Many homes do and you don’t even know it. I am talking about bad air. One of the principle considerations in building a green home is Indoor Air Quality (IAQ)
We know that many building components themselves are made up of hundreds of Volatile Organic Compounds (VOCs) that off gas into the air we breathe. For example many types of press board, particle board, cabinets, counter tops, carpet & paint just to name a few have compounds in them that are proven carcinogens. These are unhealthy to breathe but have been a component of building products for many years.
As cancer rates and allergy related problems continue to rise IAQ is serious concern and the green building industry is paying attention. As houses become more energy efficient and built tighter this becomes an even more important issue to address. There are now alternative Low or No VOC building materials available that can replace almost every product containing VOCs and have been becoming more popular the last few years.
Other areas of concern that contribute to poor air quality are leaky, drafty walls, improperly sealed crawl spaces or basements but we will discuss those later.
Here is one area that may be the most over looked; an old or improperly installed HVAC system. Ductwork that is installed in an unconditioned space is one of the biggest No No’s in energy efficiency, yet that is how a very large percentage have been installed. HVAC systems are typically installed as an afterthought, not in the initial planning as they should be, so they get the area that is left over, typically the attic or crawl space. Some air returns are actually nothing more than sheet metal over the floor joist below, this is not an acceptable practice. Any leak however slight in that return air duct is sucking that surrounding unconditioned air directly into your system and circulating it throughout your home. It could be hot humid attic air or cool damp humid air from a crawl space. Either way it is not healthy air and it is certainly not energy efficient. Here is the other problem with leaks in your ductwork. Your HVAC system is designed to operate at balanced or slightly positive pressure, but with leaks in the duct work you create negative pressure which means your home is now sucking air through any area it can in the building envelope, including leaky walls that may have a variety of contaminates including mold issues, but the biggest problem with this situation if you have a gas appliance or furnace is that it can now suck or backdraft those gases right back into your home and put excess carbon monoxide in your living area. This can be an immediate danger to all occupants.
There are many things that contribute to the IAQ of your living area, but the HVAC system can be a big concern if not installed properly.
For more in depth information on energy efficient housing check out Greentite.com