Join Early Retirement Today
Reply
 
Thread Tools Search this Thread Display Modes
Controlling crawl space humidity
Old 09-27-2011, 01:54 PM   #1
Thinks s/he gets paid by the post
 
Join Date: Mar 2010
Posts: 1,648
Controlling crawl space humidity

Am interested in others' solution to this problem...if you have it. We live in the very humid south. The AC ducts under my house drip with condensation July August and September. A couple of years ago, a "guy" told me to close my outside vents and leave them closed all year. I did that. Well...it just so happens that was also about the time I started seeing some inside mold on the ceilings in that area. This has happened each year for about the last 2. Usually if I wipe the mold down with bleach it doesn't reappear.
BUT...I'm tired of this so ....am thinking about 2 solutions. One involves what is called a "Conditioned Crawl Space", the other is to simply put dehumdifiers under the house.
The theory around the Conditioned Crawl Space is to seal everything up ...including vents.....with plastic and foam insulation- sealing the outside humid air outside and preventing it from coming in. Next is to route a vent or two from the HVAC system under the house - making the crawl space feel like the inside of our house. Theory is my AC duct work under my house will not form condensation. With this solution there also should be some dehumidfication that is a normal part of AC functioning.

I'm concerned about the dehumidifier equipment solution.......as they become "another" piece of equipment to maintain. I need two. With this solution, the vents also have to be sealed and plastic used up the walls as well.

How have others solved their humid moist crawl space issues
__________________

__________________
sheehs1 is offline   Reply With Quote
Join the #1 Early Retirement and Financial Independence Forum Today - It's Totally Free!

Are you planning to be financially independent as early as possible so you can live life on your own terms? Discuss successful investing strategies, asset allocation models, tax strategies and other related topics in our online forum community. Our members range from young folks just starting their journey to financial independence, military retirees and even multimillionaires. No matter where you fit in you'll find that Early-Retirement.org is a great community to join. Best of all it's totally FREE!

You are currently viewing our boards as a guest so you have limited access to our community. Please take the time to register and you will gain a lot of great new features including; the ability to participate in discussions, network with our members, see fewer ads, upload photographs, create a retirement blog, send private messages and so much, much more!

Old 09-27-2011, 02:11 PM   #2
Give me a museum and I'll fill it. (Picasso)
Give me a forum ...
 
Join Date: May 2004
Posts: 11,615
The conditioned crawlspace option is a good one with solid science behind it, but it relies on careful detailing. You have to get the plastic sheeting down very carefully over the dirt, overlap the seams a couple of feet and tape them with foil tape for good measure, the plastic has to be well sealed up the sidewall, and the insulation of your crawlspace walls has to be as good/nearly as good as the R-value of the walls of your house. If you don't tend to these things, you risk bringing pollutants/moisture into the living space and increasing the cost of heating and esp A/C. But done right it can reduce your moisture issues, make your house more comfortable, and reduce electric bills.

Don't scrimp on the plastic (use thick stuff). Wall insulation: 2-3" thick extruded polystyrene (brand name Styrofoam, etc) is cheap, sturdy, and simple to work with, but it can be a pain to get it in place reliably in the confines of a crawlspace. The spray-on foam (comes in large tanks, can be used by a DIYer) has as good/better r-value per inch, seals things up tighter and is quicker to apply, but somewhat pricier. It's available in versions with low flame spread/flammability at no additional cost--get that kind. The spray-on foam approach is worth it (compared to just rigid board insulation) unless you've got much more time than money or an easy installation environment. It's sometimes easy/less expensive to spray on an inch of foam on the walls and up to the rim joists, let it set up. Then spray on a light coat (1/2") on the large wall areas, pressing rigid foam sheets into the foam before it sets up. Then spray on another inch in hard-to-get-at places (rim joist/mud-sill areas, pipe penetrations, etc). This mixed approach lets you use the foam to seal against air penetration all over the wall and saves money by using the cheaper rigid panels to gain r-value in the "easy" large, flat wall spaces.

