Clean Space encapsulation versus venting

[DaveH2]

Does anyone have (or know anyone who has) a crawlspace that has been equipped with the 'Clean Space' encapsulation system? What are your thoughts and experiences with this approach? http://www.all-dry.com/crawl-space.php

Here's my issues: I had a new heatpump/ac system and duct work installed a little over a week ago (the indoor unit is in the 1150 ft2 crawlspace), and it is much more efficient than the old system....the supply/plenum end is sweating profusely, as well as the outside foil of the duct insulation. I can smell slight musty odor when I enter the side entrance (the dampest end of the house's crawlspace).

It's been raining a lot this past week, and the RH in the crawlspace is in the mid 90's%....even during drier weather, and using a vent fan, I've never been able to get the RH under the low 80's%. During a dry day, the vent fan would pull the RH down a few%, but if left to run past 6:00pm the RH would go back up. The house has had a poly (6mil) moisture barrier down for a long time, although it's far from being sealed....there is some exposed earth in a few places, but it's mostly covered. However, the crawlspace has ALWAYS had that dank, musty smell to it. There is no standing water that I've seen, except for now with a puddle on the poly barrier under the plenum from the colder air of the new system.

Here is what I'm trying to decide on:

1) Putting down a new 6mil barrier, and installing a Santa Fe dehumidifier. Possibly blocking off the vents to cut on humid air coming back in, although this would be far from actually sealing off the crawlspace.
2) Contracting the local Clean Space guys to encapsulate the crawlspace. The estimator said he didn't think I would even need a dehumidifier with the Clean Space system installed (they also sell their dehumidifier which is a version of the Santa Fe Advance). This option has a lot of promising claims and sounds very good to me, and the cost isn't really *that* bad if I don't have to buy a dehumidifier. It's hard to shake the old wisdom of needing to have ventilation in the crawlspace though.

Sorry so long, but it's hard to find any reviews or first-hand customer opinions online....lots of hits for the companies that install it though.

Help?

[drk]

Those system are very nice but a 6mil VP installed correctly will serve just as good. I would not get the dehumidifier up front on ether job. You may not need it. Venting the crawl will just dump humid air into a cool crawlspace. Look to pay about 4 times the cost for the crawlspace systems.

[billygoat22]

If you live in the South or around gulf, can't dry a wet crawl w/ wet air. only works in cold weather up north.
I put down plastic in mine, sealed vents and put in portable dehum. keeps down to 55% easy down there. Also, the crawl walls have less heat loss than if I insulated the entire floor of house.

Seen a few of the encapsulated crawls. very nice.

[teddy bear]

Plastic down, close the vents the best you can, and install a Santa Fe Compact at a minimum. That will get 50%RH and help keep the mainfloor dry also. Regars TB

[DaveH2]

Those system are very nice but a 6mil VP installed correctly will serve just as good. I would not get the dehumidifier up front on ether job. You may not need it. Venting the crawl will just dump humid air into a cool crawlspace. Look to pay about 4 times the cost for the crawlspace systems.

drk, thanks. I'm in SC, so I expect I'll HAVE to install a dehumidifier if I just put down plastic. I've had plastic (it's a bit torn up, but mostly there) down for a long time and have always had high humidity issues....I just didn't realize how bad it really was until recently when I put a hygrometer down there.

A dehumidifier and 6 mil poly will run about half of what the Clean Space encapsulation will run.

[DaveH2]

If you live in the South or around gulf, can't dry a wet crawl w/ wet air. only works in cold weather up north.
I put down plastic in mine, sealed vents and put in portable dehum. keeps down to 55% easy down there. Also, the crawl walls have less heat loss than if I insulated the entire floor of house.

Seen a few of the encapsulated crawls. very nice.

Thanks billygoat.

I live in upstate SC, so it's quite humid like where you're at. A few questions on what you said:

- How did you put down the poly...is it on the 'floor' of the crawlspace only, or did you run it up part way on the walls?

- What does the crawlspace temperature get down to in the winter time where you're at, with the vents being sealed off?

- Are you saying that you don't have any insulation under the floors?

[DaveH2]

Thanks for your replies TB (both here and other threads).

How do you suggest doing the plastic barrier....crawlspace floor only, or up the sides as well?

I really like the specs on the Santa Fe Advance, but I'm a little hesitant in regards to the low-end temp/operating spec. If it gets down to 20 degF outdoors, do you think the crawlspace temp be high enough (with sealed vents) to support the use of the SF Advance?

