# Crawl space vent and mold question



## joecaption (Nov 30, 2011)

Is there a 6 mil. vaper barrier on the ground under the house?
Has the crawl space been air sealed? (sealing up all the holes where plumbing and wiring was run thorugh the bottom plates)
Insulated the rim joist?


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## jimleahman (Mar 5, 2011)

joecaption said:


> Is there a 6 mil. vaper barrier on the ground under the house?
> Has the crawl space been air sealed? (sealing up all the holes where plumbing and wiring was run thorugh the bottom plates)
> Insulated the rim joist?


there is nothing in the crawl space besides what was there when the home was built originally in 1954.

there is just exposed floor boards, a slab foundation, dirt floor, and crawl space vents. no insulation and no vapor barrier. I wondering what I need to do to get rid of the mold from forming?


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## joecaption (Nov 30, 2011)

Really need your location/ PLease go back and edit your profile.
Without that vaper barrier all the moisture that rises is going eight up into the home.


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## Windows on Wash (Aug 30, 2011)

Southern California. Listed in first post. 

Put a vapor barrier on the floor and seal it to the wall. Insulate the crawl space wall and seal up the crawl to create a conditioned space.


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## jimleahman (Mar 5, 2011)

Windows on Wash said:


> Southern California. Listed in first post.
> 
> Put a vapor barrier on the floor and seal it to the wall. Insulate the crawl space wall and seal up the crawl to create a conditioned space.


so a conditioned crawl space would be the best route? i would imagine there would be no need to spray foam the floor boards and joists then?

thanks.


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## Windows on Wash (Aug 30, 2011)

You are correct.

Move you insulation and air barrier layer to the outside stem wall and then just condition the space after you put down the vapor barrier on the floor.


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## Gary in WA (Mar 11, 2009)

Conditioning; http://www2.iccsafe.org/cs/committeeArea/pdf_file/RE_06_64_07.pdf

Termites, local AHJ will know: http://www.termites101.org/termite-basics/termites-by-region

Radon: http://energy.cr.usgs.gov/radon/rnus.html

Gary


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## jimleahman (Mar 5, 2011)

I got one quote to condition my 1140 sq foot crawl space and it came out to 7k. That would include labor and materials to lay down 20mil vapor barrier, close off all vents, and insulation the foundation walls. He also mentioned a possible need for a dehumidifier but cost additional to the original quote. 

That is way out of my budget. I am looking into a cheaper route.

I also got a quote for closed cell spray foam on the sub floors only at two inches thick for 2k. That is more in my range but I am a bit concerned.

I read the excellent article on the building science website and they recommended at least three inches of closed cell foam along with the joists if not a pier type constructed crawl space. 

My crawl space is all vented and maybe about three feet in height. I wanted to know if you guys would agree that a closed cell spray foam on sub floors ONLY at three inches thick and leave all the vents kept open would be fine? My may concern is dew forming on the joists in the future. 

Just some pertinent background, I do not have the pier construction crawl space, all my crawl space vents are currently all open with about three feet of space to crawl, and I live about two miles from the ocean in Southern California. 

Thanks for you time.


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## Gary in WA (Mar 11, 2009)

I presume you were referring to this article; http://www.buildingscience.com/documents/insights/bsi-009-new-light-in-crawlspaces/

If so, notice no vinyl flooring above the foil-faced Polyiso. Your floor requirements for Zone 3 are R-19. Eg.- San Diego: You could use cavity R-13 batts with 1/2" Foamboard and not see any condensation or thermal bridging on the joists until 59%RH. With 1" f.b., at 70* inside, the joists would be safe at 64%RH in the crawl space. OR, add some housewrap on the joists after installing R-19 cavity insulation, no worries about vinyl above, and good for 50%RH in the crawl (air seal any wiring/plumbing holes in the sub-flooring first). The housewrap will stop all drafts if carefully installed. Foamboard/canned foam the rims, regardless; http://www.buildingscience.com/docu...joist/files/bscinfo_408_critical_seal_rev.pdf

As the rims in older/newer houses (if solid wood) change size with the moisture change in the air, pp. 51; http://books.google.com/books?id=iw...um=3#v=onepage&q=cutting floor joists&f=false

Gary


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## ddawg16 (Aug 15, 2011)

Jim....chances are you are pretty close to me.....

Let me guess.....your house was built in the 50's? And the mold is on a North facing wall?

Just so you know....there is NO insulation in those walls. the only 'vapor barrier' is the tar paper between the stucco and studs.

I would not waste any money on trying to condition your crawl space...the humidity in our area is not enough of an issue. I live 4 miles from the beach....deal with the marine layer nightly.....we 'used' to have a mold problem on one back wall....but it was a north facing wall....the issue was not the crawl space....

The walls are pretty much sealed from the crawl space. All of your wiring is going to be in the attic.

Assuming all of the above is correct for your house....about the only solution will be to yank off the dry wall....insulate and re-drywall. As it was explained to me...once you get mold....you never really get rid of it....just make it dormate....