You can also remove any fiberglass insulation now stapled under your floor and use it elsewhere after you get this crawlspace insulated, since your crawlspace will be almost the same temperature as the inside of the house. Some folks put the old insulation in their attic, some affix it to the inside of the new foam on the walls of their crawlspace (this depends on the foam providing sufficient insulation so that the air in the fiberglass insulation would never get colder than the dewpoint at the expected RH level in the crawlspace. It can be a complex calculation and depends on knowing and estimating a few things. It's probably safer to use the fiberglass in the attic if you need it.)

If all this sounds like too much work, you could try incremental approaches. First, definitely put plastic down all over the ground and do a neat job of it, at least piling dirt on top of it around the edges to seal it to the walls (better to stick it to the walls with mastic). Then add more insulation to your ducts so they don't get cold enough to "sweat," which will also save you some money. Then, make sure you've got a good vapor barrier under any insulation that is under your floor--if it's just the kraft paper from batt insulation it's probably tearing apart and gapping at the seams, allowing warm, moist air to infiltrate into the space and condense against your colder floor in the summer time, a nice place for mold to form.

The conditioned crawlspace solution is the most bulletproof, energy efficient, and costly approach.
__________________

__________________
"Freedom begins when you tell Mrs. Grundy to go fly a kite." - R. Heinlein
samclem is offline   Reply With Quote
Old 09-27-2011, 02:37 PM   #3
Give me a museum and I'll fill it. (Picasso)
Give me a forum ...
RunningBum's Avatar
 
Join Date: Jun 2007
Posts: 5,175
Closing the outside vents seems like a very, very bad idea. You need them open for air movement to dry out the ground. You *might* close them in winter to keep your floors from being cold but you really need to remember to get them open in spring.

I had mild mold issues in my last house and along with keeping vents open, I put down the plastic sheeting, I think with a 5 mil sheet. I'm pretty sure the exterminator guy who also looked at dampness issues told me to leave a few inches at each wall, but I can't remember why.

For the condensation issue, I would see if there is a way to channel it and pipe it out of the crawl space, if you have any pitch at all to the ground.

What about a fan in the crawlspace to circulate air to dry things out? I like that better than cooling your crawlspace as a cheaper crawlspace, though I agree that the A/C should act as a dehumidifier.

Make sure rain and sprinkler water is channeling away from your foundation and not into your crawlspace. A berm can help keep it away, so can landscaping to absorb the water.
__________________
RunningBum is offline   Reply With Quote
Old 09-27-2011, 09:20 PM   #4
Thinks s/he gets paid by the post
 
Join Date: Mar 2010
Posts: 1,648
SAmClem...I talked with my brother in law tonight ..and he and my sister did a conditioned crawl space in their new home. Along with the things you said, he also suggested I have the... guys lay plywood on top of the plastic. Not all the way ..but as "crawl paths" to get to the things that need getting to under the house ....so that when the pest control guy or the HVAC guys go in they won't move the plastic around or tear it. Should I use any higher mil than 6 mil? The crawl space people quoted me a plastic that has fibers in it. Is 20 mil worth the extra costs?

Your point about removing the insulation under the floor is interesting as the crawl space guy ...quoted me $100 to put it back up (the parts that have fallen down) or $1000 to replace all of it. ummmm....

There is an old HVAC system under there ( no longer operational) ...that I THOUGHT the HVAC guys removed....when I bought the new self contained one. Just found out today it is still there.

The pest control guy....says...he doesn't like conditioned crawl spaces...as it leaves no room to do a visible inspection for termites. Any validity to this statement.?
Interestingly enough it is the pest control guy that has given me a quote for the dehumidifier route...which at first glance is higher than the conditioned crawl space. (another ....ummmm....)