The AH and duct work are under the house and should contribute to keeping the temp up a bit, I just don't know how much.

[teddy bear]

Evaporation of moisture from the earth and moisture in the outside air are the largest sources of moisture. The masonary walls are a very small source moisture. Covering earth and closing vents stops 90% moisture. Wind will still introduce some fresh air. Addition sealing and covering up walls reduces the dehu load some.
The When the outdoor dew point drops below 50^F, dehumidification is no longer needed. Therefore the dehu does not operate when the crawlspace is cold. The Santa Fes are designed to operate in the crawlspace/basement conditions. Keeping the crawl dry also helps the humidity levels in the home.
Regards TB

[Baseboard Gord]

I'm a big fan of sealed and conditioned crawl spaces. I did the poly on the ground, styrofoam insulation on crawl walls, sealed the vents, and put a Humidex in. This was when I lived up north. Crawl space smell disappeared completely. Interior house humidity went from mid 50's % down to mid 30's %. My dehumidifier was retired since it would never turn on after doing the above.

In a hotter humid south, I'd do exactly the same as the video here: http://www.youtube.com/watch?v=IGU0prkWhgQ

[teddy bear]

I'm aand put a Humidex in.
. My dehumidifier was retired since it would never turn on after doing the above.

In a hotter humid south, I'd do exactly the same as the video here: http://www.youtube.com/watch?v=IGU0prkWhgQ

Nice video, but a word of caution about Humidex. This is an exhaust device that exhaust air to the outside. The ideal is that damp air exhausted out of the crawlspace or basement. This works real good as the replacement outside air that infiltrate the home to replace the Humidex exhaust is dry. So a great device for dry climates with low dew points. In the typical green grass climates, exhaust basement/crawlspace means wet air is being sucked in the home to replace the exhaust. This is a big problem during most summer weather. Forget about the exhausting air, use the dehumidifier as the back-up. During windy weather, enough fresh air will infiltrate, that the dehu is needed. Regards TB

[DanW13]

I used a piece of Rubber roofing to cover my crawl space and sealed the perimitter to the base of the foundation, no problems to date and insulated the floor joist above with R-19 my Kitchen satys nice and warm and the crawl space is dry as a bone.

[Baseboard Gord]

I agree with Teddy Bear on the above comments. The Humidex worked great summer and winter in the Pacific Northwest. I wouldn't do that down here in south Texas though.

[DaveH2]

I used a piece of Rubber roofing to cover my crawl space and sealed the perimitter to the base of the foundation, no problems to date and insulated the floor joist above with R-19 my Kitchen satys nice and warm and the crawl space is dry as a bone.

No dehumidifier needed? Whereabouts are you located?

[DanW13]

I'm in Wisconsin, my house also sit up higher than my neighbors so I have no water infiltration and all the air leaks are sealed up.

[billygoat22]

sorry, been awhile since I could get on intnet. my crawl stays warm in winter and cool in summer. acts like a closet in the house, no air supply but temp like in house.

was no insulation on anything under house when I bought it. not on duct, water pipes or in floor. must have been some major heat loss to keep pipes from freezing in a vented crawl.

[TalkingHead]

I was converted to the overall benefit of sealed crawlspaces by the www.crawlspaces.org research. Watch this video that answers the question 'To vent or not to vent.' This will answer a lot of questions.

http://www.advancedenergy.org/buildi...0To%20Vent.wmv

[DanW13]

Don't know if you have solved your problems to date, but was re-reading the post here and thought that if you were to seal the floor with a VP,and close the vents to the outside, and insulate your floor above and maybe add a box fan on one side of the crawl space to pull in air form the rest of the basement into the crawl space it will help in keeping the crawl space dry by keeping the air moving thru out the space. By using the rubber roofing for your VP and sealing it to your side walls will be half the battle in controlling the humidity with the addition of a box fan to circulate the air will be a huge help with the musty smell,odors.

[TalkingHead]

Think of an enclosed crawl space as a very short basement. Then condition it as such. It makes more sense that way. The attached Builder Magazine article explains what is going on.

[DaveH2]

That is a very interesting article, thanks for sharing. I've already been convinced on the merits, and I'm just about ready to do it at this time. I've held off on doing this for the past couple of months due to refinancing, and completing some projects that required me to put through-holes in the outside walls (I wanted all of that done so they would be sealed correctly to begin with). So all the projects are completed now, except for building a new crawlspace entry framing and door.....and as soon as this is finished I am scheduling Carolina All Dry to encapsulate my crawlspace. Thanks for the continued responses!