# Crawl space issues, wet fiberglass



## diyrwbuck (Mar 12, 2017)

Apologies for the long story, want to make sure I cover everything.

Have a 16x20 crawlspace, under a family room addition. A couple of months ago I noticed a squeaky area in the floor and went into the crawl space to check it out. Hadn't been in it since it was built 14 years ago. Have to take up deck boards to gain access. 

Once in, it was a mess. The bottom of the joists close to the exterior wall were rotted, as was the the rim joist on 1 1/2 of the 3 walls. 

Existing condition was stone floor with plastic barrier under it. Walls are 4 courses high, some areas are damp (same location as rotted joists). They are not wet. Where the blocks are damp, the stones are wet, only about 4" out from the wall. The rest of the space is bone dry. Insulation is fiberglass in the joist, paper side next to the floor. Plastic sheeting was stapled to the bottom of the joist. The plastic closest to the damp block wall had moisture laying on top, the insulation in this area had a white fungus growing on it.

So, I take it the cause of the issue was a combo of the plastic sheet on the joists and the dampness?

Moving on, tore out the plastic sheet on the joist bottoms and the affected insulation. Repaired joists by sistering in new joists. Installed new rim joists. Then spray foamed the the new rim joist, did the entire perimeter. Also replaced the ripped out fiberglass.

Fast forward another month, went in to check out things. All looked good, except I noticed two small spots of wet insulation. Both were dead center of the batts, adjacent to the damp wall. Only about 2" x 2" area was wet, about an inch up in. 

So... I am thinking I still have some work to do here. Thinking of installing foam board over the damp blocks. Or, installing foam board to the bottom of the joists.

Does any of this seem reasonable? Should I be looking at something different?

Thanks for reading.


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## Windows on Wash (Aug 30, 2011)

Is/was the space vented?


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## diyrwbuck (Mar 12, 2017)

Not vented.


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## SeniorSitizen (Sep 10, 2012)

Vented or non-vented the word _ PLASTIC_ reared its ugly head by just reading the title. The scientists that promoted plastic aren't about to admit they were wrong, come back and recommend it all be removed.


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## radioman99 (Nov 21, 2016)

where is this water coming from? you didnt fix the problem, you repaired the issue.


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## Bud9051 (Nov 11, 2015)

Hi Buck,
Sounds like it is time to get serious and solve that problem.
First, where are you climate wise? We need to establish the outside humidity before we suggest you invite any (any more) of that air into your crawlspace. 
Maybe I missed it, but is the floor of that crawlspace dirt, no plastic or concrete?
Do you use ac as well as heat?
Is your heat forced hot air or other? 

At some point you will need to decide whether to isolate the crawlspace and vent it to the outside or to seal it up and share the space with the conditioning used in the house. Leaving the moisture isolated down there is bad as you have discovered.

Bud


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## diyrwbuck (Mar 12, 2017)

Location is central PA. Floor is dirt with plastic over it, topped with crushed stone. Heat and AC are geothermal.


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## Bud9051 (Nov 11, 2015)

In a heating climate I recommend a sealed and insulated (exterior walls) crawl. Then add that space to your forced air system to control moisture (should be minimal).

Some related reading:
http://www.greenbuildingadvisor.com/blogs/dept/musings/building-unvented-crawl-space

Bud


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## Windows on Wash (Aug 30, 2011)

Hopefully the joists aren't rotted to a point where they require replacement or are impacting the structure.


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## diyrwbuck (Mar 12, 2017)

Here is a link to a photo of the crawl space.
The insulation that is getting wet is adjacent to the block wall.
The rest of the space is fine.
You can go back 3' and it is dry as a bone.


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## diyrwbuck (Mar 12, 2017)

Trying the photo again...
https://www.flickr.com/photos/rogerbuck/33481061804/in/dateposted-public/


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## Bud9051 (Nov 11, 2015)

You will want to get that dried out some how. With no windows or easy access not sure what to recommend. A dehumidifier but it will need to be emptied if no drain. Is there a basement next to this crawlspace? 

Bud


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## lenaitch (Feb 10, 2014)

It looks like you have moisture wicking through the block walls that was aggravated by the plastic encased joists and insulation and the sealed off space. To solve the problem I think you need to seal the walls from the outside, which will likely be significant money and effort. In the short term, you should ventilate that space. I think even a good sized fan would be a big start. Rigid foam insulation panels are their own vapour barrier but I don't know enough whether they would be appropriate in your situation.


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## SeniorSitizen (Sep 10, 2012)

The room has a slight positive pressure forcing warm air to collide with the cold concrete blocks in the areas the were the damage is. Insulate the blocks from the cold air on the outside and the condensation will stop.


