Thursday’s 6pm ET Zoom session is titled, “Psycrometric Chart.”
Thursday’s 6pm ET Zoom session is titled, “Psycrometric Chart.” This week we’ll cover a problem from NCARB’s practice exam (spoiler alert, NCARB’s answer is very very wrong.) You’ll take the first five minutes of class to answer the question alone, but if you would like to get a head-start on that, here is the assignment.
Put the building systems into the boxes on the psycrometric chart to indicate the system that is most appropriate for each climate condition. Not all building systems will be used.
The Zoom session will take place at 6pm ET Thursdays in our Zoom link: https://us02web.zoom.us/j/83922907346
It’s free for everyone, so join us. You’ll increase your odds of passing the exam. . . Plus, it’s fun.
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Hard to say. . . The "real" correct answer:
A: Roof ponds
B: Ceiling fans, operable windows, or dehumidifier unit
C: None of the choices are great, but roof ponds is the best one.
NCARB's answers are different (and incorrect). You can see them in the PPD practice exam, I think at number sixty-something.
The lightly-edited video of the Zoom call you missed can be found in Amber Book PPD flash cards, number 187.
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I’m studying this psychrometric stuff now. I think Mermann’s answers are wrong. How can a Roof Pond effect WBT inside. I think System A corresponds to Ceiling Fans as they move air around and air movement promotes evaporative cooling inside and the shape of system A is clearly following the WBT lines. No?
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Hi jfairbanks,
I'm not entirely convinced by all those answers either - you'll be glad to know though that since drag-and-drop questions have been eliminated, that question isn't on the practice exam anymore, and there's not really a way to test on a topic like that that requires you to know all of those things without the help of some process of elimination. There have been some improvements made since 2022!
A is a bit too hot and too dry - comfort is improved with evaporative cooling. Ceiling fans do promote evaporative cooling, I think you're more right there than Michael is. Roof ponds are really more a thermal mass thing than they are a direct evaporative cooling thing. B is a little too humid and a little too hot - air movement will help promote evaporative cooling, especially natural ventilation so that air changes remove the excess humidity. Operable windows would be best, a dehumidifier and fan would probably also work. C is very hot and a little dry. That zone is usually labelled something like "mass cooling + night ventilation" - so you'd need something like the roof pond plus operable windows, really - as Michael notes, none of the answers are great, the roof pond is about as good as possible among the available answers.
There's a labelled psychrometric chart here, there's more discussion in the Ladybug plugin forum with images here, and ClimateConsultant is a great piece of free software to pull up actual climate data and see the impact those kinds of design decisions can have on reducing the number of hours a year a building will need mechanical cooling or heating for. There's a youtube video showing the basics of ClimateConsultant for psychrometric charts here.
Happy studying,
Ralph, the Amber Book Team -
To follow up - the Society of Building Science Educators has a whole page of Energy Design Tools, including Climate Consultant and a couple of tutorials about psychrometric charts here: https://energy-design-tools.sbse.org/. You may find it useful!
Cheers,
Ralph, the Amber Book Team
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