Building Science

The Fundamentals of Rigid Duct Design

Posted on January 4, 2017 by Allison A. Bailes III, PhD

At the end of this month, I'm giving a little presentation at the ASHRAEAmerican Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). International organization dedicated to the advancement of heating, ventilation, air conditioning, and refrigeration through research, standards writing, publishing, and continuing education. Membership is open to anyone in the HVAC&R field; the organization has about 50,000 members. conference in Las Vegas. Actually, I'm doing one third of the whole presentation, which is titled Flex Ducts, Hard Ducts and No Ducts: Migration Patterns for Duct Hunters (or not) in the Land of Thermal Comfort. My part is on hard ducts.

Chris VanRite is doing flex duct, and Robert Bean will cover the no-ducts part (which doesn't refer to ductless minisplits but rather to hydronic distribution). We get 15 minutes each, so I'll elaborate on my part a bit here.

Pete’s Puzzle: Mold in Certain Closets

Posted on December 22, 2016 by Peter Yost

Author’s Note: I am setting up a series of building investigations that I have done over the years as puzzles, presenting successive pieces as an interesting way to tell the story. As with any story, you can read the end first if you want, but that approach cuts down on the drama (admittedly not a bad thing for some folks…)

The Uniform Mechanical Code Looks to Limit Flex Duct

Posted on December 21, 2016 by Allison A. Bailes III, PhD

Some people love flex duct. Some people hate it. Some of us are OK with it if it's done right.

As I've documented here numerous times, many flex duct installations leave a lot to be desired. They sag. They're kinked. They're twisted around pipes.

If there's something bad that can be done with flex duct, someone has done it. And the result of all those mangled flex duct installs is poor air flow, which creates comfort problems, uses more energy, and is one reason systems get oversized.

Can This Panelized System Solve Your Enclosure Problems?

Posted on December 14, 2016 by Allison A. Bailes III, PhD

If you want to build a superinsulated, airtight house, you run into some difficulties. How do you deal with the extra thickness of your walls and ceilings when you add all that extra insulation? What's the best way to ensure you hit your airtightness goal? And how do you do all that while keeping the process manageable and the cost affordable?

The new Build SMART panelized system has some answers.

Using David White’s Global Warming Calculator

Posted on December 7, 2016 by Allison A. Bailes III, PhD

Everyone knows about the impact of burning fossil fuels on global warming. Maybe not everyone believes it, but scientists first started focusing attention on increasing carbon dioxide levels way back in 1827. The impact of insulation on global warming, however, is relatively new.

Revisiting the Debate Over Global Warming and Insulation

Posted on November 23, 2016 by Allison A. Bailes III, PhD

At the 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 in Philadelphia in September, I gave a presentation on the global warming impact of insulation, an issue I've discussed a few times since Alex Wilson wrote his paper on the topic back in 2010. In my presentation, I covered two different aspects of the issue: (i) the problem with Wilson's payback calculations and (ii) using David White's global warming impact calculator to make more informed decisions.

SEE STACK is a Cool Stack-Effect Tool

Posted on November 17, 2016 by Peter Yost

In 2003, as part of their presentation (“Ventilation Myths and Misconceptions”) at the Affordable Comfort conference, Collin Olson and Paul Francisco debuted a software tool they developed called SEE STACK. (If you want to experiment with the software, click here to download the executable file and training manual).

Do Humidifiers Create IAQ Problems?

Posted on November 16, 2016 by Allison A. Bailes III, PhD

It's that time of year when heating systems start coming out of their summer hibernation. (Except maybe in Vermont. Michael Blasnik's Nest data showed that Vermonters are about the last to start heating their homes in the fall.) Then everyone starts looking for their lotion and lip balm. Gaps appear in hardwood flooring as it dries out. Buildings begin to creak and pop. And then the humidifiers come out.

Yes, humidifiers can help with low indoor humidity. But what effect might they have on indoor air quality?

Using Rooftop Solar to Meet the Energy Code

Posted on November 9, 2016 by Allison A. Bailes III, PhD

Supply and demand are two different things. When you think of an energy code, say the International Energy Conservation Code (IECC International Energy Conservation Code.), you probably think of demand, not supply. Conserving energy, after all, means reducing demand. It's related to supply only indirectly.

As a result, you might expect an energy conservation code to have requirements that affect only the demand side of the equation. With the 2015 IECC, however, that's not true anymore.

High Humidity in Spray Foam Attics

Posted on October 26, 2016 by Allison A. Bailes III, PhD

I recently investigated an attic with spray foam insulation where we observed an interesting humidity pattern. We placed data loggers near the ridge and floor of the attic as well as in the living space and outdoors.

The graph at below shows dew point data for the four locations. The really interesting part is the big difference in dew point between the highest and lowest points in the attic, shown by the red and green curves in the graph.

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