Building Science

Measuring (and Understanding) Humidity

Posted on January 26, 2017 by Peter Yost

Author’s Note: I can’t even start this blog before thanking Lew Harriman of Mason-Grant Consulting. Lew very patiently and gently hammered me into a much better understanding of humidity in air and its measurement. While any errors or lack of clarity regarding humidity and its measurement are mine, much of the insight and many of the resources mentioned here are Lew’s.

City of Aspen Dumps Energy Rating Index

Posted on January 25, 2017 by Allison A. Bailes III, PhD

The city of Aspen, Colorado has bucked the trend. Well, actually two trends, but first things first.

Designing Duct System Vents for Good Air Flow

Posted on January 18, 2017 by Allison A. Bailes III, PhD

You're at a cocktail party when, as it so often does, the discussion turns to HVAC(Heating, ventilation, and air conditioning). Collectively, the mechanical systems that heat, ventilate, and cool a building. design. What do people talk about? Load calculations. Manual J. Oversizing. Maybe a little about duct sizing or location. But how many times have you been in that conversation and heard someone talk about what happens at the end of the ducts? Yes, I'm talking about the often overlooked part of HVAC design in which the designer selects the proper terminations for the duct runs.

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).

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