QUESTION
From: Fred R.
I have a new addition to my home - about 1,900 sq.ft. of crawl space.
The crawlspace is approx 44" high from the bottom of the floor
joist to the top of the stone base floor. The crawl space is well
vented with foundation vents and I have 6 mill visqueen on the dirt
floor covered with 4" of crushed gravel. I also have two sump
pumps.
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The problem is that during construction, the floor
got wet and there is some white and black mold on the floor joist
and the underside of the floor sheathing. My thought is to dry out
the crawl space and the mold will go away before it gets too bad.
Would a dehumidifier work for this problem or do I need to force
some more air circulation under the house with fans?
Thanks for your help,
Fred
ANSWER
Hi Fred,
Getting the humidity under control will help your
mold problem but not eliminate it all together. The mold will remain
active as long as the humidity remains high usually 60% or higher.
Therefore, if you lower the humidity with a dehumidifier to 50%
and maintain it there, the mold will become inactive and not get
any worse. However, it will not die and disappear and it will still
emit mold spores. For this reason, it would be beneficial to eradicate
the mold by cleaning it up and removing it. There are several ways
you can do this. First, you can kill the mold with heat by using
a vapor
steam cleaner. This is a dry vapor steam at 180 to 220 degrees,
which will kill most mold. Keep in mind, there are many different
kinds of mold and some of them are heat resistant. Second, you can
spray a solution of tea tree oil and water approximately 2 teaspoons
to 2 cups of water. The only problem with this method is that the
smell is very strong and tea tree oil is expensive but a little
goes a long way. Third, grapefruit seed extract or citrus seed extract
and water can be used. You mix 20 drops of citrus seed extract with
2 cups of water and mix it in a spray bottle and spray on the problem
areas. Do not rinse. Fourth, you can use straight vinegar in a spray
bottle and apply it to the problem areas and do not rinse it. This
is the cheapest method but like the tea tree oil the smell is very
strong.
I would caution you to be careful when cleaning up
mold. I recommend you wear a mask to prevent your inhaling the airborne
mold spores that will be present especially when you disrupt the
mold. Also, you should isolate the area as much as possible so the
mold spores cannot circulate to another area of the basement where
it can begin to develop in a new area.
In answering your question as to whether or not it
is helpful to run fans, this is a good idea because when there is
water in a liquid state it will aid in the evaporation of the water
and then the increased humidity caused by the evaporation should
be removed with a dehumidifier. In addition, mold likes a dark environment
with no air movement to develop so circulating the air with fans
will discourage its development.
Keep in mind there are three things necessary for
mold to grow. You need mold spores which there will always be a
supply of because it is in the outside air and infiltrates inside
to your home. You need a porous surface for the mold to feed on
like wood, wall board, etc. which we all have. The final thing needed
is moisture with humidity 60% and higher. This is why if you eliminate
any moisture and control the humidity with a dehumidifier, you will
not develop mold. Keep in mind, you will still need to remove the
mold you already have.
Based on the dimensions you gave me, you would need
to remove approximately 38 pints of moisture per day to maintain
a relative humidity of 50%. You could consider the 50
pint Comfort-aire dehumidifier for $319.95 or Delonghi
50 pint with built-in pump for $329.99.
Besides
a dehumidifier, another way to prevent mold from redeveloping would
be to remove the mold spores that are airborne. This is normally
next to impossible especially if there is mold already present in
a particular area. However, assuming the mold in the area will be
removed eventually this can be accomplished over a 4 week period
through the use of a fairly new product we have on our website.
It is called the Airfree
air sterilizer. The way it works is the mold spores
enter the air sterilizer through convection where they go into a
chamber where they are incinerated at 400 to 600 degrees. The air
is then cooled and the sterilized air is emitted back into the room.
Slowly over time the amount of mold spores in the air will be reduced
down to zero and by leaving the unit running continuously, any new
mold spores introduced into the air will be removed. The net result
is if conditions arise to encourage the formation of mold like water
or excessive humidity, mold will not develop because you have removed
one of the three things necessary for mold to develop. In your case,
you would need 4 of the units because one of these units will sterilize
an area of 250 square feet with a ceiling height of 8 feet, which
is 2000 cubic feet. You have approximately 7600 cubic feet so 4
units would be recommended. The nice thing about this unit is it
is completely quiet and there are no filters to change and zero
maintenance. The electrical usage is like a light bulb so it might
cost you a couple of dollars a month to run one of these.
One final note, I failed to mention to you that the
most important thing to do when you have mold is to consider the
source of the mold to begin with and make sure the reason for the
mold occurring in the first place has been remedied. It sounds like
you have already taken care of this based on the fact the mold was
a result of water leaking during construction.
I have a few websites to give you where you will be
able to get additional information on mold removal.
At our own website
Mold Solutions
Mold Center
Other web sites
MoldFree.com
Environmental Protection Agency Mold Remediation FAQ
OSHA Fact Sheets
Please feel free to contact me to discuss any of the
products we offer from our website.
First Published: late April 2003
Updated: April 2007
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