Called another friend who did the contitioned crawl space when they built their new house. They ended up with water in one far corner....above the plastic. Had to bring in sand and run a drain pipe or something. I gather it was something about the drainage on that side of the yard.
So....my lot slopes slightly left to right....with the low side being the right hand side. When it rains hard...I can get a small lake affect on that side. But it drains fast once rain stops. By rain..I mean hurricane like rain. I spent a LOT of money years ago....putting a drain pipe in on the at entire side...tieing in the gutters...etc...that obviously has now collapsed and has been collapsed for probably over 5 years. Any concern about yard grade with conditioned crawl spaces?
__________________
sheehs1 is offline   Reply With Quote
Old 09-27-2011, 09:41 PM   #5
Thinks s/he gets paid by the post
 
Join Date: Mar 2010
Posts: 1,648
Quote:
Originally Posted by RunningBum View Post
Closing the outside vents seems like a very, very bad idea. You need them open for air movement to dry out the ground. You *might* close them in winter to keep your floors from being cold but you really need to remember to get them open in spring.

I had mild mold issues in my last house and along with keeping vents open, I put down the plastic sheeting, I think with a 5 mil sheet. I'm pretty sure the exterminator guy who also looked at dampness issues told me to leave a few inches at each wall, but I can't remember why.

For the condensation issue, I would see if there is a way to channel it and pipe it out of the crawl space, if you have any pitch at all to the ground.

What about a fan in the crawlspace to circulate air to dry things out? I like that better than cooling your crawlspace as a cheaper crawlspace, though I agree that the A/C should act as a dehumidifier.

Make sure rain and sprinkler water is channeling away from your foundation and not into your crawlspace. A berm can help keep it away, so can landscaping to absorb the water.
Running Bum...Yes...it seems closing my vents was not a good idea. Believe it or not...that came from the pest control guy. I think I can pretty much say this is what ...has actually increased the humidity in my house. My vents are now all open. I was having humidity, moisture problems before I closed them...so I now know closing them only exacerbated the problem.
In past years....I dumped extra sand into the crawl space, new plastic...etc. I have gutters and either tied the gutters into a drain pipe or put in the concrete splashes. There is landscaping all around the house with build up beds to absorb moisture. Still there is a humidity problem...and the "experts" that have been under there...tell me it is my AC ducts forming condensation. My duct work is insulated. Which brings me to my next question. How can duct work that is insulated have water condensation or be the source of the condensation situation under my house. ?

I'm finally ready to do something once and for all as I have been listening to suggestions over the years. Anything from power vents...to sand to plastic, to dehumidifiers. The crawl space guy told me today ...the dehumidifiers would not do any good without a fan to move the air around. Makes sense. As I said above, the dehumidifier solution is actually more expensive than the conditioned crawl space and has on going maintenance issues.

I live in south eastern Virginia, very humid 3 months out of the year. So it is technically a 3 month problem.
__________________
sheehs1 is offline   Reply With Quote
Old 09-27-2011, 09:46 PM   #6
Give me a museum and I'll fill it. (Picasso)
Give me a forum ...
harley's Avatar
 
Join Date: May 2008
Location: Following the nice weather
Posts: 6,428
We put in a conditioned crawlspace when we built the dream home, but it doesn't have plastic in it. It's a sealed concrete and cinderblock crawlspace, with a couple of hvac vents open into it to help control temperature and humidity. We've gone through 4 summers in a beach location with no mold or mildew or water problems. I go under there a few times a year, storing a few items under there. We also installed light fixtures so the workmen can see more easily. I use a auto mechanics dolley to roll around under there when I need to do anything.

The reason we went to the extra expense is because my family members have significant asthma and allergy issues, and we wanted to minimize any possibility of mold in the walls and floors. So far I would call it a good decision. It's also made it easier for me when I wanted to pull Cat6 and coax cable into a different room.
__________________
"Good judgment comes from experience. Experience comes from bad judgement." - Will Rogers, or maybe Sam Clemens
DW and I - FIREd at 50 (7/06), living off assets
harley is offline   Reply With Quote
Old 09-27-2011, 10:11 PM   #7
Full time employment: Posting here.
JakeBrake's Avatar
 
Join Date: Sep 2008
Location: Southeast USA
Posts: 548
Quote:
Originally Posted by harley View Post
We put in a conditioned crawlspace when we built the dream home, but it doesn't have plastic in it. It's a sealed concrete and cinderblock crawlspace, with a couple of hvac vents open into it to help control temperature and humidity. We've gone through 4 summers in a beach location with no mold or mildew or water problems. I go under there a few times a year, storing a few items under there. We also installed light fixtures so the workmen can see more easily. I use a auto mechanics dolley to roll around under there when I need to do anything.

