The most recent blogs at Green Building Advisor

Choosing a Base Temperature for Degree Days

Posted on December 17, 2014 by Allison A. Bailes III, PhD, GBA Advisor in Building Science

Degree days are a combination of time and temperature. We looked at their uses and where they come from in Part 1 of this series, and now it's time to go a little deeper.

The temperature enters as a temperature difference, ΔT (delta T), but it's not the ΔT between inside and outside of the building. It's the difference between the outdoor temperature and the base temperature. But what is this thing called base temperature?

Tilt/Turn Windows Are Fabulous

Posted on December 15, 2014 by Alexi Arango in Guest Blogs

As they set out to build a single-family PassivhausA residential building construction standard requiring very low levels of air leakage, very high levels of insulation, and windows with a very low U-factor. Developed in the early 1990s by Bo Adamson and Wolfgang Feist, the standard is now promoted by the Passivhaus Institut in Darmstadt, Germany. To meet the standard, a home must have an infiltration rate no greater than 0.60 AC/H @ 50 pascals, a maximum annual heating energy use of 15 kWh per square meter (4,755 Btu per square foot), a maximum annual cooling energy use of 15 kWh per square meter (1.39 kWh per square foot), and maximum source energy use for all purposes of 120 kWh per square meter (11.1 kWh per square foot). The standard recommends, but does not require, a maximum design heating load of 10 W per square meter and windows with a maximum U-factor of 0.14. The Passivhaus standard was developed for buildings in central and northern Europe; efforts are underway to clarify the best techniques to achieve the standard for buildings in hot climates. on Potwine Lane in Amherst, Massachusetts, Alexi Arango and LeeAnn Kim asked themselves, “Is it possible to live without burning fossil fuels?” One measure of success would be meeting their goal of net-zero energyProducing as much energy on an annual basis as one consumes on site, usually with renewable energy sources such as photovoltaics or small-scale wind turbines. performance. This is the tenth blog in a series.

Is OSB Airtight?

Posted on December 12, 2014 by Martin Holladay, GBA Advisor in Musings of an Energy Nerd

UPDATED on December 16, 2014

Most builders assume — and GBAGreenBuildingAdvisor.com has long reported — that oriented strand board (OSB) is a good air barrierBuilding assembly components that work as a system to restrict air flow through the building envelope. Air barriers may or may not act as a vapor barrier. The air barrier can be on the exterior, the interior of the assembly, or both.. If a builder uses a high quality tape like Siga Wigluv, Zip System tape, or 3M All Weather flashing tape to seal sheathingMaterial, usually plywood or oriented strand board (OSB), but sometimes wooden boards, installed on the exterior of wall studs, rafters, or roof trusses; siding or roofing installed on the sheathing—sometimes over strapping to create a rainscreen. seams, OSB wall and roof sheathing can act as a building’s primary air barrier.

A Tinkerer’s Quest for Green Perfection

Posted on December 11, 2014 by Scott Gibson in Green Building Blog

It was Eric Brattstrom's interest in a far-fetched scheme to heat his chicken coop with compost that eventually landed him in the Home & Garden section of the The New York Times, but the story turns out to be a lot more interesting than how to keep chickens warm in winter.

Energy Efficiency Is Narrowing the Stupid/Hurt Gap

Posted on December 10, 2014 by Allison A. Bailes III, PhD, GBA Advisor in Building Science

The gap is narrowing. What gap, you ask? Why, the gap between stupid and hurt, of course. So says Dr. Joe Lstiburek. Allow me to explain.

Sometimes when you do something stupid, it hurts immediately. A toddler touches a hot kettle, for example, and instantly starts crying in pain. That's a learning experience.

If that pain didn't happen until an hour or a day had passed, however, the child would have a tough time learning not to touch hot kettles. Building or remodeling homes is a lot like that.

Second Guessing an Insulation Upgrade

Posted on December 8, 2014 by Scott Gibson in Q&A Spotlight

Is there anything worse than getting midway through a renovation and then suddenly wondering whether you've got some important detail all wrong?

That seems to be the predicament of William Lucrisia, who's in the midst of an insulation upgrade at his house north of Seattle.

"The house was heated by propane," he explains in a Q&A post at Green Building Advisor. It was a cost that was hard to get hold of, especially with some of the design [features] of the house (high ceiling)."

How to Use the Psychrometric Chart

Posted on December 5, 2014 by Martin Holladay, GBA Advisor in Musings of an Energy Nerd

When you drive a borrowed car, it takes a few moments to figure out how to operate the windshield wipers and the headlights. But in your own car, your hand reaches for these switches without thinking.

Using the psychrometric chart is a little like driving a car. If you use the psychrometric chart every day, you don’t have to orient yourself. But if you are like me, and you only consult the psychrometric chart two or three times a year, it’s useful to refer to a cheat sheet every time you use it.

The Importance of Defining the Building Enclosure

Posted on December 3, 2014 by Allison A. Bailes III, PhD, GBA Advisor in Building Science

The photo at right shows a common problem in new homes. It's also one that can make it difficult to pass the blower door test required by many building codes these days. If I tell you that the wall pictured here separates two rooms in a basement and one of them is not conditioned, can you see the problem? If so, how many mistakes do you see here?

Drainwater Heat Recovery Comes of Age

Posted on December 2, 2014 by Marc Rosenbaum in Guest Blogs

The EcoDrain is a wastewater heat recovery device that replaces a section of horizontal drain pipe. The devices enables heat from water flowing down the drain to be transferred to cold water flowing toward a shower valve.

A New Green Building Ordinance in Decatur, Georgia

Posted on December 1, 2014 by Carl Seville, GBA Advisor in Green Building Curmudgeon

The city I live in, Decatur, Georgia — a great, if possibly overly gentrified, place to live — recently passed a unified development ordinance (UDO) requiring green building certification for all new buildings and most renovations — both residential and commercial.

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