Musings of an Energy Nerd

If you are considering investing in an energy-efficiency improvement for your home — for example, additional attic insulation or a 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. system — you probably expect the investment will lower your energy bills. So it’s only natural to ask, “Is this a good investment?”

For example, let’s say that you are considering spending $5,000 on an improvement that will save you $350 a year on your energy bills. Does the investment make economic sense? The answer, of course, is “it depends.”

Act 1, scene 1. An empty lot near Scotland Drive.

Thunder and lightning. Enter three sisters, all RESNET-certified.

First rater:
When shall we three meet again,
In thunder, lightning, or in rain?

Second rater:
When the drywall work is done,
When the zoning battle’s won.

Although I usually only publish one blog a week, I can’t resist posting a rare Saturday blog to rail against bad advice to homeowners from the Federal government and a national green building organization.

Lots of things can go wrong with roofs: bad flashing can cause leaks, a poorly designed valley can turn into a slow-moving glacier, and misplaced gutters can do more harm than good. Experienced roofers see a lot of stupid roofs.

Two new books that might interest green builders recently caught my eye: The BuildingGreen Guide to Insulation Products and Practices by Alex Wilson and The JLC Guide to Energy Efficiency by the editors of The Journal of Light Construction.

Full disclosure: I was a minor participant in the creation of both books. At Wilson’s request, I reviewed portions of his manuscript before publication and provided feedback. I also wrote several of the articles appearing in the JLC book.

A new distributor of building products from Europe has set up shop in Brooklyn, New York. The company, called Four Seven Five, was recently founded by a trio of 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. consultants: Floris Keverling Buisman, Sam McAfee, and Ken Levenson. Four Seven Five plans to import air-sealing products and ventilation fans from Germany, as well as HVAC(Heating, ventilation, and air conditioning). Collectively, the mechanical systems that heat, ventilate, and cool a building. equipment from Denmark.

Although the GBAGreenBuildingAdvisor.com website already contains many articles on the topic, we continue to receive frequent questions about the best way to insulate a cathedral ceiling. It’s therefore time to pull together as much information on the topic as possible and publish it in one place, to clarify the building science issues and code requirements governing insulated sloped roofs.

Energy myths are persistent, in spite of the fact that energy experts spend a good deal of time performing debunking duty. Many energy experts collect misguided energy-saving tips as a hobby, and pick the myths apart with the dedication of an 18th-century amateur scientist.

In a previous blog, I presented my own list of ten energy myths.

UPDATED 11/8/2011: Guardian Building Products has apologized to Allison Bailes. See full information at the end of the article.

On October 19, 2011, blogger Allison Bailes, a frequent contributor to GBAGreenBuildingAdvisor.com, posted a blog on his Energy Vanguard website about the difficulty of installing fiberglass batts well. You can read his excellent blog here: A Visual Guide to Why Fiberglass Batt Insulation Underperforms.

UPDATED February 1, 2012

In 2004, researchers at the National Renewable Energy Laboratory (NREL) developed BEopt, a software program that finds the least-cost solution to designing a zero-energy house. Now that the software developers — a team that includes Craig Christensen and Scott Horowitz — have spent seven years improving the program, it has finally been released to the public. The development of BEopt was funded by the U.S. Department of Energy.