Musings of an Energy Nerd

WUFI Is Driving Me Crazy

Posted on May 2, 2014 by Martin Holladay, GBA Advisor

Is it possible to describe all of the factors that influence heat and moisture movement through a wall during a single day? Perhaps. We could start by listing the outdoor conditions, including air temperature, relative humidity, wind speed, wind direction, the angle of the sun with respect to the wall (its altitude and azimuth), the cloud thickness, the precipitation rate, and the depth of snow on the ground. Needless to say, many of these factors change from minute to minute.

Does a Home with an HRV Also Need Bath Fans?

Posted on April 25, 2014 by Martin Holladay, GBA Advisor

A balanced ventilationMechanical ventilation system in which separate, balanced fans exhaust stale indoor air and bring in fresh outdoor air in equal amounts; often includes heat recovery or heat and moisture recovery (see heat-recovery ventilator and energy-recovery ventilator). system — for example, a system with 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.) — exhausts stale air from some rooms in a building, while simultaneously introducing fresh outdoor air to other rooms. The best balanced ventilation systems use dedicated ventilation ductwork. Usually, these systems pull exhaust air from damp, smelly rooms — bathrooms and laundry rooms — and introduce fresh air to the rooms where people spend most of their time — bedrooms and the living room.

All About Radiant Floors

Posted on April 18, 2014 by Martin Holladay, GBA Advisor

So-called radiant floors have an excellent reputation. Many customers report that this type of heating system is comfortable and quiet. Moreover, some suppliers of radiant floor materials and equipment claim that these systems can save energy.

In spite of the purported benefits of this type of heating system, few green homes include a radiant floor heating system. This article will explore why.

Thermal Barriers and Ignition Barriers for Spray Foam

Posted on April 11, 2014 by Martin Holladay, GBA Advisor

Do building codes require spray foam insulation to be protected with a layer of drywall or a comparable barrier for fire safety? The answer is yes, usually — but not always.

There is no simple answer to the question, for several reasons. The first reason is that the code is complicated.

The second reason is that the code is poorly written.

The third reason is that the code is subject to interpretation by local code officials.

Residential Commissioning

Posted on April 4, 2014 by Martin Holladay, GBA Advisor

Building a new home usually requires work by several subcontractors, including electricians, plumbers, and HVAC(Heating, ventilation, and air conditioning). Collectively, the mechanical systems that heat, ventilate, and cool a building. installers. At the end of the job, someone — usually the general contractor — has to verify that all of the specified work has been completed.

Has the water heater been installed? Check.

Air conditioner? Check.

Ducts? Check.

Ventilation system? Check.

Deep Energy Retrofits Are Often Misguided

Posted on March 28, 2014 by Martin Holladay, GBA Advisor

All through the 1980s and 1990s, a small band of North American believers worked to maintain and expand our understanding of residential energy efficiency. These were the pioneers of the home performance field: blower-door experts, weatherization contractors, and “house as a system” trainers. At conferences like Affordable Comfort, they gathered to share their knowledge and lick their wounds.

These pioneers understood what was wrong with American houses: They leaked air; they were inadequately insulated; they had bad windows; and their duct systems were a disaster.

Stay Away from Foil-Faced Bubble Wrap

Posted on March 21, 2014 by Martin Holladay, GBA Advisor

Most brands of foil-faced bubble wrap are only 3/8 inch thick or less, and have an R-valueMeasure of resistance to heat flow; the higher the R-value, the lower the heat loss. The inverse of U-factor. of only 1.0 or 1.1. Since the product often costs more per square foot than 1-inch thick rigid foam rated at R-5, why would anyone use bubble wrap as insulation?

When the Gas Pipeline Shuts Down

Posted on March 14, 2014 by Martin Holladay, GBA Advisor

In the wake of the recent military crisis in Crimea, energy experts have been discussing whether Vladimir Putin will be tempted to gain political advantage by shutting the valves on the Russian natural gas pipelines that supply Ukraine and Western Europe. Regardless of whether this scenario is likely, such speculation raises the question: How would urban residents in a cold climate cope if the supply of natural gas were suddenly turned off?

All About Washing Machines

Posted on March 7, 2014 by Martin Holladay, GBA Advisor

About 82% of U.S. homes have a clothes washer. Each of these appliances is used, on average, to wash about 300 loads of laundry per year. On an annual basis, residential clothes washers use more energy than dishwashers but less than refrigerators.

Exhaust-Only Ventilation Systems and Radon

Posted on February 28, 2014 by Martin Holladay, GBA Advisor

Articles on mechanical ventilation commonly warn builders that exhaust-only ventilationMechanical ventilation system in which one or more fans are used to exhaust air from a house and make-up air is supplied passively. Exhaust-only ventilation creates slight depressurization of the home; its impact on vented gas appliances should be considered. systems can pull radonColorless, odorless, short-lived radioactive gas that can seep into homes and result in lung cancer risk. Radon and its decay products emit cancer-causing alpha, beta, and gamma particles. into a house through foundation cracks. The warning makes intuitive sense: after all, an exhaust-only ventilation system works by depressurizing a house with respect to the outdoors, and it seems obvious that 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. could pull soil gases into a basement.

One thing I’ve learned over the years, however, is that just because an idea is intuitively obvious, doesn’t mean it’s true. Throughout history, many observers have speculated; far fewer have actually made measurements.

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