Musings of an Energy Nerd

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.

All About Earth Tubes

Posted on May 12, 2017 by Martin Holladay

An 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. is a buried ventilation duct. The idea behind burying ventilation ducts — the ducts conveying fresh outdoor air to a building — is that the soil surrounding the ducts will warm the ventilation air during the winter and cool the ventilation air during the summer.

Earth tubes can work, as long as:

  • the duct is installed in a climate with useful soil temperatures,
  • the duct has a large enough diameter,
  • the duct is long enough,
  • the duct is buried deep enough,

All About U-Factor

Posted on May 5, 2017 by Martin Holladay

The familiar NFRC sticker found on most new windows sold in the U.S. includes a number in the upper left-hand box labeled “U-factor.” For many homeowners and builders, an encounter with this sticker represents their first exposure to U-factor.

Once people understand that a window has a U-factor, they might learn that walls and ceilings can have a U-factor, too. At that point, confusion may begin.

Revisiting Net Zero Energy

Posted on April 28, 2017 by Martin Holladay

An 6-kW 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.) system can be installed for about $18,000 in many U.S. locations. With a 30% federal tax credit, the system costs the homeowner only $12,600 — or even less if utility or state rebates are available.

This 6-kW system will produce about 8,000 kWh per year in Boston (worth about $1,600) or 10,300 kWh per year in Phoenix (worth about $1,230). That’s a lot of electricity.

The Exterior Rigid Foam is Too Thin!

Posted on April 21, 2017 by Martin Holladay

Let’s say you’ve owned your house for several years. Your growing interest in energy efficiency brought you to the GBAGreenBuildingAdvisor.com web site. GBA taught you that it’s a great idea to install rigid foam on the exterior side of your 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. , as long as (a) the rigid foam is thick enough to keep your sheathing above the dew point during the winter, and (b) your walls don’t have any interior polyethylene.

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