Crawl Space .... To encapsulate or no?

If this is the wrong forum, feel free to move. Wasn't sure where to post.

I have a 2 story house built in about 1978 in southwest Va. The crawl space is approximately 800 sq feet and is vented and a very tight space. Previous owners failed to put vapor barrier down to cover the entire area, so only about half is covered. Much of the back half which didn't have a barrier has wet and saggy insulation and I just recently had to get a termite treatment where I noticed they've taken advantage of the damp space.

I know I need to basically yank everything and do it right but I'm very confused about leaving it vented or going for encapsulation and enclosing the space. I know encapsulation can get pretty expensive and I'm not entirely sure that's the way to go, but this is pretty far outside of my knowledge base. I've googled the topic a bit and I see pros from those sites who make their business from doing encapsulations and cons from others. I don't want to go down that path and spend a lot of money if it's not going to be effective and if it's going to cause other issues down the line.

I had a company to come assess the situation today and they ball parked the fix at 12.5k for a 4 day job (pretty nice profit if you ask me). The recommendation was to put it drainage around the perimeter of the crawlspace (thought we were getting some water run off that was coming in from the vents being too low to the ground as well as humid air), sealing up all vents, complete encapsulation, and install of a humidifier. There was also a big "IF" they would even do it b/c the space is so limited (around 18" in a few areas) and the HVAC vents would have to be removed by an HVAC contractor before they'd do it.

There's no way I can see that I can justify that kind of money for this. I've got another company next week for an evaluation.

Anyone care to give me some experience in the area and a push in the right direction? It will certainly be appreciated.
Thanks

Welcome to the site.
We have had this discussion here a few times. The pros that have argued for this sealed system have not convinced me of anything. The perimeter drain is a must either way.
Did you also read that the space has to be conditioned after this is done as if it is a completely sealed unit and you do end up with moisture in there anything that used oxigen like rust or mold or rot will deplete the supply and make the crawspace a deadly place for a homeowner to crawl in.
So now you have to ask if HVAC systems are big enough to handle the extra space and the extra expence of conditioning.

Last year we framed a large custom home that is set up for this system, they didn't even have a floor drain in the crawl space even though the furnace and hot water were down there. Before the roof was on the crawl space had picked up a few inches of rain water. They cut huge holes in the subfloor and installed three big fans that ran for 2 weeks before it was dry.
So what happens in a finished house that has plumbing leak, roof leak or what have that puts water in the craw space.
If I can find one of the old threads I will post it here for you read.

Virginia is a humid place, as such a vented crawl space is not a good idea.

The problem is, that warm wet air always heads for a cold surface to condense.
A crawl space is likely to be below "dew point" on a number of days every year, this can result in mold and wood rot.

There are ways to deal with this.

If you keep wood warm and above "dew point" then condensation is not a problem. This can be done by sealing the crawl space, fitting a thermostat and heater.

If you install a dehumidifier, then it presents a colder surface (than your floor) to the water vapor in the air, and the water vapor, which is
programed by nature to head for the nearest cold surface, will do just that and condense inside the dehumidifier.

Both of these are expensive long term solutions. A better way is to use a static system of insulation, plus plastic sheet barrier, to keep the wood warm and the water vapor away from the wood. This is a one off thing,
once done it will work for ever at no further cost. Simply fit sheets of polystyrene below the joists, boxing them in, fit plastic sheet below the polystyrene, making sure to block all holes and cracks, with tape and canned foam.

Problem. If you are running air conditioning then you are adding to the problem, as you are making the floor cold.

Drainage. The questions are, does the ground round your home slope away or towards, what happens to the rain water? Does is drop into waste pipes, is then routed away from the home to a point downhill?

You aren't suggesting that you would insulate between the joists and then apply a vapor barrier to the joists are you? I've read that is a definite no no.

That's the benefit of a crawl space that you can leave it open, that way the air will flow freely. Why mess with a good thing?

You can staple a layer of Typar under the house and some roxul batts for insulation. Same Typar goes on the ground with some gravel on top.

Johnboy2978 said:

You aren't suggesting that you would insulate between the joists and then apply a vapor barrier to the joists are you? I've read that is a definite no no.

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You probably know that wood is hygroscopic, and that it absorbs water from the air, this is the reason it fills with water vapor and sometimes reaches the point where mold forms and wood rot starts.

Mold spores cover the Earth from pole to pole, but you don't see mold growing on everything, mold needs food and water like every other living thing. Mold basically lives on wood (its food) and it gets its water from the air.

When wood is cold below dew point, water is absorbed into it, if a mold spore is in place, then mold starts to grow. Mostly, the heat from inside a home keeps the wood above dew point, this works by radiation and conduction from the room above.

