Daylighting a commercial building with a well-designed skylight system is a cost-effective way to save on energy expenses and reduce a building’s carbon footprint. Even in a retrofit environment, skylights can be added to the roof assembly with very little disruption to the workplace below.
However, most building owners express an aversion to skylights for multiple reasons, often associating them with troublesome leaks even though the real culprit is typically dripping condensation. Unless skylight manufacturers can visibly demonstrate their products’ leak-proof designs effectively, building owners will defer on the side of safety and omit skylights form the scope of renovation work, no matter the potential energy savings.
A recent advancement in the skylight manufacturing process could go a long way toward dispelling this common objection of building owners. The production process is called RIM, an acronym for reaction injection moulding. RIM parts are created through a process that begins when two liquid reactants are held in separate tanks at an elevated temperature with agitators. When this process is used in conjunction with the manufacturing of skylights, the skylight glazing (glass or plastic) is placed into a mould and the RIM process creates the retainer frame around the glazing with a material called aliphatic polyurethane. Aliphatic polyurethane has been used in the automotive industry for more than 25 years, encapsulating sunroofs, tailgates and slider windows – basically, all assemblies that require waterproof performance or operation. As a result, the weatherability and performance of this material has been time-proven.
Because of this improvement in glazing technology, some manufacturers are offering warranties on RIM-encapsulated skylights with complete coverage against leaks for up to 20 years. However, leaks can also result from poor installation techniques, a factor that has driven some manufacturers to design and market prefabricated accessory products that help improve integrity by reducing the likelihood of human error during installation. Most of these installation-friendly flashing accessories are designed for single-ply roof systems. Such accessories include new one-piece TPO and PVC flashing sleeves that slip over the curb and require simple heat welding to the deck membrane.
Building owners’ objections to the potential of heat gain and heat loss through the building envelope by skylights must be addressed as well. Owners need to be reminded that their operation of electrical lights in a space actually contributes to more heat gain than the infrared light spectrum transmitted by skylights. In fact, the heat produced by 30 to 40 fluorescent fixtures would require 0.67 tons of additional HVAC equipment to be installed in order to mitigate the heat produced compared with 0.27 tons for the same amount of visible light transmitted by diffusing skylights. Metal halides and some high-intensity discharge lamps are even worse in regards to heat versus lumen production.
Heating loss can be managed by selecting better insulating glazings for skylights and better thermal break strategies. One other advantage of the aliphatic polyurethane skylight frame assembly is its ability to greatly deter temperature transference through its mass (for example, it does not conduct heat or cold, which, in the case of aluminum framed skylights, contributes to lowering the inside surface temperature of the glazing).
One of the most important factors for building owners considering skylights is the expense, a major potential hurdle to overcome in today’s economic climate. However, skylights actually pay for themselves over time, as long as some form of lighting control is utilized that takes advantage of the natural daylight being transmitted through the skylights in conjunction with turning off electric lights.
One final consideration for building owners contemplating a skylight system installation is the area of roof support requirements. In situations involving typical metal decks, there are now some cost-effective solutions available that eliminate the high labour cost and fire danger of welding steel angle irons in place.
Daylighting a commercial building is one of the most cost-effective strategies for building owners to save operating dollars, reduce their carbon footprint and demonstrate their commitment to sustainability policies. For property management companies, it is a strategy to attract lessees because it will lower their energy costs compared with conventionally lit spaces. Most, if not all, of typical building owner objections to skylights have been met and answered by many of the new techniques and innovations that have been developed over the past few years.
Kenneth Laremore is the skylight product manager for Carlisle Syntec Systems.
