Building Science

The Principles, Uses, and Limitations of WUFI

Posted on November 26, 2014 by Allison A. Bailes III, PhD, GBA Advisor

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p title="his Passive HouseA residential building construction standard requiring very low levels of air leakage, very high levels of insulation, and windows with a very low U-factor. Developed in the early 1990s by Bo Adamson and Wolfgang Feist, the standard is now promoted by the Passivhaus Institut in Darmstadt, Germany. To meet the standard, a home must have an infiltration rate no greater than 0.60 AC/H @ 50 pascals, a maximum annual heating energy use of 15 kWh per square meter (4,755 Btu per square foot), a maximum annual cooling energy use of 15 kWh per square meter (1.39 kWh per square foot), and maximum source energy use for all purposes of 120 kWh per square meter (11.1 kWh per square foot). The standard recommends, but does not require, a maximum design heating load of 10 W per square meter and windows with a maximum U-factor of 0.14. The Passivhaus standard was developed for buildings in central and northern Europe; efforts are underway to clarify the best techniques to achieve the standard for buildings in hot climates. conference keynote address">Dr. Joseph Lstiburek started it in 2012 when, in his keynote address at the Passive House conference, he said igloos were the first passive houses and you don't need WUFI,1 the hygrothermalA term used to characterize the temperature (thermal) and moisture (hygro) conditions particularly with respect to climate, both indoors and out. modeling tool, to design and build a good house. Dr.

How NOT to Install Windows in a New Home

Posted on November 19, 2014 by Allison A. Bailes III, PhD, GBA Advisor

I see a lot of interesting stuff at construction sites and in people's homes. I also see stuff I never got to see because people send me photos. I like photos! Remember that
ice chest someone had incorporated into a duct system? That was sent to me. So are the first two photos in this article.

Calculating Heating Degree Days

Posted on November 12, 2014 by Allison A. Bailes III, PhD, GBA Advisor

Let's say you did some work on your home to make it more energy-efficient: air sealing, more attic insulation, and a duct system retrofit. You've got your energy bills for 12 months before and 12 months after you did the work, and now you want to see how much energy you saved. So you sit down with all 24 months worth of utility bills, convert everything to a common unit if you use more than one type of fuel, and take a look at the numbers.

A Best Practices Manual That Can Help You with the Details

Posted on November 5, 2014 by Allison A. Bailes III, PhD, GBA Advisor

When I was building a home in 2001, I came up against a gazillion little things that I needed guidance on. I'd never built anything larger than a bookcase, so new home construction was quite a big step.

How Worried Should You Be About Asbestos in Older Homes?

Posted on October 29, 2014 by Allison A. Bailes III, PhD, GBA Advisor

AsbestosMineral fiber once commonly used in many building materials, including insulation, fireproof siding, and resilient flooring. Inhalation of invisible asbestos fibers can lead to chest and abdominal cancers as well as scarring of the lungs. The use of asbestos in some products has been banned by the EPA and the U.S. Consumer Products Safety Commission; manufacturers also have adopted voluntary limitations on its use. When found in older buildings (most commonly in floor tiles, pipe and furnace insulation, or asbestos shingles), the product's friability is a major determinant in how it must be handled during renovations. More information: http://www.epa.gov/iaq/asbestos.html was a popular material for most of the twentieth century, mainly because of its ability to insulate and act as a fire retardant. In fact, it's still used heavily in some parts of the world, such as India and China. We know enough about the risks now, though, that it's banned outright in more than 50 countries and banned for some uses in the U.S.

But how worried should you be if you find it in your home?

Spray Foam Insulated Homes Need Ventilation

Posted on October 22, 2014 by Allison A. Bailes III, PhD, GBA Advisor

Most installations of spray foam insulation, when properly installed, act as an air barrierBuilding assembly components that work as a system to restrict air flow through the building envelope. Air barriers may or may not act as a vapor barrier. The air barrier can be on the exterior, the interior of the assembly, or both.. When you use it instead of the fluffy stuff (fiberglass, cellulose, cotton), a house will be more airtight. That's good.

When a house is airtight, the nasties in the indoor air tend to stick around. Volatile organic compounds (VOCsVolatile organic compound. An organic compound that evaporates readily into the atmosphere; as defined by the U.S. Environmental Protection Agency, VOCs are organic compounds that volatize and then become involved in photochemical smog production.), water vapor, odors, 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., and other stuff you don't want to immerse yourself in make the home's indoor air quality worse.

The Diminishing Returns of Adding Insulation

Posted on October 15, 2014 by Allison A. Bailes III, PhD, GBA Advisor

If you're building a house and want to have a really good building enclosure, you need it to be airtight, handle moisture properly, and have a good amount of insulation. Ideally, you'd also consider the effects of solar radiation on the home, but for now let's just focus on the insulation. What exactly is "a good amount" anyway?

Using Server Farms to Heat Buildings

Posted on October 8, 2014 by Allison A. Bailes III, PhD, GBA Advisor

Last week in my ASHRAE newsletter, I saw an interesting story about a cool thing that Amazon.com is planning to do with heat. Amazon, in case you didn't know, is a heavy user of computers. Not only do their run their online store but they also have a popular cloud computing service. Computers turn electricity into kitten videos, celebrity tweets, and waste heat.

The Difference Between Efficiency and Efficacy

Posted on October 1, 2014 by Allison A. Bailes III, PhD, GBA Advisor

When I was doing research for an article on ceiling fans a while back, I noticed that fans don't have energy efficiency ratings; they have efficacy ratings.

There's certainly confusion about the terminology among different sources, but since light bulbs are also described by their efficacy, I started wondering about the term. I'd just accepted it before, with a vague understanding that there was something different about how efficacy was defined. Now I know why.

Highlights from the North American Passive House Conference

Posted on September 24, 2014 by Allison A. Bailes III, PhD, GBA Advisor

The 9th annual North American Passive HouseA residential building construction standard requiring very low levels of air leakage, very high levels of insulation, and windows with a very low U-factor. Developed in the early 1990s by Bo Adamson and Wolfgang Feist, the standard is now promoted by the Passivhaus Institut in Darmstadt, Germany. To meet the standard, a home must have an infiltration rate no greater than 0.60 AC/H @ 50 pascals, a maximum annual heating energy use of 15 kWh per square meter (4,755 Btu per square foot), a maximum annual cooling energy use of 15 kWh per square meter (1.39 kWh per square foot), and maximum source energy use for all purposes of 120 kWh per square meter (11.1 kWh per square foot). The standard recommends, but does not require, a maximum design heating load of 10 W per square meter and windows with a maximum U-factor of 0.14. The Passivhaus standard was developed for buildings in central and northern Europe; efforts are underway to clarify the best techniques to achieve the standard for buildings in hot climates. Conference happened two weeks ago in the San Francisco Bay Area of California. The Passive House Institute U.S. (PHIUS) has been holding this conference every year since 2006, and it just keeps getting better.

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