The reason we went to the extra expense is because my family members have significant asthma and allergy issues, and we wanted to minimize any possibility of mold in the walls and floors. So far I would call it a good decision. It's also made it easier for me when I wanted to pull Cat6 and coax cable into a different room.
There's no question, that's the best way to do it. However, retrofitting an existing crawlspace is much more difficult. I, too, like to inspect the interior of my crawlspace walls for termite tunnels. But, the fact is that as long as any dirt is visible, moisture will rise from the ground into the crawlspace. Until the crawlspace can be totally sealed and insulated, it's better to have plenty of ventilation through the crawlspace.
__________________
JakeBrake is offline   Reply With Quote
Old 09-27-2011, 10:55 PM   #8
Thinks s/he gets paid by the post
 
Join Date: Mar 2010
Posts: 1,648
Quote:
Originally Posted by JakeBrake View Post
There's no question, that's the best way to do it. However, retrofitting an existing crawlspace is much more difficult. I, too, like to inspect the interior of my crawlspace walls for termite tunnels. But, the fact is that as long as any dirt is visible, moisture will rise from the ground into the crawlspace. Until the crawlspace can be totally sealed and insulated, it's better to have plenty of ventilation through the crawlspace.
That is part of my concern...JakeBrake. Can a retrofit be successful? Should it even be done to an existing space?
Anyone have any concern about radon in regards to converting an existing space?
__________________
sheehs1 is offline   Reply With Quote
Old 09-28-2011, 07:54 AM   #9
Give me a museum and I'll fill it. (Picasso)
Give me a forum ...
travelover's Avatar
 
Join Date: Mar 2007
Posts: 9,878
Here is an interesting article on the subject.

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

Essentially their argument is that crawl space vents can contribute to problem, as they let warm humid air into the cooler space, where it condenses.

In my previous home in Michigan, I installed a gravel lined drain inside the outside wall, which emptied to the footing drain, then covered the floor with plastic which I sealed to the walls. I closed off the vents permanently and insulated the walls. Plywood runs would have been a good idea on the floor, but I didn't do it. The overall project seemed to work very well. Termites aren't a problem in this area.
__________________
Yes, I have achieved work / life balance.
travelover is offline   Reply With Quote
Old 09-28-2011, 10:15 AM   #10
Give me a museum and I'll fill it. (Picasso)
Give me a forum ...
 
