Why
Now?
I get phone calls from homeowners
that live all over the U.S. and Canada asking me about the closed or
conditioned crawl space. No one seems to wonder if it will work but rather how
it works. If we look back to the 30’s and 40’s there was no such thing as a
conditioned crawl space. Yet today, as some crawl space companies put it, you
can die if you don’t have it done their way and right away. So how did we live
without it back then? Well, the answer is much more complicated than the
question. Looking back to the early part of the last century there were many
things that we had never heard of like plasma televisions or a laptop computer.
But that did not stop the technology and research from making it possible. The
conditioned crawl space concept is no different. In the 30’s and 40’s we had a
different lifestyle, the windows were open in the summer and there was no air
conditioning. The homes were built with different technology and guidelines so
they were not as air tight as they are today. In fact many of the homes that
were built in this era have added air conditioning and have been improved and
updated to today’s standards for energy conservation. This is a good thing but
it also means that these homes get less fresh air than they use to. By
tightening up these homes they have confined the occupants to the environment
created inside the homes envelope. As environmentalist study the causes of
pollution in the air outside and make headway to improve and control the
emissions given off by factories and vehicles, there is very little push to
improve the air in a families home. Even the indoor air in public buildings is a
strong focus today with banning cigarette smoking in cities and states across
the country. Yet there are no guidelines for healthy air inside a private home.
It is up to the families to identify and correct this problem. It is known,
however, that the air inside an average home is seven times more polluted than
the air outside and up to twenty times more polluted during the winter months.
How can this be? It simply comes down to the lifestyle of the occupants and the
environment in which the home was constructed. In this article I will be more
focused on the latter of the two but more specifically homes that are built on a
crawl space.
The Issues
The crawl space
environment
The crawl space environment is no different than that of a
cave in the side of a mountain. It’s dark, dirty, and smelly and has small
animals and bugs living in it. When the home was first built the crawl space was
not considered part of the house. Excess building materials and waste was thrown
down there because it was easier than picking it up and discarding it in the
dumpster. I have personally taken out old refrigerator doors, tires, old pipes,
a toilet with the seat and drop ceiling panels among other things. It is also
not uncommon to remove the carcass of a dead animal or two. This is the
condition before anyone tries to improve it. Back in the day it was required to
have vents in the foundation to promote cross ventilation in order to help
control the moisture that would escape from the ground. This caused a few other
problems, cold air getting under the home and making the floors cold, allowing
even more moisture to get in by way of the humid summer air and a constant
supply of mold, mildew and fungus spores. The cold floors were addressed by
installing fiberglass insulation in the floor joist cavity and the other two
problems were thought to be unavoidable. Now we have a dark, dirty, smelly place
that has small animals and bugs (powder post beetles, termites, creepy looking
bugs about 1 ½ inches with long furry legs that run faster than my eleven year
old son) living in it, we add more moisture via the vents and plenty of mildew,
mold and fungus seeds. The next thing we do is add a fiberglass nesting material
for the animals to bed in and then through the open vents in the foundation we
make it cold enough in the winter to raise the heat bill and chase these small
animals and bugs into the home in search of food and a warmer place to live.
By spring, a few mouse traps and a can of ant spray the home is ready to
start this cycle over again. This is a reality for most crawl spaces so it is no
wonder nobody wants to go down there.
Did I mention that
crawl spaces are prone to flooding?
We all know that water runs down hill, with that being said
crawl spaces are generally lower than the ground around the home because we
backfill the foundation so that water shed will run away from the home. Over the
years the backfill settles to a negative grade and allows water to rest against
the foundation of the home. So when it rains hard in the spring and fall the
ground becomes saturated. Once the ground will not take on anymore water it
begins to run to the lower lying areas like ditches, storm drains and crawl
spaces. Once standing water is introduced into the crawl space the homeowner
runs the risk of major foundation failure and joist and beam rot. The major
reason the standing water can be so devastating is because it goes unnoticed for
long periods of time. The homeowner may periodically look in the crawl space for
water or the source of an odor and not see any water. That does not mean in the
last six months while the crawl space went uninspected water did not come and go
several times. Keep in mind the conditions described in the last paragraph and
now add scum and rodent feces floating on top of the water inside the crawl
space. It becomes extremely hard to reason that the old way of maintaining a
crawl space is working just fine.
