Musings of an Energy Nerd

Blower Door Basics

Posted on January 29, 2010 by Martin Holladay

Leaky homes are hard to heat and hard to cool. The only way to know whether your home is leaky or tight is to measure its air leakage rate with a blower door. A blower door is a tool that depressurizes a house; this depressurizationSituation that occurs within a house when the indoor air pressure is lower than that outdoors. Exhaust fans, including bath and kitchen fans, or a clothes dryer can cause depressurization, and it may in turn cause back drafting as well as increased levels of radon within the home. exaggerates the home’s air leaks, making the leaks easier to measure and locate.

An energy-efficient house must be as airtight as possible. Many older U.S. homes are so leaky that a third to a half of the home’s heat loss comes from air leaks.

HRV or ERV?

Posted on January 22, 2010 by Martin Holladay

After investigating various ventilation options, many residential designers conclude that they want either a heat-recovery ventilator (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. ) or an energy-recovery ventilator (ERV(ERV). The part of a balanced ventilation system that captures water vapor and heat from one airstream to condition another. In cold climates, water vapor captured from the outgoing airstream by ERVs can humidify incoming air. In hot-humid climates, ERVs can help maintain (but not reduce) the interior relative humidity as outside air is conditioned by the ERV.). They often remain confused, however, about which of the two devices to choose.

Every tight home needs a mechanical ventilation system.

Home Dashboards Help to Reduce Energy Use

Posted on January 15, 2010 by Martin Holladay

In recent years, the technology of our cars has advanced at a more rapid rate than the technology of our homes. A new car’s dashboard has gauges that display all kinds of information, including the amount of fuel in the car’s tank, the oil pressure, the electrical system voltage, and sometimes the tire pressure. Many new cars even have a real-time fuel-efficiency gauge that displays miles per gallon.

The Uncertain Future of Phoenix and Las Vegas

Posted on January 8, 2010 by Martin Holladay

The American Southwest is running out of water. For a powerful reminder, if any is needed, of why builders in Western states should integrate water-conservation strategies in all new buildings, check out a new book by James Lawrence Powell, Dead Pool: Lake Powell, Global Warming and the Future of Water.

Powell’s message is stark: according to scientists’ best predictions, millions of Americans living in the Southwest will face unprecedented water shortages in the next few decades.

Top Ten News Stories of the Decade

Posted on December 31, 2009 by Martin Holladay

For those interested in energy efficiency and residential construction, what were the top ten news stories of the decade? I propose the following list — a list inevitably influenced by the years I spent as editor of Energy Design Update.

’Twas the Night Before Christmas

Posted on December 23, 2009 by Martin Holladay

’Twas the night before Christmas, when blizzards and chills
Strain my budget by raising my energy bills;
All the stockings were swaying — a cold winter breeze
Made my home’s leaky envelope feel like Swiss cheese
(The old windows and ceilings have so many gaps
That the kids have to sleep in their kerchiefs and caps) —
When out on the lawn there arose such a clatter,
I sprang from the bed to see what was the matter.

Away to the window I flew like a flash,
And I yanked up the creaky old single-pane sash.

Martin’s Energy Quiz

Posted on December 18, 2009 by Martin Holladay

This week’s blog is an energy efficiency and building science quiz. Remember, using Google for research is cheating. Answers are at the bottom of the page.

1. During the winter, a home inspector climbs into an attic and notices that the underside of the roof sheathing is covered with frost and the rafters have stains indicating mold. The most likely cause of these problems is:
a. A roof leak
b. Insufficient insulation on the attic floor
c. Air leakage paths between the wet basement and the attic.
d. Bats or squirrels.

Windows That Perform Better Than Walls

Posted on December 11, 2009 by Martin Holladay

UPDATED on March 18, 2015

The common perception that windows are “energy holes” is a bad rap. Since today’s high-solar-gain triple-glazed windows gather more heat than they lose, good windows perform better than an insulated wall. After all, a wall can only lose energy, while windows can gain energy during the day to balance energy lost at night.

Roofing and Siding Jobs Are Energy-Retrofit Opportunities

Posted on December 4, 2009 by Martin Holladay

Unlike governments in Germany and the U.K., the U.S. government hasn’t yet enacted an energy policy aimed at addressing global climate change. As a result, prices for carbon-based fuels in the U.S. are far lower than in most European countries.

If Americans continue along our current energy path, wrenching climate change is almost inevitable. That’s why many energy experts advise Americans to prepare for the eventual implementation of steep carbon taxes on heating fuel and electricity.

One prominent environmental organization, the Union of Concerned Scientists, has called for an 80% reduction in U.S. greenhouse gas emissions by 2050, and two states (California and New Jersey) have adopted that target as a state goal. The 2030 Challenge, a program endorsed by the American Institute of Architects, sets a goal of implementing energy retrofits designed to reduce energy use by 50% at 1.5 million U.S. homes annually between now and 2030.

It's unclear whether the U.S. will be able to meet these challenging targets. But attaining the targets would require almost every U.S. home to under a deep-energy retrofit. In most cases, the work would require walls and roofs to be covered with a thick layer of exterior insulation.

The logical time to do this work is when siding or roofing is replaced.

Houses Versus Cars

Posted on November 27, 2009 by Martin Holladay

You’re striving to minimize your carbon footprintAmount of carbon dioxide and other greenhouse gases that a person, community, industry, or other entity contributes to the atmosphere through energy use, transportation, and other means. , and your house is energy efficient. Through diligent conservation efforts, you’ve greatly reduced the amount of natural gas and electricity required to run your home.

Bravo! But how does your residential energy budget compare to your transportation energy budget? You may be happy to brag about your low utility bills — but if you’re anything like me, you’re probably a little ashamed of your gasoline budget.

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