[APinNY]

Our summer place has a crawlspace. Years ago the pipes and beams had a lot of condensation. We laid plastic sheets on the dirt and added ventilation which stopped the condensation but the first floor of the house is still damp most of the time. The thin plastic is beginning to decompose and some of it has been moved around over the years. I believe that most of the dampness is coming up from the crawlspace. From what I've read, the new theory is not to ventilate but to seal it off completely. They do this by laying a 20 mil vinyl fabric on the dirt, sealing the pieces together. They also run it up the block walls and seal it at the top and around the footings. Then they close off all the vents and place removable covers on the access points. Sealing drains and dehumidifiers are also available if necessary. The job is fairly costly. I could get the materials and do it myself but I hate going down there anymore because some areas have only 1 foot of clearance. Has anyone sealed their crawlspace with "Clean Space"?

 

[JGANDEE]

my father did his new house last year and wow what a difference. the air was completely clean, no mold, mildew or insects once the humidifier was installed, stays around 50%. I think he used 1" foam board on the block walls and heavy plastic on the floor.

 

[APinNY]

:thanku: for the response. The company states that the difference is shocking but they won't guarantee it in writing so it is good to hear that it works. Anyone else have experience with this?

 

[Blasterway]

As an Insulator for 22 years I agree with JGANDEE. Except in your area. I would use 1 1/2" to 2 1/2" FOIL FACED FOAM such as Thermax for an exposure rating to fire, with all joints taped with FSK or a foil tape. Anything else needs to be covered with drywall for a fire rating.(check your local codes for your exact needs in foam) Good luck, Its not too difficult of a job.

 

[APinNY]

:thanku: Blasterway. This company has been doing this in my area for 12 years so they are probably aware of local codes but you make a good point. I will check with them on this.:fing32:

 

[jinjimbob]

What is the cost of sealing it off?

 

[APinNY]

The price depends on the size of the area and any other components you may need, eg. dehumidifier, outside drain with ice preventer, floor drains, sump pump, vent covers, etc. Mine will be about $5k...expensive yes but as stated above, I'm just not into doing it myself. :Stop: If you are, the materials are available for a lot less money. I am sure it will also add value to the house. If I get the intended result then it's well worth it for me.:thThumbsU

 

[Bentworker]

The crawlspace has to have some air movement.

The newfangled way of doing it is called a "conditioned" crawl space. That's what we did on our place. Put down some sand, then the plastic membrane which got glued to the foundation walls with nasty poly caulking. Then we had a spray foam contractor come and spray the inside of the foundation walls with about 4" of foam.

We do not have any insulation in the floor.

Works great, but you do have to move some air.

Normally with a HVAC system you leave a large gap at the bottom of your interior doors to act as you return. In our house we have a vent to the crawl space in each room to act as the return. Then we have a HRV (heat recovery ventilator) that comes on intermittently and sucks stale are from the crawlspace, spits it outside, draws fresh air from outside and introduces it into the HVAC return air. This is a great thing to install if your house is pretty tight and you keep your windows closed during the seasonal extremes. It has a heat exchanger in it, so it splits the difference between the incoming and outgoing air... these things have been used for years on commercial buildings.

It is a neat system, so far has worked well for us. Electricity is pretty expensive out here, we've been pleased with our utility bills in the new house. Our July bill was about $90.00, for a 2500 square foot house, in a dry climate with seasonal extremes. (gets into the 100's in the summer).


You will probably have to get some sort of alternative building material variance permit, or something like that. Our house was the first conditioned crawlspace our local building inspector had seen. Or just get busy under the house... (probably what I would do).

If you decide to go with spray foam... shop around! I had quotes vary from $2400-$4000. (this was for about 770 square feet of area)

 

[HiPocket]

I have a mostly stand up height crawlspace in my current house.

It has 6 - 8 mil sheet film laid on the dirt with 2 ft overlap at seams. The crawlspace vents are closed but not necessarily 100 % sealed.

I have a LG 40 pnt Dehumidifier set at 50% running down there. The air is clean and dry. The joists are clean and dry with no mold and look new(14 yr old house). Its a safe place to store metal items with no fear of corrosion or mold. Previous owner had it set up this way which I've continued.

I live in a fairly humid part of country, piedmont NC.

Sealing at least as good as mine with dehumidifier or better if you don't think my minimalist system will keep it dry is a good idea.

 

[Kbeitz]

I have a mostly stand up height crawlspace in my current house.

It has 6 - 8 mil sheet film laid on the dirt with 2 ft overlap at seams. The crawlspace vents are closed but not necessarily 100 % sealed.

I have a LG 40 pnt Dehumidifier set at 50% running down there. The air is clean and dry. The joists are clean and dry with no mold and look new(14 yr old house). Its a safe place to store metal items with no fear of corrosion or mold. Previous owner had it set up this way which I've continued.

I live in a fairly humid part of country, piedmont NC.

Sealing at least as good as mine with dehumidifier or better if you don't think my minimalist system will keep it dry is a good idea.

With standup room I would be putting in a basment.. Or at least a door to drive my tractor into...

 

[Bentworker]

Tyvek tape is great for plastic seams... figured that might be useful info.

 

[LLigetfa]

Code here says that if a crawlspace is not conditioned space, it has to be vented to the outside. I argued with the building inspector that venting in the Summer causes hot moist air to condense in the coolness of the crawlspace creating conditions for mold and mildew.

My former home had a crawlspace that was not vented to the outside. It had poly over an earthen floor that wrapped up onto the walls. The poly was not sealed where the wall met the earth so I had a lot of humidity problems in Winter. The contractor that built the house put 2000 watts of electric baseboard heat in the crawlspace but then put the thermostat up inside a closet. Since the thermostat didn't sense the temperature in the crawlspace it was either too cold or too hot. I kept turning it down but the wife always turned it up because the floors got too cold. Too much heat in the crawlspace caused moisture to be evaporated from the soil which migrated up the poly and condensed on the cold side of the batt insulation and air infiltration over-humidified the entire house. I don't know how it passed inspection because it wasn't to code. Code says the thermostat has to be in the living space but did not specify that it has to be remote sensing. I argued it with the inspector and he let me move it down to the crawlspace.

I put in a claim to the new home warranty people and raised a big stink with the building inspector. I had pull down all the poly and the batt insulation to dry everything out. It was then I found out the builder used 3 - 1/2 inch batts in a 2x6 stud wall leaving a 2 inch air space on the cold side. I got the builder to supply 2 inch rigid foam insulation that I cut to fit between the studs on the cold side and put back the batts after everything dried out. I sealed the bottoms of the stud cavities with 2 inch foam and sealed the poly to it.

If a crawlspace is not vented to the exterior it is considered conditioned space and as such has to be fire rated. When I built my current home, I drywalled the crawlspace and a painted concrete floor over crushed stone for drainage. In the Summer, I don't move any air through it as hot moist air would only condense in the coolness. In the Winter I draw air up from the crawlspace with a 650 cfm blower that moves it across my wood burning fireplace. The makeup air is drawn down at the opposite end of the house so it evens out the heat and warms the floors.