Read This Before Insulating Your Crawl Space

Saturday, January 19th, 2019 by Ben Bates


Help for cold floors advanced basement systemsHalf awake, you get out of bed only to feel like you’re standing at centre ice at Scotiabank Arena… barefoot!

It’s well past the time to insulate your crawl space!

Whether you’re an experienced DIYer or are just starting the process of getting quotes, please consider the following before doing anything in your crawl space.

Your cold floors are caused by the cold air in your crawl space. This fact alone is quite telling, very likely you have “open” or at the least “unsealed” vents which allow in the cold air.

But the vents need to be open for air circulation, right? Wrong! A crawl space should be treated just as you would a basement – completely closed off from the outside environment.

Okay, step one, seal the vents, step two, install fibreglass insulation to the floor above. Wrong again!

This is what will happen:

Most fibreglass insulation is either foil, plastic or paper-faced, with the goal of being a radiant barrier. However, to work properly, there needs to be an airspace between the facing and the floor above, this is nearly impossible to do as the insulation needs to be jammed up to the floor sheathing and in-between joists to stay in place.

Let’s say you’re confident that there is the necessary airspace. Remember that fibreglass is a loose material. The cold air will pass right through it, and you’ll be relying on the thin facing to keep your home warm! The space in between actually acts as a “thermal bypass” with cold air able to travel above and below the facing; rendering it completely useless.

But one minute… the crawl space air should be “warm”… because you sealed the vents, right? Sorry, wrong again!

Even with the vents and access doors sealed, the cold air will come up from the ground, and this is when things can get really funky in your crawl space!

The exposed ground in your crawl space is not only cold, but it is also subject to fluctuations in humidity. The cycle of cold and dry, then wet and warm causes excess humidity, which results in moisture: which then manifests as mould, mildew, rot and musty smells in the home above. Also, important to note is that the fibreglass insulation will absorb the moisture, become saturated (making it even more useless) and eventually it will fall to the ground.

If you think the answer to keeping the humidity at bay is to then “lay down plastic”, you’re close, but that’s not the solution.

As we mentioned above, a crawl space should be treated the same as a basement: completely closed off from the outside environment. Air particles, even ones holding moisture, are minuscule and can make their way up through the plastic where it meets the walls, supports and between seams.

The ground needs to be encapsulated and sealed along the seams, supports and outside walls with a heavy-duty, long lasting, vapour barrier.

As you can now understand, the process of improving the comfort of your home may not be as simple as adding insulation, sealing vents and “laying down plastic”. Since 2003, we’ve visited thousands of homeowners in southwestern Ontario who’ve wasted time and money in their crawl spaces.

At Advanced Basement Systems, we believe and practice, “If it’s worth doing, then it’s worth doing it right – the first time”. If you have an extra minute, please check out some photos of our work in crawl spaces and testimonials from our customers.

We invite you to reach out to us for a complimentary inspection and written estimate: 1-866-277-1277 or click here to submit your information to us online.

About the author
Ben Bates lives in the Chatham-Kent area and has been involved in the basement, crawl space and foundation industry since 2008. He has a passion for improving homes the right way and knows what it takes to waterproof, encapsulate or stabilize homes in Ontario. He assists with over 900 projects per year.

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