The title of this editorial will probably raise a few eyebrows. Notice that it's called IAQ vs. SEER, not IAQ vs Energy Efficiency. IAQ and efficiency can co-exist. In fact, if a system is designed and installed correctly, you get the best of both.
Unfortunately, in my opinion, the current definition of SEER has become less than a true measure of efficiency. In fact, at times, the quest for higher SEER can be a major contributing factor to lowered efficiency.
I believe that with current designs, using fintube coils and existing compressor technologies, we have reached, and in fact are trying to defy the physical limitations of DX (Direct Expansion) design.
True, we can squeeze out higher theoretical SEER using larger coils with more fins to the inch, supposedly improving heat transfer, but what's really happening is we're robbing from Peter to pay Paul. For example, as evaporator coils have become tighter, they increasingly restrict airflow. Add to that the use of restrictive "high efficiency" filtration media and other devices, and we're really choking down our systems.
With standard blower technology, usually designed to handle total static pressure of .5-in. wc or less, higher statics are often knocking down airflow to the point of systems being unable to deliver air to all the rooms of a home. In some cases higher static pressures cause coil freeze ups and other mechanical problems.
This can be somewhat overcome on higher end air handlers with variable speed motors. The flip side is these motors draw higher amps as they try to overcome system resistance.
Why do manufacturers keep chasing these phantom SEERs, thereby making the system more restrictive and ultimately less efficient on the back end?
The reason: SEER has become a yardstick used to satisfy DOE (Department of Energy) and NRDC (National Resources Defense Council) requirements and keep the feds off the manufacturer's backs. There are no federal requirements for field-measured SEER, so it's easy to play this zero sum game when the only measurements are being done in the lab.
Furthermore, we've heard numerous reports that some coils designed for higher SEER are so restrictive that the resulting high air velocity is literally causing coils to spray condensed moisture into the plenum. That can’t be good for indoor air quality.
There's also an industry debate brewing about the latent removal capability of higher efficiency systems. We're still studying this one, but there seems to be some merit to the argument that higher efficiency systems aren't removing as much moisture. Some manufacturers say it's an installation problem. There may be some truth to that, but some responsibility also lies in marginal equipment design.
On the other hand, equipment is becoming so sensitive that unless it's placed on a perfect duct system, performance drops significantly. When we look at fan curves on typical air handlers and furnaces, we find many can't even produce 400 CFM/ton at .5-in. wc. Some coils out there have .3-in. wc of static (clean). A high efficiency filter can create anywhere from .1 to .3-in. wc of static (clean). When you add in the ductwork, grills, and registers, we're seeing total statics of .6 to .9 in. — or higher — on a consistent basis. What this means is the system doesn’t have a chance.
The bottom line is our systems greatly affect the potential for poor comfort, IAQ problems, and mold formation in homes. As their ability to properly distribute air while removing moisture and indoor contaminants is reduced, we’ll see an increasing number of IAQ and mold complaints and lawsuits.
So what’s the solution? I can think of four steps that would help clean this mess up very quickly:
- ARI needs to revisit the current SEER rating system and modify test conditions to reflect field realities.
- Manufacturers, ARI, and other industry associations need to stand up to DOE, NRDC and any other watchdog organizations, and get them to back down on raising minimum SEER ratings.
- Manufacturers must make equipment that can handle the ever-growing barrage of accessories designed to improve IAQ and still deliver sufficient airflow to maintain comfortable conditions and remove humidity.
- Contractors must learn to measure true field operating conditions and educate customers that both air distribution systems and equipment need to be improved to deliver real comfort and performance and maintain a healthy indoor environment.
Is any of this easy? Absolutely not. Is it necessary? Absolutely.
What are your thoughts on this growing debate? Send your comments to Mike Weil at [email protected].
Dominick Guarino is chairman and CEO of National Comfort Institute (NCI), a national training, certification, and membership organization. He can be reached at 800/633-7058, or at [email protected]. For details on training topics and schedules visit www.ncinstitute.com.