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Old 01-03-2012, 09:40 AM   #1
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Unvented crawlspace question


I'm going to try this post here. I've read the buliding science material on the web regarding how to insulate a crawlspace. My situation is a little tricky. I thought I did the right thing a few years ago. There is a standing crawlspace underneath my kitchen. House was built in 1920. It has a small basement type window and an access door. SInce it's a dirt floor, 2 years ago I put 6mill plastic over it and taped of the seams. Also, insulated the walls with batt insulation. The previous homeowner insulated the ceiling between the floor joists with the paper side facing the dirt (now plastic) floor. A few things I've noticed and quesetions:
1. Under the plastic is damp/wet in the winter. I live in PA and temps are starting to get into the 30's and 20's. I feel like I'm trapping moisture by using the plastic. Is this a problem?
2. Above the space is my kitchen which has a small baseboard heater. From what I've read, it says not to insulate the joists in an unvented space, just the walls. I feel that I need some type of insulation because the floor gets pretty cold. Should I flip the batt insulation so that the paper is facing the warm side of the floor?

Thanks for your insight.

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Old 01-03-2012, 09:57 AM   #2
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Unvented crawlspace question


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Originally Posted by mjarema414 View Post
Unvented crawlspace question...standing crawlspace underneath my kitchen.
House was built in 1920.
It has a small basement type window and an access door.
When built in 1920... that window and door was (likely) adequate enough ventilation without other slits and gaps covered over by insulation.

Quote:
Since it's a dirt floor, 2 years ago I put 6mill plastic over it and taped of the seams. Also, insulated the walls with batt insulation... The previous homeowner insulated the ceiling between the floor joists with the paper side facing the dirt
You'll probably need to knock out a couple of those concrete blocks to re-establish adequate enough ventilation... but in the mean time I'd take down that paper faced insulation in the joists altogether and replace it with a foil face (foil toward the floor and with an air gap).

hth


Last edited by TarheelTerp; 01-03-2012 at 10:00 AM.
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Old 01-03-2012, 10:06 AM   #3
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Unvented crawlspace question


The vaper barrier is dong it's job of stopping the moisture from rising.
Craft faced Batts are always suppost to be installed with the paper on the conditioned side. Yours is installed up side down.
I know a lot or other posters on here seem to like unvented and sealed crawl spaces but, when I worked for an exterminator 90% of the homes I found with seal crawl spaces had fungus growing and needed a treatment of boric acid.
I know work mainly on 100 plus year old houses, when I see one that has never been closed up at the foundation I never found fungus, mold, powder post bettles or termites.
The ones the insurance companys made them close up (because of the ballon wall constrution being a fire spreading hazzard) or the home owner thougth it would make the floors warmer would be in very poor condition.
Even newer homes with the maunual opening vents often times would have damage because no one thought to open them.
I always strongly suggest replacing them with auto opening vents. If it's warm they open, cold they close.
The current trend seems to be to condition the crawl space.
I'm am not an expert but, seems like a waste of heat, and the last thing I would want is a return line in a crawl space sucking up mold spores.
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Old 01-03-2012, 12:26 PM   #4
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Unvented crawlspace question


The window was an old one that was replaced with a newer crank-out style basement window. So technically I can open it during the summer. I do need as much warmth as possible during the winter months due to most of the plumbing being located in this area. Also, my kitchen floor gets pretty cold when the temps dip into the 20's. So either flipping the batt insulation around or using the foil faced sounds like it would suit my needs in this space. It sounds like the plastic is doing it's job considering the moisture underneath. Should the walls still be insulated in this situation? Thanks.
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Old 01-03-2012, 12:50 PM   #5
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Unvented crawlspace question


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So either flipping the batt insulation around or using the foil faced sounds like it would suit my needs in this space.
It will suit part of your needs.
My comment about removing the paper backed insulation is the mold aspect.
Mold loves fiberglass and mold loves poorly ventilated moist crawls.

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Should the walls still be insulated in this situation?
You're insulating for good reasons. The issue is HOW you insulate (and ventilate).

hth
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Old 01-03-2012, 01:08 PM   #6
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It will suit part of your needs.
My comment about removing the paper backed insulation is the mold aspect.
Mold loves fiberglass and mold loves poorly ventilated moist crawls.
hth
So far I have not seen mold in this space. I would crack the window but I don't want pipes to freeze. The joists are completly dry. The only moisture I've seen is under the plastic on the dirt floor and the paper on the batt insulation (walls) is damp. I was thinking of possibly replacing that with a rigid foam when I get time.
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Old 01-03-2012, 09:32 PM   #7
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Unvented crawlspace question


Here are a couple of pictures of my crawlspace. As you can see the ceiling insulation is installed incorrectly. My kitchen is above this space. The floor is covered and the side walls are covered with batt insulation paper facing the space. The door is not covered due to access. A few questions: If I remove the ceiling insulation, should I install the foil insulation board between the joists with a little space between the board and ceiling or should I install over the joists? Lastly, should I remove the batt insulation on the walls and replace with some type of foam board to avoid moisture issues with the paper/fiberglass? Thanks for any insight.

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Old 01-03-2012, 10:05 PM   #8
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Unvented crawlspace question


R408.3 Unvented crawl space. Ventilation openings in under-floor spaces specified in Sections R408.1 and R408.2 shall not be required where:

1. Exposed earth is covered with a continuous Class I vapor retarder. Joints of the vapor retarder shall overlap by 6 inches (152 mm) and shall be sealed or taped. The edges of the vapor retarder shall extend at least 6 inches (152 mm) up the stem wall and shall be attached and sealed to the stem wall; and

2. One of the following is provided for the under-floor space:
2.1. Continuously operated mechanical exhaust ventilation at a rate equal to 1 cubic foot per minute (0.47 L/s) for each 50 square feet (4.7m2) of crawlspace floor area, including an air pathway to the common area (such as a duct or transfer grille), and perimeter walls insulated in accordance with Section N1102.2.9;
2.2. Conditioned air supply sized to deliver at a rate equal to 1 cubic foot per minute (0.47 L/s) for each 50 square feet (4.7 m2) of under-floor area, including a return air pathway to the common area (such as a duct or transfer grille), and perimeter walls insulated in accordance with Section N1102.2.9;
2.3. Plenum in existing structures complying with Section M1601.5, if under-floor space is used as a plenum.From: http://publicecodes.citation.com/icod/irc/2009/icod_irc_2009_4_sec008_par002.htm


http://www.buildingscience.com/documents/insights/bsi-009-new-light-in-crawlspaces/

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Old 01-04-2012, 02:29 AM   #9
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Unvented crawlspace question


Why waste the fiberglass insulation you already have between the joists? Just turn it around or, if it's easier, tear the paper out leaving the fiberglass as it is (your kitchen floor will be the vapor barrier).
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Old 01-04-2012, 09:08 AM   #10
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Unvented crawlspace question


Thanks for the info. I've read the material regarding code for this space. It's pretty well ventilated as is with the window and access door. There's no way I'd feel comfortable putting in other ventilation due to the pipes in this area and also my itchen above. Thanks for the suggestion to flip or deface the insulation. Would flipping the paper side make the kitchen floor slighly warmer or not do much with regard to warmth? If not, I'd probably be messy but easier to take off the paper. THanks.
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Old 01-04-2012, 02:58 PM   #11
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Unvented crawlspace question


Saving the paper by flipping the batts would do nothing for warmth.

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