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Sustainable Heating and Cooling: Digging The Foundations

By L.D. Gussin

Dec 28, 2009

"Between now and 2030, the agreement will save 3.7 quadrillion Btu of energy nationwide, equivalent to the energy consumed by 18 million households in one year. ... It will raise the minimum efficiency of residential central air conditioning systems by 8 percent and furnaces by 13 percent, and result in a 5 percent reduction of the total heating energy load and a six percent reduction of the total cooling energy load in 2030."

In California, where energy efficiency is a mandate, the 97-page Building HVAC chapter of the Title 24 (signed in 2008, to take effect in 2011) Residential Compliance Manual creates minimum efficiency requirements for every kind of HVAC component. Even more convincingly, it recognized the scope of the sustainable HVAC challenge by going beyond detailed component standards—such as unique rules for air conditioners with, and without, louvered sides.

The holistic eye it casts on what the private sector would call the entire HVAC value chain goes from efficiencies in products to finding solutions to the ineffective ways in which the products are installed and then maintained. So it is challenging the habits of not just consumers and manufacturers but also of a mostly mom-and-pop service industry.

Therefore, the California Energy Commission (CEC), with its counterparts in a few other states, Obama's DOE, and some industry participants, is putting muscle behind an effort to move an entire product ecosystem from a long held model of sell it and forget it (least first cost) to a new one of achieving least total cost via end-to-end efficiency.

110 Million Service Calls (Oh, My!)

Noting that the rising size of houses and the percent with central AC has led to HVAC accounting for 25% of peak power usage in 2009, up from 6% in 1979, the CEC attacked installation and maintenance. It wrote new standards, made utilities and manufacturers invest in solutions, and funded R&D.

In the space (no pun intended) between building envelope inefficiencies and the remaining inefficiencies in the newer SEER components is the problem area of HVAC integration. All of the components may be good or even best quality, but if they aren't sized right or don't match, or if the refrigerant charge or the air flow isn't rightly calibrated, or if the ducts leak or aren't sized right, then from some to most of the energy that the HVAC system uses just leaks outdoors.

On average today in the U.S., integration issues cause 75% of the total energy waste (meaning that the highest SEER components can only improve the overall efficiency 25%).

Most systems in houses today were either installed or are being maintained ineffectively, or both. Best practices are being developed, but they contend with the least first cost model of the service industry. In California, 90% of HVAC installations occur without the contractors either pulling permits or having the systems inspected. Few consumers know how well their HVAC is working.

Because nationally there are 20,000 HVAC contracting businesses, more than half with fewer than eight employees, and because nearly all of these small businesses take any work that they can get, working on all kinds of systems, there is, in addition to an ingrained least first cost problem, a daunting service education problem.

The DOE, some states and efficiency advocates are, again, working on these integration issues, as are trade groups and private companies. The issues split, though, into solutions and enforcement. Like the AHRI standards, the 2007 standards developed by a stakeholder team led by ACCA (Air Conditioning Contractors of America) for quality HVAC installation (QI) and maintenance (QM) are voluntary — contractors can use them or not as they choose.

Both the QI and the QM manuals combine prescriptive statements (a little boring for those not in the game):

"The contractor shall ensure that heat loss and heat gain load calculations are performed for every HVAC system installation or replacement ... shall verify that the airflow across the indoor heat exchanger is within acceptable ranges... shall ensure the ducts are sealed and that air leakage is minimized."

With specific requirements and directions (more boring still):

"For cooling coil (e.g., refrigerant, water) and heat pump applications 1: Airflow across the coil, at fan design speed and full operating load, is within 15% of the airflow required per the system design. And II: Airflow across the coil is within the range recommended by the OEM product data."

The manuals cover heating, cooling, ventilation and humidity and provide detailed requirements for different kinds of systems (like gas or electric heat) and different kinds of buildings. Their intentions are to spell out for the first time how to detect and solve problems. But because most dwellings and small commercial spaces have unique HVAC installations, usually the result of tweaking done over decades, often by multiple generations of owners, contractors need training and experience to get much actual help from the manuals.

The QI manual, in fact, requires HVAC installers to complete a 12-hour North American Technical Excellence (NATE) course each year. But as reading the manual is itself voluntary, its requirements are only guidelines.

Energy Auditing

A simple energy audit can tell homeowners what needs to be done and what will be the most cost effective measures. Stimulus in this area could lead to consumer demand that will stand on its own.

Print option

would you be willing to have a print option? It would be so helpful for me as I often want to print and share and article that I read on your site> Thanks

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