The procedure is the fix the polystyrene sheets below the joists, to capture the heat from above and keep the water vapor and mold spores at bay, the practice of covering the polystyrene with plastic is to provide a cheap second line of defense, to ensure there are no holes or cracks left open for water vapor and mold to get through.

Water vapor molecules are incredibly small, they exist between the air molecules that are gigantic in comparison, an example is a cardboard box full of footballs (the air) with a mass of tiny ball bearings floating in the gaps.

There is no need to place insulation between the joists, merely overkill.

I had a second company come in this past week to give an assessment. This company also seems to make encapsulation their bread and butter. The estimate came to between 8-10K depending on the vapor barrier applied. Essentially, it boiled down to sealing the vents and insulating the walls with silverglo (graphite infused expanded polystyrene insulation) and then applying a "cleanspace" vapor barrier. They have two grades of barrier, a 6 or 20mil which accounts for the cost differential. The price also included a $1400 dollar dehumidifier and mold remediation. These guys were not concerned about the HVAC vents and weren't asking for them to be removed like the first company.

His assessment was that we don't have water coming in from the foundation, but rather our moisture issues are due to humidity and the water coming up from the ground.

Johnboy2978 said:

I had a second company come in this past week to give an assessment. This company also seems to make encapsulation their bread and butter. The estimate came to between 8-10K depending on the vapor barrier applied. Essentially, it boiled down to sealing the vents and insulating the walls with silverglo (graphite infused expanded polystyrene insulation) and then applying a "cleanspace" vapor barrier. They have two grades of barrier, a 6 or 20mil which accounts for the cost differential. The price also included a $1400 dollar dehumidifier and mold remediation. These guys were not concerned about the HVAC vents and weren't asking for them to be removed like the first company.

His assessment was that we don't have water coming in from the foundation, but rather our moisture issues are due to humidity and the water coming up from the ground.

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Going back to your original post, wet insulation. Insulation is wet because it is cold and below dew point. There is probably either a hole nearby in the crawl space wall, letting warm wet air in, or a hole in the floor where your home is pulling the air into the crawl space.

I would be surprised if your crawl space walls were not wet. The walls are in contact with damp ground and that means water is climbing up through the walls to four feet above ground level. At four feet the effect of capillary attraction and gravity cancel each other out.

I wonder why you want to have all this work done, and why you want to spend all this money? You won't live in the crawl space, so what do you expect to gain from this work? What do you hope to achieve, and how will you know the work has done what you want? Where is the visible benefit?

Perry525 said:

I wonder why you want to have all this work done, and why you want to spend all this money? You won't live in the crawl space, so what do you expect to gain from this work? What do you hope to achieve, and how will you know the work has done what you want? Where is the visible benefit?

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Believe me, I would much rather spend $8-10k on a big portion of remodeling the kitchen rather than throwing money literally in a hole under the house. The problem is that I have a moisture problem that is causing the floors to rot and I have to some how take care of that. I'm not sure if what I'm dealing with is the cumulative effects of 40 years of the house having no vapor barrier or if there is something more substantial going on. I would much rather spend the weekend putting down a solid vapor barrier for a couple hundred bucks like it should've been if that will take care of the problem. My problem is that I need to do something to offset the moisture/condensation that is getting in and I'm not sure what the best way to accomplish that is. The companies I've contacted so far seem to live off doing encapsulations and of course, if you have only a hammer in your tool box, everything looks like a nail. They don't tell you up front, all we do is $10K encapsulations, so I need someone who has actually looked at it to make some suggestions.

I think you are right they want to sell the product they are invested in. The options Perry525 is talking about are high on labor and low in cost. If you want to do it as a DIY what he is describing is logical to several members here that are in the trades. Foam to trap the warmth from above and plastic to stop the moisture from below moving up.

I would be doing that before I spent 10k.

Just for the record encapsulation is BY FAR the best way to go IF you live in a hot HUMID area, no ifs ands or buts. If you live in a dry arid climate like Arizona or some place like that then not necessary.

Several multiyear long studies have confirmed this irrefutably.
This one here that started in 2000 and I think still ongoing shows without any doubt that sealing all vents, covering the ground with poly, removing all floor insulation and installing the insulation on the crawl space walls plus installing a vent from your HVAC Plenum in the crawl space to supply "conditioned air" both heated and cooled to keep the space conditioned is the way to go.

http://www.advancedenergy.org/portal/crawl_spaces/pdfs/Field Study - 2005.pdf

I just did my own encapsulation, our crawlspace is NOT quite the average as we are on a hillside, so in front of the house highest on hill the height of crawlspace is about 4' and in the back it is about 9+' tall so plenty of room to work. But also is LOTS of crawl space wall to insulate so my material cost would probably be a bit higher than most.
Foot print to cover with poly was roughly 50'x26'.
I used 12mil high quality virgin poly 4 layer "Dura Skrim" which should last probably more than 50 years.
The cheap non virgin regular 6mil poly you usually see at hardware stores do not block the moisture nearly as well and you're probably lucky if it last 6-10 years tops.

