Retrofit: Basement Foundation Wall Insulation Choices

Basement block foundation wall insulation

I have been auditing & retrofitting homes as an additional service to my remodeling company for 3 years now. My all-star insulator sadly passed away recently and I am just getting started with a new provider.

This new provider has specified Polypropylene Scrim Kraft to insulate unfinished basement block walls:  

Thus far, I have used Thermax on my projects: 2" foil faced poly-iso taped at ALL seams. He indicated that the PSK (Polypropylene Scrim Kraft) is cheaper, also satisfies the code for fire, and has a white finish which looks better. The JM product is formaldehyde free.

The 2 products have very close thermal values and I suspect will perform similarly when taped at seams and installed continuously.

My concern is moisture and durability. We know that moisture moves through block walls. This home does not have active bulk water infiltration issues, but I am still hesitant to use a fiberglass product against a masonry wall.


What do you use? How do you install it?

I look forward to your input.

Thanks in advance.

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I am going to be upfront and say this is one application of our insulating coating that I have not performed myself.


Our distributor in Texas has painted / coated basements and foundation walls for many years.  All of his referrals are by word of mouth and he has never bothered to gather data, statements or pictures, at least none that he can find on his computer.  If you go to our site, at the top is his name and Cell number, Joe Merrell.


Give Joe a call and he can tell you all about the jobs, results, cost, etc.  He has had excellent results spraying the block walls, A/C and heatibg ducts and under the floors of houses.


Oh yeah, we are rated at 4.93 US Perms and are a Class A Type 1 Fire Retardant



I have no experience with Polypropylene Scrim Kraft.  However, we all know that Thermax does a great job and that wet fiberglass is a huge problem.  I can't see how fiberglass on a basement wall would be anything other than a huge headache.  I surely wouldn't switch without a multiple house third party study that showed Polypropylene Scrim Kraft effective.

I am really suspicious when I read on their site that Polypropylene Scrim Kraft Non-Perforated (according to site, resists water vapor transmission) is recommended for most basement walls.  We have known for years that nothing should be put on basement walls (that are below grade) that resists water vapor transmission.  Below grade walls can only dry to the inside. Any vapor barrier would trap moisture inside the walls leading to possible mold and rot problems.

Until our local building code converted to 2009 IEEC this stuff was used by a number of builders in this area.  I bought a house with it draped on the basement walls.  Removed draped insulation package and installed 2" foam to concrete, sealed seams and framed and rocked interior so we could use basement.  The draped material did not fully cover wall, had gaps, tape seams were open,  and in no way did a reasonable job of insulating the basement walls.  It was just the cheapest way to meet the code - again proving a house built to code is the worst possible house you can buy!

Applied to concrete basement walls with rollers and brushes.  Cerama-Tech's perm rating is 4.93 US Perms.  Never had a moistrue problem reported and has solved many mold problems.

I would like to offer my two cents and say it is always preferable to insulate on the outside so the foundation stays warm instead of the inside where the foundation is cold and runs the risk of condensation if air by-passes the interior insulation.  It is often difficult to insulate on the inside unless the basement is tottaly clear of items.


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