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## diyrwbuck (Mar 12, 2017)

First option I'm going to try is foam board on the damp wall. I have two sheets in the garage and some 6 mil plastic, might as well use them and see what the results are. I'm going to run the plastic up behind the foam board, then fasten the foam board to the block wall with tapcons thru 1x3s. 

I'll let you know the results.


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## Bud9051 (Nov 11, 2015)

Hi again,
I'm not sure your approach is addressing the moisture issue down there. Sealed will never work and you need to either vent it to the outside of share that air with the inside. Even putting a dehumidifier down there requires some circulation.

If you put a remote humidity gauge and temp meter down there and adjust that reading so you can compare it with outside RH then you will have an idea as to where the moisture is originating. If readings are similar, moisture is from infiltrating air. if crawlspace if a lot higher, then moisture is through the walls of floor (holes in existing plastic).

As for air leakage it can be a surprisingly high number. A typical ho9ne will exchange ALL of its inside air every 3 hours. Even if this crawl is more isolated it may be ALL in 6 hours. That means the humidity down there will be affected greatly by the weather outside.

Using rigid foam board on the crawl walls is not intended to stop the moisture coming through. In fact the opposite, a small amount of moisture migration helps to prevent the walls from getting wet behind the plastic. The foam board is there to prevent any warm inside air from reaching a cool surface and depositing condensation.

Get some temp and humidity reading from down there and similar reading from outside at the same time and we can show you how to adjust them for comparison, it uses the dew point.

Bud


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## 123pugsy (Oct 6, 2012)

From the pic, it appears as though water is entering under the blocks.

Is there a perimeter footing drain tile?


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## SeniorSitizen (Sep 10, 2012)

I doubt any relative humidity readings will be of value until next winter when the blocks appear to become wet from the top down. At that time read the interior block surface temperature and compare that reading to dew point temperature.


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## Bud9051 (Nov 11, 2015)

SS, althiugh I agree summer and winter conditions are different it is always good to have a base line and now is a good time to start, especially if changes are going to be made. Outside RH is higher in summer and a crawlspace is usually cooler so that represents one potential source of the moisture. Numbers never hurt.

Bud


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## SeniorSitizen (Sep 10, 2012)

Bud9051 said:


> SS, althiugh I agree summer and winter conditions are different it is always good to have a base line and now is a good time to start, especially if changes are going to be made. Outside RH is higher in summer and a crawlspace is usually cooler so that represents one potential source of the moisture. Numbers never hurt.
> 
> Bud


I agree with warm air being capable of holding more moisture but those blocks really don't care about that. Those blocks or any surface are only concerned with dew point temperature and the air at their surface can see 100% relative humidity in the winter just as well in as summer. In fact it is very uncommon for dew point temperatures to attain a number above 80°F.

As stated earlier, if the room along the wall / floor junction of the problem area is leaking warm to the cold blocks in the winter heating season, that warm air which we agree can hold more moisture, is certain to loose that moisture when it contacts the cold blocks, plastic, insulation or whatever surface it contacts.

As seen in the attached pic information, it is easy for cold air to reach dew point just as well as warm air.


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## diyrwbuck (Mar 12, 2017)

Ok, back with an update. Over the past 3 weeks I have worked in this. The block walls now have 1" of insulated foam boards with a total R value of R11. I ran 6 mil poly up the wall before installing the foamboard. As stated before the rim has been spray foamed. I left a 3" strip visible above the foamboard and below the rim. The 6 mil poly covers from wall to wall. 

I then installed a 150 cfm (variable) transfer fan in the adjoining basement ceiling. Cut a floor register in the room above above the fan, the fan now pulls air from the room above and ducts it thru the inline fan to the crawl space. I cut a relief vent into the adjacent basement. Temp and humidity have gone from 62 degrees and 97% to 68 degrees and 64%. The humidity continues to drop each day.


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## Cedrus (Feb 25, 2011)

Try this for a couple of weeks: The outside dew point should be below the crawl space temperature. Local weather website will show you outside dew point....and a digital thermometer in the crawl space, with a readout upstairs.. Keep track for a couple of weeks. 

Yesterday, here in OR....dew point was 42 deg and crawl space temp was 53 deg. We have had water intrusion into our crawl space after crazy, heavy rain and snow melt. 

You might want to talk to Will Judd at ATMOX about his expensive remedies.


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## msaramak28 (May 3, 2017)

May be a odd question, but where does the 3" strip of poly terminate too? Just trying to picture this, for i may be in the same boat as you with my house.


Thanks


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