circulation but wasn't sure it would be any real benefit as long as the block can "breath" to the outside, which it should be able to do. I think. 

Doug


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## jlc791 (Mar 17, 2009)

I've been following this thread with interest as I'm facing a very similar situation with my concrete block house. It seems that there are three ways to add insulation to these types of houses: remove the drywall and add foam panels, inject foam into the ~1.5" void between the drywall and the block, or construct a whole new insulated stud wall inside the exsisting walls.

Since I'm dealing with a relatively small house, the third option is out but this still leaves me with the question what to do (if anything). Based on tables of R-values that I've been able to find online, my current walls have a total R-value of around 2.4 (brick facing, 8" concrete block, drywall). Regardless of which method I use, the most I can add in the ~1.5" gap that I have is foam with ~R-8 for a total of around R-10.

My quesiton is, how much of an energy savings will I see with this relatively small increase in R-value? As much as I'd like to save energy, I'm beginning to think that the energy savings may be so small as to give the project an extremely long payback period.

Thanks in advance,
Jeff
Trenton, NJ


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## DougDobbs (Mar 18, 2009)

Jeff,

I don't know the numbers off hand, but it sounds like a trade off for you between space and R-value. 

If it was up to me, I'd rip it back to the block, sheath it with 1" blue board, put up a 2x3 stud wall and shoot it with foam, you'd only lose about two inches into your room and you'd have about a R17 wall with a great vapor barrier. Way more comfortable than R2.4, and with the tax credits out now it would knock the price way down. You'd have to make sure your attic insulation was up to par to match it, but I think it would pay off sooner than you'd think at the rising rates we can expect for energy.

There is considerable disruption to your household as a negative factor, but it's a great chance to upgrade electrical wiring, add cable, etc. as well. 

Let us know what you decide to do.

Doug


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## ArchTech (May 18, 2010)

The best way to do it if you are in Toronto is to pull the wall out and add R20 insulation. I`m an architectural technologist and if you were my client that is what I would recommend. Double masonry wall by itself is of course perfectly adequate however it comes down to your own preference.

Jeff,

I caution the spray foam now adays. There have been cases were vermiculite insulation has been found within it recently. Please be cautious about any decision you make. Batt insulation is still the more prefered choice.


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## Ron6519 (Mar 28, 2007)

ArchTech said:


> The best way to do it if you are in Toronto is to pull the wall out and add R20 insulation. I`m an architectural technologist and if you were my client that is what I would recommend. Double masonry wall by itself is of course perfectly adequate however it comes down to your own preference.
> 
> Jeff,
> 
> I caution the spray foam now adays. There have been cases were vermiculite insulation has been found within it recently. Please be cautious about any decision you make. Batt insulation is still the more prefered choice.


 What are you speaking of when you caution about spray insulation? Which spray insulation? Where was vermiculite found?
What's an architectual technologist?
Ron


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## stuart45 (Jun 20, 2009)

If it's a cavity wall ( brick external wall/ 2-3 inch cavity/brick or block internal wall), the usual way is to drill holes in the exterior wall and inject insulation such as mineral fibres or polystyrene balls. This is quite a simple and cheap method. I wouldn't recommend ripping down a wall to put insulation in the cavity.
http://www.thinkinsulation.co.uk/cavity-wall-installation.htm


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## Wildie (Jul 23, 2008)

stuart45 said:


> If it's a cavity wall ( brick external wall/ 2-3 inch cavity/brick or block internal wall), the usual way is to drill holes in the exterior wall and inject insulation such as mineral fibres or polystyrene balls. This is quite a simple and cheap method. I wouldn't recommend ripping down a wall to put insulation in the cavity.
> http://www.thinkinsulation.co.uk/cavity-wall-installation.htm


 Just for the record, this thread is more than a year old and the OP has probably completed his project!
The wall only had a 3/4" cavity and the R value payback for injected insulation wouldn't make it worth while!
My present home had a 3 1/2" wall cavity and I did have cellulose insulation blown in! It would be a waste of time and money to do so with a 3/4 cavity!


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## Wildie (Jul 23, 2008)

ArchTech said:


> The best way to do it if you are in Toronto is to pull the wall out and add R20 insulation. I`m an architectural technologist and if you were my client that is what I would recommend. Double masonry wall by itself is of course perfectly adequate however it comes down to your own preference.
> 
> Jeff,
> 
> I caution the spray foam now adays. There have been cases were vermiculite insulation has been found within it recently. Please be cautious about any decision you make. Batt insulation is still the more prefered choice.


 I doubt that anybody would be happy about losing 6" of room space so as to install R20 insulation! 
Usually rooms in these old houses are small to start with!


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