Cumberland, ME (207) 829-3900 
Covering Central & Southern Maine


C wWHEREmberland, ME (207) 272-0272
Covering Maine, New Hamshire, Vermont & Massachusetts

Foundation Wall Insulation | Closed Cell Spray Foam |Rook Energy Solutions

If you read through our previous post (option #1) and have realized that rigid insulation is not the answer for your basement/crawlspace, then option #2 most likely will be. Rigid board insulation works very well for flat foundation walls (i.e. poured concrete, cinder block, etc), but is not a viable solution for older stone, granite, or even some brick foundation walls. For any non-flat foundation surface, closed cell spray foam is the optimum solution.

Where should Spray Foam Insulation be installed and at what depth?

foundation wall spray foamIn the same location(s) as the Rigid Insulation Board in Option #1 – starting at the top of the foundation wall (or even at the bottom of the basement/crawlspace ceiling as seen in the photo provided) and continued down to 2′ below grade (frost line). Since spray foam is difficult to install at a consistent depth, we like to say at least an average depth of 2-3″ (see photo at right).

With this depth you will get high R Value (roughly R6-7 per inch) and an improved moisture barrier. Concrete, stone, brick and masonry all wick moisture, so the application of spray foam will certainly help slow the migration of moisture into your home from the foundation wall. (If your basement/crawlspace has high moisture content you ABSOLUTELY SHOULD manage the moisture level prior to air sealing/insulating your basement, crawlspace, or home)

Why Closed Cell Spray Foam? (vs. open cell)

Open cell spray foam has its place and can be a very cost effective solution, but never within a basement or crawlspace. Unless you live near/on the water, most of the moisture within a home enters from the lowest levels (basement/crawlspace) and travels upwards via stack effect. Ask yourself, do you ever have standing water in your basement/crawlspace? Do you have mold on the base of your foundation wall? Does your basement (or even your home) have a musty smell? Most people will answer yes to at least one of these questions…and this is why you need to use Closed Cell Spray Foam, as it helps block moisture intrusion occurring through the foundation wall. The difference between the two types of foam are as simple as their names. Closed Cell blocks/slows moisture intrusion and Open Cell reacts more like a spunge. Since the last thing you want to do is retain moisture within your home, open cell spray foam should never be used within the basement/crawlspace.

How do I know if my basement/crawlspace moisture level is too high to air seal/insulate properly without first managing the moisture level?

Best to leave this up to the professionals – have an energy audit or at least a consult with a specialist to rule out a bad scenario. Some good rules of thumb:

  • if your basement/crawlspace has standing water intermittently throughout the year then you should contact a professional
  • if you have exposed dirt floors, moisture management should be done first
  • if you are constantly cleaning mold off your foundation walls, moisture management should be done first
  • if the ceiling joist nails are rusted, moisture management should be done first

Some moisture management solutions could be…

  • Vapor barriers to cover dirt floor
  • Mechanical ventilation (i.e Humidex)
  • French Drains within your basement/crawlspace
  • Exterior drainage or improved grading
  • Installation of gutters

foundation wall closed cell spray foamfoundation wall closed cell spray foam






Both photos show what properly installed closed cell spray foam insulation should look like on a foundation wall. Installing 2' below grade will insulate to the frost line.


Spray Foaming 101


I own a beautiful 1885 stone home in ontario canada. During the summer, the house is perfect. Over the winter is a different story. The house consists of laughing plaster walls, a newer furnace which was updated in 2002, all new windows except for a big bay windows(double pane) and modern finishes throughout. I have been working on the finishes of the house over the past year and in the fall, i started doing extra insulation in the bathroom and bedroom cieling.

The major problem areas are: front door (nearly original with house), back door (doesn't seal properly and needs replacement) and the 'cellar' of the basement. The basement has poured concrete throughout but is moist due to the stone structure. to combat the heat I wanted to get an opinion on doing a full spray foam application of 30% exterior walls (70% has finished drywall on them) and 100% of the floor.

My plan thus far: remove the drywall on the ceiling on the finished part of the basement (1 room of 3 rooms) and have the insulators come in to spray the exterior walls where possibly and the entire floor. After this, I look to replace both front and back doors.

Is there any other recommendations? or do you see any issues with my ideas?
Cambridge hits a few lows of (-25 C) with wind chill in the winters but on average is (-10 C)

Thanks and I look forward to hearing your response.

Ontario Reply

Hi Brandon, 

Thanks for the comment. Prior to providing any answers to your questions, we will require a little more info from you. You say that the basement has poured concrete, but that it is an 1885 stone structure. What areas are poured concrete (foundation walls, foundation slab, etc) and what areas are stone? In the 70% of the basement that is finished, what is the detailing? For exmple; is it a stud wall with fiberglass insualtion behind the drywall? If so, do you know how much space was left between the studs and the foundation wall?

Additionaly, you say that you are interested in spray foaming 100% of the floor? Is it a dirt floor or concrete slab? There are many other, more practical solutions to block moisture from coming through the floor besides spray foaming - and they would be much less money too. What is the exterior grade on your home like? Does it slope away from the house? Do you have gutters? Can you attach photos of your basement so we can see what you're talking about?

Many thanks.

Rook Energy 

New construction

I am planning on building a new home in Massachusetts and am exploring the idea of using closed cell spray foam as insulation for the foundation walls, (rather than the closed cell boards). Is there any issue with this approach?

