Energy Efficient Recessed Ceiling Lights: Air-Tite™ Recessed Light Fixtures Halt Air Leakage, Reduce Energy Use
(HIT) - Nature, in its curious way, actually works against energy conservation. Wind blowing on one side of a house creates high pressure areas upwind and areas of low pressure downwind. And, because nature tries to correct this imbalance, the house obligingly lets air enter on the windward side and then escape on the leeward. Light fixtures that penetrate your ceiling offer a natural path for this air transfer.
The bottom line is that Mother Nature makes us consume more energy than is absolutely necessary. This is particularly ironic in an era when energy conservation has become increasingly important, both to the environment and our finances.
Demands for reduced energy consumption typically have resulted in increasing insulation requirements. Unfortunately, however, the all-important ceiling insulation values too often fall short of rated performance values.
This tends to happen for two reasons:
- Air leading through or moving around insulation reduces the insulating value.
- Damp, moist air trapped within the insulation greatly reduces the R value.
To combat the air leakage problem, Halo Lighting offers a series of Air-Tite™ recessed lighting fixtures for ceilings. In addition, these fixtures help maintain the vapor barrier between conditioned and unconditioned spaces.
Halo IC rated recessed ceiling light fixtures feature a gasket designed to seal the space between the housing and the ceiling to significantly reduce air flow. Further, sealing the housing with a gasket eliminates the need for taping or caulking fixture openings, constructing drywall vapor barriers or caulking socket holes in trims during finishing.
When considering the extra cost to the consumer for airtight recessed ceiling lights compared to non-airtight lights, it is minimal when compared to energy saved. Though the payback period from energy savings will vary based upon local energy rates, in most cases, it is less than one year. According to air flow tests at the Universtiy of Illinois and to actual measurements performed at Pennsylvania State University, one conventional recessed ceiling light fixture loses between $5 and $45 per year worth of energy, and it can dump about one-third of a gallon of condensed moisture daily into a cold (32° F) attic.
Up to the advent of Air-Tite recessed ceiling fixtures, recessed light fixtures have long been acknowledged as a major source of leakage in air barrier systems. In 1992, for example, the State of Washington revised its building code to require that all recessed ceiling fixtures meet strict airtightness guidelines. Since that time, several other states have adopted similar energy codes, including California (Title 24) and Minnesota (Code 7670). While energy loss was one motivation, the primary reason was to limit moisture transfer from humid indoor air up into cold attics.
In the Penn State tests, air leakage through a recessed ceiling light fixture was found to vary from about 2 to 10 cubic feet per minute (cfm), depending on the degree of "stack pressure’’ against the ceiling. The university’s scientists measured the air leakage under various pressure differentials ranging from 0 to 3 pascal (Pa) and assumed that in a single-story home in winter, the stack pressure across the ceiling typically is between 1 and 5 Pa. With a 100-watt lamp, the measured air leakage varied from 2.3 cfm at 0.5 Pa pressure to 9.7 cfm at 3 Pa pressure.
Another significant finding is that as much as nine gallons of moisture leaks into an attic every month from just one typical recessed ceiling light fixture.
Indoor air that is 70°F with 40 percent relative humidity contains 0.000055 gallons of moisture per cubic foot of air. When leaked into a 32°F attic, less than half of that moisture theoretically condenses into liquid water – specifically, 0.000021 gallons per cubic foot of air.
Although these may seem like microscopic amounts, with 10 cfm continuous air leakage, the total condensation adds up to about 0.3 gallons per day or an amazing nine gallons per month. And these statistics are for just a single light fixture. Imagine the total moisture load in the attic of a home with 20 recessed light fixtures. Now, we calculate the energy cost of that leakage. If the air leakage is 10 cfm per fixture during the entire heating season, the total energy penalty would be approximately 1.3 million Btu per fixture. That translates to about $10 per year with 80 percent efficient gas heating at average gas price ($.60/ccf).
Taking into account the significant variations that naturally exist between homes in the real world, these moisture and energy calculations actually may vary 100 percent or even more. For example, a study performed by Ecotope, Inc. of Seattle estimated that air leakage through recessed fixtures is about 5 cfm and that the total energy cost penalty for a typical house in the Midwest is about $5 a year.
Even with that rather significant degree of error, the results definitely indicate that non-airtight fixtures can cause moisture problems in attics. Furthermore, they show that replacement with airtight fixtures not only should reduce moisture problems, but also save enough energy to easily compensate for the slight extra cost.
One unexpected observation in the Penn State study is that the wattage of the lamp had little effect on air leakage thanks to the chimney effect. Although you might expect that a hot 275°F 100-watt incandescent lamp would pull more air up through the fixture than a cooler 95°F 13-watt compact fluorescent lamp, almost no difference is discernible.
Air-Tite lighting fixtures from Halo Lighting make good sense and should be the logical choice of today’s energy-conscious home builders and buyers. These units add substantially to the tightness of today’s construction, while providing the quality lighting people want. For more information visit www.haloltg.com.
Courtesy: Home Improvement News and Information Center
|
