Musings of an Energy Nerd

Once again, the “in” box on my desk is beginning to fill up with a stack of brochures describing interesting new products.

I've selected four products to review in this latest roundup: an insert panel to improve the thermal performance of insulated concrete forms (ICFs); a new wall system for manufactured stone veneer; and two new water-resistive barriers (WRBs).

Here at GBAGreenBuildingAdvisor.com, we regularly receive questions from readers about the best way to insulate a basement wall. Since these questions pop up frequently, it’s time to pull together as much information as possible on this topic.

In this article, I’ll try to explain everything you always wanted to know about insulating basement walls.

If you’ve ever been confused by the difference between 500 BtuBritish thermal unit, the amount of heat required to raise one pound of water (about a pint) one degree Fahrenheit in temperature—about the heat content of one wooden kitchen match. One Btu is equivalent to 0.293 watt-hours or 1,055 joules. and 500 Btu/h, you probably can use a handy cheat sheet to explain energy units. As a guide through the thorny thickets of energy, power, and the units used to measure them, I’ve assembled some questions and attempted to answer them.

Dr. Joseph Lstiburek needs little introduction. The well-known Canadian engineer is a principal of the Building Science Corporation in Massachusetts. He’s also a regular GBA podcaster and Fine Homebuilding author.

On Wednesday, June 6th, I attended an all-day building science class presented by Dr. Joe in Westford, Massachusetts. As usual, his presentation combined salty language, corny jokes, light-hearted insults, and rock-solid building science information.

Years ago, when I worked as a home inspector, I was hired to perform a capital needs assessment at a Buddhist retreat center in rural Vermont. In an obscure mechanical closet I discovered a heat-recovery ventilator that the facilities manager didn’t even know existed.

The HRV(HRV). Balanced ventilation system in which most of the heat from outgoing exhaust air is transferred to incoming fresh air via an air-to-air heat exchanger; a similar device, an energy-recovery ventilator, also transfers water vapor. HRVs recover 50% to 80% of the heat in exhausted air. In hot climates, the function is reversed so that the cooler inside air reduces the temperature of the incoming hot air. had been installed at least a dozen years before. The filter, which had never been changed since the day it was installed, was totally clogged. The HRV was no longer working — perhaps the motor had burned out years ago. I advised the owners to call an HVAC(Heating, ventilation, and air conditioning). Collectively, the mechanical systems that heat, ventilate, and cool a building. contractor to have the unit serviced.

The first single-family Passivhaus in the U.S. was completed by Katrin Klingenberg in 2004. Klingenberg’s superinsulated home in Urbana, Illinois includes two unusual features: a ventilation system that pulls fresh outdoor air through a buried earth tubeVentilation air intake tube, usually measuring 8 or more inches in diameter and buried 5 or more feet below grade. Earth tubes take advantage of relatively constant subterranean temperatures to pre-heat air in winter and pre-cool it in summer. In humid climates, some earth tubes develop significant amounts of condensation during the summer, potentially contributing to indoor air quality problems., and walls that include an interior layer of OSB. These details were not invented by Klingenberg; she adopted practices that were commonly used by European Passivhaus builders.

Window-mounted air conditioners (also called room air conditioners) aren’t particularly efficient; the best available models have an EEREnergy-efficiency rating or energy-efficiency ratio. As most commonly used, EER is the operating efficiency of a room air conditioner, measured in Btus of cooling output divided by the power consumption in watt-hours; the higher the EER, the greater the efficiency. of about 10 or 11. Central air conditioners (also called whole-house air conditioners or split-system air conditioners) are significantly more efficient; it’s possible to buy one with an EER of 14 or even 15.

So if you care about energy efficiency, you should use a central air conditioner, not a window air conditioner — right? Well, not necessarily.

Because federal appliance efficiency standards have gotten more stringent, new refrigerators use much less energy than those sold in the 1970s. These days, it’s fairly easy to find a full-size refrigerator that requires only 350 to 500 kWh per year — significantly less than the 1,000 kWh/year energy hogs of yore.

In my last three blogs, I discussed the basics of heat-loss and cooling load calculations. The unfortunate truth about these calculations is that fast methods aren’t particularly accurate, and accurate methods require making measurements, checking specifications, and entering data into a computer program — in other words, a significant investment of time.

So how should builders go about making these calculations?

A few decades ago, residential air conditioning was very rare in colder areas of the U.S., and cooling load calculations were usually unnecessary. These days, however, new U.S. homes routinely include air conditioning equipment, even in Minnesota, so most U.S. builders are faced with the need to calculate cooling loads.