Building Science

Ventilating a Home in Cold Weather

Posted on January 10, 2018 by Allison A. Bailes III, PhD

When I woke up Saturday morning, the temperature outdoors was -40 degrees. The wind chill was -100 degrees! It was just unbelievably, impossibly, inhumanly cold outside. Fortunately, that was on a mountaintop in New Hampshire and not where I was. I happened to have woken up on a mountaintop in North Carolina, where the temperature was a much warmer -3°F.

Night Surveys: The Lights Are On, But Nobody is Home

Posted on December 21, 2017 by Peter Yost

Julie Paquette has been Director of Energy Management at Yale University for about 6 years. That means the buck stops at Julie’s desk for the energy consumption of over 400 buildings on campus. Yale has a pretty sophisticated approach to energy, including the Yale Facilities Energy Explorer, an energy dashboard system that shows energy consumption and details for every one of those 400 Yale buildings.

The Buy-in Problem

Posted on December 20, 2017 by Allison A. Bailes III, PhD

Last week I read a nice little article by Steve Baczek about getting buy-in from the various stakeholders involved with building a home. He's an architect who works closely with the people who build the homes he designs. He's also a former U.S. Marine who understands the importance of what he calls "a ladder of leadership and responsibility."

Exterior Insulation on 2x4 Walls Versus 2x6 Walls With Cavity Insulation Only

Posted on December 13, 2017 by Allison A. Bailes III, PhD

UPDATED on December 18, 2017 with a corrected energy savings table.

If you live in the world of 2x4 walls, as I do, you may have wondered about the savings you'd get by going to a more robust wall assembly. The typical house in southern climes has 2x4 walls with R-13 insulation in the cavities. The two ways to beef that up would be to add continuous exterior insulation or to go to a thicker wall. But which saves more energy? And how do they compare to the plain old 2x4 wall?

How Does a Heat Pump Get Heat From Cold Air?

Posted on December 6, 2017 by Allison A. Bailes III, PhD

Cold weather is coming back to Atlanta this week, so let’s talk about heat. An increasingly popular way to heat buildings these days is with heat pumps, even in cold climates. But how do they work?

Extending the Reach of a Moisture Meter

Posted on November 30, 2017 by Peter Yost

Typical pins on moisture meters are ½ inch long, meaning you can only determine moisture content by weight near the surface of building assemblies and materials (including wood, gypsum wallboard, and concrete). But I often find myself needing to assess moisture content of first condensing surfaces in walls and ceilings or well below the surface of basement slabs.

This article looks at ways to extend the reach of a moisture meter. (For introductory information on moisture meters, see Tools of the Trade: Moisture Meters.)

Two Rules for Humidity

Posted on November 29, 2017 by Allison A. Bailes III, PhD

Because I've written so much about moisture in buildings, I get a lot of questions on the topic. Some are about walls. Some are about the attic. Some are about windows. Some are about the crawl space (which generates the most questions on this topic).

The key to answering a lot of those questions boils down to an understanding of how water vapor interacts with materials. Once you know that, it's easy to see the two rules for preventing damage from humidity.

The Four Laws of Thermodynamics

Posted on November 15, 2017 by Allison A. Bailes III, PhD

Building science is an odd subject. Few colleges and universities teach it. The majority of those who work on buildings call themselves engineers, architects, and contractors, not building scientists. And many of those who do invoke the term can explain at least one implication of the second law of thermodynamics (we'll get to that below) but may not know what the other laws of thermodynamics are, why their numbering is so peculiar, or even how many there are. Do you?

How Many Tons of Air Does a 2.5 Ton Air Conditioner Move?

Posted on November 8, 2017 by Allison A. Bailes III, PhD

We live in this invisible stuff called air. (But of course you knew that.) We pump it into and out of our lungs. We exhaust it from our bathrooms and kitchens. We cycle it through our heating and air conditioning systems. If we're lucky, we live in a home that even brings outdoor air inside as part of a whole-house ventilation system. But we're missing something.

Water Tables and Basements

Posted on October 26, 2017 by Peter Yost

When we bought our home (built in 1907), I called in a favor from an electrician friend of mine to upgrade the 60-amp to a 100-amp service. Having worked together in New Hampshire where many of our projects were on sites full of ledge, he smirked when he told me: “Here, you go try and drive this 12-foot copper grounding rod.”

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