[Home Improvement] Pro's and Con's of Crawl Space Encapsulation?

[LoneRanger]

Perhaps you've seen the forms of encapsulating a crawl space, such as the Clean Space system. But I was thinking, while these sort of total encapulation systems sure make the space look nice, wouldn't a disadvantage be that you can no longer see if you're getting water incursion in the crawl space since it would be underneath the non transparent (usually white) barrier ?

I for one want to know if I'm getting any standing water in there, so as to take action to correct the cause.

What made me think about this is the other evening after work I was in the crawl space and while everything looks good I noticed some minor puddling along the west exterior foundation block wall. Very minor maybe 1/2" depth a few feet long extending maybe 10" out from the foundation wall for a few feet, but I'm always leery of any visible water in a crawl space. Call me a perfectionist. We have had a very wet winter and in particular a sheit ton of rain in the past several weeks.

I was thinking, if this crawl space had been Clean Space encapsulated, I never would have seen that puddle at the west wall. Ignorance would have been bliss in that scenario, but knowledge is power and knowing some water is coming in helps one investigate the cause. Hummm...

 

[PimTac]

In all likelihood it's a lot of money spent for little benefit. Make sure your crawl space has a good vapor barrier down. Make sure it is well vented. Check your downspouts and make sure they drain away from the house. That's all you need. Standing water ten feet away just means a low spot or that area needs some grading by hand to rectify the problem.

 

[Donald]

Originally Posted by PimTac
In all likelihood it's a lot of money spent for little benefit. Make sure your crawl space has a good vapor barrier down. Make sure it is well vented. Check your downspouts and make sure they drain away from the house. That's all you need. Standing water ten feet away just means a low spot or that area needs some grading by hand to rectify the problem.


Actually venting mostly does not help. You want to pull the humidity in the crawlspace down to about 40%. Venting will not help as the outside air is typically higher than 40%. Many homes have vented crawlspaces. The smart ones blocked them off and installed a dehumidifier.

The crawl space encapsulation typically only goes to within 4" of the top of the wall to allow for termite inspection.

 

[BMWTurboDzl]

Pros;
-humid exterior air and wildlife will no longer set up shop in your crawlspace. Consequently indoor air quality/comfort in the house will go up.
-Depending on your climate zone you can insulate the exterior walls of the crawlspace which will also increase comfort.
-Due to the air barrier the cost of utilities will drop.

Cons:
- Cost
- May have to install a small continuously running exhaust fan (along with transfer grills onto the crawl) to pull air from the house into the crawlspace and then to the outside.

 

[slo town]

When my wife and I lived in the Los Gatos hills, we owned a house with a crawl space that had lots of water intrusion. We bought the house in the days prior to full disclosure in real estate transactions. During our first winter there we were noticing a damp smell inside the house. Eventually I opened up the cover to the crawl space and saw over a foot of water flooding the area. The water was so deep it completely covered the concrete pier posts. Only the top halves of the 4x4 wooden posts remained visible!!!

This caused extensive damage to the home. The entire center of the house settled about 3 inches. Long story short; 1) I installed three industrial sump pumps, 2) I regraded large areas of the crawl space so that it drained towards the pumps, 3) and a jacked up almost the entire house - replacing 40 of the 52 pier posts so I could re-level the place. I also put 2x6 sister joists on both side of the existing floor joists in order to strengthen them. It was a gigantic amount of work and I did all of it.

Anyway, with respect to the OP's original question, if I were ever to build a new home with a raised flooring I would have the entire crawl space paved with rebar reinforced concrete. I would design it to drain to one area, and at that area I would have a large concrete lined sump. The concrete surface would offer many benefits, the ability to roll around under the house on a creeper being a big one.

Also too, I would install extensive crawl space lighting.

Scott

 

[Donald]

Originally Posted by BMWTurboDzl
Pros;
-humid exterior air and wildlife will no longer set up shop in your crawlspace. Consequently indoor air quality/comfort in the house will go up.
-Depending on your climate zone you can insulate the exterior walls of the crawlspace which will also increase comfort.
-Due to the air barrier the cost of utilities will drop.

Cons:
- Cost
- May have to install a small continuously running exhaust fan (along with transfer grills onto the crawl) to pull air from the house into the crawlspace and then to the outside.


Again venting or a fan will not work if the air its pulling in is higher than about 40%. Dehumidifier.

 

[PimTac]

Originally Posted by Donald
Originally Posted by BMWTurboDzl
Pros;
-humid exterior air and wildlife will no longer set up shop in your crawlspace. Consequently indoor air quality/comfort in the house will go up.
-Depending on your climate zone you can insulate the exterior walls of the crawlspace which will also increase comfort.
-Due to the air barrier the cost of utilities will drop.

Cons:
- Cost
- May have to install a small continuously running exhaust fan (along with transfer grills onto the crawl) to pull air from the house into the crawlspace and then to the outside.


Again venting or a fan will not work if the air its pulling in is higher than about 40%. Dehumidifier.




It must vary by region then. In the Seattle area where I am the humidity is higher than that. We have a lot of rainy days. For a standard concrete foundation with a crawl space, vents are required at a specified distance. I don't know that off the top of my head but it usually means two vents on each side of the foundation for a typical 1600 sf rambler. A vapor barrier is put down. That's it. As long as drainage is flowing away from the structure then all is good.

