Garland AC Repair Serviceowner Steve Lauten, President of Total Air and Heat Co. Describes Things That Impact Your Comfort
Truss Mounted HVAC Ducts
Part 1-Duct Design
This is the 1st in a series of articles I am writing that covers issues that impacts your comfort level in your home or office. In addition I will address ways to reduce your cooling and heating bills, and extend the life of your HVAC system.
I would like to begin by discussing duct design, it seems to be one of those dark secrets that many air conditioning and heating contractors don’t want to talk about. Yet a correctly installed and designed duct system yields the biggest benefits, including a fantastic return on investment.
What are the issues with duct work?
According to the studies done by the EPA/DOE, Utility Companies, and many universities 70% or more of all residential air conditioning systems have inadequate airflow. Most air conditioning systems should be designed to move 400 CFM per ton of air conditioning. If you have a 3 ton system, the duct system should be designed to move 1,200 CFM of air.
There are many reasons that duct systems are short on airflow. In most cases the duct system is simply not large enough, i.e. the ducts are too small and not capable of move enough airflow for the size system that is installed. These problems typically arise during the construction phase of the home or office building. While it does not make sense to me, most new construction jobs are awarded to the lowest bidder. The winning bidder typically sub contracts out the installation. While there are building inspectors to review system installation for meeting code, the installation is not reviewed to see if it will actually work properly or keep you comfortable.
Is there enough space to run the duct work? In many cases there is not enough room to run the size duct that is necessary to cool the space.
Challenges for duct work installation include:
- Trusses - 2 story homes normally have laminated trusses or web trusses. It’s easier to run duct through web trusses, but in many cases the space within the web are still too small. It’s more costly to use web trusses, but they do provide a better path for ducts, electrical and plumbing. Laminated trusses are more common, and less costly. However they provide a much larger challenge for duct work. Holes can be cut in these trusses only in limited areas or they lose structural integrity. The bottom line is the duct system should be included as part of the design phase by the Architect. Duct chases need to be considered in advance. If necessary, framed out drop downs need to be included to give duct work a path to get from point “A” to point “B”.
- Wall chases - In many cases wall chases are used for return air. That’s fine but………….be sure the chase is large enough to allow sufficient air to move through it. In addition make sure the chase is sealed! It’s very common to see electrical wiring and plumbing to run through return chases and these penetrations are not sealed. Leaking return chases can account for over 30% loss of system capacity and efficiency.
In summary a duct system can only work as good as the company that designs and installs it. As a rule…..any duct work located between floors or in chases is a permanent part of the structure, and will be a critical factor in controlling future comfort and operating costs.
Next article will discuss supply and return grill location.
About the author: Steve Lauten is President of Total Air & Heat Co. located in Plano, TX. Steve can be reached at 972-881-0020 or by email at sales@totalair.com
Total Air & Heat Co. has been serving the North Dallas/Collin County area since 1957 and has been voted the “Best Heat and Air Contractor in Collin County” 14 times by the Readers of Star community Newspapers.
Garland AC Repair Service, Total Air and Heat, is owned by Steve Lauten, the second generation owner. Founded in 1957 by Steve’s dad, Fred Lauten, Total Air and Heat is proud to have received some of the highest awards for quality and service that are offered in the Industry. Among those awards are the Readers Choice Awards from the Collin County Newspaper, the Trane Pacesetter Award in 2002, and designation as a Trane Comfort Specialist.