Ductwork is used to distribute conditioned air throughout your home. Your ductwork system can make a big difference in the energy efficiency, comfort, and safety of heating and cooling the air in your home. Unfortunately, Energy Star estimates that typical homes lose about 25 - 40 percent of cooling and heating energy through ductwork leakage. Ductwork air leakage happens when air moving through the duct system is lost due to leaks, holes, and poorly connected or sealed ducts. On top of the energy wasted by these air leaks an unsealed or uninsulated duct system creates indoor air quality and comfort issues.
Ductwork replacement or ductwork sealing and repairs can be the most important energy saving improvement for your home if your ductwork is located in the attic. For most homeowners, the cost to seal or replace ductwork will be repaid in 3 – 5 years, with 10 – 15 years of additional energy savings creating a high return on investment. Ductwork loses energy in two ways: conduction and air leakage.
Conduction occurs when a material transfers heat to another material is touching. In Houston, our ductwork is mainly housed within our extremely hot attics. Anytime your ductwork comes into contact with the hot attic floor (or any other part of the attic) heat is transferred from the attic floor and into the ductwork. As the ductwork heats up, the air traveling through it, the air you paid to cool, is heating up as well. This means that your home will be more difficult to cool. The typical response is to lower the temperature on the thermostat, driving up energy costs. This same process happens in the winter time as well, only in reverse. Heated air traveling through ductwork in a cold attic slowly transfer heat out of the air and ductwork and into your attic, raising heating costs.
The Solution: Special insulation wrapped around ductwork can effectively slow and reduce the transfer of heat. For Houston, Energy Star recommends R-8 rated duct insulation. (More information on Insulation and R-values). Proper ductwork insulation can help keep the air traveling through ducts cold in the Summer and warm in the Winter.
Air leakage can occur due to poorly sealed connections, tiny holes, tears, and cracks. On top of the cost of losing conditioned air through ductwork leakage, this air creates pressure that causes homes to leak significantly more than normal. Imagine a very small hole in an inflatable mattress, air will naturally slowly leak out. Now imagine you press down on the mattress creating positive air pressure, the air rushes out of the same hole several times faster. In your home your air conditioning and heating system create pressure when sending and pulling air through your ductwork. Whenever there is an imbalance in pressure air can rush into or out of any tiny penetrations in your home or attic, just like the air rushing out of the tiny hole in the air mattress. Typical causes of uneven pressures are penetrations but a well sealed poorly designed ductwork system can create imbalances as well.
In addition to energy and comfort losses, air leakage and pressure imbalances can be harmful to your health. Pressure imbalances can cause your home to pull in massive amounts of dirt, dust, bacteria and dangerous particles like fiberglass insulation from your attic. This is a serious health and safety concern.