http://ravenefd.com/files/6213/8022/5597/Dura-Skrim_8-12.pdf

On the walls I used RMax TSX-8500 polyiso double foil sided insulation (R-13) which has a 15+ min thermal barrier.
I also used about 25 cans of fire retardant spray foam to seal all holes in floor boards around electrical wiring, plumbing pipes etc and also to seal in all the polyiso sheeting in the band joist, I also fire foamed sides and top (not bottom) of all polyiso boards then taped all seams with thick foil tape.
All boards were fastened to walls with Tapcons and large stainless fender washers. I left the required 3" termite inspection gap between insulation and joist band.

Prior to encapsulation my crawlspace both leaked like a sieve through the concrete and brick wall in front, and had absolutely insane condensation where in the summertime I could stand in there and literally hear it RAINING under the house from water dripping off the AC ducts from the hot humid air being sucked in from open vents and condensing on every cooler surface. So I repointed the entire wall with hydraulic cement then applied 3 thick coats of "Sunny Dry" which is basically a thin portland cement coating that completely waterproofs the entire surface of the cement blocks, bricks and mortar.
I also dug and installed a French Drain along the entire front wall, the uphill section of crawlspace just in case a leak comes in that wall again in the distant future then it will go into drain and out the back and not under the poly.

http://www.oneprojectcloser.com/sunny-dry-basement-waterproofer-sealer-review/

I researched the pure T hell out of all this prior to attempting it, found LOTS of info, went on Forums of the particular Home Inspectors in my area, the ones that would be coming out to inspect if I were to sell my house, asked questions, got answers and printed out those answers so that when we do sell our house some inspector wont be waving his bony finger saying that something is incorrect because I will show them THEIR responses to my very specific questions.
I actually went beyond code in both materials and in installation technique.

All in all for materials and I bought nothing but the highest quality and installed it all BETTER than any encapsulation company ever would have and I spent about $1,700 in materials and did all the work by myself with zero help.

Was by far the best $1700 I have ever spent on our house.

No more mold or mildew, crawlspace is literally a 50x26' fully sealed and conditioned storage space now that stays between 68-72 degrees year round with low humidity.
Our hot water heater is in the crawl space also so even it is far more efficient because its not sitting in freezing temps in the winter.
About a 18% energy savings.

Its a win/win/win situation.

I applaud your research and effort and if you are going to do it, you may as well do it well and that's what I think you have done. I really like the fact that you went after the perimeter drain also.
My problem with this system is that I have seen two houses built like this up here. We framed one of them, a huge house that took what seemed like forever to get the roof on and water tight. And when you live in a rain forest some surprize it rained and the crawl space had a foot of water in it and started to smell. When I asked why it haddened drained I was told it was a closed conditioned space so it had no drains. Big holes were cut in the floor and fans were running for month to dry it out. When I asked what happens in years to come when the roof leaks or the plumbing leaks I just got a bunch of dumb looks.
The other house belongs to a friend of mine and it was built as an R2000 house with air exchanger and sealed crawspace. BTW our crawlspaces have the poly on the floor and 2+" skim coat of concrete. They were getting a smell from the crawlspace and what we found was dampness at the base of the foundation wall and as that wall was 20 ft below ground level out side as it is on a hillside.. The quick fix was to open vents into the crawlspace and put in a fan to move the air, we insulated the coldwater pipes and built an insulated room around the boiler and water tanks.
One hot water tank leaked from the bottom and that mess was nearly dry after about 2 week when the other tank went, where do we think that water went to??

Usually in a closed conditioned space that is flat not on a hillside like we are people put in a sump pump.
You sort of grade the ground, add sand or pea gravel prior to putting down the poly so that it all drains to ONE spot.
At that spot you dig a hole about the size of a 5 gallon bucket , in fact you can just bury a 5 gallon bucket and put a pump in it like you have on a boat, a water activated bilge pump, it has a little float on it and once the water hit the float it rises and automatically turns on the pump. the pump then simply pumps the water out of the crawl space through the wall.
Since ours is on a hillside it all already goes to one spot anyway and that is where the French drain goes out the back, I just simply installed a drain hole right there just in case the house ever gets a plumbing leak it will just drain right on out so we have no need for any sort of pump.

Here are a couple different ones.