Insulating Old Granite Foundation

I have a 200+ old barn in North Hampton, NH that I am doing over into retail space and need to insulate the 14' high granite basement/foundation walls. A very small amount of water dribbles down the wall but basically dry. We are hoping to work with the Park Service on this project and thus some concern about how we do this too. Ideas?

Reply - Insulating Old Granite Foundation

Hi Peter, 

Thanks for the note. Sounds like spray foam is the best option. Of the 14' high foundation walls, how much is exposed to the outdoors? In a New England climate, we always recommend insulating to 2' below grade, there is not much reason to go too far below that though. Some things you want to consider are: the condition of the foundation wall, how much moisture is coming through the wall, exterior grade, exterior drainage, etc. In older homes with field stone or granite walls where moisture is present, we will sometimes only insulate to grade - if excessive moisture is present that should ALWAYS be mitigated prior to insulation. 

It's also very important to make sure the foundation wall is in good conidtion. If so, covering the wall with foam is a great option as the foam will in fact improve the structural integrity of the wall. 

Another option - depening on the slab configuration (or lack of), you can always cover the floor with a reinforced 12 mil poly, run it up the walls and then bring the spray foam down over the edges. This is only recommended if the foundation wall is in good condition with adequate exterior grade and no signs of extensive moisture through the foundation wall. We like this solution as it get's rid of that old musty smell and controls ground gasses extremely well. Good Luck!

Poly Ground Cover to Grade & Spray Foam

Granite Foundation Insulation

Thanks for the quick reply and some photos.

Do you work in the North Hampton, NH area? Is this a project you would consider looking at to do?



That is just beyond our work territory - however, depending on the scope and timeline we may be able to make an exception. We would need to discuss the scope and see some photos of the space prior to making a site visit though. If you're willing to provide some information ( - (207)829-3900) we may be able to help you out. Give me a call or send an email and I can let you know what info we'll need.  


Spray foam on exterior of foundation below grade

We are restoring a 1770 cape in Nova Scotia. Its built into a hill and the front walk out area of the basement was very wet. Floor had rotted out, poor drainage and holes in the stone foundation. We have done extensive drainage including digging down to the footings in one area. We have repaired & parged the foundation stones. The basement is DRY!! Before filling in the hole, should we spray foam on the exterior walls below grade and if so should we go below the frost line?


Thanks for your comment Martha. My apologies for the tardy reply, this time of year is quite busy for us. If the basement remains dry and you've been able to test it through some wet weather, then yes I would say it's safe to insulate the foundation walls to ~2' below grade. Not too sure what the frost line depth is in Nova Scotia, so maybe verify that first to make sure you're going deep enough, but 2' is most likely sufficient. Just to verify, when you say you dug down to the footings, was that digging down from the exterior or the interior (due to a dirt basement floor)? Also, are you asking if you should insulate the exterior (outdoor) side of the foundation walls? If so, I have honestly never been asked that, and would not know the proper answer. Whomever your spray foam contractor would be, I would have them contact the manufacturer of the foam and reference any Ground Contact information they may have (it may not be safe from Geological angle). My guess is that it would be fine, but I would certainly check first. Since the basement is dry now, you can always spray the interior side of the foundation walls to 2' below grade - it works extremely well. 

Thanks again for your post. 


trapping moisture in a wall

Is a capillary break necessary between a rubble wall and sill beams? I have an 1830s timber framed house and the rubble foundation walls have lots of efflorescence, indicating they've been transmitting water vapor into the basement forever. We are interested in encapsulating the crawlspace/cellar to prevent high humidy. If we have the walls spray foamed, won't all that moisture be trapped in the wall? Won't it saturate the wall and rot the sill beams? There are no footer drains on a house this old. Lifting a house to install a capillary break is expensive, but not doing it if it is needed is even more expensive. Is an interior perimeter drain to sump with no capillary break sufficient to keep the sills from rotting? We are on a hill with proper grading, gutters, and downspouts.

RE: Jim Dunkel

Thanks for your comment Jim. This is a difficult question as it sounds like you really need someone onsite to take a look at the space. I am not a fan of covering up any stone foundation walls that have excessive moisture, unless there is adequate moisture management within the floor. Spray Foaming directly on the foundation surface in above grade sections of field stone walls is doable, but going below grade in areas with high moisture coming through the foundtion wall is not ideal - the foam will simply not stick if it's wet. As long as the timber sill has room to breath in one direction (to the outside) it should be fine to cover with foam from the inside. I've attached a link for a case study on showing an approach that may be valid for you (click this link: /sites/default/files/ec_pro/rookenergy/BSI%20-%20Rubble%20Stone%20Foundations.pdf). 

Per the article, since you would be covering up the foundation wall with poly and spray foam, you really need to trust that your moisture management system is working as it should as the last thing you want to do is have to tear through a section of foam/poly to inspect the foundation walls condition. If your foundation walls are in good condition, you install a properly functioning drainage system that drains to a low side of the home - then this should work well. Since the walls show signs of moisture, with the info given in this post, I would utilize the approach of a vapor barrier prior to spray foam. 

I hope this helps - let me know if the link doesn't work. 


Using closed cell flash coat

We have new construction. The first level is 10 foot high block wall. Is it possible to use this closed cell foam on the outside of the block wall. It has already been painted with a double coat of Drylock.

Re: Lynn Haneke


I would need to see some photos of the space (interior and exterior). Where are you located? What is the finish design on the interior side of the block wall (framing & insulation)? 


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