False water table,
what’s that?
A false water table can be the culprit of why your crawl
space keeps getting water in it no matter how waterproofed the foundation is. A
false water table is the retention of excess water by none virgin soil. That
means when a home is built there is a hole dug in the ground for the foundation,
whether a basement or crawl space. After the foundation is in the dirt is filled
back in around the outside of the foundation walls, this is called backfill. The
backfilled dirt is not as compact as the undisturbed virgin soil that surrounds
it; ultimately the backfill holds more water. The water in the backfill sets
against the foundation and the virgin soil. Water will find its own level, so as
the pressure builds around the foundation it naturally starts to spread itself
out. If you picture a bowl that is 6” deep with 3” of water in it, the water is
not on one side or only at the edges. It is evenly distributed across the entire
bowl. As long as water is poured
into the bowl the water will keep rising toward the top. This is what happens
around the home and that is why it is critical to have the proper elements in
place to protect your foundation. The virgin soil and evaporation will slowly
reduce the water levels around the foundation but meanwhile the concrete
foundation takes a beating.
I think it’s time to
take a look at the research.
Is this where it gets complicated? No, its common sense
really it’s just too bad that it took so long to be common. In order to figure
out the solution one has to first identify the problem. So what is the real
problem? Is it the standing water or the bugs? Maybe it’s the vents or is it the
smell? The answer lye’s with what’s common with all of these symptoms. I’m not
trying to confuse you with riddles, I want you to see that what seems like the
problems are only symptoms and if you only address the symptoms you will not fix
the problem. Lets take the bugs for example, to many people go to the grocery
store and buy those bug bombs and let them off in the crawl space thinking
“that’ll fix ‘em”. Well it probably does but they also just let off a half dozen
cans of poison in their home. One home I inspected had Stick-Ups on the heat
ducts to help the smell, it didn’t work though. If you pump the water out it
will just come back, if you seal off your vents the moisture from the dirt will
be trapped inside the home. If you only address each symptom you will get either
a new semi full time hobby, make the other symptoms worse or actually create new
problems. What all of these symptoms have in common is moisture or humidity.
Insects, wood rot, mold, fungus, mildew, odor, cold floors and high heating cost
are all the result of attempts or the byproduct of the attempt to control
moisture. Now that we know this and agree that moisture is the problem we can
now properly address it.
Four ways
moisture enters the crawl space.
There are four main ways that
moisture enters a common crawl space. The first and most
obvious way is through the open dirt. As the ground
outside the home is saturate with rain the moisture
level in a crawl space raises rapidly. The warmer the
air the more moisture it can hold. This means the most
devastating months are the warm ones. This excess
moisture condensates to cooler surfaces like water lines
and the foundation walls. It also settles on the ground
when the temperature falls, gets absorbed by the wood
structure and any insulation that is installed in the
crawl space. The building code in nearly every area of
the country requires a vapor retarder with a perm rating
of less that 1 to be installed on the floor of the crawl
space. There are no requirements to how it should be
installed, just that it must be.
This leaves a wide gap in the final performance
of a vapor retarder. If anyone wants to find
recommendations on how to install; there are many
opinions on the internet. It is not really a mystery if
you know what it is suppose to do. For the sake of
conversation, let’s say we go down to the local hardware
and buy some plastic and install it in the crawl space
according to the local building code. The problem of
moisture entering the crawl space from the ground is
fixed! Right? Well not entirely, any gaps in the plastic
(at the seams, around supports and where it meets the
wall) will still allow moisture to escape. It will
continue to allow this to happen until the air, the wood
structure and the concrete foundation are saturated. To
make it more complicated, when the temperature falls in
the evening the excess moisture leaves the air and
settles like dew on top of the plastic only to evaporate
again when the warmer air returns. Then the next time
your plumber has to go down there to fix a frozen water
line the plastic will probably not be in the same place
as it was when you installed it causing your efforts to
be wasted. The other common issue is when the crawl
space floods water gets on top of the plastic and can
not be absorbed by the earth. This of course leaves a
breading ground for bacteria and mosquitoes while
introducing a new long lasting supply of moisture.
