The most recent blogs at Green Building Advisor

Blue Heron EcoHaus: Placing the Concrete Floors

Posted on May 30, 2016 by Kent Earle in Guest Blogs

Editor's note: Kent Earle and his wife, Darcie, write a blog called Blue Heron EcoHaus, documenting their journey “from urbanites to ruralites” and the construction of a superinsulated house on the Canadian prairies. Their previous blog on GBAGreenBuildingAdvisor.com was called Adding Walls and Roof. The blog below was originally published in July 2015. (A complete list of Kent Earle's GBA blogs is provided in the “Related articles” sidebar below.)

How Much Insulation is Too Much?

Posted on May 27, 2016 by Martin Holladay, GBA Advisor in Musings of an Energy Nerd

In a presentation at this year’s BuildingEnergy 16 conference in Boston, three energy experts joined forces to tackle a common question: “How much insulation is enough and how much is too much?”

The presentation had an opaque title and subtitle: “How We Sleep at Night: Energy Metrics and Decision Making in Residential Design.” Although presenters' intended meaning may have been obscure, they were trying to answer two questions: At what point are envelope improvements a waste of money? And what metrics or rules of thumb should we use to determine when enough is enough?

Getting More Energy from the Sun

Posted on May 26, 2016 by Tara Dhakal in Guest Blogs

Global demand for energy is increasing by the hour as developing countries move toward industrialization. Experts estimate that by the year 2050, worldwide demand for electricity may reach 30 terawatts (TW). For perspective, one terawatt is roughly equal to the power of 1.3 billion horses.

Energy from the sun is limitless – the sun provides us 120,000 TW of power at any given instant – and it is free. But today solar energy provides only about 1% of the world’s electricity. The critical challenge is making it less expensive to convert photo-energy into usable electrical energy.

Transforming the Electric System

Posted on May 25, 2016 by Beia Spiller and Kristina Mohlin in Guest Blogs

Electricity markets around the world are transforming from a model where electricity flows one way (from electricity-generating power plants to the customer) to one where customers actively participate as providers of electric services. But to speed this transformation and maximize its environmental and cost benefits, we need to understand how customer actions affect the three distinct parts of our electric system: generation, transmission, and distribution.

Sizing a Modulating Condensing Boiler

Posted on May 24, 2016 by Dana Dorsett in Guest Blogs

For the past few decades, an increasingly popular space heating option is a system with a modulating condensing (mod-con) boiler. Because these boilers can potentially have a high efficiency (90-95% or higher), they are often promoted by state and utility subsidy programs.

In a well-designed system, the boiler’s efficiency can hit or even exceed its nameplate AFUEAnnual Fuel Utilization Efficiency. Widely-used measure of the fuel efficiency of a heating system that accounts for start-up, cool-down, and other operating losses that occur during real-life operation. AFUE is always lower than combustion efficiency. Furnaces sold in the United States must have a minimum AFUE of 78%. High ratings indicate more efficient equipment. . But as installed, most fall well short of their AFUE test numbers and often suffer an abbreviated lifespan. Efficiency problems and lifespan-crippling sizing errors could be avoided with a modest amount of analysis.

Installing a Concrete Slab the Right Way

Posted on May 23, 2016 by Scott Gibson in Q&A Spotlight

As part of a remodel of his San Francisco area home, Torsten Budesheim is converting the 700-square-foot lower level into living space. An existing slab has been removed, and Budesheim has removed a few inches of material to increase the finished ceiling height. Now, he's nearly read to place a new 5-inch-thick slab that will include tubing for radiant heat.

How to Order Windows

Posted on May 20, 2016 by Martin Holladay, GBA Advisor in Musings of an Energy Nerd

Anyone who needs to choose windows for a new home has a lot of decisions to make. In this article, I’ll try to provide an overview of some of the factors to keep in mind when ordering windows.

Should You Worry About PFOA in Your Water?

Posted on May 19, 2016 by Veronica Vieira in Guest Blogs

Over the past few months, several communities in upstate New York and New England have detected PFOA — perfluorooctanoic acid, or C8, a chemical linked to a range of health issues from cancer to thyroid disease — in their drinking water.

PFOA is a fluorinated compound that is absorbed into our bodies through inhalation or ingestion. The chemical can then accumulate in our blood serum, kidneys, and liver.

Five Types of R-Value

Posted on May 18, 2016 by Allison A. Bailes III, PhD, GBA Advisor in Building Science

We talk about R-valueMeasure of resistance to heat flow; the higher the R-value, the lower the heat loss. The inverse of U-factor. all the time. "I've got an R-19 wall," or "Code requires R-38 in my ceiling." But what are those numbers? As it turns out, when we talk about R-value we usually give the R-value of the insulation material itself. That's the case with both of those statements above. But what's the real R-value of the wall or the ceiling? Insulation makes up only a part of each. There's also wood and drywall and 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. and claddingMaterials used on the roof and walls to enclose a house, providing protection against weather. and...

A Pretty Good Retrofit in Montana

Posted on May 17, 2016 by Jim Baerg in Guest Blogs

This is a story of a wonderful, tempestuous relationship. For me, it began nine years ago as an unplanned series of events: a chance encounter between a wandering idealist and small town girl. The happenstance meeting quickly progressed to an impulsive, long-term proposal. Soon thereafter, the commitment was formalized by the exchange of legal documents through the mail.

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