The ABCs of R-value

By the Green Team. 

If you’re a homeowner, you probably already know that the R-value of your house has an enormous impact on your energy use.  For those of you like me, who let the landlord worry about such things, R-value is the resistance that walls, ceilings, floors, etc. have to thermal energy transmission. That is, R-value is the degree to which a building is insulated against heat (or cold) loss; a bigger R-value indicates better insulation.  The new College of Law (CoL) building is designed with R-25 rated insulation in its walls and R-30 roof insulation. However, unless you’re in a building with no doors and windows, insulation’s only part of the energy conservation/temperature regulation story.

The Salt Lake City area is blessed with about 222 days of sunlight a year and the new CoL building is taking great advantage of all this natural light with large South- and West-facing walls of glass, a large atrium skylight, and many tall windows in individual offices.  While all this glass may help keep Seasonal Affective Disorder at bay and reduce energy consumption for daytime lighting, it could also create energy waste both in summer (by creating a solar furnace at the front of the building) and in winter (by letting out much of the precious output generated by the efficient new heating system).  You’ll be glad to know that our LEED-conscious architects planned a way to give us the best of both worlds.

The glass used in the building is low emissivity and high performance; it reduces both the transmission of thermal energy and glare, so we’ll be able to take advantage of stunning vistas without heating or cooling all outdoors.  In addition to the superglass, the building comes equipped with fixed sun shades on its South side to provide solar protection during the long days of summer.  In fact, the building itself acts as its own parasol in certain sections where aesthetically pleasing overhangs shade lower floors of the building.  Seems like the architects thought of everything, huh?  Well, there’s another large and free-willed variable in the building’s overall R-value equation: its human residents.


Office workers rejoice!  Many of the windows in the new CoL building are operable and will open to provide occupants fresh air on nice days.  Of course, open windows reduce a building’s overall R-value when the temperature outside is above or below standard office temps.  To account for this, clever designers put sensors on windows that send signals that shut down the HVAC in rooms with open windows!  The HVAC won’t reengage until the window is fully closed, but if room doors are ajar, the building’s main HVAC is going to crank up to counter the thermal draft.  At the end of the day, it’s going to be up to individuals to realize the potential R-value of any building, no matter how intelligently designed.