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March 4, 2010 -
Today's topic is the importance of trying to reduce loads before replacing HVAC systems..
HVAC equipment is expensive and long-lived. What's more, these systems are sometimes so large that it is difficult to get new units into place without significant construction costs. So it's no surprise that decades may elapse between the time a boiler, chiller or air handler is installed and the day it is replaced.
The demands on an HVAC system depend to a considerable extent on the performance of other building systems. A one-story building in Texas, for example, will cost considerably more to cool if it has a conventional black roof than if it has a reflective roof. The same building in Minnesota will cost more to heat in the winter if it doesn’t have adequate roof insulation.
The roof isn't the only part of the building that has an effect on HVAC loads. Solar gain through windows, air infiltration, heat load from lighting systems – all have some effect on HVAC loads. So does equipment from computers to coffee makers. And improvements can be made in all areas.
The time to consider building system improvements and other load reduction measures is before a major capital investment in new HVAC equipment. If the load on a system can be trimmed, it may be possible to reduce the size of the HVAC unit as well. Optimizing the performance of the air distribution system may provide an opportunity for further reductions in chiller or boiler size. And the savings provided by the smaller units can be used to help pay for the load-reducing measures, or for more efficient HVAC equipment.
More widespread use of energy modeling software makes it possible to evaluate what-if scenarios more easily than in the past. Although energy modeling adds cost, that cost may be justified by the savings available from load reduction and HVAC savings. What's more, if energy savings are great enough, the project may qualify for federal tax deductions under IRS Section 179 (D), widely known as EPAct tax deductions.
By looking at load-reduction measures in conjunction with HVAC system replacements, facility executives may find cost effective ways to lock in lower energy consumption for several decades.