fixing up my crawlspace
November 18, 2005 7:17 AM Subscribe
Crawlspace questions:
1) should I permanently block the vents that are open to our crawlspace? I have heard conflicting answers.
2) when insulating the crawlspace should I be concerned about mold growing on the insulation during the humid summer?
We have a vapor barrier and dehumidifier in the crawlspace. There is a dug out area where the heating system and the water heater are. It gets very warm and humid in the summer, very cold in the winter.
For the vents, a contractor friend of mine says that the vents are required and should only be blocked in the winter. A basement guy I talked to said that we should block them and that the idea of leaving them open is outdated.
For the insulation, we know we need to do it b/c there is a huge energy waste and our floors are freezing. The insulation guy I talked to said that the insulation will actually kill any mold we may have and that I should not worry about it.
We have a vapor barrier and dehumidifier in the crawlspace. There is a dug out area where the heating system and the water heater are. It gets very warm and humid in the summer, very cold in the winter.
For the vents, a contractor friend of mine says that the vents are required and should only be blocked in the winter. A basement guy I talked to said that we should block them and that the idea of leaving them open is outdated.
For the insulation, we know we need to do it b/c there is a huge energy waste and our floors are freezing. The insulation guy I talked to said that the insulation will actually kill any mold we may have and that I should not worry about it.
As long as the crawl space stays dry, mold won't grow on the insulation. Don't block off the vents. They may actually be counter productive with your current set up in the winter but air exchange is a necessary evil if you don't want moisture building up. The dehumidifier alone probably won't be enough in the summer.
posted by 517 at 7:45 AM on November 18, 2005
posted by 517 at 7:45 AM on November 18, 2005
It's a basement that you can only crawl in, not stand up.
posted by 517 at 8:04 AM on November 18, 2005
posted by 517 at 8:04 AM on November 18, 2005
Response by poster: even if it is very warm and humid, mold won't grow?
posted by GrumpyMonkey at 8:12 AM on November 18, 2005
posted by GrumpyMonkey at 8:12 AM on November 18, 2005
It would depend on the airflow between the crawlspace and the house.
The crawlspace should definitely get some air circulation from outside, except maybe in the very coldest weather (freezing pipes) but other than that, there are a lot of variables.
Mold needs a constant source of moisture, and something organic to eat, such as wood, various adhesives, etc. If it is dry down there, no worries.
(I do mold as part of my job. . if you wanna email me, I will talk to you at more length about this.)
posted by Danf at 8:13 AM on November 18, 2005 [1 favorite]
The crawlspace should definitely get some air circulation from outside, except maybe in the very coldest weather (freezing pipes) but other than that, there are a lot of variables.
Mold needs a constant source of moisture, and something organic to eat, such as wood, various adhesives, etc. If it is dry down there, no worries.
(I do mold as part of my job. . if you wanna email me, I will talk to you at more length about this.)
posted by Danf at 8:13 AM on November 18, 2005 [1 favorite]
I wouldn't really call a crawlspace a "basement". A crawlspace is generally not a usable area. I consider it part of the house's foundation. It's an area underneath a house in which — surprise! — one can crawl in order to investigate the underpinnings and perform various maintenance tasks. Some of you may be surprised to learn that houses generally don't rest on concrete slabs, but stand on wooden piers that rest on concrete footings. This small bit of elevation serves all sorts of useful purposes, such as protecting from water accumulation, certain pests, etc. As somebody who has owned two houses with sections without a crawlspace, I can testify that crawlspaces are keen and that the non-crawlspaced areas are frickin' pains in the ass. ("Come out, you goddamned cat. If there were a crawlspace, I'd wring your neck!")
I am not a contractor, but I've had plenty of work done on my house. Also, I recently sold one house and moved to another. It is my understanding that crawlspace vents serve various vital ventilation functions. Where I live (Portland, Oregon), I'm under the impression that it is a violation of building codes to block them. I'm absolutely certain that when you sell a house (in Portland), you're required to have properly-screened crawlspace vents. If you don't, the inspector will make you open the vents and/or replace the screens. (This happened to me when selling the old house.)
