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There are several different types of insulation used in crawl spaces, some work better
than others and one in particular should not be used in crawl spaces at all
except on the cement foundation. There are correct and incorrect places to
install the insulation depending on what environment you are working with. If it
is installed improperly you will waste your money and ultimately cause damage to
your home. Insulation does not make your home warmer, heat
does. Insulation only helps to hold in the heat. Here are two more
links about
crawl space insulation and the
crawl space building code showing their regulations.
Typical Crawl Space Design The open crawl space
There are three major environment situations that call for
insulation in a crawl space. The first is your standard dirt floor (may have
some plastic laid on the floor) crawl with open vents which is referred to as an
open crawl space. This environment is similar in temperature to the outside air
in the winter which causes the homes floors to be cold and rooms farthest from
the furnace to be drafty. Frozen water lines are common in this situation as is
an odor in the warmer months. Most often these crawl spaces will have a lot of
bugs and maybe even a rodent problem. This is the most common environment for a
crawl space. Here you will find
R-19 insulation (usually) in the floor joist
cavities. This is required by code in most areas because of the
open vents and the problems they cause with energy loss. When I say open vents,
I am referring to any permanent foundation vent whether it mechanically opens
and closes or not. On a side note, closing a mechanical vent does very little to
keep the cold air out. It would be similar to a window in your home with metal
louvers instead of double pane glass. The insulation is meant to keep the warm
conditioned air in your home from being absorbed by the cold winter air in the
crawl space. This however causes the problem with frozen water pipes because
there is no heat source to protect them. The other problem with this design is
most homes have their heat ducts running through the crawl space which are
cooled by the winter air before they reach their destination. This causes the
furnace to run more often and in longer cycles to keep the home at the desired
temperature. Some construction professionals will recommend stuffing some R-30
in the open vents for the winter to keep the winter at bay. This will work and
is a very low cost solution to the threat of frozen water lines. However you may
be causing a new problem by doing this. Yes, it will be warmer in the crawl
space but that also means your moisture levels will raise inside the crawl space
and home during the cold months. This will continue any moisture problems you
may already have with the open crawl space design. You will also have to be
quick to take the insulation out of the vents in the early spring to avoid
worsening the moisture and odor
problem. In this environment anything you do to correct one problem will most
likely cause a different problem to occur.
Upgraded Crawl Space The concrete floor
In this design a concrete pad called a “mud pad” is poured on the crawl space
floor. This is essentially a concrete vapor barrier meant to help control
moisture in the crawl space. This is done several ways; with and with out a
vapor barrier. The traditional mud pad is a poured concrete pad over a roughly
graded dirt floor. There is little prep work done to flatten the area so the
concrete thickness can range from 2” to 6” thick. The final grade of the
concrete will appear flat. A good contractor will install a vapor barrier on the
floor prior to pouring the mud pad. This is done because the concrete itself is
not a good moisture barrier. Water and moisture will pass through a concrete
slab that does not have a vapor barrier with little trouble. The reason this is
important is because if a vapor barrier was not used then closing the vents will
cause other issues unless a dehumidifier is used. But if a barrier was used,
then you will have more options on how to best control the humidity. Closing the
vents is the key to fixing the cold crawl space problem. The insulation
installed in this application would be R-19. Install the insulation above the
foundation wall inside the rim (or band) joist cavity only. Think of this
design as a mini basement. Next time you are in a full size unfinished basement
take a look up and you will see there is no insulation in the joist cavities.
The most recent
building code (IRC 2006) states that the insulation in the floor
joist cavity is no longer needed if the exterior foundation walls are
insulated. One option is to have (closed cell) spray foam installed on the foundation walls. The real benefit here is to cover the portion of the foundation that is above
the outside grade. The cost of this insulation is usually by the square foot, so
the more you have sprayed on the more it will cost. Do not have the rim joist
sprayed with this type of insulation. You could end up with problems repairing
or replacing any wood that may get damaged due to insects or water damage. It
also does not allow for termite inspection and that could be a huge issue if you
plan to sell your home in the future. It would be a wise move to add a few heat
ducts to the crawl space to keep it warm. A few words of caution, although this
design is far superior to the open crawl space it potentially has some of its
own problems. Even with a vapor barrier under the mud pad you will have to find
a way to control the moisture that comes in the crawl space from the unprotected
foundation walls. This area has the same potential for moisture and water
problems as a mud pad that does not have a vapor barrier. If you close the vents
in this design you will have to install a dehumidifier to control excess
moisture.
All The Problems Are Covered A conditioned crawl space
 This design is referred to
by many different names;
encapsulated crawl space, closed crawl space, conditioned crawl space. All of
these names refer to essentially the same result but may have a different
process. The vents are permanently closed. The crawl space is completely sealed
off from any moisture infiltration by using a heavy duty vapor barrier like
DrySpace™. In a conditioned
crawl space the foundation walls need to be insulated with a rigid foam to keep
any cold air from entering the crawl space from this area. Then the crawl space vapor barrier is draped down the foundation walls and the entire
floor is covered. All the seams are lapped by at least 8” and taped with a
waterproof seam tape and the supports are wrapped and sealed. The vapor barrier
is sealed to the foundation wall with either a polyurethane caulk, butyl caulk
or Foundation Seal Tape™
to keep the moisture from escaping from under the
barrier. The next step is using
Foundation Pins™
to permanently fasten the
DrySpace™ to the foundation. R-19 insulation is installed in the rim joist
cavity to keep the outside air outside. Once this has been completed you can
successfully condition the crawl space air. Conditioning the air is controlling
the temperature, humidity or both. Now that the vents are permanently closed and
the perimeter is insulated, heat ducts are opened into the crawl space along with
an air return (if needed). This is not about heating the crawl space, it is about
introducing heat to the home one level lower than it is now. Heat naturally
rises so it will come up through the floors and keep them warm. The heat is not
lost as it would be if the vents were open. This process
will save you between
10 – 30% on your heating cost because you have eliminated cold air from entering
the homes envelope. In an open crawl space design your home is being attack from
all six sides but in a closed crawl space you have eliminated the largest
exposed square footage of the home and created a new clean environment that is
only inches from where you live, eat and sleep. A conditioned crawl space can
be created by most able bodied homeowners with the right products, guidance and
information. Contrary to what some large franchise companies offer, you don’t
have to mortgage the house to be able to afford this home improvement.
For more information on how the
DrySpace™
vapor barrier is installed take a look at our
"How To" video.
If you have any question please feel free to contact us at our email -
info@crawlspaceinfo.com or call 877.379.7658
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