4 FM quick reads on HVAC
1. Infrared Cameras Can Help Find Leaks in Ductwork
Today's tip is finding leaks in HVAC ducts.
Leaking ducts can be a pernicious energy waster. They lose heat or cooling &emdash; into the ceiling plenum or other space &emdash; rather than delivering it to occupied areas. What's more, they increase fan energy use because more air has to be moved.
Infrared cameras &emdash; more formally known as thermal imagers &emdash; offer an easy way to find leaks in ducts. The cameras capture an image of heat patterns in objects. An image of a duct would show hot and cold spots, allowing the facility staff to pinpoint leaks in the duct.
Advances in technology have produced cameras that are smaller, offer better resolution, have more features, and cost less than cameras in the past.
Repairing leaks in ducts can produce significant savings. That's because fan energy use is proportional to the cube of the speed of the fan, so they become more efficient at lower speeds. Once duct leaks are repaired, fans will save energy because they are moving less air and moving it more efficiently.
2. Retrocommissioning Quickly Pays for Itself in Energy Savings
Today's topic is payback for retrocommissioning.
Problems with controls &emdash; HVAC controls in particular &emdash; can waste energy and raise operating costs significantly. The way to find and fix those problems is well-established but too rarely used. Retrocommissioning applies the principles of commissioning to existing buildings rather than to new ones. Studies have shown retrocommissioning to be a cost effective way to improve the performance of controls and to remedy other problems within a building.
Retrocommissioning takes a relatively modest upfront investment. According to a study by Lawrence Berkeley National Laboratory (LBNL), the average cost for retrocommissioning is $.30 per square foot. But the return on that investment comes quickly: The median payback time is a little more than a year. That's not surprising considering that the median energy savings is 16 percent. And those savings last, says LBNL: "Energy savings tend to persist well over at least a 3-to-5 year timeframe." Savings may last longer than that, but the study didn't have data for longer periods.
4. With HVAC Upgrades, Reduce Loads First to Maximize Energy Savings
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.