Sunday, April 5, 2009

Daylighting design and structural integration tip

Good daylighting design and daylight harvesting requires coordination with an unlikely discipline or two.  Above vision windows able to helpful for building occupants to look throught, often an upper band of windows are used to bounce daylight deeper into a space.  (note this requires often a taller floor to floor height and reflective ceiling surfaces to reflect light) To best utilize this daylight harvesting building element it's important to control the ceiling layout.  That way less electric lighting can be specified and overall building energy intensity can be lowered.  This also results in less cooling to treat the extra lighting heat output and mechanical systems can be down-sized. (But more on that later, integrated design can be spider-like in it's interconnectivity.)
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For daylight to be effective in a room it needs to penetrate as far into it as possible from the window face.  To help this daylight reflection / penetration along it's really important not to block the daylight with some kind of obstruction such as a structural beam or low-hanging duct in front of a window.  It may seem obvious but it's not.

Be careful to work with your structural engineer when planning for daylighting and pay attention to the direction structural framing such as beams and joists run.  Don't orient them to perpindicular to the window face where the daylight is coming from.  For the daylight to penetrate deep, orient structure parallel to the light and the same goes for HVAC duct work.  

Early on, it's crucial to talk with your lighting designer, mechancial engineer, structural engineer and acoustical consultants; practically anyone whom is interested in using the ceiling plane for services or equipment.  Establish an understanding early on for daylighting success and coordination and you will be sure to enjoy successuful results later rather than crushing disappointment or a loss of much needed LEED point and most importantly client satisfaction.

This integrated design necessity is an example early on a subject everyone on the design team can rally around and hold valuable through the life of the project.   Having more of these kinds of conversations earlier rather than later is a step along the high-performance building design path.

This image shows an example of structure, the ceiling plane. lighting, light guiding reflective blinds and other elements working together in a typical office space.  The lighting is on a low-level in a stepped lighting mode.  

Any feedback or other ideas?


Sunoptics said...

Daylighting through toplighting (skylights) is the most effective way to daylight a space. The light output through toplighting is 3 times per square foot more effective then daylighting with windows. Solutions exist that allow you to get 100% diffusion with high visible light transmission that eliminates UV damage, glare and heat into the space with the use of lighting control. Utilize high performance prismatic skylights with side lighting from windows and you will find an even distribution of light into the space that maximizes proper lighting levels without drop off and makes your daylighting design explode into the space. For ideas, visit or Good luck!

Stephen Frey | AIA, LEED AP said...

Thanks for the great comment on how to provide even more effective daylighting in combination with top lighting from skylights. You're absolutely right that in order to achieve a more even distribution of daylight. You will also bring needed views to the sky from hard to reach internal spaces.

Selecting the right glazing combination based on your energy goals and light transmission strategy is also important. Choosing clear glass provides more high-lights and sharper sun-light which can provide a distraction to work areas with bright hot spots of light. This can also be a good thing in more centrally located common areas or corridors where hot spots are fine.

This can be solved by using transluscent glazing instead of clear to deliver diffuse light. But I believe it cuts down on light transmittance some.

Also, selecting high performing glazing with Low-e / argon filled is important. Double glazed is good, triple glazed is best. Depending on the manufacturer and type of skylight there are choices here.