Musings of an Energy Nerd

Crawl Spaces vs. Skirts

Posted on July 21, 2017 by Martin Holladay

Many older homes in rural areas have pier foundations. The piers may be made of wood (for example, creosoted posts or pressure-treated lumber), poured concrete, CMUs, or bricks. The space between the dirt and the underside of the floor framing may be enclosed or may be entirely open to the wind.

Air Conditioner Performance In Extreme Heat

Posted on July 14, 2017 by Martin Holladay

During the last week of June, many major U.S. news outlets sent reporters to Arizona to issue updates on the area’s extreme heat wave. Outdoor temperatures hit 119°F in Phoenix. Some airplanes were grounded because the hot air was too thin for small jets to take off. Car steering wheels were so hot that some drivers wore oven mitts. VinylCommon term for polyvinyl chloride (PVC). In chemistry, vinyl refers to a carbon-and-hydrogen group (H2C=CH–) that attaches to another functional group, such as chlorine (vinyl chloride) or acetate (vinyl acetate). records delivered by mail arrived warped. Emergency room physicians reported an increase in burn cases: hands were burned when people touched their cars, and children’s feet were burned when they went barefoot outdoors.

PV Systems That Divert Surplus Power to a Water Heater

Posted on July 7, 2017 by Martin Holladay

In some U.S. states, electric utilities refuse to offer a net-metering agreement to owners of 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. Instead of a net-metering agreement — an arrangement that provides a homeowner with a one-for-one credit for every kilowatt-hour (kWh) of PV-generated electricity fed into the grid — these utilities want to sell electricity to users for 12 cents or 15 cents per kWh, while buying it back for only 4 or 5 cents per kWh.

R-Value Advice from Building Science Corporation

Posted on June 30, 2017 by Martin Holladay

To reduce energy use, green builders often install above-code levels of insulation. Thick insulation is expensive, however, so it’s sometimes hard to know how much insulation is optimal.

To help guide builders wrestling with R-valueMeasure of resistance to heat flow; the higher the R-value, the lower the heat loss. The inverse of U-factor. questions, I wrote an article in May 2016 (“How Much Insulation Is Too Much?”) reporting on R-value recommendations from three energy experts: David White, Marc Rosenbaum, and Rachel Wagner.

In Praise of Scientists and Scholars

Posted on June 23, 2017 by Martin Holladay

Most educated Americans still listen to scientists and believe in established methods of scholarly inquiry. That said, a strange side effect of our country’s recent slide into extreme political polarization has been an increase in the number of Americans who reject the conclusions of scientists and scholars.

Comfort Problems Related to Radiation

Posted on June 16, 2017 by Martin Holladay

Our homes include insulation to reduce heat flow through floors, walls, and ceilings. Some parts of our homes’ thermal envelopes (for example, insulated ceilings) are well insulated and have a high R-valueMeasure of resistance to heat flow; the higher the R-value, the lower the heat loss. The inverse of U-factor. ; other parts (like windows) have a much lower R-value. But during the winter, as long as we have an adequate heating system that keeps the indoor air temperature at 72°F, we should be comfortable — right?

Not quite. Even when the air temperature is held to a steady 72°F, occupants can be cold during the winter — especially if they are standing or sitting next to a large window.

Fixing Energy Star Version 3

Posted on June 9, 2017 by Martin Holladay

The Energy Star HomesA U.S. Environmental Protection Agency (EPA) program to promote the construction of new homes that are at least 15% more energy-efficient than homes that minimally comply with the 2004 International Residential Code. Energy Star Home requirements vary by climate. program has been in trouble since 2012, when the Environmental Protection Agency rolled out a new version (Version 3) of the program’s requirements. Many builders found the Version 3 requirements so onerous that they dropped out of the 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. program. The number of new homes that have been certified under the Energy Star program has fallen 36% in recent years — from 130,305 in 2011 to 83,897 in 2015.

How to Design an Off-Grid House

Posted on June 2, 2017 by Martin Holladay

A very small percentage of U.S. homes are off the electricity grid — far fewer, for example, than in Africa. That said, North American designers of off-grid homes often end up posting questions on GBAGreenBuildingAdvisor.com.

To help this subset of builders avoid common design errors, I’ll share what I’ve learned from living in an off-grid house for 42 years.

Night Sky Radiation

Posted on May 26, 2017 by Martin Holladay

Let’s say you walk into an unheated room. The air temperature is only 50°F. There is a wood stove in the room, but the wood stove is unlit.

Your body is at about 98°F. Since your body is warmer than absolute zero, it is radiating heat in all directions. (All objects that aren’t at absolute zero emit infrared radiation). The wood stove is cool — it’s at 50°F. Still, the wood stove is also radiating heat in all directions.

Natural Gas Pipelines Are Leaking

Posted on May 19, 2017 by Martin Holladay

The CO2 emissions associated with the burning of natural gas are less than the CO2 emissions associated with burning an equivalent amount of coal. Because of this fact, natural gas is seen by many policy makers as a “clean” alternative to coal.

In the last few years, however, climate activists have been pointing out two worrisome facts: (1) methane (natural gas) is a potent greenhouse gas — about 80 times more potent than CO2 (on a mass basis) during the first 20 years after the methane is released; and (2) our nation’s natural gas pipelines are much leakier than some people thought.

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