Crawlspace advice needed

[alex3610]

Recently I ventured into the crawlspace to sweat some pipes in replacing a bad hose bib and noticed how nasty my crawlspace is. We live about a block from an 1800 acre reservoir and the ground is typically pretty damp. There is a sump pump in the crawlspace under the sun room (lowest corner of the house) and it runs like crazy whenever we get a lot of rain. There is a fairly decent vapor barrier down on the ground right now but it is simply laying down and there are gaps and spaces where dirt is visible (and often damp). I also noticed what I believe to be fungus or mildew starting to form on some of the floor joists. The house was built in 1986 and has the basic foundation vents, most of which function. Several are seized up and stuck in the open position. I also noticed the holes where the a/c line sets come in are huge and basically wide open. There is also a significant gap near where the duct work from the air handler in the attached garage comes in.

Obviously there are some issues here and I have a few questions.

1. Foundation Vents - Growing up in the NE, everyone had a basement and I never had to deal with these. To me, it seems like keeping these open in the summer would mean hot humid air would hit the cold surfaces under the house and cause condensation. Should they just be left closed? Why does the code require them anyway?

2. Crawlspace Encapsulation - I see a lot of guys advertising this around me and I'm told it's very expensive. Any idea what it would cost (or should cost) to do an 1800ish sq ft. crawl space? I like the idea of sealing everything up and keeping the moisture OUT.

3. Conditioned Crawlspace - I've heard several variations here. One, the homes hvac system is used to treat the crawlspace as another room in the house. I see this as a bad idea, why would I want to bring air from the crawl space into the house if I didn't have to? Some have a dehumidifier on a humidistat. Others have fans that vent to the exterior to change out air in the crawl space. I feel like this puts us right back at where we started with the foundation vents.

Thanks in advance for the help!

 

[1967mgbgt]

I'm finishing up work on a house in western NC. The area it's located in averages 66 inches yearly rainfall (that's a lot of rain) so high humidity is/was a problem. Originally the house had a conventional crawlspace with vents. Heating was electric radiant heat. With that setup average humidity in the crawl was 75-80% and the interior was around 70%. Not matter what you tried the interior was never comfortable.

I put in a new heat pump for HVAC which helped some but not much. Then I sealed up the foundation vents, sealed part of the walls and most of of the floor with heavy plastic and then installed a quality dehumidifier (plumbed to drain outside).

Major change for the better. Interior of the house is in the 40-50% range and crawl averages less than 50%.

Cost of materials to partially seal and enclose the crawl space was less than $200.00. I found the dehumidifier (an as new Santa Fe unit that retails for $1300) on CL for $400. Even if I had to pay full retail for the dehumidifier and for the crawlspace sealing (figure $3-4000 total at highest) the improvement in comfort and air quality would be worth the $$.

Asking around I found that prices for encapsulation vary greatly-likely worth your while to shop several different companies. I figured I saved 1-2K by doing it myself and it took less than two days working alone.

As for doing a conditioned crawlspace I think it would depend on the climate where the house is. For me and my area I didn't feel it would be worth the additional $$.

I have to admit that when I first heard about encapsulating and conditioning crawlspaces I was skeptical. Now I'm convinced its the way the best method for my climate and will be encapsulating the crawl at my home in the Piedmont region of NC. In an area with high humidity like the Carolinas I think its the way to go.

 

[alex3610]

I didn't really consider the humidity levels in the house. I think a lot of the comfort from air conditioning comes from dropping the humidity rather than just the cooler temperature. I should have mentioned I'm in central VA so basically the same climate as NC. This sounds like it may even slowly pay for itself over time. The more I think about it the more I may try and do the bulk of the work myself. I will need an electrician to run power to the dehumidifier however.

 

[DougWil]

The ventilated crawlspaces work well in the West with a drier climate, the East not so much.

