Musings of an Energy Nerd

We’ve all seen tables that list the R-valueMeasure of resistance to heat flow; the higher the R-value, the lower the heat loss. The inverse of U-factor. per inch for a variety of insulation types. These tables are handy, of course, but because old information is endlessly republished, in some cases long after the old information becomes obsolete, the tables are often flawed. Most authors make little effort to update these tables in light of the latest information from researchers.

A few weeks ago, I accompanied my wife Karyn, who is a pediatrician, on a three-week trip to Cambodia. She volunteered her services at the Angkor Children's Hospital in Siem Reap, in response to a request from hospital administrators. The hospital invited her to Cambodia to provide two weeks of specialized medical training for the hospital staff.

Lucky me: I got to tag along.

Siem Reap is a bustling town in northwest Cambodia, only a few miles away from the world-famous temples of Angkor Wat.

Rural residents are surrounded by greenery and breathe fresh air. Urban residents are surrounded by concrete and breathe polluted air.

On the other hand, rural residents live in wasteful single-family homes and depend on private cars for transportation. Urban residents live in efficient apartments and use public transportation.

So which lifestyle is greener? According to most analysts, urban living is better for the planet than rural living. But a few aspects of the question remain unsettled.

GBAGreenBuildingAdvisor.com has published a lot of articles about resilience — for example, articles pointing out that well-insulated buildings with low levels of air leakage are more resilient than code-minimum buildings. In other words, in the event of a disruption to energy supplies, such a building can ride out a cold spell — even one lasting for weeks — without risking frozen pipes.

A few GBA bloggers, including Alex Wilson and Tristan Roberts, advise anyone concerned about resilience to consider where their food will come from during an emergency.

One of the liveliest sessions at this year's NESEANorth East Sustainable Energy Association. A regional membership organization promoting sustainable energy solutions. NESEA is committed to advancing three core elements: sustainable solutions, proven results and cutting-edge development in the field. States included in this region stretch from Maine to Maryland. www.nesea.org-sponsored conference (BuildingEnergy 16) in Boston was a panel discussion featuring four remodeling contractors. These energy-conscious New England builders talked about the challenges they face as they try to incorporate energy improvements into remodeling projects.

These days, lots of builders are installing a continuous layer of rigid foam on the exterior side of their wall 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. . The usual approach is to sheathe the wall with OSB or plywood, and then to install one or more layers of rigid foam outboard of the sheathing.

Some builders are beginning to simplify this process by switching to nailbase panels — rigid foam panels with a layer of OSB or plywood glued to one side. Since nailbase panels provide sheathing and foam insulation in a single panel, they should (in theory) simplify the construction process.

Most insulation materials have an R-valueMeasure of resistance to heat flow; the higher the R-value, the lower the heat loss. The inverse of U-factor. lower than R-5.6 per inch. As David Yarbrough, a nationally known insulation expert, explains, “At 75°F, the theoretical maximum R-value of a product is 5.6 per inch. That represents the maximum R-value if there is no convection and no radiation — it represents the pure conductivity of air. That’s as high as you can go unless you are talking about a product that incorporates encapsulated gas, or a vacuum, or nano-scale powders.”

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?

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.

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: