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With Radiant Floor Heating Systems, Thermal Mass is not the Answer

Posted by Terry Alsberg, Guest Columnist

Jan 9, 2017 9:22:55 AM

High mass radiant is an outdated technology. The secret to performance, comfort and energy savings is low mass, high conductivity.

For decades, the term "thermal mass" has been used when describing radiant floor heating systems. Used in this context, it refers to the ability of a high mass radiant floor assembly to store heat.

This concept went mainstream in the 1960s and 70s when "passive solar homes" were growing in popularity. A dark colored, high mass slab made of Portland cement (or gypsum concrete), would sit under south-facing windows and soak up the heat from the sun all day long. When the sun went down, the slab would emit its stored heat to the habitable space for the next several hours.

While this method worked in some locations in the house, it was not an adequate heating method for an entire home. So tubing was installed and covered with concrete in other parts of the home. These homes were therefore a combination of radiant floor heating and passive solar. Because this combined system was common during this era, the term "thermal mass" and "radiant heat" are often thought to be synonymous, when in fact, they are not.

However, this same thermal mass which is so essential to a passive solar home is also the cause of the most common complaint with  radiant heat – it's slow. In every home, the heat load changes – up or down – can change quickly making it impossible for high mass systems to respond. It is common for these homes to be too cold in the morning and too hot in the afternoon (overshoot and undershoot). If the house has been unoccupied for a stretch of time, homeowners may have to wait over 24 hours for the system to adequately heat the home.

While the history of passive solar with radiant heat is interesting, given a blank sheet of paper, no one would design a heat system that acted primarily as a storage device. Any heating system, whether forced are or radiant floor heating, has the sole purpose of transferring heat into a specific space. Homes lose heat because heat flows from the warm interior to the cold exterior. A low mass radiant heating system with more conductivity allows heat to be produced at the same rate at which it is leaving the house, allowing the interior to maintain a constant level of comfort.

Conductivity, as we know, is the property of a material that allows heat to flow through it. Concrete is inherently a mediocre conductor, making it a poor choice for conducting heat. But aluminum is 240x more conductive than concrete. Because the amount of heat that must be supplied by a radiant panel is constantly changing due to weather changes, occupancy or just personal preference, the ideal heating system is able to quickly or decrease output in order to maintain optimum comfort.

With a high-mass system, the conditioned space is inconsistent and slow to respond to the needs of the occupant. On the other hand, highly-conductive, low mass radiant floor systems provide greater comfort through fast response.

Remember – Conductivity, not mass, is king.

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Live from CES 2017: An Ocean of Innovation

Posted by Sara Gutterman

Jan 5, 2017 9:50:59 AM

This week, I’m reporting live from the Consumer Electronics Show (CES) in Las Vegas, where today’s smartest, zaniest, and most innovative minds have converged to showcase ingenious technologies.

If you’ve never been to CES, allow me to paint a picture for you—imagine Disneyland for tech geeks filled with endless gidgets and gadgets that do almost anything you can think of, drones filling the skies, robots roaming the hallways that would make even Rosie from the Jetsons jealous, connected electric vehicles that run on solar power, Artificial Intelligence powered products that make your home smarter than you are, wearables that track your every biorhythm, and TVs, oh those illustrious high –def TVs, everywhere (literally, everywhere!) in a wall-to-wall jam-packed, high-energy sea of human invention. 

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Green Roofs, Green Buildings

Posted by Matt Lee, Guest Columnist

Jan 3, 2017 12:08:17 PM

Vegetative roof systems are one of the most sustainable options available in commercial roofing today.

Vegetative or green roof systems are being seen on commercial buildings around the world. This innovative system uses actual, living plants, which grow above a waterproofing membrane on top of a commercial building where a roof would normally be found. In addition to being beautiful and to increasing the aesthetics of the building itself, vegetative roof system have a number of benefits, all of which add up to one, very attractive roofing option.

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Study: Total Energy Created by Solar Panels Has More Than Compensated for CO2 from Fossil Fuel Used in Their Manufacture

Posted by Matt Power, Editor-In-Chief

Jan 3, 2017 11:11:07 AM

One of the few criticisms of photovoltaic panels has been put to rest by a new study that looks at total energy output from solar 1975-2014, compared with the oil used to make them.

Here's an excerpt:

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States That Ignore Energy Codes Could Be Making A Fatal Mistake

Posted by Matt Power, Editor-In-Chief

Jan 2, 2017 1:27:41 PM

Wild variations in the jet stream are pushing colder air south, where homes are poorly insulated, and scientists say this may be the tip of the iceberg.