Maybe the codes have changed but for a couple of houses I've seen that are under ten years old it appeared to be the same as what I described. The biggest difference is the under floor insulation which I find is more of a mouse and squirrel nesting point than anything.

 

[LoneRanger]

Originally Posted by SLO_Town
When my wife and I lived in the Los Gatos hills, we owned a house with a crawl space that had lots of water intrusion. We bought the house in the days prior to full disclosure in real estate transactions. During our first winter there we were noticing a damp smell inside the house. Eventually I opened up the cover to the crawl space and saw over a foot of water flooding the area. The water was so deep it completely covered the concrete pier posts. Only the top halves of the 4x4 wooden posts remained visible!!!

This caused extensive damage to the home. The entire center of the house settled about 3 inches. Long story short; 1) I installed three industrial sump pumps, 2) I regraded large areas of the crawl space so that it drained towards the pumps, 3) and a jacked up almost the entire house - replacing 40 of the 52 pier posts so I could re-level the place. I also put 2x6 sister joists on both side of the existing floor joists in order to strengthen them. It was a gigantic amount of work and I did all of it.

Anyway, with respect to the OP's original question, if I were ever to build a new home with a raised flooring I would have the entire crawl space paved with rebar reinforced concrete. I would design it to drain to one area, and at that area I would have a large concrete lined sump. The concrete surface would offer many benefits, the ability to roll around under the house on a creeper being a big one.

Also too, I would install extensive crawl space lighting.

Scott



Agree about pouring cement for a new crawl space floor during initial construction of a home. Always thought gravel and sheets of plastic was a big old cheap arse cop out but all builders do it.

 

[Donald]

Originally Posted by PimTac
Originally Posted by Donald
Originally Posted by BMWTurboDzl
Pros;
-humid exterior air and wildlife will no longer set up shop in your crawlspace. Consequently indoor air quality/comfort in the house will go up.
-Depending on your climate zone you can insulate the exterior walls of the crawlspace which will also increase comfort.
-Due to the air barrier the cost of utilities will drop.

Cons:
- Cost
- May have to install a small continuously running exhaust fan (along with transfer grills onto the crawl) to pull air from the house into the crawlspace and then to the outside.


Again venting or a fan will not work if the air its pulling in is higher than about 40%. Dehumidifier.




It must vary by region then. In the Seattle area where I am the humidity is higher than that. We have a lot of rainy days. For a standard concrete foundation with a crawl space, vents are required at a specified distance. I don't know that off the top of my head but it usually means two vents on each side of the foundation for a typical 1600 sf rambler. A vapor barrier is put down. That's it. As long as drainage is flowing away from the structure then all is good.

Maybe the codes have changed but for a couple of houses I've seen that are under ten years old it appeared to be the same as what I described. The biggest difference is the under floor insulation which I find is more of a mouse and squirrel nesting point than anything.


Well all I can say is put a RH meter in crawl space and see what the RH really is. I bought a wireless one for my DE home so I can see it from the kitchen. Whatever you want to do, you want the RH in the crawl space 40 to 45 %. I have some plastic on the ground and 2 sump pumps that I have never seen go on. I run a dehumidifier 24x7 on a humidistat that is set so its kept in the 40% RH roughly.

I see many homes built with vents that are latter blocked off and a dehumidifier installed.

 

[Fitter30]

Southern Missouri in the ozarks closed off outside vents and insulated, 10 mil plastic of the ground no duct work in c space. Water pipes in summer sweating, insulated both hot and cold and installed c space dehumidifier to keep dew point low. Set point 50% temp stays 50* - 55* year round. Without dehumidifier the c space would be mold growth zone. My next step is to insulated the floor with spray foam since high RH flows to lower RH. Dehumidiers are not all rated the same. A.H.A.M is a certification for the better dehumidifier vs the typical box store dehumidifier thats one reason there is a big difference between the two.

 

[BMWTurboDzl]

Originally Posted by Donald
Originally Posted by BMWTurboDzl
Pros;
-humid exterior air and wildlife will no longer set up shop in your crawlspace. Consequently indoor air quality/comfort in the house will go up.
-Depending on your climate zone you can insulate the exterior walls of the crawlspace which will also increase comfort.
-Due to the air barrier the cost of utilities will drop.

Cons:
- Cost
- May have to install a small continuously running exhaust fan (along with transfer grills onto the crawl) to pull air from the house into the crawlspace and then to the outside.


Again venting or a fan will not work if the air its pulling in is higher than about 40%. Dehumidifier.


As I said a fan would vent to the exterior. This would bring conditioned air from the home into the crawlspace and then to the outside. An alternative would be adding a small supply and return duct. I'm not talking about a lot of air movement. It's like 50 cfm/1k sqft. Whichever approach depends on local codes.

 

[DejaVue]

I didn't think any part of the country builds with vented crawlspaces anymore. Over the years, more people in more areas noticed it hurts more than helps. And now the usual recommendation is to treat the crawlspace as a basement and have heating and A/C or dehumidifier going into it and no vents to the outside. And be careful if putting a vapor retarder/barrier on its ceiling.

That's not to say the space should be vapor barriered/sealed off entirely like the OP's post is more about. Nor does it answer his actual question of how are you supposed to see a small leak if it's behind an opaque plastic barrier.