Article: With energy Conservation in mind…
By Bill Hodge
The building envelope has the largest impact on energy use—more impact than HVAC efficiency, more than site orientation, and even more than the building’s geometry. Here, I’ll focus on the windows, walls, and roof.
ASHRAE 90.1 is the most widely used design resource for architects who want to comply with the Energy Codes in your respective regions. The 90.1 manual is exhaustive, but once you get a feel for it how it works, it becomes pretty straightforward.
I highly recommend you use ComCheck, a web-based program with extensive information on local and state building energy codes. ComCheck is a free program (yes, absolutely free) that allows you to vary the building envelope components to compare your proposed building envelope against the code reference you choose. Find ComCheck at https://energycode.pnl.gov/COMcheckWeb/index.html.
As an example, you may choose to compare your building against the 2007 version of 90.1, or the 2009 version, or the 2013 version, or the latest 2016 version. You may also choose different versions of the International Energy Conservation Code (IECC.) ComCheck even has some other state codes such as Florida, Oregon, Vermont, etc. An appealing feature of this program is the instant feedback you get as you input your building envelope components.
Once you’ve entered which code you want to compare your building against, start modeling your building using the Envelope tab, then add walls, roofs, windows, doors, etc. No need to worry about the other tabs, such as Interior Lighting, Exterior Lighting, and Mechanical requirements, because your favorite MEPF consultant (for example, HP Engineering) will complete those sections for you when you send your file. As you add walls, doors, windows, and roofing, you’ll get feedback on how you’re doing against the code you’ve chosen; it will tell indicate not only if you “pass” or “fail” but also by what percentage you passed or failed.
The beauty is that you can mix and match the U-values of the different components to get an “overall” score for the building envelope. For example, you can use better roof insulation if you want to use a more economical glass. You can upgrade the wall insulation and use more cost-effective roof insulation. You can use premium glass windows in conjunction with basic doors. If at first you don’t succeed, keep playing with different wall insulation values, roof insulation, and window factors until you pass or exceed the code minimums for the overall building envelope. You could find that you can beef up the roof insulation or use wood stud walls so that you may not need continuous rigid insulation on the walls in addition to the typical wall cavity insulation. What?!? You’re welcome!
For more complicated buildings, where you want to trade off the HVAC efficiency or lighting for building envelope components, you’ll have to perform a full-blown computer energy simulation. (By the way, I can recommend a good engineering firm to do that for you.)
If you would like to schedule an AIA approved lunch-and-learn on how to use 90.1 properly, please contact me. HP Engineering has a presentation that is accredited for one Health, Safety and Welfare (HSW) credit. Or feel free to call your local HP Engineering office or the central office at 479-899-6370.