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## jimleahman (Mar 5, 2011)

GBR in WA said:


> I presume you were referring to this article; http://www.buildingscience.com/documents/insights/bsi-009-new-light-in-crawlspaces/
> 
> If so, notice no vinyl flooring above the foil-faced Polyiso. Your floor requirements for Zone 3 are R-19. Eg.- San Diego: You could use cavity R-13 batts with 1/2" Foamboard and not see any condensation or thermal bridging on the joists until 59%RH. With 1" f.b., at 70* inside, the joists would be safe at 64%RH in the crawl space. OR, add some housewrap on the joists after installing R-19 cavity insulation, no worries about vinyl above, and good for 50%RH in the crawl (air seal any wiring/plumbing holes in the sub-flooring first). The housewrap will stop all drafts if carefully installed. Foamboard/canned foam the rims, regardless; http://www.buildingscience.com/docu...joist/files/bscinfo_408_critical_seal_rev.pdf
> 
> ...


yes, that was the exact article i read. it confused the heck out of me the first read. i'm still not 100% in what it states is the best methods and which are OK.

thanks for the relative humidity breakdown. from what you are telling me, the best route to take is the 1" foam boards because they take higher RH levels. should i housewarp the joists anyways with the 1" foam boards? i would imagine it would keep the joists closer to the subfloor temperature?

I live in redondo beach which is about two hours north of san diego. the relative humidity and weather is more or less the same in the southern california region though. 

thanks again for the info.


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## jimleahman (Mar 5, 2011)

ddawg16 said:


> Jim....chances are you are pretty close to me.....
> 
> Let me guess.....your house was built in the 50's? And the mold is on a North facing wall?
> 
> ...


i live in redondo beach. and yes, the home was built in 1954 with plaster walls and an "air" barrier within the walls. i have read that back then, they thought the "air" provided enough insulation. boy, that was wrong.

the north facing walls tend to be more of an issue but the other sides get the mildew as well if furniture or anything leans against the wall and doesn't let it "breathe." The problem is all along the walls where the crawl space vents are located. so it leads me to think that the draft is coming through subfloor/rim joists and causing humidity to be high in the walls inside my home that are adjacent to the crawl space vents. but yes, the north facing is more of an issue and i am glad you brought that up because i never thought about that. 

i have a friend that lives a few blocks from me that had the same issue. he pulled down the plaster and took a look inside and he said there was no mold inside. he said it was all a surface issue. he put fiberglass batts in between the joists and he said the problem went away. i just didn't want batts if it was going to collect moisture because it renders it useless and ends up being mold candy later on. my friend looked in his crawl space and he says it is fine thus far. been about a year.

I have somewhat slowed the mildew formation down by using damp rid near the most problematic walls but it doesn;t solve the problem completely. i want a more permanent solution because it is occurring mostly in my kid's room. 

thanks for the info.


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## ddawg16 (Aug 15, 2011)

Jim....I live right down the road from you.......as in....near El Camino College.....

I don't think you need to do anything with your crawl space. 

The mold issue we had was caused by furnature up against the wall. Where ever there was furnature against the wall...we had mold.

Let me guess....your also still using the in floor heater? Half in the hallway...other half in a main room?

We installed forced air heating about 6 years ago and that pretty much took care of the issue.

Moot issue now....the back half of the house is gone now.....click on the link in my signature and you will see why.....

In fact...drive down Manhattan Beach...and you will see my house...stop by...have a beer...


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## RobbyCoffee (Nov 8, 2012)

ddawg16 - That sounds about right, forced air heating solves more than people initially realize.


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## ddawg16 (Aug 15, 2011)

Robby.....normally I would keep quiet on this kind of subject....the only mold expierence I have is with my house....but seeing how he most likely lives within a mile or two of me....and all these houses were built the same way and about the same time....well....worth sharing my thoughts...

Now...I hope he posts back as to if he has the floor heater like I think he does.


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## jimleahman (Mar 5, 2011)

ddawg16 said:


> Jim....I live right down the road from you.......as in....near El Camino College.....
> 
> I don't think you need to do anything with your crawl space.
> 
> ...


I know exactly where you are located. I am near the corner of Palos Verdes Blvd and PCH. 

Well, the mold issue is worse with furniture up against the walls but it is still present without the furniture as well. I just bought a hygrometer and I measured the RH at 65% in my home! That is high. I been running my dehumidifier all day to drop the level. The damp rid also helps. 

This great article from MSU states one of the causes of high humidity is from the crawl space especially with mold in closets. One room has this issue. 

http://www.msue.msu.edu/objects/con...sion_id.498942/workspace_id.-4/01500575.html/

When I bought the home three years ago, the previous owner placed a forced air heater in the attic. There is no form of an air conditioner as my neighbor noted that none of the original homes in this area had an air conditioner. 