Join Date: May 2004
Posts: 11,615
Here are some good links to a reputabe source regarding conditioned crawlspaces. They have done their research and the information is much better than you'll get from your typical tradesman:
Conditioned Crawlspaces and codes
Top 10 Dumb Things to do in the South (Re: Building Construction)
Quote:
Originally Posted by sheehs1 View Post
. . .he also suggested I have the guys lay plywood on top of the plastic. Not all the way, but as "crawl paths" to get to the things that need getting to under the house ....so that when the pest control guy or the HVAC guys go in they won't move the plastic around or tear it.
That's a good idea.
Quote:
Originally Posted by sheehs1 View Post
Should I use any higher mil than 6 mil? The crawl space people quoted me a plastic that has fibers in it. Is 20 mil worth the extra costs?
I don't know how much the extra thick plastic will cost. Intuitively, it seems to me that if folks won;t be down there mucking around very often that 6 mil ought to be good enough. OTOH, something with fibers in it (to prevent a long rip) could be worthwhile. Don't use Tyvek or other housewraps--they are tough, but they are designed to allow water vapor to pass through them, and that's exactly what you don't want.
Quote:
Originally Posted by sheehs1 View Post
There is an old HVAC system under there ( no longer operational) ...that I THOUGHT the HVAC guys removed....when I bought the new self contained one. Just found out today it is still there.
Seems outrageous, but it's not uncommon. I found an old AC unit in the attic of a house we bought. It takes a lot of guts to charge the homeowner and leave something so obviously wrong in their path, but I guess they are pretty confident folks aren't going to even look under the house or in the attic before paying the bill. I guess they are right most of the time.
Quote:
Originally Posted by sheehs1 View Post
The pest control guy....says...he doesn't like conditioned crawl spaces...as it leaves no room to do a visible inspection for termites. Any validity to this statement.?
Yes and no. Those termites are a lot less likely to build tunnels in a 60% humidity, 75 deg F crawlspaces than in a 95% humidity, 90 deg F crawlspace. You can also treat the walls with borate compounds (before you add the insulation) so they buggers won't want to be be there. You can also get foams pre-treated with borate that they don't like and are very unlikely to tunnel through. But, if you want to go the extra mile you can screw a strip of aluminum flashing to the concrete or block so it sticks out about 4" before you add the insulation. This would force the termites to go around the flashing and expose their tunnels to an inspection of the inside of the insulation. Alternatively, some folks leave a narrow strip (4-6") of bare wall uninsulated so any tunnels can be seen during an inspection.

Ask your termite guy how he inspects the inside of those hollow-core concrete blocks for mud tubes. He can't, and he knows the cracks and penetrations in "termite caps" and all the penetrations of the wall provide other means for the termites to get up to your tasty floor and walls
Quote:
Originally Posted by sheehs1 View Post
Any concern about yard grade with conditioned crawl spaces?
No, you need to fix the problem with or without the conditioned crawlspace. It's possible the drainpipe you installed is silted up (which can be fixed) or that the drainage bed is silted up (which can't be fixed without digging everything up). I don't know why folks use that cheap plastic corrugated slinky pipe for drainage jobs. Smooth DWV PVC pipe doesn't cost much more, it doesn't collapse, it collects less silt, it's straight so it's easy to know you have good fall over the entire length of it, and it can be cleaned out much easier. I guess just because the slinky pipe it is cheaper and a little easier to work with. And lasts long enough for the check to clear.

Regarding your duct condensation: Yes, the ducts may be insulated now, but probably not very much. Generally they just have the equivalent of R6 to R-8 on them, and the air going through them is plenty cold. The outside of the insulation gets colder than the dew point (not hard in a crawlspace in Dixie!) and they sweat. In truth, any duct going through unconditioned spaces (e.g. attic or crawlspace) should be sealed well and insulated at least as well as the walls of the house (typically R13). If you go with a conditioned crawlspace you can leave the present insulation on them and they won't sweat anymore (because the relative humidity down there will be much lower). As a bonus, all the duct leakage and loss of cooling from the outside of the duct won't be truly lost, since the crawlspace becomes part of the heated/cooled building space.

Creating a conditioned crawlspace is an unpleasant job that is within the capabilities of the typical homeowner. If you DIY, the materials won't cost more than a few hundred dollars. If you contract it out, the cost could be low or high depending on labor rates in your area.
__________________
"Freedom begins when you tell Mrs. Grundy to go fly a kite." - R. Heinlein
samclem is offline   Reply With Quote
Old 09-28-2011, 11:12 AM   #11
Full time employment: Posting here.
JakeBrake's Avatar
 
Join Date: Sep 2008
Location: Southeast USA
Posts: 548
This is a link to Doug Rye's website. Mr. Rye is based in Arkansas and specializes in the Southeast USA. He has a weekly program on many radio stations in the Southeast. He often discusses crawlspace problems. Don't let his accent fool you. He knows some stuff. He does not recommend things with a 100 year payback time.

Official Website of Doug Rye
__________________
JakeBrake is offline   Reply With Quote
Old 09-28-2011, 07:24 PM   #12
Thinks s/he gets paid by the post
 
Join Date: Mar 2010
Posts: 1,648
I will look over all the links provided. Am studying the "situation" and today the "conditioned crawl space" is winning. Here is why. Until I stop the humid air from entering the crawl space...via the vents....my AC ducts will always form condensation...in these humid hot months....and this problem will never go away.

