Been doing a bit of research on getting my crawl space encapsulated, meaning, closed off completely with a thick plastic covering and installing a ventilation fan. The reasons to do this are to stop moisture/mold and reduce energy costs.

In doing the research it appears new building codes that will be put forward will require completely enclosing all crawl spaces. Studies have shown that the vented crawl spaces, for a variety of reasons, are not effective in eliminating mold/moisture.

I have minor moisture problems like all crawl spaces. The big issue for me is energy. When you pop off the hatch to the crawl space the cool air just rushes into the house, so I am sure that cool air is finding its way in through other open places. Encapsulating the crawl space is supposed to stop that.

Any of you builder types ever heard of this? Looking for thoughts and opinions as to whether this is worth doing. Another question is home inspection. When I sell the house someday, would a home inspector be suspicious or unaccepting of crawl space that has been completely enclosed?

Thanks.

M

I can't give you an opinion one way or the other Mike, but it might be worth consulting with a local home inspector on the issue, since they may end up doing the walkthrough down the road anyway. Look for one that is listed on your local Homebuilder Association website

This is not that popular in the PacNW but I hear of it gaining popularity in other places. I acutally just did some work on a building that used an encapsulated crawl space, with insulated stemwalls and no ventilation. Everything got moldy in there.

You may have a minor issue with an inspector, but what you are suggesting is allowed by the building code in one of two ways.

1) You need a Class I vapor retarder and your vent fan will need to be "continuously operated provided at 1 cfm for each 50 square feet of crawl space"

or

2) "ground surface is covered with a Class 1 vapor retarder, the perimeter (stem) walls are insulated and the space is is conditioned per the int'l Energy Conservation code.

Now in the case that I worked on recently, they used Option 2 and it did not work. We added some mechanical ventilation and will see how it fares. I have seen a lot of pro and con arguments for both.

Mike,
The matter is addressed in Chapter 12 of the International Building Code (IBC). Section 1203.3 deals with under-floor ventilation and the requirements for providing adequate cross-ventilation. 1203.3.2 lists the exceptions for continuous mechanical ventilation. Shoot me a PM if you want me to scan the text for ya....

I'll add that I have yet to see a properly vented crawl space with natural cross-ventilation exhibit mold problems either in the crawl space or occupied space above.....

One of the problems with crawl spaces is no or poorly installed footing drains. Even though in some instances they are not required i always install one when I can. Another problem we see is in the types of venting in the crawler. Old style was to cut into the rim joist 14"x8" in btwn the joists. problem is that inevitably when insulation contractor shows up, they place insulation to close to vent, blocking good air flow. New IBC call for R-30 in floor systems which if you are on top of it requires either a 2x12 floor joist or a 11 7/8" TJI style floor joist. Otherwise the insulation hangs down below say a 2x10 or 2x8 joist. The best method is to place vents in foundation prior to pouring to vent "below" insulation and floor. Mechanical vents can be placed on a humidistat which can be set to turn on vent fan when humidity reachs a certain level. ($25.00 Home depot, available next to the attic fans display). Also, make sure to use 6-mil black poly vapor barrier. the absolute best. Make sure any and all wood debris is removed also. cheers.

I don't spend a whole lot of time looking in and throughout crawl spaces. Almost every case of mold I see in homes is due to electric baseboard heaters and aluminum double pane windows.

Make sure you dig up and remove all the dead hookers before you start getting bids.

Thanks you all have put a different perspective on it for me. Mike

There is supposed to be a laugh icon here.

I agree. I have a hard time believing they would now think enclosing crawl spaces would be healthy for a home. As a former appraiser I had the pleasure of being required to inspect the crawl space of every home. If I remember correctly, the three things I looked for were:
1) a minimum height
2) vapor barrier
3) proper ventilation

In fact, if the crawl space vents were covered up with styrofoam or cardboard, I made the owners remove them. IMO you want/need adequate ventilation in your crawl space. You want it to be cold and drafty down there, not warm and moist. Warm, stagnant, moist areas encourage mold, dry rot, and pest/rodent infestation. Moisture ants, rats, mice, (and larger critters) all love a nice warm dry place to inhabit for the winter.

Ike

Great point tydy

I agree 100% for your comments concerning the lack of good footing drain installations.......in this neck of the woods, and for the costs, it is asanine NOT to install them. When we get called to offer solutions, we try to pothole around the uphill side of the structure and quite often solve the wet crawlspace problem with a curtain drain.

Here is one of many articles I read on enclosing the crawl space. Seems to be popular in the SE part of the country. I am going to give the person who inspected our home last year a call. Again, appreciate the input. M

http://knol.google.com/k/crawl-space-encapsulation#

The whole idea is a very site specific type issue. There are generalizations that apply, but even curtain drains...which are in most circumstances a terrific idea.....won't do anything for you if your site is the lowest point around, unless you use a sump pump.

Building on stilts works the best, but I doubt it will ever be a high-participant method.

Years ago, when I first started working a builder I was working with bought the wettest lot I had seen. We dug a foundation only to watch it fill up to the top with water. We left it until spring at which time I was charged to pump it out. Another builder came out and looked at it and came up with a brillant plan. We were sitting on a layer of fairly hard soil and impentibrible soil, upon which was 4 feet of saturated, poor soil. He put in a wider footing, built up the walls and pads to almost 7 feet. The then brought in load after load of pit run and packed the inside of the foundation to above the outside trade. He then packed almost 1 foot on the outside and graded it slightly away. This put the ground level of the inside of the foundation 1 foot above the normal grade of the lot and had adequate flow away from the lot. It worked perfect. Ended up with one of the driest crawlspaces around on a lot that was pretty much flooded. I was surprised he got away with building on the lot and am sure we never could today, but man, it saved the guy I was working with from losing $40 to $50 thousand. Never, ever, heard of one problem with the set up.

Along the lines of Krjack's story, I have been working for one of these TBTF bank's asset managers lately. I think she is out of Dallas. Anyway, they forclosed a subdivision down along the Columbia river near Bonneville. 60 lots, 10 completed new houses.

I got there and noticed that there was a pretty big creek almost uphill from the subdivision. I thought it was a little weird. Stepped off the driveway into the yard, and squish, like a sponge. I go into the first house and get ready to check the crawl space. It is the kind of crawl space where you enter from under the stairs. I swing my feet down in expecting to hit the ground, but it is way down there. My feet are running in the air and I fall into the space. It is about 5' to the ground level and I am sitting in 6" of water.

Apparently these lots were platted on the edge of a mapped floodway, and so they could not be graded up (displacing the floodway). So the solution was to build tall stemwalls and install sump pumps. Only they hadn't turned any of the pumps on after the buildings were complete. No better way to start the work day than to take a bath in a crawl space. I ended up doing all the crawls one after the other while I was wet (and frozen). Then I changed into the only other stuff I had for the rest of the work (rain-gear, extra tuffs, and a basketball jersey). Looked very professional.