With a seemingly endless number of articles on daylighting, it’s a little overwhelming to try and figure out where to start (especially when a lot of the contents seem to be in code – from U-value to SHGC, where do we begin?). Thankfully I happened to come across the Laboratories for the 21st Century: Best Practices article, which guides its reader through a basic understanding of this daylighting “code.”
While the guidelines for daylighting in laboratories are somewhat different than in offices and public spaces, the article takes a look at conditions for both. When it is well planned from the beginning stages of the design process, successful daylighting has the ability to save energy, improve productivity and reduce building energy costs. So, with the proper type of daylighting, well thought-out visible transmittance, a good u-value and properly calculated solar heat gain coefficient, it is possible for buildings to successfully reduce their energy consumption by large amounts. But what do all of these terms really mean? Here’s a brief breakdown:
Side Lighting: A common technique used for daylighting in which windows are situated below ceiling height; used both for views and daylighting
Top Lighting: Vertical windows situated above ceiling height; effective when side lighting or security is an issue
U-Value: U-values are a measure of the rate in which heat is transferred through the glazing of a window. This depends on the temperature change between the indoors and outdoors. The smaller the u-value, the better job a window will do of keeping out heat and cold.
Solar Heat Gain Coefficient (SHGC): The measure of solar energy that is transferred through windows as heat gain. A transfer value of 1.0 would mean that 100%of solar heat gain enters the building, while a transfer value of 0.0 would indicate that 0% enters.
Visible Transmittance (VT): the amount of visible light that is able to pass through the glass of a window. The higher the transmittance, the more suitable a window will be for daylighting (as it blocks out less lighting)
Low-Emittance: energy-efficient layers applied to windows or skylights to reduce the u-factor through absorption or reflection of solar radiation
So there you have it – a quick and easy breakdown of the language of dynamic shading. Besides the clarity that the article brings to the terms used in dynamic shading, it’s also a great read for pointing out some other basics for understanding solar shading. Did you know that the distance daylight travels into the interior of a building is approximately 1.5 – 2 times the distance from the floor to the top of the window (when we’re looking at side lighting)? EPA suggests that, when considering the design of a building, a daylighting consultant is absolutely necessary – particularly if the architect you’re working with isn’t familiar with designing using daylighting. A few questions to keep in mind when working on daylighting projects:
How can we integrate daylighting into an overall design to ensure that this project saves energy and dollars?
How can we ensure that light will be distributed normally?
What shading strategies will be compatible with the building’s appearance?
What shading strategies will be compatible with the building’s appearance? ; And
How will lights be controlled?
Keeping these questions in mind, remember also that it’s the integration of a daylighting system into the building’s design, interior, electric lighting and mechanical systems that leads to the greatest energy savings. So now that we have an understanding of the basics, hopefully the abundance of articles on dynamic shading will be a little less overwhelming!
This blog entry was written by Kaitlyn Morris.
Thank you to Kaitlyn Morris for her writing and contribution to this blog.