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ASHRAE Conferences — Where Theory Meets the Real World


I’ve been going to the meetings of the ASHRAE residential ventilation committee (SSPC 62.2, to be specific) for the past few years.  As a matter of fact, I’m writing this article from my room in Houston, the site of the summer meeting.  It’s always interesting to go to these things because the attendees are people who have a broad range of knowledge and experience in best practices for buildings, the latest research results, and some even have practical experience.

And then I look around the building we’re meeting in.  It’s a rare meeting when there’s not some kind of problem with the ventilation or heating and cooling.  In Orlando a couple of years ago, the room was small, crowded, and stuffy.  I wish I’d had a carbon dioxide monitor because I’m sure it must have been at least two thousand parts per million.  (Experts recommend that it stay below one thousand ppm.  At least one study found that high levels of CO2 may affect cognitive function.) 

And then there was Las Vegas last year.  There aren’t many places — at least not in North America — where you can smoke indoors but Caesar’s Palace in Las Vegas is one them.  They don’t let you smoke in the meeting rooms, but still, you can’t walk through the building without accidentally smoking a cigarette or two.

This summer, the conference is in Houston, just a few miles from where I was born.  It’s the land of humidity, as you know all too well if you’ve been here in the summer (which usually lasts about six months).  And that gets us to the photo at the top of this article. 

Kimberly Llewellyn (with Mitsubishi Electric), standing next to the grille in that photo, called me over to check it out.  I put my hand in front of it and felt warm air.  But the air was more than just warm.  It felt wet.  It was sticky.  Our guess is that the ventilation system for this hotel brings in unconditioned air straight from outdoors. 

One potential problem with dumping unconditioned air right into a building are comfort.  That area was noticeably different from the rest of the space.  One person said the women’s restroom, which is right there near the grille, was about 20° F warmer than the other areas.  It might also explain why the rooms were so cold.  They had to turn down the thermostat in an attempt to control the humidity.

Another potential problem is that the outdoor air may not have done much ventilation.  With the exhaust fans running in that restroom, much of the air may have gotten pulled right out.

And then of course, there’s the possibility that introducing a lot of humid air in one area could start an unintentional biology experiment through accidental dehumidification

Meanwhile, back in the residential ventilation committee meeting, people discussed superposition, block schedules, and filtration efficiency.  Oh, and hyperbolic cotangents.  It was quite a meeting.


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Green Buildings Can Make You Smarter


Photo by Nikki Krueger of Therma-Stor, used with permission.


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This Post Has 9 Comments

  1. So…if I interpret the
    So…if I interpret the picture correctly, the big outside air grill is dumping right near the entry to the Ladies’ loo. The loo is almost certainly continuously exhausting to outdoors, so replacement air comes straight in from that huge grill…Oops!

      1. Question. I have a 4 year old
        Question. I have a 4 year old house that is totally open foam insulated. The gas furnaces and the air conditioner air handlers are in the sealed attic. The system is vented to the outside for supply air. I recently had the conditioner cooling coils rust and leak out the refrigerant in one of the units. I am being told by one company (Selling ERV Equipment) that I shoud install ERV equipment for each of my three air handlers. The original Company that installed my equipment claims I don’t need the ERV equipment.

        I am very comfortable living in the house so I don’t think I have a ventilation or humidity issues but I am concerned about future problems with the air conditioning equipment. The ERV equipment cost $5,500 each and I do have 3 systems.

        What is your current thinking about whole house foam insulation and installing ERV equipment? Is it necessary?

        Thank You
        Tom Horan

        1. Rusted fridge coils??? I’m a
          Rusted fridge coils??? I’m a coder, not an installer, but… Is anything else turning up moist in this sealed attic space??? Anyone check for obstructions in the condensate drain? Seems like moisture would have to be on the copper pretty persistently to rust it like that…

    1. And the sad part is two
      And the sad part is two problems could be solved at once with the right design. Just put an aggressive package DX stage over the outdoor air intake, on the slow side of airflow to maximize latent cooling capacity, with a nice tall drain going down for gravity drive, a filter stage or two and a storage tank at the bottom, and you have a source of potentially potable water, AND the remaining air for the supply grill is cool and dry. Probably could run the thing off a nice little PV array on the roof right next to it during the day, if it’s big enough throw on a battery pack for nighttime.

  2. Hyperbolic cotangents? My my
    Hyperbolic cotangents? My my y’all got rowdy! Did that get presented by someone doing an unintentional Ben Stein impersonation? Sounds about like the American Coatings Association’s conference a few years ago in which participants sat through a demonstration on the effects of vapor pressure differences in the drying time of fluid applied colloid latex coatings.

  3. I suspect you may be
    I suspect you may be confusing hyperbolic cotangents with tendentious hyperbole….

  4. The “grill” in the picture
    The “grill” in the picture looks like a return air grill to me, not a supply air “diffuser” or “register”. Are you sure that air was blowing from the grill rather than being sucked into it? That sure looks like a strange location for a large supply air register.

  5. To me this looks like a
    To me this looks like a return air grill but the air handler is not running so the negative pressure of the building is causing air to flow the wrong way down the air handler.

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