Building Science

Manual J Doesn’t Tell You Equipment Capacity

Posted on March 8, 2017 by Allison A. Bailes III, PhD

Here's a little conundrum for you. To get the right amount of heating and cooling to each room in your home, you need a load calculation. Rules of thumb don't work. But if you do a load calculation, the result isn't the size of air conditioner, heat pumpHeating and cooling system in which specialized refrigerant fluid in a sealed system is alternately evaporated and condensed, changing its state from liquid to vapor by altering its pressure; this phase change allows heat to be transferred into or out of the house. See air-source heat pump and ground-source heat pump., furnace, or boiler you need. It's only the first step to sizing your system.

Do you know why? Let's take a look.

Building Enclosure Commissioning

Posted on February 23, 2017 by Peter Yost

I have been advising architects and builders on high-performance design, materials, and construction — particularly for residential buildings — for many years. But to do this work on commercial buildings, a building science training and credentialing program seemed really important (yet elusive).

This past November I bit the bullet and spent three days in class, a half day in exams, and several thousand dollars, and fulfilled the requirements for these two certifications:

  • Building Enclosure CommissioningProcess of testing a home after a construction or renovation project to ensure that all of the home's systems are operating correctly and at maximum efficiency. Process Provider (BECxP)

This Radiative Cooling Material Could Supplant Traditional Air Conditioners

Posted on February 22, 2017 by Allison A. Bailes III, PhD

When it's hot out, we want cold. At night, we like to be able to turn on the lights. During the daytime, it can be hard to find the darkness.

All these things — hot and cold, day and night, light and dark — can seem like opposites. Chinese philosophy suggests, however, that these opposing forces, known collectively as the yin and the yang, aren't separate. And science has proved it. Let me tell you about the latest yin and yang science and how it could revolutionize air conditioning.

Buried Ducts Allowed in 2018 Energy Code

Posted on February 15, 2017 by Allison A. Bailes III, PhD

Water vapor from the air condenses on air conditioning ducts in humid climates. It's as normal as poorly insulated bonus rooms making occupants uncomfortable or cigarettes causing lung cancer. Condensation on ducts is most common in crawl spaces and basements, where the air is more likely to have a higher dew point.

Should Balanced Ventilation Be Required?

Posted on February 8, 2017 by Allison A. Bailes III, PhD

"You know where this is going, right? Codes will eventually require 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). ." I've heard people say this more than once in the past year or so. As someone who has been attending the semiannual meeting of the ASHRAE 62.2A standard for residential mechanical ventilation systems established by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers. Among other requirements, the standard requires a home to have a mechanical ventilation system capable of ventilating at a rate of 1 cfm for every 100 square feet of occupiable space plus 7.5 cfm per occupant. committee, I've been skeptical. Then I read the new Aspen energy code and saw the first evidence that this really could happen.

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…)

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