Use the Sun to Your Advantage

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The most sustainable form of indoor lighting is not derived artificially from consumable energy, rather transposed via strategically emplaced daylighting solutions.  This ancient technology, originating from Roman architecture as incorporated in the Pantheon, has evolved to meet the demands and requirements set forth by clients within our industry.  Although the concept has been around for centuries, skylights are often avoided or forgotten due to the fact that a hole must be cut in the roof or allocated project budgets are industrialized towards forms of electrically reliant lighting.  However, understanding the true value of passively transmitting the sun’s light through total system approaches by way of the roof allows the effortless and confident integration of skylights into projects utilizing simple design tools that yield significant dividends for clients beyond the obvious light conveyance.

                Everyone is familiar with the emotional health benefits from increased serotonin production due to exposure to the sun; but along with the feel good anatomical response, skylights provide long term energy savings for building owners.  Objectively, top lighting reduces the consumption of energy specifically when business operations fall primarily within daylight hours and that level of energy reduction can be quantified by designing a building with an understanding of the following metrics:

1)      Solar Heat Gain Coefficient is the amount of radiation transmitted from the sun via the daylighting assembly which for instance can be strategically placed on Western facing roofs maximizing shade to reduce cooling costs in warm regions.

2)      U-Factor is the permissible heat loss through a defined media; for example, projects in cold regions should specify low U-Factor skylights to retain heat.

3)      Visible Light Transmittance is the perceptible light conveyed through a window that can still be leveraged in central areas of a building through top lighting solutions.    

So before considering all those extra light switch and thermostat locations during the preconstruction process, understand that artificial light and heat sources become obsolete when the space is properly illuminated by the sun.

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                When appropriately applied to the design of a building that is purposed predominantly for daytime operations, energy robbing equipment can be substituted for skylights.  Technology and initiatives for sustainability have led to the development of resources such as SkyCalc 3.0®; which is a spreadsheet application available at no cost that assists designers in planning the correct relation of skylight size, quantity, type and electrical controls to the building footprint to maximize lighting and HVAC savings.  This tool is simpler to use than COMcheck™ and allows comprehensive preprogrammed or user configurable weather data to be analyzed for optimum output in relation to the building’s natural use of the sun through top lighting.  Similar to the calculations ran by HVAC design software to balance negative pressure based on a building’s equipment, venting and fenestration, SkyCalc 3.0®  is a no charge software tool for designers that can be leveraged to take advantage of benefits provided from skylights.

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                While there are several glazing options available for skylights, the acrylic domes with prismatic layers seem to be the most prevalent within the metal building industry due to their consistent diffusion of sunlight.  Prismatic top lights eliminate glare, ultraviolent damage and hot spots by refracting sunlight throughout the prismatic dome layers for consistent dispersion of ambient illumination.  Contrarily, non-prismatic or lightly colored, semi-transparent panes require the design element of location to be considered to avoid wasting the directional light produced.  Taking the eave height of a building and placing the non-prismatic skylight at that numerical distance up the slope of low pitch roofs will greatly reduce the likelihood of wasting direct illumination on a wall within the building unless that is the intention of the client.  Furthermore in the discussion of location, it is critical to consider the exposure of maintenance workers that service rooftop equipment within a close proximity to skylights.  There are several OSHA compliant safety cages available as accessory items with internally and externally mounted assemblies that pair best with prismatic domes for alleviating shadows and protecting workers.  Ensuring each of these components integrate with one another can be achieved by procuring a turnkey skylight solution from companies that take a total systems approach.           

Historically, roof penetrations have been minimized due to the complex nature of individually sourced parts and assemblies required to prevent leaks.  However, the combination of qualified installers coupled with proven skylight and curb systems allows the dependable use of the roof as valuable, sustainable real estate.  Although skylights are not new technology, advancements in design tools, materials and flashing systems ensure the ongoing success of projects and inevitable energy savings for clients.  Let the light in, use the sun to your advantage.

Written by: Clifton Reasor and featured in Metal Construction News' Know Your Products section of the December 2017 Issue