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Solutions To The Five Most Common Daylighting Problems

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Buildings that are illuminated with daylight consume less energy and electricity than those that aren’t; in fact, daylighting can lower utility bills by a third. But perhaps more importantly, it makes employees happier, healthier, and more productive. Although major retailers like Wal-Mart and Kroger are incorporating daylighting into their energy-saving plans, many businesses cite the same reasons over and over for hesitating to make the investment. Here are our solutions for the five most commonly cited deterrents to skylights.

1. Problem: Skylights Leak Water

Most skylights start out dry but eventually leak. Leaks typically happen where two dissimilar materials meet, such as an acrylic or polycarbonate bubble and an aluminum frame. The typical solution employed is to create a seal with a bonding agent to repel water and air. But the problem is, plastic and metal expand and contract at much different rates when subjected to cold and heat. The resulting relative motion can all too-easily shear off the bonding agent. Once the bonding agent fails the skylight leaks. This happens only after being exposed to extreme cold or extreme heat, perhaps after one extreme weather event or perhaps ten.

Solution: The design of seals need to take the thermal expansion and contraction of materials into careful consideration. This can be mathematically predicted accurately and the seal design established to permit sufficient motion without exceeding the capability of the bonding agent to flex. The best day lighting solutions are then tested from freezer to oven (-40F to 150F), guaranteeing them suitable for use in both the coldest winter and hottest summer conditions.

2. Problem: Skylights Darken Over Time

When you see a yellow or brown skylight that no longer lets in much light, the culprit is inappropriately selected material in terms of ultraviolet light stability. UV rays cause sun damage not just to people, but also to things. For example, UV light exposure discolors furniture, carpet, merchandise, walls and fabric.

Solution: The outer dome material should utilize a UV light protection package that will enable the material to serve 30+ years in full sun with only minimal yellowing. This serves a triple purpose: it keeps the outer dome clear, it protects the inner components of the daylighting system, and it also protects the fabric, carpet, and other material inside the commercial building.

3. Problem: Skylights Create Hotspots

Any traditional clear skylight projects a sharp, rectangular beam of light that travels across the floor below as the sun changes position in the sky. Most people find it too hot and too bright in this beam, and yet cold and too dark outside the beam. These hotspots produce too much contrast, which is very hard on the eyes.

Solution: Our design uses a dual diffuser on the bottom of the unit to diffuse the incoming light, distributing it evenly throughout the building interior. When light is directed in all directions, including the opposite direction of whence it came, it eliminates the hotspot effect. People in the building can comfortably benefit from the light – whether directly beneath it, or simply in the same room. When an array of such diffuse light sources exists in a building, there are no drastic contrasts and no stark shadows, producing a pleasing environment that is easy on the eyes.

4. Problem: Many Skylights Don’t Generate Enough Light

Prismatic skylights for example typically employ a prismatic diffuser as the outside bubble, and sometimes even employ dual prismatic diffusers facing the sky. For these units, most of the available sunlight is redirected to outer space, to the roof curb, and to the building structural elements such as purlins or trusses. This means that only a small percentage of the available incoming light is brought down to the floor of the building where the people are.

This fundamental deficiency is especially bad at low sun angles such as sunrise, sunset, in cloudy conditions, and in winter in northern climates. In order to help make up for poor optical efficiency, these units are usually made very big (often 5×6 foot or larger). But bigger means more thermal losses and other problems too complex to tackle in this brief article.

Certain skylights models on the market use tracking mirrors with electrically powered moving parts. While these achieve good light redirection efficiency under sunny conditions, their tracking does not help under cloudy conditions where the available sunlight is diffuse. Furthermore, in order to avoid malfunction, it’s ideal to avoid moving parts in skylight designs.

Solution: The best optical design requires three steps in the correct sequence: 1) high light admission, 2) efficient redirection, and 3) uniform dispersion.Our daylighting system allows up to 92 percent of visible light to enter the outer dome from every direction, including very low angles. Parabolically curved mirrors then reflect that light downward onto the diffuser with only one or two bounces on average. Since the light only bounces once or twice before it is diffused, a very high percentage of the available sunlight reaches the diffuser. Finally, the diffuser is made of clear material embedded with tiny glass beads that scatter the light without much loss, illuminating the entire interior space at the utmost level. We therefore do not need a large 5×6 foot aperture to produce adequate usable light, and this has many other benefits.

5. Problem: Skylights Transfer Heat and Produce Condensation

Typical skylights have two panes joined at the edge. The dual pane system provides a local R-value of approximately 1.5 in the middle, lowering to about 1.0 where the two panes touch. The aluminum frame is of course highly thermally conductive and so they use a “thermal break” made of plastic or rubber about 1/16th of an inch thick. This isn’t much of a thermal break , despite the name. This frame system lowers the overall R-value of the entire system to about 1.2 (U-value of 0.83). This poor R-value results in very cold surfaces on which condensation forms inside the building in normal winter conditions in northern climates. Many leading skylight manufacturers have therefore included drip channels and drainage systems in their frame design to try to channel this water away, rather than solving the problem at the root cause and preventing condensation in the first place.

Solution: We’ve designed a daylight with four panes to create a superior thermal insulator: an outer dome, an inner dome, and two diffusers. The integrated curb and frame is constructed of stainless steel (much stronger and lower thermal conductivity than aluminum) and is insulated with thick polyurethane foam from one to two inches thick at all locations. Now that is a real thermal break.

Our skylight domes have an overall R-Value of 4 and a U-Value of 0.25. With this quad-pane system and a well-insulated curb and frame system, the interior surfaces of the unit stay close to room temperature, preventing condensation from forming. The result is that there is almost no scenario in which condensation can form – at least not in typical North American nor European climates.

There are so many reasons commercial and industrial building owners should consider daylighting for their buildings: from lower electricity bills to more efficient staff, the benefits certainly outweigh the potential problems, when the retailer has high quality daylighting installed that avoid these common problems.

To prevent human error, owners should choose a manufacturer whose systems are laser cut, welded, riveted, and assembled in the factory — never in the field where mistakes can more easily be made. To get the full spectrum of daylighting benefits without the headaches, choose daylights designed to harvest the most light possible from every angle and level of sunshine, without discoloring, leaking, drawing condensation or transferring heat for a guaranteed 30 years.

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11 Mount Vernon Avenue
Mount Vernon, OH 43050
sales@replex.com 
1-800-886-8847 (U.S.A Only)
1-740-397-5535

 

 

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