The most recent blogs at Green Building Advisor

The Mixed-Up IAQ and Infiltration Limit Blues

Posted on December 18, 2013 by Allison A. Bailes III, PhD in Building Science

Last week, I caught the second day of Building Science Corporation's Experts' Session. (Click the link to download the presentations from the BSC website.) Joe Lstiburek spoke the whole day about ventilation, and I’ll be writing an article about that soon. At the end of that day, though, we got a little surprise.

Why Is This Sheathing Moldy?

Posted on December 16, 2013 by Scott Gibson in Q&A Spotlight

Brian Lent has discovered something in his walls that no homeowner wants to see: mold.

Preparing a ground-floor room for drywall, Lent pulls some fiberglass batt insulationInsulation, usually of fiberglass or mineral wool and often faced with paper, typically installed between studs in walls and between joists in ceiling cavities. Correct installation is crucial to performance. from a 2x6 stud cavity and notices the back side of the OSB 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. is damp. A moisture meter reveals that in 80% of the bay, the moisture content is 66% or higher. Moisture and mold are heaviest at the bottom of each bay.

In Cold Climates, R-5 Foam Beats R-6

Posted on December 13, 2013 by Martin Holladay in Musings of an Energy Nerd

Researchers have known for years that most types of insulation — including fiberglass batts, extruded polystyrene (XPSExtruded polystyrene. Highly insulating, water-resistant rigid foam insulation that is widely used above and below grade, such as on exterior walls and underneath concrete floor slabs. In North America, XPS is made with ozone-depleting HCFC-142b. XPS has higher density and R-value and lower vapor permeability than EPS rigid insulation.), and expanded polystyrene (EPSExpanded polystyrene. Type of rigid foam insulation that, unlike extruded polystyrene (XPS), does not contain ozone-depleting HCFCs. EPS frequently has a high recycled content. Its vapor permeability is higher and its R-value lower than XPS insulation. EPS insulation is classified by type: Type I is lowest in density and strength and Type X is highest.) — perform better at low temperatures than high temperatures. The phenomenon was described by Chris Schumacher, an engineer and researcher at Building Science Corporation, at a conference in 2011: “If you measure the R-value of an R-13 fiberglass batt, you’ll get different results at different outdoor temperatures. If the outdoor temperature rises, the R-value goes down.

Power Storage in Flywheels

Posted on December 12, 2013 by Alex Wilson in Energy Solutions

The great thing about writing a regular blog is that reader feedback sometimes introduces me to new products and systems. So it was last week when I wrote about a company developing power grid electrical storage systems using lithium-ion battery technology.

From a reader, I learned about another, very different approach for storing electricity to make the utility grid more stable and resilient: flywheels.

Will More Ventilation Keep Students from Missing School?

Posted on December 11, 2013 by Allison A. Bailes III, PhD in Building Science

A new study from Lawrence Berkeley National Laboratory (LBNL) makes a bold claim that increasing ventilation rates can cut the number of student absences related to illness.

Sticking With Spray Foam for My Renovation

Posted on December 10, 2013 by Carl Seville in Green Building Curmudgeon

Over the past dozen or so years my opinion on spray foam insulation has evolved from being a strong advocate to being slightly skeptical.

I have come to the conclusion that any well-designed new building can be insulated with any properly installed insulation. When it comes to renovations, however, spray foam often has some distinct advantages.

An Update on the Pretty Good House — Part 1

Posted on December 9, 2013 by Christopher Briley in Green Architects' Lounge

The status quo of newly constructed homes here in America is, well, disappointing. Despite some strong market-transforming rating systems (such as LEEDLeadership in Energy and Environmental Design. LEED for Homes is the residential green building program from the United States Green Building Council (USGBC). While this program is primarily designed for and applicable to new home projects, major gut rehabs can qualify. , Energy StarLabeling system sponsored by the Environmental Protection Agency and the US Department of Energy for labeling the most energy-efficient products on the market; applies to a wide range of products, from computers and office equipment to refrigerators and air conditioners., 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., etc.), the classic American home is still being designed and built exactly as it was 20, 30, or even 40 years ago. Why?

There's a few reasons, the biggest of which is market demand. People buy what's on the market, and builders build what sells. The only ones pushing the market are those few who are willing to go the extra distance, and do that extra homework to make their projects substantially better. This is actually a very small percentage of those building or buying a new home.

All About Attic Venting

Posted on December 6, 2013 by Martin Holladay in Musings of an Energy Nerd

Most homeowners and builders believe that attics should be vented. If you walk down to your local lumberyard and lean on the counter, the employees and nearby customers will offer a variety of opinions about why attics need to be vented. Unfortunately, it’s highly unlikely that the statements you hear will be true.

Solar Energy Can Make the Grid More Resilient

Posted on December 5, 2013 by Alex Wilson in Energy Solutions

In my blog last week, I reported on The Navy Yard in Philadelphia, a remarkable 1,200-acre business campus with 300 companies employing 10,000 people — with as many as 35,000 employees projected eventually. What had attracted me to the facility while I was in town for a conference, was an innovative demonstration that’s been launched showing how solar-electric (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.) systems with battery back-up and smart controls can help to create a more resilient power grid.

How to Get Your Ducts Inside the Building Enclosure

Posted on December 4, 2013 by Allison A. Bailes III, PhD in Building Science

I'm a big advocate of getting ducts inside the building enclosure. In cooling climates, getting ducts out of an unconditioned attic can save you 15% on your electricity bills. It can reduce the size of air conditioner you need by 25%. If it's not in such a harsh environment, your air conditioner will last longer, too.

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