The most recent blogs at Green Building Advisor

Cold Floors and Warm Ceilings

Posted on November 25, 2016 by Martin Holladay, GBA Advisor in Musings of an Energy Nerd

During the winter, the air near your floor is cold, while the air near your ceiling is hot. Similarly, during the summer, the air conditioner keeps your first floor comfortable, while the rooms on the second floor are unbearably hot. What’s going on?

The usual answer is, “Heat rises.” But that explanation isn’t quite accurate. (It’s true that hot air rises by convection. But heat travels in all directions, including sideways and downward, by conductionMovement of heat through a material as kinetic energy is transferred from molecule to molecule; the handle of an iron skillet on the stove gets hot due to heat conduction. R-value is a measure of resistance to conductive heat flow. and radiation.)

Break It or Lose It

Posted on November 24, 2016 by Andrea Love in Guest Blogs

Over the past 20 years, the building industry has experienced renewed interest in reducing the energy demand of buildings. At the building code level, groups such as the American Society of Heating, Refrigerating and Air-Conditioning Engineers (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. ) have been steadily raising the bar on performance criteria for building envelopes and systems. Designers have been challenged to find and implement technologies and solutions that can practically and economically affect the energy demands of our buildings.

Revisiting the Debate Over Global Warming and Insulation

Posted on November 23, 2016 by Allison A. Bailes III, PhD, GBA Advisor in Building Science

At the North American Passive HouseA 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. Conference in Philadelphia in September, I gave a presentation on the global warming impact of insulation, an issue I've discussed a few times since Alex Wilson wrote his paper on the topic back in 2010. In my presentation, I covered two different aspects of the issue: (i) the problem with Wilson's payback calculations and (ii) using David White's global warming impact calculator to make more informed decisions.

Operating at Net-Zero Energy

Posted on November 22, 2016 by Paul Eldrenkamp and Rachel White in Guest Blogs

A few months ago we completed a deep energy retrofit of a house that we hope will be 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. — in other words, that we hope will produce as much energy as it consumes on an annual basis. If we succeed, this will be our first net-zero project.

There are two key strategies for designing a net-zero-ready home: you minimize the amount of energy the house needs to operate; and you maximize the amount of energy that the house can produce onsite, usually with a photovoltaic(PV) Generation of electricity directly from sunlight. A photovoltaic cell has no moving parts; electrons are energized by sunlight and result in current flow. system (PVPhotovoltaics. Generation of electricity directly from sunlight. A photovoltaic (PV) cell has no moving parts; electrons are energized by sunlight and result in current flow.). In short, you create an energy budget that balances consumption with production.

Designing a Combined Hot Water System

Posted on November 21, 2016 by Scott Gibson in Q&A Spotlight

Vladimir Polyakov's two-story colonial is undergoing a down-to-the-studs rehab, with insulation upgrades and a new heating system on the way.

Drywall Finishing Tips for Owner-Builders

Posted on November 18, 2016 by Martin Holladay, GBA Advisor in Musings of an Energy Nerd

Plenty of owner-builders are happy to hang drywall. When it comes to taping and finishing, however, most feel less confident. Some just shrug their shoulders and announce, “I’m going to hire a contractor to do the drywall.”

Spreading drywall mud is like frosting a cake. You need to have the right touch, and the right touch takes experience. The first time you frost a cake, you’re going to damage the surface of the cake and get cake crumbs mixed with the frosting. You need to take a deep breath, slow down, and adjust the pressure on your knife.

SEE STACK is a Cool Stack-Effect Tool

Posted on November 17, 2016 by Peter Yost in Building Science

In 2003, as part of their presentation (“Ventilation Myths and Misconceptions”) at the Affordable Comfort conference, Collin Olson and Paul Francisco debuted a software tool they developed called SEE STACK. (If you want to experiment with the software, click here to download the executable file and training manual).

Do Humidifiers Create IAQ Problems?

Posted on November 16, 2016 by Allison A. Bailes III, PhD, GBA Advisor in Building Science

It's that time of year when heating systems start coming out of their summer hibernation. (Except maybe in Vermont. Michael Blasnik's Nest data showed that Vermonters are about the last to start heating their homes in the fall.) Then everyone starts looking for their lotion and lip balm. Gaps appear in hardwood flooring as it dries out. Buildings begin to creak and pop. And then the humidifiers come out.

Yes, humidifiers can help with low indoor humidity. But what effect might they have on indoor air quality?

On College Campuses, Signs of Progress on Renewable Energy

Posted on November 15, 2016 by Anonymous in Guest Blogs

By BEN GOLDFARB

The soul of Arizona State University is Memorial Union, a hulking brick-and-glass community center that opens onto a sprawling pedestrian mall. Although the building sits at the heart of campus, its outdoor plaza was once virtually uninhabitable for four months each year, when summer temperatures in scorching Tempe often hover over 100 degrees.

So in 2014, the university — Arizona’s leading energy consumer — completed construction on a PowerParasol, a 25-foot-tall shade canopy composed of 1,380 photovoltaic(PV) Generation of electricity directly from sunlight. A photovoltaic cell has no moving parts; electrons are energized by sunlight and result in current flow. panels capable of producing 397 kilowatts of electricity.

Getting Into the Details

Posted on November 14, 2016 by Carl Seville, GBA Advisor in Green Building Curmudgeon

Carl Seville and his wife are building themselves a new home in Decatur, Georgia. The first blog in this series was titled The Third Time’s the Charm. Links to all of the blogs in this series can be found in the “Related Articles” sidebar below.

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