The most recent blogs at Green Building Advisor

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.

Blue Heron EcoHaus: Adding Walls and Roof

Posted on May 16, 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 Dealing With Really Bad Water. 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.)

Domestic Hot Water: No Perfect Solution

Posted on May 13, 2016 by Martin Holladay, GBA Advisor in Musings of an Energy Nerd

Some questions are easier to answer than others. For example, there is a fairly straightforward answer to, “How should I insulate the floor of my unconditioned attic?” — namely, “With a deep layer of cellulose.” (There’s more to say on the topic, of course — but even a full answer isn’t very complicated.)

There is no easy answer, however, to, “How should I heat my domestic hot water?” Every type of water heating technology is flawed; every solution involves compromise.

Many factors affect the decision about what type of water heater to choose, including:

Testing Air Leakage in Multifamily Buildings

Posted on May 12, 2016 by Sean Maxwell in Guest Blogs

In a previous article, I explained why it's important to prevent air leaks between individual apartments in multifamily buildings — a type of air sealing known as "compartmentalization." With my compartmentalization rant over, let me tell you how we can change our building codes to find a solution to the problem of leaky apartments, and why you should support a change to the language of the International Energy Conservation Code.

The World Needs Sustainable Forestry

Posted on May 11, 2016 by Joshua Axelrod in Guest Blogs

The Forest Stewardship Council (FSCForest Stewardship Council. An independent, nonprofit organization that promotes responsible forest management through the use of a third-party certification process. FSC certification includes a chain-of-custody requirement that tracks sustainability of wood products from growth to end use.), the world’s leading independent certifier of sustainably managed forests, is facing increasingly vitriolic attacks from various industry trade groups and players in Canada, who argue that the FSC’s policies — specifically their move toward requiring protection of threatened intact forest landscapes — will cause them to lose access to significant wood volumes they need to maintain their current operations.

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