The second way moisture gets in the
crawl space is through the open foundation vents. This
is a huge area of confusion and there is a lot of very
technical information out there on how the foundation
vents impact the crawl space. You will read about
relative humidity and vapor pressure. How the high and
low pressure weather fronts impact the crawl space and
how the vents being open or closed makes no difference.
You will also read how the temperature affects these
different technical conditions. On a quick side note,
when the reports say it makes no difference if the vents
are open or closed, they are referring to manually
sliding the vent to the closed position. If you’re like
me you will read these reports a few times just to feel
comfortable with what it is saying. Some of the research
is bent and formed to justify their own product line
they want to sell you. I will give you a good example;
the article titled “CRAWL
SPACE MOISTURE CONTROL - A Fundamental Misunderstanding”
written by Peter Carpenter
explains, in quite a bit of detail, why you need mechanical
ventilation to the outdoors in order to control moisture
in the crawl space. To me this theory is more based on
selling a product line than correcting a problem. The
bottom line of the article is to install foundation
vents with electric fans in them which are controlled by
a humidistat. By doing this the idea is the fans in the
vents will come on when the humidity near the vent rises
past a desirable level. Essentially the fans are meant
to keep the warm moist air out by turning on when the
outside moisture levels rise. Think of a vertical wind
tunnel with a fan at the bottom and a balloon falling
down the tunnel toward the fan. Each time the balloon
gets close to the fan it will turn on and blow the
balloon away. This theory has solid standing
IF the crawl
space vents were an absolute requirement. It is, in my
opinion, a compromise between actually fixing the
problem and doing nothing. If you read between the lines
the article clearly states that the
problem is the
foundation vents allowing moist outside air to
enter the crawl space. Their solution is to create a
negative pressure in the crawl space, (take air from the
home, pull it into the crawl space and then discharge it
outdoors) in order to actively keep the moisture at bay
using the same vehicle that causes the problem in the
first place. It is my own deduction that the air is
pulled from the home; there is no other obvious source
of air that will replace the air being blown out of the
crawl space by the electric fans. This theory is put
into practice by Humidex, E-Z Breathe and other power
ventilation manufactures. Here are the flaws to this
theory as I see it; the process they describe works
against the natural air flow of the home (which is up
not down), it does not address the other conditions in a
crawl space such as odor (when the fan is off),
condensation, air quality, energy loss, cold floors or
frozen water lines. Like I said it is a compromise, and
it only attempts to address one source of moisture. It
also potentially increases the energy loss in your home
by pumping your conditioned (heat or cooled) air into
the crawl space and then outside.
The hot topic is whether a
homeowner can close the foundation vents in the crawl
space. Not just sliding the vent closed but completely
removing any way for air to move into the crawl space
from the outdoors all year long. In other words
permanently close the vents. You can find the answers in
the International Residential Code - 2006 IRC 408.3 and
subsections. Like any subject, to find the correct
answer you have to ask the question correctly. If
someone asked “do I need my vents?” the answers would
range greatly. Some would say yes, some no and some
would need more information. If you asked “do I need
ventilation in my crawl space” you would likely get the
same mixture of answers. The two questions are, however,
completely different and with different answers. Like
any new ideas there is going to be a clash of correct
and incorrect answers. Most of the incorrect answers
will be a result of ignorance on this subject; ignorance
is defined as a lack of knowledge. While our own lack of
knowledge brings us to asking the question we find the
blind leading the blind. My intention is not to be
critical but to encourage everyone to do their own
research. If you’re
not sure where to start I would be glad to point you in the right direction.
The third way moisture enters the crawl space is through
the foundation wall. Concrete block foundations have a much bigger problem with
this than a poured concrete foundation wall. Concrete block has two hollow cores
in each block. These hollow cores have a history of filling with water as the
ground get saturated during a rain, by leaving the garden hose on or by a
leaking hose bib. The concrete block is very porous and will allow water to pass
through it. Once in the core of the block the water will level out until it
finds a compromise in a motor joint or in the block itself. At this point the
water moves freely into the crawl space. If the water does not find a compromise
it will slowly migrate through the block to the driest side of the foundation;
either back into the dirt outside or into the air of the crawl space. Since the
water came in from the outside it is not likely that it will return there unless
the ground dries out extremely fast. With a poured wall foundation the
weaknesses are poorly patched rod holes and foundation cracks. Both of these
issues will allow water to move freely into the crawl space. If the home has a
problem with a false water table the water in the crawl space can also come up
through the dirt floor.