I am not sure if I'm barking up the wrong tree blaming the crawl space but it seems logical considering my problem spots happen to be located where the vents are open on the exterior of my home. When I last crawled under there, the presence of mold was none. I did not look corner to corner but from what I saw there did not appear to be mold on the joists nor subfloor.


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## ddawg16 (Aug 15, 2011)

I would be inclined to think that the only corrolation between the crawl space vent and your mold is the temp. Where you are, the marine layer is a bit more than me....but....the humidity level in your house is actually more of a function of what is going on inside....

Because of the crawl space vent, the temp in that area drops....which condenses any moisture on the wall...which feeds the mold. 

I'm assuming you close the windows in the winter time?

Your heater is gas fired?

Do you by any chance have carpet in the affected areas?

As I said before, once you have mold....it's in there....as far as I know, the only real way to get rid of it is to remove the material it is in.

Have you tried pulling the furniture away from the wall? This would allow more air flow and thus cut down on the condensation in that area.


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## jimleahman (Mar 5, 2011)

ddawg16 said:


> I would be inclined to think that the only corrolation between the crawl space vent and your mold is the temp. Where you are, the marine layer is a bit more than me....but....the humidity level in your house is actually more of a function of what is going on inside....
> 
> Because of the crawl space vent, the temp in that area drops....which condenses any moisture on the wall...which feeds the mold.
> 
> ...


Thanks for your input. 


Yes, windows closed almost all winter except some occasions to get fresh air. 


My heater is gas driven. I rarely run it unless its very cold. I have not turned it on since last winter yet. 


The only form of carpet we have are rugs but they are no where near the windows nor walls with the issue. I pulled away the furniture and placed damp rid in the most problematic areas. It helps but mildew forms over time even in the areas where nothing is near the walls. 


What do you think is causing the high humidity? The air hears always seems humid being near the ocean.


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## ddawg16 (Aug 15, 2011)

I think the combination of the crawl space vent and no insulation causes that part of the wall to be colder and condense any moisture in the air....thus....mold.

It's not really that hard to yank off the drywall and replace it....while your at it...insulate the wall.

I have been doing that to my house....I'm now down to just one section of wall without insulation....and it's such a small section...and East facing so I'm not going to worry about it.


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## ddawg16 (Aug 15, 2011)

Tony Scott said:


> Yes insulate your crawl space. You can close your vents also which will prevent humid air to escape through walls. If you have moisture problem then vapor barrier can solve your problem.


Very bad advice for the area the OP is in....


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## SeniorSitizen (Sep 10, 2012)

ddawg16 said:


> Have you tried pulling the furniture away from the wall? This would allow more air flow and thus cut down on the condensation in that area.


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I've never heard of furniture needing to be moved from the wall but I still see all kinds of shrubs and flower beds being planted next to the structures world wide which certainly isn't an asset in situations like being discussed not to mention fire danger*.*


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## ddawg16 (Aug 15, 2011)

Fairview said:


> ---------------------------------------------------------------------
> I've never heard of furniture needing to be moved from the wall but I still see all kinds of shrubs and flower beds being planted next to the structures world wide which certainly isn't an asset in situations like being discussed not to mention fire danger*.*


He has stucco on the outside.....

As for moving the furnature.....with a dresser up agains the wall, it reduces/prevents air flow....and because there is no insulation in the wall....that section of wall gets cold which in turn condensed moisture in the air...which causes the mold.


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## ddawg16 (Aug 15, 2011)

Jim.....the building code in our area is pretty specific about crawlspace ventilation....here is a blurb from my drawings....note...this is current requrements...

UNDER FLOOR AREAS SHALL BE VENTILATED BY MECHANICAL MEANS OR BY OPENINGS INTO THE
UNDERFLOOR AREA WALLS. SUCH OPENINGS SHALL HAVE A NET AREA OF NOT LESS 1 SQUARE FOOT
FOR EACH 150 SQ. FT. OF UNDER FLOOR AREA. OPENINGS SHALL BE LOCATED AS CLOSE AS POSSIBLE
TO CORNERS AND PROVIDE CROSS VENTILATION. THE OPENINGS SHALL BE APPROXIMATELY EQUALLY
DISTRIBUTED ALONG THE LENGTH OF AT LEAST TWO SIDES. CORROSION RESISTANT MESH WITH
MINIMUM !” OPENINGS

I think if you go into your crawl space you will not see any mold....mine is pretty dry....and stays that way....

Like I said...I had the same problem....on walls where I have insulated....no issues....

Check you PM


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## jimleahman (Mar 5, 2011)

ddawg16 said:


> He has stucco on the outside.....
> 
> As for moving the furnature.....with a dresser up agains the wall, it reduces/prevents air flow....and because there is no insulation in the wall....that section of wall gets cold which in turn condensed moisture in the air...which causes the mold.


I found this to be the case. The more furniture up against the wall equated to less air flow and mold would aggregate in that area worse than other spots. 


I guess I'm going to have to insulate the walls then. I didn't want to do anything interior. The insulation via foam on the outer walls by drilling holes is an expenisve alternative I guess.


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