Wet bulb temperature tells you how easy it is for water to evaporate. Sounds simple enough, right? Today I'll give you a couple of examples to see how well you really understand that simple statement. First, early last month my…
Energy codes have all kinds of requirements. You have to have certain R-values in walls, floors, and ceilings. Your windows have to have the right U-values and solar heat gain coefficients. The infiltration rate and duct leakage have to be…
Who among us doesn't love spending time in crawl spaces and attics? I've certainly done my time there. A lot of my friends hang out there, too. I found out in an email from the Building Performance Institute (BPI), however,…
As long as we're exploring the wonderful world of water, we ought to show some of the cool stuff it does. In my article Introduction to the Physics of Water in Porous Materials, I described hydrophilic, hydrophobic, and hygroscopic materials.…
This time of year, air conditioners are running like mad to keep people cool in their homes. Here in Atlanta, we've had a couple of weeks of hot, muggy weather, with a little break on Sunday. Now we're heading back…
Yesterday I had lunch with Robert Bean and Eric Griffin at the ASHRAE conference here in Atlanta. As we talked about how we got into the field of building science, I began thinking of the reasons I love doing what…
Psychrometrics, you may recall, is the science that involves the properties of moist air and the processes in which the temperature or the water vapor content or both are changed. To understand how all that works, we need quantities and…
Your air conditioner does two jobs: It cools down the air and it dehumidifies the air. If you live in a dry climate, you want the AC to dehumidify as little as possible because it uses extra energy and makes…
I have a confession to make: I've fallen in love with psychrometrics! After water itself, moist air has got to be the most interesting substance in building science. And the psychrometric chart, in all its many manifestations and with its…
The Nest Learning Thermostat has been on the market for nearly four years now. One of the biggest things the Nest folks use as a selling point is energy savings. "Programs itself. Then pays for itself." That's the first thing…