Fans ..while they may work....they require monitoring, turning on and off ...depending on what's going on with air temps and relative humidity.

Dehumidifers....I'd just rather not introduce another piece of equipment into the equation. Plus the cost is just as high as the "conditioned crawl space option. Plus...the guy that told me to close my vents is the guy recommending the dehumidifier. Don't trust him much anymore.

So...if I do the conditioned crawl space retrofit option......any concern over drying my house out TOO MUCH
__________________
sheehs1 is offline   Reply With Quote
Old 09-28-2011, 07:37 PM   #13
Thinks s/he gets paid by the post
 
Join Date: Mar 2010
Posts: 1,648
Quote:
Originally Posted by samclem View Post

You can also remove any fiberglass insulation now stapled under your floor and use it elsewhere after you get this crawlspace insulated, since your crawlspace will be almost the same temperature as the inside of the house. Some folks put the old insulation in their attic, some affix it to the inside of the new foam on the walls of their crawlspace (this depends on the foam providing sufficient insulation so that the air in the fiberglass insulation would never get colder than the dewpoint at the expected RH level in the crawlspace. It can be a complex calculation and depends on knowing and estimating a few things. It's probably safer to use the fiberglass in the attic if you need it.)
SamClem: Do I HAVE to remove the fiberglass under my floors? Is it a problem if I leave it there? I ask...because the company doing this work quoted me a $1,000 to remove it.
__________________
sheehs1 is offline   Reply With Quote
Old 09-29-2011, 07:05 AM   #14
Give me a museum and I'll fill it. (Picasso)
Give me a forum ...
 
Join Date: May 2004
Posts: 11,615
Quote:
Originally Posted by sheehs1 View Post
SamClem: Do I HAVE to remove the fiberglass under my floors? Is it a problem if I leave it there? I ask...because the company doing this work quoted me a $1,000 to remove it.
IF you are going the conditioned crawlspace route, you can either remove it or leave it right where it is. It won't hurt anything staying right there, at least from a moisture/energy perspective. Ask the folks doing the conditioned crawlspace to slash the kraft paper liberally while they are down there just to be sure you don't have an inadvertent vapor barrier that might cause problems.

The only reasons to remove the insulation is is you are concerned with vermin nesting in it or if it is moldy and you'd prefer not to have the mold nearby your living space.

$1000 sounds like a lot--how big is your building footprint and how hard is it to get into/around this crawlspace of yours? I would think it would take about 3-4 hours to remove 1000 sq ft of insulation between the floor joists in a typical crawlspace.
__________________
"Freedom begins when you tell Mrs. Grundy to go fly a kite." - R. Heinlein
samclem is offline   Reply With Quote
Old 09-29-2011, 08:03 AM   #15
Thinks s/he gets paid by the post
 
Join Date: Mar 2010
Posts: 1,648
Quote:
Originally Posted by samclem View Post
IF

$1000 sounds like a lot--how big is your building footprint and how hard is it to get into/around this crawlspace of yours? I would think it would take about 3-4 hours to remove 1000 sq ft of insulation between the floor joists in a typical crawlspace.
I'd say it is at least 2000 square feet. Original 2 story house was around 2,400 to 2,600. We added a tall one story master suite addition around another 1000 square feet over 15 years ago. Current crawl space height measurement is 42 inches. It can be tight...depending on the size of the person going under.

R factor on this foam is 7 per inch and he quoted 1 1/2 inches...
R factor in my walls is 13 (looked at drawings to make sure). Should he go to 2 inches of foam?
__________________
sheehs1 is offline   Reply With Quote
Old 09-29-2011, 08:27 AM   #16
Thinks s/he gets paid by the post
 
Join Date: Mar 2010
Posts: 1,648
Also....I've already asked about drying it out before this condition process starts. He said conditions are not wet enough to have to do that. (but they are wet enough to suggest doing this process...). Any concern about putting foam over possible wet conditions. ( I know if it is too wet it won't stick).

