The most recent blogs at Green Building Advisor

A Report from the Passivhaus Front Lines

Posted on February 18, 2016 by Catherine Ruddell in Guest Blogs

Editor's note: Canada's northernmost certified 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. is an 1,895-square-foot home in Fort St. John, British Columbia, where the average number of heating degree days over the last five years has been more than 10,500 annually. The house, completed in 2014, is owned by the city and was described in a Green Building Advisor report in 2014. For more than a year, the house has been occupied by two caretakers, Catherine Ruddell and Paul Gillis, who act as hosts for tours of the project. Catherine recently sent this report of what it's been like to live there.

What Should Be Done With This House?

Posted on February 17, 2016 by Paul Eldrenkamp and Ken Neuhauser in Guest Blogs

In this blog, Paul Eldrenkamp and Ken Neuhauser look at a range of houses and ask these questions: “If this house is to be part of the solution rather than part of the problem in the year 2050, what will it probably look like? What sort of master plan will get it there?” Paul and Ken will be presenting a workshop on this topic (“What should be done with this house?”) at the upcoming BuildingEnergy 16 conference in Boston.

Desperately Seeking Quality

Posted on February 16, 2016 by Carl Seville, GBA Advisor in Green Building Curmudgeon

It’s been quite a while since my last post. The good news is that the recession is over and business is good, leaving me little time to write these days. The bad news is that there is so much work going on, which, combined with a shortage of skilled labor, ends up with large knowledge and communication gaps that create problems in the field.

Solar Now or Later?

Posted on February 15, 2016 by Scott Gibson in Q&A Spotlight

Prices for 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. (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.) systems have been dropping steadily, making the investment in residential-sized arrays more appealing than ever. Lower prices and a decision in Congress to extend the federal investment tax credit means that ever larger systems are within reach of more homeowners.

But what about homeowners whose construction budgets strictly limit the size of the PV system they can realistically afford? They are people like James Timmerberg, who is building an all-electric house in Ohio and would like to invest in solar — if it makes economic sense.

Insulating Walls in an Old House With No Sheathing

Posted on February 12, 2016 by Martin Holladay, GBA Advisor in Musings of an Energy Nerd

When the owners of an old wood-framed building say that they’re doing a “gut rehab job,” that usually means that they’re demolishing the lath-and-plaster walls to expose the studs — the first step of renovation work that usually includes new wiring, new plumbing, and new insulation.

Green Groups Harness Data from Space

Posted on February 11, 2016 by Jacques Leslie in Guest Blogs

When Brian Schwartz, a Johns Hopkins University epidemiologist researching the public health impacts of hydraulic fracturing, read about an environmental group that uses satellite imagery and aerial photography to track environmental degradation, he was intrigued.

Unvented Gas Appliance Industry Fails to Impress ASHRAE

Posted on February 10, 2016 by Allison A. Bailes III, PhD, GBA Advisor in Building Science

Unvented combustion appliances were added to the scope of 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. 's residential ventilation and IAQIndoor air quality. Healthfulness of an interior environment; IAQ is affected by such factors as moisture and mold, emissions of volatile organic compounds from paints and finishes, formaldehyde emissions from cabinets, and ventilation effectiveness. standard (standard 62.2) recently. The committee has begun their deliberations on the issue, and at ASHRAE's winter meeting in Orlando last month, the unvented gas appliance industry folks attempted a defense of their products. Based on the results they presented and the reaction from most committee members, I'd say they failed.

How to Improve Energy-Efficiency Programs

Posted on February 9, 2016 by Steven Nadel in Guest Blogs

In the past year, a growing number of papers from economists have questioned the effectiveness of energy-efficiency programs and policies. We have reviewed many of these studies and blogged about several of them (see here, here, here, and here).

Smug About Your Solar Roof? Not So Fast.

Posted on February 8, 2016 by Severin Borenstein in Guest Blogs

If you've installed solar panels on your roof and feel aglow with environmental virtue, you may be in for a rude awakening. There's a good chance someone else has purchased your halo and is wearing it right now.

Choosing Rigid Foam

Posted on February 5, 2016 by Martin Holladay, GBA Advisor in Musings of an Energy Nerd

Maybe you’ve decided that your floor, wall, or roof assembly needs one or more layers of rigid foam. Which type of foam should you choose: polyisocyanurate, 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.), or 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.)?

The answer depends on several factors, including your R-valueMeasure of resistance to heat flow; the higher the R-value, the lower the heat loss. The inverse of U-factor. target, your local climate, whether the insulation will be in contact with soil, and your level of environmental concern.

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