ONE OF THE GREAT PLEASURES of living in places such as North Carolina and Northern Florida is the temperate climate. I've lived in both places, each time in a cinder-block ranch with no insulation, aluminum window frames and central air conditioning and baseboard electric radiators. The Florida home even had jalousied windows, little more than a translucent shutter system. But that was 20 years ago. And things are changing in a way that none of us could have anticipated. It's possible that much of the United States could be facing a "big chill."

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Green Builder’s Top Ten Blogs of 2016

Posted by Matt Power, Editor-In-Chief

Jan 2, 2017 10:44:50 AM

From big picture politics to front-yard curb appeal, our readers left behind an intriguing record of their interests and concerns, but somehow they all fit together.

1. Hillary Clinton's Unforgiveable Sin: Fracking the World

Our story on Hilary Clinton’s efforts to strong-arm fracking operations into many parts of the world during her tenure as Secretary of State apparently hit a nerve with readers. Of course, timing is everything, and this story had almost a whole year of non-stop campaigning to help it build up steam. While we certainly didn’t endorse Trump’s candidacy, we made it clear that choosing the democratic candidate would not ensure any sort of progressive action on Climate Change. READ THE BLOG

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3BL Media Puts a New Spin on Corporate Greenwashing and Censorship

Posted by Matt Power, Editor-In-Chief

Jan 2, 2017 8:00:00 AM

A paid distributor of "news," 3BL Media now runs cover for some of the worst environmental offenders, including Nestle and Monsanto.

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White House Report Uncovers Resiliency Risks and Opportunities

Posted by Sara Gutterman

Dec 28, 2016 8:29:54 AM

Last week, the White House released a report that reveals threats posed by a changing climate and opportunities to make our homes and buildings safer and more resilient.

Resiliency has become one of the most important and urgent issues of our time, given the daunting fact that we now spend more on disaster recovery from super storms, floods, and wildfires, than we do on education. 

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Building Codes: The Right Tool for Achieving our Climate Goals?

Posted by Sara Gutterman

Dec 22, 2016 9:18:01 AM

In a recent webinar, Building Codes Assistant Project (BCAP) President Maureen Guttman questioned whether building codes are effective when it comes to successfully reaching our energy efficiency and climate goals.

Building codes are a unique and complex animal, and their development is driven by a diverse spectrum of vested interests.  The recent 2018 code hearings exemplified how motley agendas could at least temporarily align to craft a middle-ground solution for a tough issue (namely, building envelope performance tradeoffs for onsite power production), setting an important precedent for cooperation, but certainly not realizing the gains that many sustainability professionals were hoping for.

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Video: Preparing for Climate Change in New England

Posted by Matt Power, Editor-In-Chief

Dec 19, 2016 9:24:50 PM

This lecture by climate scientist Dr. Cameron Wake reviews recent climate data, and offers both a prognosis and possible mitigation options for cities in New England facing sea level rise and other major impacts.

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Sustainability: Transcending Politics

Posted by Sara Gutterman

Dec 15, 2016 12:18:26 PM

In preparing for our upcoming Sustainability Symposium 2017: Ready for Anything, I’ve had the opportunity to speak with a wide spectrum of professionals in the sustainability, energy efficiency, renewable energy, smart tech, and green building sectors from both sides of the aisle. Their overriding message: progress will continue.

One of the most exciting aspects of planning a big event is the opportunity to speak ahead of time with presenters and participants about the issues that are top of mind.  In planning for the Sustainability Symposium 2017: Ready for Anything, taking place on January 9 at the Dr. Phillips Center for Performing Arts in Orlando, I’ve had the good fortune to speak with some of today’s visionary leaders and most passionate professionals in the sustainability sector.

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Orlando, A Sustainable Beacon

Posted by Jay Egg

Dec 13, 2016 2:47:11 PM

NO MATTER WHAT SIDE OF THE FENCE WE'RE ON WITH CLIMATE CHANGE, the definition of “Sustainable Development” speaks to our collective hearts:

“Sustainable Development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs”

What are the needs of the present and the future? When speaking of sustainable buildings, we need:

  • Buildings in which we can work, live and play
  • Buildings that are energy efficient with cost effective measures throughout
  • Buildings and systems that are long lasting
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Trends in Green Buildings from 2016

Posted by Megan Wild, Guest Columnist

Dec 13, 2016 2:39:56 PM

Here were a few of the popular trends in residential green homes this year.

Green building is booming, and this sector of the construction industry is outpacing traditional building and creating millions of jobs. As the average consumer’s awareness of climate change increases, buyers are actively seeking to make responsible purchases that will decrease their carbon footprints.

Home building is no exception to this trend, and every year there are more ways than ever before to green up your building. Whether you are looking to build a home from the ground up that incorporates the latest green technology or you’re considering retrofitting your existing home to make it a little more eco-friendly, here are the biggest green building trends to look out for from 2016.

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