I also have 2 fireplaces.

Quote for the conditioned crawl space is $3,700 + $1,000 for insulation removal = $4,700. (The $1,000 for insulation removal surprised me as it was not talked about before he put pen to paper)

Verbal quote for 2 dehumidifiers was $4,100....which included the plastic and sealing vents...which I suppose is called an unvented crawl space rather than a conditioned crawl space. Did not include electrical work for a GFI and switch inside the house to operate...etc. Not really liking this option for reasons stated before ...but also because he left it sort of open ended "depending on what he found" (I know what those words mean!) and has not put pen to paper yet.
__________________
sheehs1 is offline   Reply With Quote
Old 09-29-2011, 09:28 AM   #17
Give me a museum and I'll fill it. (Picasso)
Give me a forum ...
 
Join Date: May 2004
Posts: 11,615
Quote:
Originally Posted by sheehs1 View Post
I'd say it is at least 2000 square feet. Original 2 story house was around 2,400 to 2,600. We added a tall one story master suite addition around another 1000 square feet over 15 years ago. Current crawl space height measurement is 42 inches. It can be tight...depending on the size of the person going under.

R factor on this foam is 7 per inch and he quoted 1 1/2 inches...
R factor in my walls is 13 (looked at drawings to make sure). Should he go to 2 inches of foam?
42"H is a fairly generous crawlspace, if you are measuring from the bottom of the floor joists.

What type of foam is he using (spray-on? rigid panels?). I don't think I'd be content with R-10, shoot for closer to R-13 if the cost is in line. Remember, you'll be paying to heat and air condition that space from now on, and those crawlspace walls will be just as exposed to the outside temps as the other walls of your house. If they transfer more heat than your insulated floor used to (compensated for relative surface area) you could find that your heating/cooling bills go up, or even that your HVAC equipment isn't up to the job. Electricity and NG are sure to go up in the years ahead, so buying a bit of additional insulation now, while the work is being done, is probably a smart move.

If he (really) applies 2" of spray foam, that should be plenty, but it will be pricey. The trick with spray foam is knowing that 2" really got applied. You need to let him know that you intend to go under the house with an ice pick and see how thick the foam is--write it into the contract that he will reapply foam 1/2 thick everywhere at no additional cost if you find any spot with less than 1.75" of foam. Does the spray foam include additives t reduce flame spread and termite infestation (borate additives being the most common)? Ask for the exact brand he will use, and for spec sheets on it (keep these in your records for when you sell the house).

If he plans to use rigid foam, it's much easier to be sure how thick it was applied. They also make this with borate additives (it's harder to find, but available). Going from 1.5" to 2" rigid foam board should cost very little materials-wise.

If I were doing this myself (cheap bastard that I am):
- Remove junk from crawlspace
- Apply silicate sealer to inside of walls (penetrates concrete and block to reduce chance of water intrusion, also reduces water vapor transmission somewhat)
- Paint walls with two coats of Zinnser BIN (provides a good vapor barrier. Helps reduce vapor transmission. Very stinky stuff, get good fan-forced ventilation under crawlspace, carbon respirator, and limit exposure).
- Spray wall, mud-sill, rim joists, and outside 24" of floorboards and joists with "Boracare with Moldcare". Repels termites, penetrates wood to assure they can't get through to the rest of the structure. Also prevents mold growth. Apply the same treatment at any piers/lolly columns, etc that they little buggers might climb.
- Put 6 mil plastic down, wrapping well up the sides of wall (12"). Use mastic to affix to wall.
- Screw aluminum termite flashing strip to wall (use short tapcons every 3-4 feet) approx 18" from dirt (convenient height for visual inspection). It should stick out 4". Caulk between wall and strip to assure the termites can't get underneath.
- Use adhesive to adhere foam planks (1.5" thick) to wall above and below the termite flashing. Start at ground and go up to floor joists. Use big pieces and put two tapcons in each (with large corrugated sheet metal washers) to hold things in place while the adhesive sets and as a backup. Then, apply a second layer of 1.5" panels, staggering the seams (just glue to those underneath, no screws). That's approx R-15 of foam now--plenty good for many years.
- Buy spray foam tanks and apply 2" of foam into all the spaces between the floor joists along the walls and to seal the top of the rigid foam panels. Also use this spray foam to seal gaps between the panels and any gaps between the panels and the termite strip, any wall penetrations, etc.
- Tear down the floor insulation, slash the backing, and staple, glue, or just jam it in place between the floor joists (on the back of the spray foam). The thickness of the foam assures the inside surface won't get cold enough in a Virginia winter to cause condensation, so you shouldn't have problems with mold growing in this fiberglass. It is free insulation, might as well put it to work on the walls.
- Figure out where to put the supply and return air to/from the crawlspace
- Address the crawlspace access. The door needs to fit tightly (add gaskets/weatherstripping) and the back needs to be insulated (screw or glue rigid foam to it--easy).

