Is your house making you sick? On average, people spend about 80% of their time
indoors, and most of that time is in their homes. The air in today’s home is
filled with dust, pollen, pet dander, dust mites, chemical vapor off gassing
and other things you can’t see that aggravate allergy and asthma sufferers.
Indoor air quality is very important to your family’s health.

How does the air in our homes become so polluted? The single most significant source is from
attached garages. Car exhaust contains many known carcinogens and can migrate
into the living space. Also, occupant activity (like smoking a cigarette),
combustion of gases from burning fossil fuels (operating a water heater), gases
released from building materials (emissions as paint cures), and gases from
cleaning products (chlorine from bleach) are some sources, though there are
many more. 

As the complexity of houses, especially with the dawn of
synthetic products, increase, so do the risks to human health, not only for the
chemically sensitive and the allergy sufferers but also for all of our
children. What is missing in our new tight homes is air leakage.

Homes that were built years ago had many air leaks because
the envelope was not sealed properly. This is not very energy efficient, but it
does make for healthier indoor air. I remember being in my grandparent’s home
and holding a match up next to a light switch on an exterior wall. On windy
days, the wind would blow the match and sometimes even blow it out. Thinking
back on this, I wonder why my grandparents let me play with matches in their
home, but that is another subject. This process of outside air leaking into the
home and pushing the stale inside air out of the home is known as air exchange
(good air in, bad air out).

We homebuilders
are now building much tighter homes than we did in the past. This is a good thing,
however these tight homes present us with an indoor air quality problem since
there is very little or no air exchange. Tighter houses prevent outside air
from getting in, but they also prevent indoor air pollutants and allergens from
carpet, pets, mold, cooking and tobacco smoke from getting out. Your family
could be breathing air that is five times more polluted than the air outside.

Every new home that is built is made up of many systems and these systems much work in harmony
with each other. Even though it makes good sense to use a new and improved
system, this could cause problems if another system has not been adjusted for
this change. When implementing the
“build it tight” system, a homebuilder should also use mechanical ventilation
to make sure the air exchange rate is high.

Proper ventilation is vital for healthy indoor air. It provides a constant source of
fresh, filtered outdoor air to flow through your home. Ventilation exhausts
harmful pollutants that are not eliminated by filtration to the outside. And ventilation
controls humidity, especially important during cold seasons. Fan-powered
ventilation is recommended to remove air from single rooms, such as bathrooms
and kitchens, where the pollutant levels from human activity, cleaning agents
and mold are high. HVAC systems use fans and ductwork to constantly heat, cool
and remove humidity from your home. Unfortunately most HVAC systems installed
in new homes are designed and installed without any means or system of bringing
in fresh air from the outside and removing stale air from indoors. This is a
real problem in our tight homes.

Energy recovery ventilators (ERVs) are designed to work with HVAC systems without
paying an energy penalty for direct fresh air ventilation. ERVs exhaust stale
indoor air while providing outdoor fresh air with only a small energy cost. ERVs
use a heat exchanger core to condition fresh air drawn in from the outside.
During hot days, energy from the cool indoor air being exhausted is used to
cool hotter outdoor air being drawn in. Many of these units help to pressurize
the house slightly reducing infiltration and resisting radon and car exhaust
intrusion.

Over the past few years, we have seen a trend of homebuyers moving away from carpet and
going more towards hardwoods, tile etc. for their flooring as carpet harbors
many pollutants. This is a good idea for source control of indoor air
pollutants.

Fresh air is critical to optimal health. Remember, there are 3 ways to improve the air in
your home – source control, ventilation and filtration. It is a good idea to
create a personal action plan. What are the sources of the problem, where are
they, and what can I do to correct them? I hope this little bit of information
helps you breathe much easier in the future.

I moved to Texas from Indiana in 1980. The first time I went into an attic in Texas in the summer, I could not believe how hot it was. I noticed that the ductwork and the air handlers for the HVAC system are all located in the attics. I asked why and I was told that we do not build basements (or many crawl spaces) in Dallas, so this is where we put the air ducts... Over the years I came to understand that builders are installing the HVAC ducts in an attic that gets to temperatures around 150 degrees and also the average duct leakage in older home was around 30%. A lot of the cool air is either heated in the ducts as it travels through the hot attic, and/or it is lost due to duct leakage. This does not make sense.

I think designing and building attics in homes in the DFW area that are non vented, insulated, semi-conditioned attics is good move. You vent a roof to let moisture out (not in). This idea was developed in Minnesota, which has a dry (and much cooler) climate. Houston has a humid climate and gets very hot, so  you do not vent a roof in Houston, because you let moisture into the attic. The Dallas Ft. Worth area is a "mixed-humid" climate. It seems like our summers get more humid every year. Most attics in the DFW area are vented, non conditioned, attics and they are really hot in the summer. A lot of builders are still building this way. Yes, radiant barriers does help to cool the attic a little, but that is not the total solution.

Our company has been designing and building our homes with fully encapsulated, semi-conditioned attics for some time now and this system is working. To accomplish this, we removed all of the vents in the attic and we have moved the insulation from the floor of the attic to the underside of the roof deck. We use spray foam insulation for this purpose. Spray foam ( if installed correctly) seals all of the air leaks in the attic. Our attics stay around 75 to 85 degrees year around. Our AC ducts (and air handlers) are now installed in semi-conditioned area which is much, much more efficient than the old way. My HVAC Contractor says that his equipment will now have a much longer life span since it is now not having to operate in very hot attics. Also, think about the items that we all store in the attic. Now they are being stored in a semi-conditioned area. This "new and improved" way of designing and building our attics in the DFW area seems like a good idea to me!