I would recommend going over to Greenbuildingadvisor and read up on the best way to resolve your issues.

http://www.greenbuildingadvisor.com/search/node/crawlspace

Especially this one....
http://www.greenbuildingadvisor.com/blogs/dept/musings/building-unvented-crawl-space

 

[matt_i]

I had this problem when I lived in middle TN in my 60yo house. I had made preparations to seal the space as best as possible, screwing 1x2 treated to the concrete block walls, I was planning to trap a plastic barrier between that and a second 1x2 with deck screws. I never completed that part.

But, I did buy a $200 dehumidifier, standard big box, knocked out the plastic cap from the garden-hose fitting and installed a tube which ran out under the foundation and out into the yard to drain via gravity. Set on a medium range this made a huge difference. My house had an "old slightly musty smell" that was gone within a day. I read that the dehumidifier might last 2-3 years, used like this, and that one could buy more seriously engineered units that cost 2x to 3x but lasted the same multiplier longer.

I felt like plastic wrapping the space would cut down on the "moisture load" that the humidifier would see, and so that one step would give me a a longer life from my low-end dehumidifier.

I moved before I could finish off the project, so I can't comment fully, but actively removing the moisture made a large difference.

 

[gregtwojeeps]

My CS had the same issues. Called a pro. that bid the 1350 sq. ft. CS to be encapsulated with dehumidifier = $8200.00 .

 

[gregtwojeeps]

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[lakeroadster]

Nice job on the crawlspace Greg. That's a bunch of work to do... crawling around in that position.

 

[USAFpj]

2. Crawlspace Encapsulation - I see a lot of guys advertising this around me and I'm told it's very expensive. Any idea what it would cost (or should cost) to do an 1800ish sq ft. crawl space? I like the idea of sealing everything up and keeping the moisture OUT.

3. Conditioned Crawlspace - I've heard several variations here. One, the homes hvac system is used to treat the crawlspace as another room in the house. I see this as a bad idea, why would I want to bring air from the crawl space into the house if I didn't have to? Some have a dehumidifier on a humidistat. Others have fans that vent to the exterior to change out air in the crawl space. I feel like this puts us right back at where we started with the foundation vents.

Not sure why someone would say that it doesn't work well in the East, but at least for the Southeast, it works well. When my house was built, I encapsulated it and conditioned it. No issues whatsoever...

After looking at a traditional crawl, I wouldn't do it any other way. Plenty of light, no smell, no moisture, no bugs. If I want to work on any piping, it couldn't get any cleaner or easier. Makes for good storage space as well!

 

[gregtwojeeps]

Nice job on the crawlspace Greg. That's a bunch of work to do... crawling around in that position.

Thanks, it took a lot of Tylenol for this 64 y.o. body to get through it.

 

[dodgejunkie]

First thing you need to do is, properly direct the water away from you foundation! You said the sump runs constantly after a rainfall event! The water has a direct path under the footings.

Our last house in Missouri was the same way. Rain and the sump would run all the time. I went and bought some of those cheap downspout extenders to see what would happen. Just that little bit cut down on 50% of the sump running. Next I corrected the grade from the foundation and added drains from the downspouts to out back to a ditch. This cut down 90% of the sump running. Vapor barrier and a dehumidifier were next as I didn't want to do that until the water was almost non existent in the CS! World of difference!

 

[alex3610]

First thing you need to do is, properly direct the water away from you foundation! You said the sump runs constantly after a rainfall event! The water has a direct path under the footings.

Our last house in Missouri was the same way. Rain and the sump would run all the time. I went and bought some of those cheap downspout extenders to see what would happen. Just that little bit cut down on 50% of the sump running. Next I corrected the grade from the foundation and added drains from the downspouts to out back to a ditch. This cut down 90% of the sump running. Vapor barrier and a dehumidifier were next as I didn't want to do that until the water was almost non existent in the CS! World of difference!

I think that is definitely part of the issue here. If you face the house from the street, the yard slopes towards the right rear corner. The front left corner of the house is the highest ground, and I am suspicious of the downspot at that corner. It run into a brown flexible plastic pipe and is buried. I suspect it doesn't go more than 4 or 5 feet from the downspout and just saturates the ground there. Obviously getting the water further away is the idea, but how I do that without it just running right back towards the house will be the tricky part.