Save Energy and Money - Insulate your Crawl Space Properly
Alright, I hate saying “Save Money” because that usually means you’re spending money. However, in this case, we really will save quite a bit of money by spending just a little.
Our home was built in 1941 with no basement, just a crawl space. Being a first-time homeowner, and being the neighbor of a frugal mind like Nick from Punny Money, I learned something valuable this past week:
Insulate your crawl space to block drafts and energy loss.
Since buying the house 2 years ago, we’ve noticed drafts coming from certain parts of the home, but we’ve focused on trying to block the air from within the home itself. However, the true problem was our crawl space vents. If you do not have a basement, you probably have noticed vents all around your home leading into the crawl space.
These vents have a single purpose: To allow humidity to escape from under your home.
Why would you need to vent the humidity under your home? Where does it even come from? Well, thanks for asking! Let me answer those questions for you!
Where does the humidity come from?
Unless you live in the Sahara, and never get a monsoon season, you need to worry about the water stored in the ground. On any spring, summer, or fall day, place an empty can, with both ends removed, on the ground. Cover that can with plastic securely. On a hot day, you’ll soon notice condensation forming on the underside of the plastic. It may take longer on a cooler day, but it’ll form. What does this tell you?
It tells you that the ground is always releasing water into the air. There’s physics or something behind it, and I’m sure there’s saturation levels involved, but rest-assured that this affects your crawl space. This leads us to our next question…
How does this affect me?
If you own a crawl space, and it is not properly vented, the moisture from the ground will go directly into your insulation and floorboards. Mold will form and your flooring will begin to rot. I don’t mean to scare you, but I hope you get the point that this moisture NEEDS TO GET OUT! (or at least be contained…read on)
What can I do to my crawl space?
Well, this answer comes in two parts.
First, make sure your vents are open in warm months. Oh, and make sure you have vents. We found that in our home the vents had metal flashing that was partially closed even in the summer months. For now, we kept them closed, and even insulated them, but I’ll get to that later.
In your case, make sure your vents are covered with mesh to prevent small intruders, and ensure there is proper flow on both the inside as well as the outside of the vent (i.e. make sure nothing is blocking either side).
Second, make sure your dirt is covered with heavy plastic. When we re-insulated our crawl space a few years ago, we laid down a good plastic covering, but not enough (we needed a break from the confined space). We need to add more, and that will happen this spring.
The images below illustrate the before and after of a properly covered crawl space. Note, though, that the ceiling is not yet insulated:
And now the last question:
But what about all that cold air in the winter???
Good question. There are vents that automatically close depending on the temperature (non-electric and electric). However, their seals may not be the tightest, and if these vents are on the windy side of your home, you may still feel a draft.
In our case, we decided to stuff R-13 insulation into plastic garbage bags, then into each vent. We noticed an IMMEDIATE and CONSIDERABLE change in temperature and draftiness (or lack of) inside our home. Nick did the same, and now notices his hardwood floors are not nearly as cold anymore.
However, we must make sure we remove the insulation before the beginning of spring so we can vent out the humidity from the crawl space.
If you have proper plastic covering on your crawl space floor, you can tend to wait longer to remove any covering or insulation from your crawl space, but it’s always good to protect yourself on all fronts.
Summary
- Make sure your crawl space is vented and the vents are not blocked
- Cover your crawl space floor with heavy plastic…all the way up the foundation walls
- Close or insulate the vents in the winter to save heating costs and you and your family from cold tootsies
- Remember to remove or unblock the vents before the temperature begins to stay above freezing for extended periods
- Be careful when working with fiberglass insulation. Wear goggles, a mask, and thick plastic or rubber gloves. Also, cover all exposed skin when working with it in your crawl space. Those little particles can lodge in your lungs and skin, and be very hard to remove
Try one of these related posts too!:
- Welcome LifeHack Readers!
- Clever Dude’s Week in Review Feb 11-16
- Weekend Project: Insulation and Ventilation Work
- Carnival of Personal Finance #88 - Quick Picks
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We’ve actually had to put a dehumidifier in our crawl space. We have a good vapor barrier and all, but we live in the South, and the ambient humidity in the summer is just too high. Even with proper ventilation, we often get condensation under the house because it’s cooler down there and, well… When warm, wet air gets cool, it condenses. And when you get condensation, you get mold. Not good. So… I installed a high performance dehumidifer in the crawl space complete with a condensate pump, and then closed the vents.
That’s actually a great idea for warmer temps. For the Northeast US, it really depends on the cost of running such a unit (or even a smaller version) versus insulating and covering your crawlspace.
Next year just buy some hay bales to set in front of or block the vents, its great insulation and you can use it for mulch in the spring, plus it’s cheap. Old farmers down here do this every year in some cases all around the foundation if it’s just up on blocks
Bad advice. Winter air is drier, summer air is moist. If you open the vents in the summer and close them up in the winter, you have let in moist air and trapped it there which is exactly what you don’t want. If you want to insulate your crawl space that is ventilated, insulate the floor above the crawl space. If your crawl space is not ventilated, then make sure all penetrations and holes are sealed and insulate the foundation walls. Also, there should be a vapor barrier on the dirt under the house (usually sheets of plastic).
@Kevin, you have no idea what you’re talking about, nor did you read the article fully. In the summer, the ground AND air are so saturated with moisture that if you don’t have ventilation, the moist air under your house can’t get out and will begin condensing on your joists. Hot air rises, so it will go out through the vents, not come IN!
And I did say that you need to add plastic across your dirt floor. It’s in bold italics. Not sure how you missed that.
Question: i have a A-Frame in nothern AZ with no insulation under the flooring of the crawl spase,As far as vents,it has metal siding all around the side touching the ground(no vents) Should i lay the plastic down on the ground?is R19 sufficient enough to install between the floor joist? We dont use the A-frame that much in the winter but when we do it is very cold when we get there.Thanks
@mike, Since I’m more familiar with the swampy climate here in Washington, D.C., I’m not quite sure what you would need in a dry area like Arizona. The ground probably doesn’t hold as much moisture as it does here, but I would still say lining the ground with plastic is generally a good idea (even if it’s to discourage bugs from multiplying under your house).
As for insulation, I recommend asking your local Home Depot or Lowes professional (or other professional), given the higher average temperature and lack of humidity in your area compared to mine.
Help,
I’m not sure what to do next. I have put down heavy plastic on the ground under the house. I want to put spray insulation under the house next to stop drafts, improve R-rating, block possible rodents, (We live on a horse farm.) and save some money. If good insulation rodents won’t chew and does mold, do I need a vapor barrier to use with the spray insulation, or is the spray foam enough. We have condensation in the morning year around in this region of the southeast.
We have a vented crawl space, and use a dehumidifier in the summer. We are considering insulating the ceiling, and may put heavy plastic on the floor. I’m concerned about the plastic, because when we get heavy rains we get water in the crawl space. The water usually drains out within a couple of hours.