Insulating/Sealing 1952 Cinder Block Home.

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Insulating/Sealing 1952 Cinder Block Home.

Post by mbaker410 »

To start I am new to the forum and have done a ton of searching but can't find exactly what I am looking for so hopfully you all can help me out.

My wife and I purchased a home in 2010 that was constructed using cinder block (hollow). It is a very strong house but it has its challenges when it comes to insulation and air gaps & cracks. We have been remodelling the home as we go and have replaced the HVAC system with a 16seer Heat Pump and had new ducts installed and insulated. We have a hard time keeping the home heated in the winter despite the new system. We don't have gas available so thats why we went heat pump and repalced the old oil furnace due to the cost of heating with oil.

We live in Baltimore, Maryland and we have cold dry winters and hot humid summers.

The house has zero insulation on the exterior walls. Starting from the outside in we have Vinyl siding, furring strips over the old Asbestos Shingles, Furring Strips (I assume), Cinder Block, Furring Strips, Lathe Board and then Plaster. So there is nothing insulating or sealing our home at all.

My Exterior Plan:
I intend on removing the siding on the exterior and all the furring stirps and asbestos shingles. I then plan on installing tyvek to the face of the cinderblock overlapping seams at least 6" and taping them with tyvek tape. I then plan on installing 2" XPS rigid insulation on top of that. I would also create a drain relief at the bottom of the exterior wall with a sheet metal drain pan installed behind the tyvek. I would also tape and seal all seams of the XPS insulation. Furring strips over the XPS and then my siding. This intention is to allow the moisture and vapors that wicks up from below grade in the cinder blocks to wick through the tyvek and down the outside face of the tyvek to the drain pan. I would also make sure that any protrusions are taped and caulked accordingly including windows and doors and would install the same drain pan over all windows and doors behind the tyvek. All the drain pans would be made using Z-Flashing.

The goal is to add some "R-Value" to the exterior while providing the correct path for moisture and vapor to escape the cinder block and block air infultration and outside moisture.

My Inteiror Plan:
I plan on removing all the plaster walls and ceilings in each room. I am most likely going to do this room by room as time allows due to the fact that we are living in the home. We plan on adding a dormer to our second floor in the near futuer so if that happens I may be able to tackle multiple rooms at once but only time and money will tell.

Once the walls and furring strips are removed I plan on repairing any cracks, gaps or holes in the cinder block. The electrical boxes are actaully notched into the cinder block due to depth so this would need to be addressed.Then I would construct new 2x4 walls that will be spaced 1/2" from the cinderblock to avoid wood touching the porous cinder block. Then I would insulate the walls with at least an inch of closed cell spray foam. That 1/2" gap would also allow me to create a full thermal break behind the studs. I would then use batt insulation in the wall cavities (no sure what R-Value probably R-13). Then just to be OCD I would most likely use Blue Board (moisture resistant/mold resisten) drywall. I wouldn't expect to have any moisture issues but if you can add another layer of protection why not?

I know that only addresses the exterior and interior of one floor but we also plan on spray foaming the roof and walls on our second floor when remodeled. I also plan on spray foaming our rim joists and walls in the basement.

That is pretty much the plan. If anyone has an suggestions or thinks that this would not work or isn't a good idea please let me know. This would be a rather big project and might even require some outside help especially on the exterior.



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Re: Insulating/Sealing 1952 Cinder Block Home.

Post by McCall »

I recall reading that people wishing to do similiar things were told it was a bad idea, I know there are other threads on this, try doing a search if you have not already.
My house is hollow Clay tile block with brick exterior and plaster interior. I wanted to so something like that and was strongly discouraged.

Hope someone else who remembers the threads comes along and can help you. unfortunately these forums are used much less not because of ongoing major spam attacks.
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Re: Insulating/Sealing 1952 Cinder Block Home.

Post by triguy128 »

You insulation isn't zero. You have the airgap of the interior furring strips, the hollow core of the block. Air leaks should be minimal on this type of construction. Th total wall assembly is probably about an R6.

I like your plan. The biggest advantage is that it moves the thermal mass of the block wall indoors. You home will change temperature much, much slower than the average home. This allows you to downsize AC and heating systems for greater effciency. Especailly AC. The smaller the better for longer run times.

One change. Leave the plaster indoors. the airgap, and thick lathe and plaster give you close to an R2. Getting a Great thermal mass properties, add some character with different accoustics to drywall, can be repaired without any sanding (drywall is so, so messy and nasty) and plaster is also antimicrobial, so it it gets damp it dosesn't dissolve or grow mold. The wood can swell and it will come loose, but it does not dossolve in water.

Repeat after me, plaster is not an inferior wall material. Its' just more labor intensive and therefore more expensive. Dyrwall only gained propulatirity because it's easier to install and cheaper. The same can be said about hot water and steam heat over forced air heating.

Why not seal the brick with a latex elestomeric paint or a rubber waterpoorfing paint from the outside, rather than the cost of spray foam on the inside. Foam on the inside will reduce the effectiveness of the thermal mass properties of your wall.
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Re: Insulating/Sealing 1952 Cinder Block Home.

Post by LindseyB »

My husband and I are in the process of purchasing a 1949 cinder block home very similar to the one described above. We did not plan to remove the plaster on the interior, but are looking into insulating the exterior in the same fashion. I'm curious how this project turned out? Did you greatly increase the house's heat retention? Have you since come across any more resources for cinderblock homes?

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Re: Insulating/Sealing 1952 Cinder Block Home.

Post by Damonkey »

I would insulate outside, but leave the plaster. Keeping the cinder block thermal mass inside the envelope will give stability. Definitely do not put bat insulation between a new interior finish wall and the structural cinder block without consulting with a professional builder from your area first. Can't say what the weather is like where you are but you do not want humidity from inside the house to pass through the insulated interior walls and reach cool structural masonry walls where it could condense into water and then freeze in cracks and gaps of hte masonry wall, slowly causing the masonry wall to deteriorate over time. Anyway, the insulation on the exterior is enough to improve the house and masonry "insulates" by preventing drafts much better than many wood frame building materials. Fix cracks in the masonry from the exterior after removing the siding. Fixing all air leaks is more important than adding batt insulation, even in a building like the one I live in which has structural brick walls and plaster interior walls but no insulation whatsoever (except in the attic). We have primarily focused on sealing all gaps and drafts, replacing doors, windows, etc.

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