Building Science

Is Spraying Mist on Your Air Conditioner the Answer to High Bills?

Posted on July 1, 2015 by Allison A. Bailes III, PhD, GBA Advisor

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 to the mid-90s with high dew points again.

As a result, some people are starting to dread those air conditioning bills arriving and wondering what they can do to save energy. Is the Kickstarter-funded Mistbox the answer?

Four Ventilation Quotes That Will Take Your Breath Away

Posted on June 24, 2015 by Allison A. Bailes III, PhD, GBA Advisor

Looking back over my last several articles, I see that I’ve been going off the deep end. Psychrometrics, hygrothermalA term used to characterize the temperature (thermal) and moisture (hygro) conditions particularly with respect to climate, both indoors and out. analysis of double-stud walls, the physics of water in porous materials... That’s some heavy stuff. So this week I’m going light with some fun quotes about ventilation and indoor air quality.

Fundamentals of Psychrometrics, Part 3

Posted on June 17, 2015 by Allison A. Bailes III, PhD, GBA Advisor

In Part 1 and Part 2 of this series of articles, we’ve taken a look at what exactly psychrometrics is and defined the top nine psychrometric quantities. Now we’re going to delve into how we can combine those quantities and create the psychrometric chart.

As you might expect, taking nine variables and putting them into one chart puts a lot of information at your fingertips. It also can take a while to figure it all out. On top of all that, having nine different variables means you’ve got a lot of options for how to show them in a chart.

The Difficulty of Stopping Air Leakage Between the House and Garage

Posted on June 10, 2015 by Allison A. Bailes III, PhD, GBA Advisor

A home with an attached garage is usually a home in which people breathe more carbon monoxide (CO). Of course, having an open carport or detached garage is better for air quality (and a feature that usually gets points for you in green building programs like LEED for HomesLeadership in Energy and Environmental Design. LEED for Homes is the residential green building program from the United States Green Building Council (USGBC). While this program is primarily designed for and applicable to new home projects, major gut rehabs can qualify. and EarthCraft House), but what if you don't want to give up that attached garage?

Fundamentals of Psychrometrics, Part 2

Posted on June 3, 2015 by Allison A. Bailes III, PhD, GBA Advisor

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 we need them to be well defined. Some are easy to understand (e.g., dry bulb temperatureAir temperature as measured by an ordinary thermometer. and barometric pressure); others are a bit more abstract (e.g., enthalpy). Here we'll take a look at the main psychrometric quanitites, define them carefully, and tell which commonly used term you should avoid.

Fundamentals of Psychrometrics, Part 1

Posted on May 27, 2015 by Allison A. Bailes III, PhD, GBA Advisor

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 multitudinous quantities, is a thing of beauty. Well, at least it is to me, and maybe it will be to you, too, after you get to know it a bit better.

Does the Nest Thermostat Save Energy?

Posted on May 20, 2015 by Allison A. Bailes III, PhD, GBA Advisor

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 you see when you go to the Nest homepage. But what do the data say? Three independent studies plus a white paper from Nest provide some answers. (GBAGreenBuildingAdvisor.com first reported on these three studies in a February 2015 news story.)

Nest Thermostat Data Revealed for First Time

Posted on May 13, 2015 by Allison A. Bailes III, PhD, GBA Advisor

The Nest thermostat has been around since October 2011, quietly collecting data on how your home — and the homes of hundreds of thousands of your neighbors — operates. It gathers information about indoor temperature, relative humidity, air conditioner runtime, auxiliary heat operation for heat pumps, and much more. Unlike the Ecobee thermostat, however, Nest doesn't let its owners see all those data (which is a problem only for energy geeks really). Enter Michael Blasnik.

The Physics of Water in Porous Materials

Posted on May 6, 2015 by Allison A. Bailes III, PhD, GBA Advisor

I like to tell people I'm a recovering academic. The truth is, though, that I haven't left physics behind. That would be impossible since I've been making a career in the world of building science. So today I'm going to delve into that subset of building science called building physics as we take a look at the physics of water in porous materials. You'll also learn about the fourth state of water, the one that's not liquid, not solid, and not vapor.

Lstiburek’s Ideal Double-Stud Wall Design

Posted on April 29, 2015 by Allison A. Bailes III, PhD, GBA Advisor

Joe Lstiburek called me last week to set the record straight. I had written an article about a study of moisture in double-stud walls in a Massachusetts home, and his company, Building Science Corporation (BSC), had done the research as part of the Building America program. They found elevated moisture content in the cold, exterior sheathing, and Joe wanted to make sure everyone knew, "I would never build that wall because I consider it too risky."

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