One of the “next steps” identified at last November’s CEE Gas DSM Summit was to explore opportunities in commercial rooftop (gas-pack) units. CEE’s Natural Gas Committee has begun to research existing opportunities, market status, and barriers to widespread adoption of this technology.

Another major focus for the committee is the investigation of a potential water heating initiative (see related story ).

According to CEE research, the furnace portion of rooftop gas-pack units have an average AFUE of 78-82 percent but efficiencies of 89-97 percent are achievable.

Estimated savings from these units are about 15-16 percent and several major manufacturers – including Lennox, Trane, Carrier, Aaon and Air Treatment – have the ability to produce this equipment on a custom basis.

“The high-efficiency rooftop units are available,” said CEE Senior Program Manager Kara Rodgers. “They tend to be used more in custom designs. What we want to find out is why more of this equipment isn’t being sold and how we can make it more available.”

One of the barriers is first cost. High-efficiency units cost in the $30,000-40,000 range with a standard-efficiency model priced at about $12,000.

Another issue is the split incentive, where the building owner buys and maintains the equipment while the company using the building is responsible for paying the utility bills. A possible solution might be to concentrate program promotion on schools and government buildings, where the building owner does pay the bills.

Virtually all of the high-efficiency models are condensing units, which raises some technical issues, such as the design challenges associated with condensate paths and cold climate installation.

It is difficult to maintain an open condensate as the water tends to freeze. Incorporating a secondary heat coil to eliminate freezing is a design challenge and could negate some of the savings through electricity usage.

Creating a condensate path by installing drainage systems can be complex and costly. Condensate from the unit is mildly acidic and could potentially damage the roof structure.

Despite these technical issues, the savings potential is significant enough for the committee to continue its exploration.

Natural Resources Canada (NRCan), Vermont Gas, Energy Trust of Oregon and Terasen Gas are either looking into the possibility of running programs or have had some experience with the technology.

The Gas Committee will be evaluating opportunities as they vary by region, focusing on applicability, technical issues, heating loads, cost-benefit analysis, efficiency gains and other benefits.

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