By Bob Baker

Over the past several years, I have held a number of conversations with contractors about residential zoning. Three of these really stick in my memory. The first was in 1991. The contractor was a well-regarded Carrier dealer and Carrier had recently introduced their zoning components for homes. I was not surprised that this dealer was quite enthusiastic, as he had just come from a sales meeting where Carrier had introduced the new system and encouraged their dealers to start selling it. The reason for the conversation was that we were discussing the design for the HVAC system in the new home I was planning. I next spoke to this contractor about six months later when we agreed on the final specs for my system and he recommended that I not include zoning because, "there seem to be some problems." I had a final zoning conversation with that individual a couple of years later when I stopped by his business and one of his crews was unloading a bunch of zoning dampers into their scrap pile. When I asked what was going on, he said an office building they were working on had a real bad air quality problem and they only way they could correct it was to tear out the zoning system and put in all new ducts.

IAQ Concerns

The next individual I discussed zoning with was a contractor in Pinellas County (Clearwater) Florida who emphasizes IAQ as an important part of his business and believes that this is the reason he has experienced such dramatic growth in the past several years. We talked in mid 1998 when I asked him his opinion of zoning. He flatly responded that zoning has no business outside of a carefully designed commercial facility with a sophisticated control system and the associated components that could assure that proper balance and airflow would be maintained.

He went on to outline several reasons for his concern. He pointed out that simple damper closing without any compensation with total airflow could well upset the pressure balance of a building envelope and cause it to go negative bringing in moisture and contamination. Second, he speculated that the loss of latent capacity caused by the short cooling cycles needed to cool only one or two zones of a large home could lead to a build up of moisture from long periods of elevated humidity. Finally, he pointed out that air cleaning from constant recirculation would be lost and air quality would suffer. Overall, he felt the risks were too great for him to take a chance with his customers.

As I had no data to refute his concerns, I could not argue with the points he made. At the same time, I am aware that more and more medium to large homes are utilizing zoning in their system design. I could not, however, find any article or review that dealt with the IAQ impact of zone control.

Complexity

The final conversation was held less than six months ago with the technician who maintains my home system. He was out replacing my accumulator (the joys of heat pumps) and I asked him his opinion of zoning systems. He is the type of technician we dream of in this business; fast, efficient and honest without question. By his own admission, he is somewhat resistant to new ideas, as he believes the most satisfactory home system is the simplest one. He pointed out that zone systems and their controls are too complex for many technicians and thus could easily be messed up while being serviced. He also replied that he had heard a lot of sad tales about the time and effort involved in properly installing a system; especially converting an existing duct system to zone operation.

He prefers to install several systems in a large or spread out home and provide each a separate thermostat. He said he would pass up a job if the owner insisted on using zoning.

A Need for Information (and Comfort)

My interest in zoning has been more that idle curiosity. First, I am concerned about the possible impact of such a simple system on the indoor air quality of a home. More important, I have a personal problem. My home has two problem areas. The master bedroom is on the north side of the home, well shaded, and separated from the air handler (located on the other side in a second floor closet) by about 40 feet of supply run. The master bedroom was always too hot or too cold even though the system in the home was as well balanced as possible.

The other problem was a couple of bedrooms located above the garage facing west. Every afternoon, the sun warmed these rooms causing the thermostat located in the hall outside them to call for cooling. Shortly, the balance of the home cooled to a temperature more suitable for aging meat than relaxation, dining and conversation. As a result, I have a high level of motivation to learn about zoning.

In addition, my home provides a great opportunity to learn what impact zoning might have on IAQ, as it is literally a building that is "on the edge". It has 3,000 square ft. of air-conditioned space and is served by a single five-ton heat pump based system. It is in a waterfront location and by code elevated with a six-foot crawl/walk space below which is totally enclosed and a potential source of moisture and mold growth. The elevation of the home leaves it open to winds and stack effect that can cause the building envelope to be negatively pressurized for long periods of time, drawing moisture and contamination from beneath. Slime in the drain pan and lines has been a constant problem threat complicated by a drain line nearly 50 ft long with 8 90-degree bends. I have been able to keep the system growth free is with regular use of BBJ MicroBiocide and annual cleaning but will note slime growth if I vary the routine the least bit.

The Test

I have decided to install a zoning system in an effort to solve my comfort problems, and develop data on the IAQ impact (if any) of the system. I will report on the difficulty of installing the system, the impact on operation, energy consumption, comfort and any change to IAQ or the factors such as average humidity, total moisture load, and building envelope pressure relationships that might impact air quality.

I will be advised by Carl Peterson a Factory Representative for California Economizer, which is a popular line of zoning components. In the next issue, we will report on the design of the zoning instillation, selection of components and instillation. That issue will also report on the initial readings on factors that are likely to impact IAQ and whether they have stayed the same, improved, or gone negative. In about six months we will look at longer-term results on air quality, comfort, energy usage and most important whether the system is still in place.

In the mean time, I would appreciate any experiences you care to share (both positive and negative) about zoning and especially converting an existing system from single control to zoned.

Mr. Baker's field of expertise is the control of contamination in air-conditioning and ventilating systems by mold, mildew and bacteria. He writes and speaks frequently about the efficacy, legal risks, and regulatory issues involved in various control strategies. He serves on ASHRAE Technical Committee TC 2.3, TC 2.4, TC 9.8, and Sampling of Airborne Particulate Concentration in Commercial and Residential Buildings GPC 17P. He also serves as a member of ASTM D22.06 (Indoor Air Quality) and is on the Board of Directors of the Indoor Air Quality Association and the Florida Public Health Foundation. Because HVAC applications encompass new uses from an U.S. EPA regulatory standpoint, Mr. Baker works closely with the EPA and industry groups, including serving as the chair of the IAQ committee of the Consumer Specialty Products Association, to help formulate policy in this area.

Bob Baker is Chairman and CEO of BBJ Environmental Solutions, Inc., a company specializing in providing clean air through environmentally responsible products, such as BBJ MicroBiocide , BBJ Micro Coil Clean , "FreshDuct Odor Eliminator ", and BBJ Mold and Mildew Remover™ as well as the revolutionary new Power Coil Clean™. For additional information, Mr. Baker can be reached at (800) 889-2251 or through the company web site at http://www.bbjenviro.com.