The fourth way moisture enters the crawl space is by way of
small cracks that are located where the wood structure meets the foundation.
This is not as serious as the other three but worth mentioning. The rim joist
and sill plate should be inspected for large gaps and poor workmanship. The
issues in this area are generally easy to correct.
Crawl space
ventilation- Yes, you need it!
Crawl space
ventilation is the most critical part of handling the crawl space moisture
problem. It is not the only part, but the one that will affect the quality of
air that is in your home. You have to get this part right or the current
situation will likely worsen. A home, a cottage or any building that is closed
up without air circulation will smell stale. It is not an uncommon practice to
“air out” a summer cottage that has been closed up for the winter. The process
of airing out is simply circulating the air inside the cottage; exchanging the
old stale air with new fresh air. The more air that is exchanged the fresher the
smell. This air exchange is also required for a crawl space. Really, that is
what the foundation vents are supposed to do. When you look at the current
condition of the crawl space, most often it will need a steady supply of fresh
air. We already went through the negative issues with exchanging the crawl space
air with the outdoor air. So, how does the crawl space get fresh air if bringing
in outside air is bad? First, I want to make sure my view on this subject is
clear. I am a huge advocate of bringing in fresh air from the outside into the
home. Open the windows when the temperature is comfortable, air out your home
regularly. Fresh outdoor air is great for your health. How does this help or
hurt the conditions in the crawl space. Well, the most important thing you can
do to properly assess and make good decisions about air exchanges in your home
is to stop separating your home into different parts when you are considering an
air circulation plan. Since the time your home was built the crawl space was not
considered part of the home, its time to change that! Whether you like it or not
a large amount of the air in the crawl space makes its way into your home. Every
tactic we have used in the past has failed to impact this particular problem.
The odor you smell, the condensation on the windows and the allergy symptoms all
remind us that there is something going on in the crawl space. Simply put, we
experience at least some of the conditions from the crawl space inside our home.
The more serious the condition the more motivated we are to getting it fixed.
Living with the more serious condition from the crawl space making its way into
the home, the last thing anyone wants is to circulate that air freely into the
home. That would make it much, much worse. Right?! This probably is the most
successful “pitch” the companies that sell the mechanical vents can use. Their
mantra can be “don’t let the crawl space air into your home”. If the goal is to
allow the crawl space to exist as is, then of course that would be a good plan,
provided you are willing to use the conditioned air in your home that you paid
for to fuel the plan and are willing to accept the other flaws. There is a
better way, I want to give you some more information first so that you fully
understand the decision you are making.
The natural air flow of any home is up. Air is pulled from
the lowest level and introduced throughout the home. The vehicle for this flow
is heat. Of course everyone that graduated middle school knows that heat rises
and cold falls. As the heat rises it is replaced by cooler air, this is what
creates the natural air flow of the home. Whether you are heating the home in
the winter or fighting it off in the summer the heat will always dictate the
circulation direction. The natural air flow, also called the stack effect, will
continue to move the air in your home toward the roof unless you allocate
sufficient resources to change it. In my opinion, using mechanical vents to
change this natural condition is an attempt to reinvent the wheel. It will not
stop the warm air from rising, it is not a sufficient resource to change the
natural air flow in the home and it will leave the homeowner with a failed
concept that was backed by a great sales pitch, while still owning the problem.
Granted the problems will be lessened and less frequent but nonetheless - not
extinct.
Cold floors, energy
loss and insulation
This is another huge topic throughout the United States and Canada. Cold floors and energy loss
are directly related to properly insulating your home and the crawl space.
However, insulation alone is not the answer. Here is what I tell my customers
that call me for advice and to help them understand the problem of cold floors
and heat loss. If you build a shed in the back yard and insulate the walls,
floor and ceiling with, let’s say R-30 and the outside temperature is 0 degrees.