But, that's just me. None of the above is meant as definitive advice. Best to consult with experts. etc
__________________
"Freedom begins when you tell Mrs. Grundy to go fly a kite." - R. Heinlein
samclem is offline   Reply With Quote
Old 09-29-2011, 09:58 AM   #18
Give me a museum and I'll fill it. (Picasso)
Give me a forum ...
travelover's Avatar
 
Join Date: Mar 2007
Posts: 9,878
Samclem touches on it, but it is well worth your while to seal the rim joists if this is a closed, conditioned space. In basements, which this will essentially become, rim joist leaks are a major source of air leakage and energy loss.
__________________
Yes, I have achieved work / life balance.
travelover is offline   Reply With Quote
Old 09-29-2011, 10:35 AM   #19
Give me a museum and I'll fill it. (Picasso)
Give me a forum ...
 
Join Date: May 2004
Posts: 11,615
Quote:
Originally Posted by sheehs1 View Post
Verbal quote for 2 dehumidifiers was $4,100....which included the plastic and sealing vents...which I suppose is called an unvented crawl space rather than a conditioned crawl space. Did not include electrical work for a GFI and switch inside the house to operate...etc. Not really liking this option for reasons stated before ...but also because he left it sort of open ended "depending on what he found" (I know what those words mean!) and has not put pen to paper yet.
I'd prefer the conditioned crawlspace option given the prices quoted.
__________________
"Freedom begins when you tell Mrs. Grundy to go fly a kite." - R. Heinlein
samclem is offline   Reply With Quote
Old 09-29-2011, 10:59 AM   #20
Thinks s/he gets paid by the post
 
Join Date: Mar 2010
Posts: 1,648
Wow SamClem..thanks so much. I am going to copy this entire thread and insert requirements in the contract. I'm sure that will drive the price up....but better safe than sorry.
I ASKED him yesterday where he was going to put the return or how was air going to be returned back to the system. His answer: He wasn't. That any air coming into that space would find it's way thru access doors...etc. This baffled me somewhat....as it's like routing air to a deadspace without reusing it. Am I right here?
Thank you too Travelover...for the point of sealing the rim joist. Any detail I need to put into this contract, I want to put in.
If not for you guys and all that have responded thus far....I would have had a one line detail spec on the contract with no idea of what needed to be done, how it should be done....etc. Except I am more wary than to have allowed that to happen...which is why I posted it here! Thank you ,....Thank you...Thank you....!!!
Any other little details..as you think about this process will be much appreciated.



To my way of thinking...this space should be as tight as my house....with insulations strips and/or gaskets around access doors...etc.
This may not be the right company to do this job. Certainly important enough to find the right company.
__________________

__________________
sheehs1 is offline   Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Got something in our crawl space golfnut Other topics 77 10-24-2011 10:42 PM
Are robots controlling stock prices? flotsamandjetsam Stock Picking and Market Strategy 6 08-07-2011 01:32 PM

 

 
All times are GMT -6. The time now is 07:44 AM.
 
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.