Tuesday, February 21, 2012

Externally Insulated Sheet Metal Ducts are Best!

Externally insulated sheet metal ducts are best. The smooth interior surface of metal allows the air to flow freely with little resistance for maximum efficiency. The smooth surface also makes it harder for dirt and contaminates to stick, and also discourages molds and fungi to grow. Metal can also be cleaned and last forever if installed and maintained properly. If you have an older but properly designed and installed metal duct system there is a good chance that the external insulation is deteriorating and is no longer as efficient as it could be. When I say properly designed, I mean if you are comfortable in your entire home the majority of the time regardless of the outdoor temperature then your duct system is probably properly designed. When it comes to proper installation, older homes were built to different codes and standards, many of which ignored energy efficiency. A lot of older round metal ducts were just stuck together with duct tape at best. Also up until the last few years, building codes in Texas did not require the seams to be sealed and secured. IF your externally insulated duct system is properly designed and is secure enough to not fall apart, then we can do what we refer to as a “peal and seal”. We remove the insulation, make sure each joint has at least 3 screws and seal all seams and joints with a code approved duct mastic. We also add or replace the hanging brackets and strapping to meet or exceed current code and then reinsulate the ducts with at a minimum 3” fiberglass duct wrap. 2” is still available but considering the high cost of energy the few bucks you would save upfront would not benefit you in the end.

Other types of insulation are available, of those, cotton is the very best available in my opinion. It’s much denser and will last longer than fiberglass and can be installed in some very tight applications where fiberglass is not as feasible. It does cost substantially more, so you have to consider all of your options.
Some other bubble foil type insulations are starting to expand in the market place. I am in favor of these, however the installation practices are much different so if choosing these, make sure it will be installed properly.

Tuesday, February 7, 2012

Replace your old leaky duct work!

Would you buy a NEW CAR and put on your OLD TIRES? That’s just what you are doing if you buy a new Air Conditioning system and leave you’re your old leaky worn out duct work! Like tires on a car take you where you want to go, the ducts carry the air your system is heating or cooling where you want it to go. If you have the most expensive, most efficient AC and Heating system in your attic, producing clean refreshing air and then that air has to pass through 20 year old, dirty, leaky ducts to get in to your home and lungs, how clean is that air when it gets there? Or how much of the air that you are paying for end up in your attic and doesn’t even make it into your home? There are other factors here as well, if your system and duct work is located in the attic, as the majority of our systems here in the south are.

Your indoor equipment, I will refer to as your air handler, removes (returns) air from the house, passes it through the cooling coil or heater (conditions it) and puts it back (supplies) into the house. Assuming no air leaks, the same amount of air that is removed from the house goes back into the house and the system is balanced and efficient. However, most systems have leaks, so what does that mean? If the leaks are on the supply side of the system, more air is removed from the house then is put back in, creating a negative pressure in the home. When this happens the many small leaks around the doors and windows (among other locations) will literally allow dirty unconditioned air to be “sucked” into the house. On the other hand, if there are more leaks on the return side of the system, then dirty unconditioned air is drawn into the system causing the blower, coils, heater, etc. to become dirty and inefficient as well as causing the system to over work to deal with the extra unconditioned air. And if you have leaks on both sides of the system, as is common, well you can imagine how much money is being wasted. If you look at the pay back cost, not counting increased comfort, less money on cleaning and maintenance, then replacing old ducts can give you a great bang for your buck.

There are many types and levels of duct work available. In future articles I will discuss these various types and the pros and cons of each.