Conditioning a crawl space along with air-sealing the exterior envelopes are two items that should be implemented by all homeowners and builders that would like to bring “Green” construction to their project. These two items alone can account for the most energy saving benefits that you will see as a homeowner.
One thing is true especially in older homes: There is a forced air heating and/or cooling system that was either added 30 years ago or placed when the home was built and it is in the crawl space or the attic. Either way one of two things is happening. 1. The system’s ducting was never insulated or was built using duct board. (If it’s duct board run away!) 2. The duct system was held together using Duct Tape, now called Duck Tape because it did not work on ducts and this tape has failed and the ducts are leaking air all over. A third option especially with 30+ year old systems is mechanically fastened galvanized ducting that is not sealed in any way but also is not potentially coming apart. Trust me this stuff would stay together in a tornado. This latter type of duct is a great candidate for a conditioned crawl space. It is already leaking enough air to keep the crawl space pressurized therefore keeping ground borne pollutants at bay. And it’s easier and better to condition the crawl than it is to mastic seal and insulate the duct. Create a conditioned space around the duct; allow it to be brought into the building envelope that is already full of conditioned air much as a Mechanical Room inside the building envelope is.
Most old homes (and a lot of new ones) are leaking air around windows, doors, walls, electric outlets, light boxes, overhead fixtures, at wall corners, thru plumbing penetrations, floor joists at the exterior, attic access stairs and doors to attics, fireplaces, chimneys, kitchen and bath exhaust fans, dryers, what did I miss? Because of this the home is essentially one big chimney where hot air rising creates a need for cool air to fill this void. Conditioning the crawl space is one way to help plug this chimney and keep ground pollutants out of your living space.