[ame]https://www.youtube.com/watch?v=T-vutaRuZXk[/ame]

[ame]https://www.youtube.com/watch?v=punQL1NXMzY[/ame]

Oddly enough on ours, we had that musty, mildew smell in our crawlspace and it was coming from all the humidity plus the one wall leaking from rain, since that front wall is about 4' under ground the ground water was pushing through the wall, I have pretty much solved that by repointing the wall with hydraulic cement.
Solved the humidity/condensation problem by sealing up the vents and pulling down all the saturated batting insulation from the floor joist.

Now our crawl space is just like walking into a room in our house.

I'm glad you put a drain in but the people who design new houses with this system don't call for a drain. I still don't think you are condition ther air with out a return, just can't happen.

If it cant happen then why is our crawl space now a perfect 68-70 degrees with low humidity winter, spring, summer and fall?
Our crawl space feels exactly like the rest of our house now.

Used to be 80+ degrees with 90++ % humidity in the summer and below freezing in the winter.

They should always put in a drain thats just common sense

For the same reason that rooms with no air flow have poor heating.

I live in a basement suite right now so you might say it is simular to your crawl space. In the summer it is cooler in the summer in my suite some time 25 degrees cooler. Goodluck if you think you could heat that space with one vent, nevermind absent the rerturn air. The upstairs has their front door and office on the basement level, both have heat vents. We couldn't get any heat in those rooms until we put a return air vent in under the stairs.

Dont need any luck, been doing for a year now, LOL

Everytime I walk under the house it feels just like I am walking into the rest of the house and its being heated and cooled by one single vent straight from the plenum.

This is how it is always done in this area, in fact they recommend to NOT put in a return. The only other way its done which technically is slightly better (humidity wise) but considerably more expensive is to install a large dehumidifier in the crawl space. In fact I could still do that anyway, it would just help during the 1-2 months that the AC/Heater is seldom running.

I will say though that at this time of year in the fall the humidity does get a bit higher in the crawl space because we really do not have either the AC or heater running much, the temp is nice and stays in the high 60s but humidity does raise a bit because its not being constantly conditioned like it is in the summer & winter. BUT as long as its not raining the humidity outside this time of year is usually fairly low anyway, today it was 38%, so regardless if the heater is running or not the humidity is not bad.
Now we live in a 2 story townhouse with a separate thermostat on each floor, each time a thermostat turns on up or down it obviously blows AC or Heat in the crawlspace, it doesn't care what the crawl space is it just goes with what the upper two floors require.
Apparently that is more than enough for the crawl space to be nicely conditioned about 10 months out of the year.
Also I might add, in the winter our hardwood floors downstairs which used to be literally freezing are now just "cool" in fact almost warm sometimes because all the heat goes up and heats the floor joist, it used to be below freezing under there.

But to me the 30-45 days we have of little to no AC/Heater conditioning is in no way worth the $1400+ it would cost for a Dehumidifier plus the running and servicing of it. That would more than negate the energy savings we are getting (about 18%) because of the encapsulation.
I am WAY more than satisfied with the condition of our crawl space today compared to what it was 2 years ago.
Back then it was literally a scary dungeon that had a river flowing through it and was like a humid rain forest in the summer, smelled musty, mildewy, mice in the soaking wet insulation in the joist, spiders and bugs everywhere.
It was like a freaking horror movie set.

If I took a cardboard box down there 2 years ago that was perfect & brand new it would be soaked 12 hours later and floppy.
I have boxes under there right now that have been under there a year and its like the the day I put them under there.

So the humidity never gets to the point to where it affects cardboard, thus no way is going to affect wood or cause mildew/mold.
Cardboard is like the canary in the coal mine, if cardboard is perfectly fine then your crawl space is good to go.

not to mention NC code says that if I were to add a return which is totally unnecessary anyway that would make my now "Encapsulated crawl space" into a "Conditioned Crawl space" thus I would have to install Gypsum board on all the walls.
(although in my case I am not sure because the polyiso foam insulation that I installed does have a 15 minute thermal barrier on one side in the form of thick foil)
Like I said I went above code.

But I do not want the air from the crawl space flowing into the house, I simply see zero reason for that extra expense and hassle with basically no "return" pardon the pun.
Crawl space is fantastic from April thru September that is 1/2 the year as the AC is running almost nonstop and temp stays right at 69-70.
Oct and part of Nov its so-so, temp is fine, humidity a tad higher but still totally acceptable, air a little bit stale but thats really about it.
End of Nov thru to about March its very good as the heat is on quite a bit, temp stays 68 to 71 even if its 15 degrees outside, humidity is more than good.
Really just Oct and maybe a bit in March is when a dehumidifier would be of some help, but Vs what it was 2 years ago its a 1000x improvement even on its worst day.

So NO I just do not need a return at all, would be of zero use or improvement in my case.