Is the shed warm or cold? The answers I get are split - 40% say warm and the
other 60% say cold. For the 40% that say warm, I help them understand why their
answer is incorrect. Insulation does not make a shed or home for that matter
warm, heat does. The job of the insulation is to retain the heat. Of the 60%
that answered correctly I only have to ask one more question; what would make it
warm? This follow up question definitely exposes the ones that guessed but
nonetheless they understand what the missing link to their problem is. If you
take the heat source out of a bedroom and closed the door that bedroom would be
cold. It is no different with the crawl space, but with a crawl space the home
will usually have open vents. Even if the vents in the foundation are
mechanically closed it will make little difference in the temperature of the
crawl space. My analogy for this- would you install those same vents in the
walls of your living area and expect them to hold out the cold of you closed
them? Of course not, that is not part of there design. The other part of this
equation is the characteristics of warm and cold air. Heat rises and cold falls,
this fact directly works against keeping the floors warm in the winter. As the
home is heated the warm air rises to the ceiling where it is picked up by the
return air ducts (in most homes) and sent back to the furnace to be reheated and
delivered again. Once the heat is delivered to the living area of the home and
the heat begins to rise (away from the floor) colder air replaces it at the
floor. So once the cycle of rising warm air starts your floors get the cold air.
Now add to this the fact that the crawl space (just inches below your feet) has
no heat source and is much colder than the living area. We must now recognize
two other characteristic of cold to fully understand the impact; cold absorbs
heat and the lack of heat is cold (not the other way around).
This is a major disadvantage to heating a home and the only reason the
furnace has to continually work to warm the home during the winter months. The
easiest way to recognize this is to think of the sun, it is summer when we are
closest to it and winter when we are farthest from it. The sun heats the earth,
without it we would be a Popsicle. Floors over a basement do not have these cold
floor problems and that is because the basement is heated. The insulation in the
crawl space ceiling does little to protect the floors from the heat absorbing
cold. However if you took the insulation out and left the crawl space as is,
your floors would be even colder. There is a fix to all of these problems and it
is probably less expensive than you may think.
The Solution
Chances are very good that I have described some negative
crawl space conditions in this article that you were not aware of. The good news
is the solution is fairly simple. The hardest part is to allow your self the
time to properly research the facts. When searching for information on the
proper way to fix a crawl space you will certainly find a vast amount of
conflicting ideas. The truth is out there and you will know it when you find it,
it will be the one that makes the most sense.
Moisture Control
Before any of the negative conditions can be addressed
properly the crawl space environment has to be controlled. We know moisture is a
major problem with crawl spaces so let’s start there. When it comes to
controlling any environment one has to know where the problems are coming from.
So far we know the foundation vents, the open earth, the foundation walls and
the cracks around the rim joist and foundation are the main source causing the
negative crawl space conditions. Some franchise companies will want to sell what
is called a vent cover to seal the open vents. On paper this product looks like
it will work, and it does to some degree but it does not work as well as the
alternative which is less expensive, a permanent solution and fairly easy to do.
Most foundation vents are an 8” x 16” metal vent. A cement block is the same
size and will fit into the opening once the vent and the excess mortar have been
removed. To seal the block you have two choices; use a concrete sealant (caulk)
around the block on the inside and outside of the crawl space or mix up some new
mortar and fill the gaps around the block. Either way, the vent will be
permanently closed and is in the same condition or better than the rest of the
foundation. How you choose to close the vents will directly impact how much of a
saving you will receive on your heating bills. The open vents are the number one
vehicle for energy loss in the crawl space so be diligent here and don’t cut
corners.
Once the foundation vents are closed it is time to address
the open earth and the foundation walls. There are many different ways to
address these two problems. If what you want is to completely eliminate these
areas from causing any problems again in your lifetime then I suggest installing
a heavy duty vapor barrier. There are some mixed reviews on how to install a
vapor barrier in a crawl space and what products are recommended. Some “experts”
will tell you that a 6 mil plastic will do just fine and in fact it will. But it
will not last as long and is prone to tears and compromises that will get you
right back to where you were when you started. Is it a temporary fix? Yes it is.
