THE CRAWL SPACE DEBATE

    I have been in more crawl spaces than I care to think about and, over the past few years, have seen more than my share of problems; mostly water/dampness related. Rotted floor joists and beams, beam pockets that are decayed and constant dampness that is, as we tighten up our homes for energy savings, causing an increasing level of indoor air quality issues are the most common of those. Now, faced with renovating my own home, making the decision as to the right steps has been one of the most investigative I have done on the “green church” project, to date.

    To begin with, we have a number of pluses. For starters, most of the stone foundation is above grade. The church is built on rock, but, as it turned out, there was a large base stone that was not secure, causing one corner to settle. On excavation, we discovered that this corner was actually sitting on a soil pocket and time, the freeze/thaw cycle and our renovations were having a detrimental effect. This meant an underpin effort, which was completed last week and which brings me to my first conclusion and suggestion. If you are planning to insulate a stone foundation, you must establish how integral it is and pay close attention to the drainage; the grades must aggressively drain away from the home. 

    In specific applications, I have been recommending spray foam for some time. There are as many opinions about its use and applications, however, as there are basements and crawl spaces, or so it seems. There is no doubt that closed cell foam is effective. Spray foam effectively reduces moisture; in fact some contractors say it fully controls it. While I am not 100% sure of this, tests have shown its effectiveness. Upwards of 40% of heat loss travels through air movement. Moisture travels with heat; the warmer the air, the greater chance of moisture being contained within it.  Closed cell spray foam creates its own air barrier to stop this; hence it helps reduce heat loss.

    Even so, since I have seen more than one “water bubble” behind a close cell application, I have been hesitant to use it on a stone foundation. This has, in the past, shied me away from this make of foam. I have seen open cell foam used in basements and, given its vapor permeable value, it has seemed like the better idea. There is one catch, though, as it is not as energy efficient. An inch provides an approximate R value of 3.5 vs. an R6 for closed cell. I put this question to Jeff at Kingston Spray Foam and his response was, “I wouldn’t recommend using open cell in this application because it promotes mold growth.” Jeff is aware that the church crawl space is not vented and will be heated.  He went on to say, “As long as the stone walls are dry on the day of the application, the closed cell foam will creep into every crack and crevice, bonding to everything, preventing the possibility of water pockets in behind,” Jeff continued on with, “If water penetrates the stone wall it will trickle through the stones to the bottom of the wall, but will not affect the adhesion”……….” If you have seen water pockets in the past, I would assume that the surface was wet or damp and that there was some separation between the stone and the foam.”

    Particularly early on in the popularity of the use of spray foam, I saw numerous applications that were poorly done and its back to one of my more frequent comments, “Hire the pros who know their materials and have the experience in the correct applications.” Jeff also made comment on the drainage and the correct height from the wood structure. Using spray foam is yet another reason to control your ground water drainage. And with that, and because we are fortunate that our stone crawl space is dry, very dry, in fact, we are going to use closed cell for the extra efficiency.

    CMHC has an excellent article in their “Keeping the heat In” section on insulating a crawl space. It’s available on their web site. It discusses insulating a heated crawl space and how they, as most now do, don’t recommend venting to the exterior. They also recommend using a liner on the floor and this practice is accepted as the benchmark for crawl space air quality. At minimum, a 4 mil liner and at best would be an 8 mill liner. I have used roofing membrane material, but I have heard some dissenting comments of late and note that this is no longer recommended. Not every idea passes the test of time, as they say and keeping up on the most recent information makes sense in this regard.

   In laying the liner, the most important thing is to overlap the seams, caulk with acoustical seal or tuck tape and seal to the wall for a complete moisture barrier. One good idea CMHC had; they found that the white polyethylene brightens the space and shows any area of leakage, good idea. Of note is that our air handler is in the crawl space and the filters must be changed, so I plan to lay a pathway of roll roofing to the air handler to protect the plastic liner from damage. If you have an area that you must enter on a regular basis, I suggest you consider doing the same.

   Jeff and his crew arrived last Thursday and completed the spray foam application in the crawl space of the “green church.” I have used Kingston Spray Foam on a number of jobs in the past and continue to be impressed by Jeff’s attention to detail and knowledge. Hire the pros, as they say, and get it done right. Go to www.kingstonsprayfoam.com to learn more on spray foam applications.

    Rather than a typical crawl space, we now have a “low” basement, correctly heated as laid out by our HVAC duct design. With that, we have controlled the moisture issues by prohibiting the evaporation of the moisture in the dirt floor and the stone walls have been insulated with 2 inches of close cell foam.

   We are on the home stretch at the church. In three weeks we will be moving in and the crew are busy working on the final push. Go to www.alltchgreenchurch.ca for more pictures and read past columns on the progress.