If I were you, I'd phone a house inspector in your city. They'll know for sure, and will probably be happy to answer such a simple question. (And the answer will be a lot more authoritative than what you get here.)
posted by jdroth at 8:20 AM on November 18, 2005
I am not a contractor, but I've had plenty of work done on my house. Also, I recently sold one house and moved to another. It is my understanding that crawlspace vents serve various vital ventilation functions. Where I live (Portland, Oregon), I'm under the impression that it is a violation of building codes to block them. I'm absolutely certain that when you sell a house (in Portland), you're required to have properly-screened crawlspace vents. If you don't, the inspector will make you open the vents and/or replace the screens. (This happened to me when selling the old house.)
If I were you, I'd phone a house inspector in your city. They'll know for sure, and will probably be happy to answer such a simple question. (And the answer will be a lot more authoritative than what you get here.)
posted by jdroth at 8:20 AM on November 18, 2005
I would be very leary of blocking any airflow due to mold issues.
posted by orlin at 9:53 AM on November 18, 2005
posted by orlin at 9:53 AM on November 18, 2005
Best answer: I am in business school doing a project involving crawlspaces. We are working with Advanced Energy in North Carolina. Advanced Energy's knowledge page on crawlspaces should have everything you want to know in there.
I'm not a crawlspace expert, but here's my opinion. If you have a vapor barrier and a dehumidifier, then keep your vents closed all the time. Mold will only grow if the relative humidity (rH) is above 50%. During a humid summer, you want to keep as much of that humidity out of the crawlspace as possible.
But, for reference for everyone else, regular fiberglass batting insulation will soak up humidity like a sponge. If you don't have a dehumidifer, then I understand the insulation can release its soaked up moisture directly onto your floor joists and rot them out. I can't speak to the mold issue with the insulation, but I know moisture in fiberglass batting will lead to floor joist rot.
Advanced Energy has been studying the best way to close a crawlspace to eliminate all the problems that vented crawlspaces have. Our school team is working with Advanced Energy to help them better define the industry, so hopefully people will become more aware of the problems and their fixes over the next few years.
posted by Sasquatch at 10:20 AM on November 18, 2005 [1 favorite]
I'm not a crawlspace expert, but here's my opinion. If you have a vapor barrier and a dehumidifier, then keep your vents closed all the time. Mold will only grow if the relative humidity (rH) is above 50%. During a humid summer, you want to keep as much of that humidity out of the crawlspace as possible.
But, for reference for everyone else, regular fiberglass batting insulation will soak up humidity like a sponge. If you don't have a dehumidifer, then I understand the insulation can release its soaked up moisture directly onto your floor joists and rot them out. I can't speak to the mold issue with the insulation, but I know moisture in fiberglass batting will lead to floor joist rot.
Advanced Energy has been studying the best way to close a crawlspace to eliminate all the problems that vented crawlspaces have. Our school team is working with Advanced Energy to help them better define the industry, so hopefully people will become more aware of the problems and their fixes over the next few years.
posted by Sasquatch at 10:20 AM on November 18, 2005 [1 favorite]
Response by poster: well if your school needs a test house, atlanta is only a short ride south....
posted by GrumpyMonkey at 3:43 PM on November 18, 2005
posted by GrumpyMonkey at 3:43 PM on November 18, 2005
Some of you may be surprised to learn that houses generally don't rest on concrete slabs, but stand on wooden piers that rest on concrete footings.
jdroth, you may be surprised to learn that here in the Northeast houses generally don't stand on wooden piers that rest on concrete footings, but rest on wooden sills laid over stone or concrete block perimeter foundations.
Surprise!
posted by Opposite George at 5:45 PM on November 18, 2005
jdroth, you may be surprised to learn that here in the Northeast houses generally don't stand on wooden piers that rest on concrete footings, but rest on wooden sills laid over stone or concrete block perimeter foundations.
Surprise!
posted by Opposite George at 5:45 PM on November 18, 2005
Actually, after I posted that it occurred to me that there are probably many and varied ways of building, and that the houses I'm familiar with are very young compared to what is out there. I was merely surprised that so many people seemed unfamiliar with a crawlspace.
posted by jdroth at 6:49 PM on November 18, 2005
posted by jdroth at 6:49 PM on November 18, 2005
This thread is closed to new comments.
posted by Thorzdad at 7:36 AM on November 18, 2005