It is also the minimum requirement for a crawl space floor. A better and a more
permanent solution is to use a product designed for the problem like the
DrySpace™ family of vapor barriers. The main differences between one vapor
barrier to another is going to be it’s durability, the perm rating (rate at
which water will pass through) and the quality of the resin that was used to
make the polyethylene. It is important to use a polyethylene barrier that is
made from virgin resins, this will insure a long life for your investment. Most
low cost polyethylene barriers are made from recycled plastic. While recycling
is good for most products in the market place it is not good for this
application because it puts your barrier closer to breaking down and becoming
brittle. Any open seams, cracks or splits in the barrier will render even the
highest quality barrier ineffective. Make sure you know what you are buying
before you buy or you could end up with an overpriced knock off. Ask the
supplier if there is a warranty for the longevity of the barrier they propose to
sell you. If they are not confident enough to give a warranty then I would
question the quality.
When hiring a professional to install any vapor barrier in
a crawl space the majority of the cost is in labor, insurance and operating
costs. So if you are going to pay $1500 for a temporary fix why would you not
pay $2500 for a permanent one? Here’s my view; do it once and do it right. Even
if you do it yourself don’t get caught up in the art of saving money, because in
the end it will cost you more. Let’s face it we don’t really know how long we
will be living in a home. It could be three years or it could be thirty. If you
plan a short term solution you could own a long term problem.
Now that the crawl space environment can be controlled the
next step is to dry it out. A quality dehumidifier is a wise investment if the
home’s structure is saturated or the home is located in a high humidity location
like Georgia.
Here are some points to consider when choosing a dehumidifier. First, even
before the price is considered, the dehumidifier has to be sized right for the
area it will be controlling. This means, once the humidity levels are under
control the dehumidifier should spend more time off than on. Most often a
dehumidifier is viewed as working great because it runs all day everyday. The
fact is it is not working at all. Look at it like this; if the dehumidifier is
running all the time it can not get the humidity levels down to the setting on
the control panel. What you have is a dehumidifier that is only helping to
remove some moisture at the expense of your electric bill. A dehumidifier that
uses 6 amps of electricity (about 700 watts) and runs 24 hours a day seven days
a week will cost between $65- $80 a month in electricity.
When the dehumidifier is sized properly
it will sit quiet and only come on when the levels raise above the control panel
settings. It will quickly reduce the moisture in the air and shut back down. No
one wants to pay more for an appliance than they have too, but in the long run a
cheap dehumidifier can cost much more in the electric bill in two years than the
entire cost of a quality unit. On top of that, the dehumidifier that is size
properly will actually keep the moisture at the desired levels.
Not all crawl spaces need a dehumidifier. It is our opinion
that a crawl space which is conditioned with the air from the home is a better
choice because there is a proper air exchange (which makes the air cleaner), the
home is more efficient and it is more comfortable. This process is the hardest
for people to understand and accept because of the current condition of the
crawl space. Keep in mind the old environment is gone and it is now clean and
dry.
Conditioned Air
There are a few components to accomplishing a conditioned
crawl space successfully; conditioned air circulation and proper insulation. To
understand the proper way to insulate the crawl space you should first know how
and why to circulate the conditioned air into the crawl space. The benefits of
conditioned air in the crawl space are; clean dry crawl space, warm floors,
lower heating bills, cleaner air in the home and a more comfortable home. This
is how it works. Air from the home, usually supplied by the furnace, is
delivered to the crawl space as if it were any other part of the home. A source
for return air is also installed to keep the crawl space from being pressurized.
When the air that is delivered is heated, in the winter months, the object is
not to heat the crawl space but to deliver heat to the home one level lower that
it currently is. The advantage to doing this, since the vents are now closed, is
the heat in the crawl space stays in the home. Heat naturally rises so it will,
without other interference, pass through the floor and enter the living area.
When the warm air passes through the floor it will leave the floor warm and
comfortable. This alone will make the investment worth it. The heat continues to
rise to the ceiling and on its way there it will help warm the living space that
is occupied by the family. When the heat comes out of the registers on the main
level it immediately heads to the ceiling without restriction. The lowest part
of the room, the floor, gets the heat last because the heat must build up at the
ceiling in order to be felt in the lower part of the home. With heat passing
through the floors the home has a longer heat retention cycle than without it.
In other words once the furnace is off and no other heat is being delivered to
the room, the heat from the crawl space will continue to make its way up. This
leaves the area in the home (below six feet), that our bodies occupy, warmer
longer because the heat in the crawl space is restricted by the floor which
slows down the rise to the ceiling. In turn this reduces the amount of heating
cycles, the furnace runs less and the heat bills are lower.
