Building Science

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."

Is Cold Sheathing in Double-Wall Construction at Risk?

Posted on April 22, 2015 by Allison A. Bailes III, PhD, GBA Advisor

Insulation is good. More insulation is better (although at some point, more may not be cost-effective). It reduces the amount of heat a home loses in winter or gains in summer.

An Interview with Building Science Pioneer Terry Brennan

Posted on April 15, 2015 by Allison A. Bailes III, PhD, GBA Advisor

Last week I got a chance to sit down and talk with Terry Brennan in Dallas at the Air Barrier Association of America’s annual conference. He may not be as famous as Joe Lstiburek, but he’s every bit the building science pioneer. Armed with a physics degree, the ASHRAEAmerican Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). International organization dedicated to the advancement of heating, ventilation, air conditioning, and refrigeration through research, standards writing, publishing, and continuing education. Membership is open to anyone in the HVAC&R field; the organization has about 50,000 members. Handbook of Fundamentals, and a desire to reduce the environmental impact of buildings, he built houses and wrote energy modeling computer programs back in the 1970s and ‘80s.

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