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How Should I Insulate My Crawl Space?

Whether you have insulation that has to be taken out or you are insulating your crawl space for the first time, it is vital to chose the correct product. You want something that will insulate correctly and be worry free in the long run. So, let's  talk about the most common forms of crawl space insulation and try to figure out the best course of action when it comes to insulating your home.

The most common form of crawl space insulation, and the most cost effective, is  batt insulation, which is made primarily of fiberglass and placed in-between the floor joists. In this form, the insulation is usually held up with either chicken wire or a flexible wire rod every few feet. The problem with this method is that the insulation will hold moisture -despite all claims otherwise- and the paper on the back side of the insulation can actually grow mold. Now this only poses a problem if you have moisture under your house or are prone to moisture in your area. If you have this kind of insulation, an early indication that you have a moisture problem would be rust on the chicken wire or flexible wire and the insulation will grow heavy with moisture and begin to fall to the crawl space floor. With insulation that is holding moisture right next to your floor joists and sub floor, it won't take long before mold begins to grow in those areas. When this happens and you want to re-insulate, it might be best to find a different form of insulation.

Another form of insulation seen in crawl spaces is a reflective bubble wrap type material. This material is very thin and does not offer much insulation. As you could guess, it is the cheapest method of insulation, though it doesn't add much value. One positive aspect of this type of insulation is that mold does not grow on it as it does not hold moisture.

Next we have spray insulation, which is a fairly popular method right now. This is obviously not the best method for the DIY'er, since it requires the proper equipment. But it is a moderately cost effective way to insulate your crawl space. This process is accomplished by spraying a liquid foam insulation onto the foundation walls throughout the crawl space that eventually hardens and 

becomes a thick foam seal around the area. Now this approach sounds great on paper, but there can be a few hidden issues with this. 

First, when spraying this foam, it is near impossible to not spray over things like electrical and plumbing. I have heard of cases where a section of plumbing was covered up by the floor joists and began to leak. Soaking the wood and rotting it out before anyone realized what had happened, costing the home owner thousands. 

Secondly, if the spray foam does not stop on the foundation walls before it reaches the wood structure, it makes it impossible for pest control companies to properly inspect for termites. Some states even have a codes requiring foundation insulation to stop a certain distance from the bottom of the floor joists.

Finally, even though it's rare it still must be addressed, the liquid foam must be mixed together correctly or the outcome could be extremely hazardous. It could become dangerous to breathe in and in some cases, condemn the whole house. 

So if you are looking at implementing this form of insulation, it is important to take these factors into consideration. This is not the worst option by any means, as the foam does not hold moisture like the batt insulation and most of the problems are the odd ball type issues, but you can make a better informed decision about what's best for your situation once you've got all your facts.

There is an encapsulated batt insulation that is a very good option, though it is a little more pricey compared to standard batt insulation. You get all the perks without the moisture issues since the insulation is wrapped in plastic. If you are looking at insulating for the first time or re-insulating, this is one of the best options.

A last option is using insulation board on the foundation walls. This is another great option since the foam board does not hold moisture, it is easy to handle, and unlike the spray foam, you can go around plumbing without a problem. It's also a very easy process for the DIY'er, without all the itching and coughing that fiberglass insulation comes with. The foam boards can be attached with liquid nails, or even better, Tapcon screws or a Ramset gun to permanently secure the boards to the foundation and then tape the seams with a good 12mil tape. 

Finally, whichever method you choose, the rim joists shouldn't be neglected. This is the area in which the majority of homes lose the most efficiency. More air travels between the crawl space and the house through the rim joists than anywhere else. The best way to mitigate this is by spray foaming all the seams with the canned expanding foam you can get at any home improvement store and cutting a piece of foam board to fit in the space between the floor joists.

If you notice your crawlspace insulation needs some attention, there are a variety of options you can pursue. If you're looking for further guidance to ensure you're going with the most cost-effective and long-lasting route for your home, reach out to a local professional who can help you narrow down your options.


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