During the summer months the efficiency works the complete
opposite. During the winter the heat supply is the key vehicle for the
efficiency while the air return supports the circulation of warm air to be
exchanged. In the summer the air return is the key vehicle for the efficiency
and the supply supports the circulation of cool air to be exchanged. Here is how
it works, the earth stays about 55-60° F at about 48” (this is a medium guide
and may very depending on location) during the summer months. With an air return
in the crawl space the home can utilize this free cool air in the home. When the
air conditioner (A/C) comes on its job is to take the air from the home, cool it
and then redeliver it. In the process the A/C will also dehumidify the air. The
air in the home is pulled to the A/C by way of the air returns and then delivers
the new cool air through the supply. We all know or should know that the air in
the crawl space is cooler than the air outside. When the air is pulled from the
home to be cooled it will take the warm air from the ceiling area of the home
and mix it with the cool air from the crawl space. Since cold absorbs heat the
cool crawl space air will lessen the work load of the A/C. This causes the A/C
to work shorter cycles and run less often which impacts the electric bill saving
the homeowner money. On a quick side note – the best solution for the home is to
have both a dehumidifier and conditioned air in the crawl space. Here’s why, in
the high humid months of summer the dehumidifier will both protect the crawl
space from high moisture and help the A/C run even more efficient. The
dehumidifier will lower the amount of moisture in the home therefore allowing
the A/C to cool the air quicker and that means running even less. During the
spring and fall months the outside temperature may be at a comfortable level and
there is no need for heat or A/C. In these months the humidity can still be a
problem and a dehumidifier can insure the moisture levels in the crawl space are
kept under control. If the budget does not allow for both, conditioned air and a
dehumidifier then the best route is to condition the crawl space. You will gain
the energy efficiency and the furnace will control the humidity in the winter
because it will cook the moisture out of the air and in the summer the A/C will
step up and dehumidify the crawl space air. The only threat in this situation is
the weeks or months the crawl space does not have conditioned air because of the
comfortable outside temperatures. One way to help this is to turn on the fan to
your furnace (no heat no A/C) to circulate the air in your home and crawl space.
The fan by itself draws very little electricity and is an efficient way to move
air.
Properly Insulating
the Crawl Space
Properly insulating the crawl space is very important to
the energy efficiency of a conditioned crawl space. Insulation in the floor
joists cavity is no longer needed if the crawl space is conditioned. Insulation
in the floor joists would trap the heat in the crawl space and would only
accomplish heating the crawl space. In order to allow the heat to pass through
the floors they need to be kept open. There for the only place that insulation
is needed is around the perimeter of the crawl space. The rim (band) joist is a
critical area of heat loss because there is only 1 ½ inches of wood between the
inside and the outside. This is also and area that will have small opening or
cracks in the wood. I recommend R-19 or higher fiberglass insulation. Close cell
spray foam insulation comes up often when discussing crawl space insulation. I
do not believe this product is good for the crawl space. When it is sprayed it
eliminates the ability to inspect the structure for water or insect damage and
would make the repair very difficult and more expensive. When selling a home the
spray foam can hinder a sale due to the inability to properly inspect the
structure. I just don’t believe that the one advantage it has over fiberglass is
worth the potential problems it could cause. Insulation on the foundation walls
is going to be guided mainly by the local energy code of where the home is
located. Every climate will have a different take on the requirement if
foundation wall insulation. This information can be found fairly easily on the
internet at any of the states websites or at the local building department.
Conclusion
There are different ways to fix the problems associated
with open crawl spaces. The best way and the wrong way can simply be separated
by a good sales pitch and the lack of research. This subject is far more
complicated that just putting in plastic. Look at the crawl space as part of the
home and treat it that way, like our society does with a basement. There are
really very little differences between a crawl space and a basement, they are
both under the home, they are both below grade and they both have problems with
moisture yet we treat them completely different. Is ‘can I stand up in the
space’ the only factor that decides if the space is worth fixing? Invest in your
home and reap the benefits while your family is living there and regain the lost
value in your home. I hope you found this article helpful and useful. If you
have a minute give me a call and let me know if it helped you.
Best regards,
Matt
Leech –
President
and CEO of CrawlSpace Concepts LLC
Farmington,
Michigan
877.379.7658