Daylighting is the practice of placing skylights or windows on a building so during the day, natural light provides effective internal lighting. This strategy allows natural sunlight to illuminate the interior space of a building without the need to rely exclusively on electrical lighting during the day. Electrical lighting can account for as much as 40 percent of power consumption in many commercial buildings, meaning reducing such loads can significantly lower energy usage. One means to lowering energy use is to install prismatic skylights and light tubes to increase natural daylighting. Although there are many myths surrounding skylights, evidence shows they not only improve energy efficiency, they also provide multiple benefits to people living and working within daylit facilities.
There are a number of different skylight categories on the market today, each with their own advantages and disadvantages. Prismatic skylights are the most widely used because they allow for the most diffused and evenly distributed light. Other, non-diffused skylights can create hotspots within the building and tend to have poor U-values with high solar-heat-gain coefficients that decrease the thermal efficiency of the skylight. Skylight spacing should be 1 1/2 times the distance from the floor to the underside of the roof. (To learn more, read “Modular Skylight Systems: Best Practices for Designing Skylights with Suspended Ceilings”.
The materials used for skylights also vary. Polycarbonates have the best impact resistance and are the most hurricane and burglar proof. Some acrylic diffusers can yellow with age. Lastly, glass skylights are commonly used in residential applications and large, custom jobs that vary widely depending upon the customer’s specifications.
Different skylight manufacturers offer various alternative designs to achieve improved daylighting. One such alternate design is a tubular skylight or “light pipe”. Tubular designs are great for drop ceilings, because the tube reflects light down through a diffuser at the bottom of the fixture and ends up looking just like a normal lighting fixture on the interior of the building.
Although skylights can be installed at any time on a flat or steep-slope roof, significant savings can be realized when you install skylights during reroofing. The cost of installation decreases because manpower is already onsite, safety is in place, and there is significant reduction in overall time and labor leading to more cost-efficiency. With larger skylights, installations can be spread out over the roof and, ultimately, that saves money, as well.
By leveraging relationships with skylight manufacturers and lighting controllers’ manufacturers, roofing contractors may be able to access additional skylight models, better pricing and longer-term warranties.
To maximize the benefits of a daylighting strategy, the building owner should consider combining new skylights with new interior lighting controls. Photo-sensor technology incorporated with skylights can further conserve energy by actively sensing when artificial lighting is not needed.
Environmentally, daylighting reduces the load on power plants, lowers greenhouse-gas emissions and lessens air and water pollution resulting from byproducts of electricity generation. The payback for energy savings and reduction of electricity is typically one to two years. For customers seeking to achieve LEED certification, a green-building program administered by the Washington, D.C.-based U.S. Green Building Council, daylighting is another green solution. Skylights can contribute to a number of LEED credits by optimizing energy performance, using recycled materials, and increasing daylight and views.
One of the most documented outcomes of increasing natural daylighting is an aesthetically pleasing environment in which to live, work and interact that improves productivity and personal satisfaction while decreasing energy costs associated with maintaining that facility. A reduction in energy costs and increase in productivity for manufacturing and office environments mean the payback period on daylighting investments can be relatively short. Schools also experience improved test scores. Hospitals see speedier recovery times and retail stores see an increase in sales all linked to increased daylighting. Daylighting can add to the value of a building, and daylit stores see an average of 5.5 percent increase in sales relative to stores without daylighting, according to “Daylight & Retail Sales”, a California Energy Commission report.
The old-school thinking about day-lighting is that it is expensive and increases the chance of roof leaks around the skylights. Some building maintenance staff members do not want to deal with skylights. However, once a sample prismatic skylight is installed, the same maintenance staff usually becomes enthusiastic about the new lighting source. As for roof leaks, prismatic skylights have a thermal break with flashing details around the curb. If water gets in the skylight, it is diverted around the skylight and not through the roof as a leak.
Another myth is that with natural sunlight from the skylights, the building will be too hot. That’s not true because there is a reflective lens on top and an opaque lens on bottom. Light is brought in from all different angles and mitigates heat transfer into the building.
When you capture sunlight and brighten the inside of your building with daylighting, there are positive effects—from boosting morale and productivity to reducing energy costs. Once the CentiMark Corp. team installs a sample skylight on a roof, our customers typically get really excited and the interest level increases. Customers then rethink skylights and the lighting inside their buildings.
PHOTOS: Centimark Corp.