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Love Thy Backup Punter, Or Pay Dearly – The Unloved Exhaust Fan

By February 10, 2014November 10th, 2021Energy Efficiency, Energy Rant

Everyone reading this blog is at least a stage 1 energy geek.  A stage 1 energy geek will notice the type of light bulbs used in their hotel room and complain that the place isn’t green enough.  A stage 2 would file a complaint if the cleaning crew takes the used bath towel that is clearly hung up to dry for the next shower.  A stage 3 will appreciate the guest room occupancy-sensing thermostat.  A stage 4 will browse the web for hotels with satisfactorily green features, before booking.  A stage 5 will actually bring their own artisanal bar of soap and organic homemade shampoo in their reusable HDPE three ounce container – to avoid using those land-filling, single-serve, pornographically packaged complimentary toiletries.

Where do I fall on this scale, as a geek obsessed with ventilation supply, exhaust, and their controls?  Probably somewhere between 4 and 5 (although note that I don’t bring my own soap – I take the partially used stuff home to finish off).

Controlling building exhaust, maintaining it, or even having it at all is the most overlooked and drastically important, forgotten aspect of building performance and efficiency.  They get the love and affection of the backup punter and all the rights, protections, and love of a wealthy cigarette-smoking, loud-mouth stranger in a high end restaurant.

Consider the four-star[1] Hilton Bayfront in San Diego where the AESP National conference was held a couple weeks ago.  It had no bathroom exhaust whatsoever.  I guess this crosses the stage 5 geek threshold, but you can tell this by placing a tissue over the exhaust grille – a trick every energy engineer should know.  It is a very sensitive test, and it demonstrated utter failure in this case.

So, what’s the problem?  Well, first of all, people stink.  Could you imagine a honeymoon in a place like this?  “I need to get some ice.”  And you quickly make your way to the lobby to use the restroom.  Totally!

From an energy perspective, particularly in a climate like San Diego, the shower fog disperses in the relatively tiny room raising the relative humidity to probably the 70% range, which is ripe for microbe growth.  The weather in San Diego includes brutal swings of temperature from 56 at night to 68F in the afternoon.  So what?  There is no cooling load, at least in guest rooms.  Result: a plume of biological pollution, an invisible cesspool hangs in the room for many, many hours, until tomorrow and the cycle repeats.  This excessive moisture prematurely ages/damages room furnishings, trim, and wallpaper, and the air quality is crap.

What’s even better, another Hilton facility we use in Cedar Rapids all the time has a dopey charcoal filter in place of a bathroom exhaust fan.  Why bother at all?  It’s placebo exhaust.

I learned, in time luckily, that the MO of our general contractor, and for the industry in general, was to install these charcoal filters for home kitchen exhaust hoods in new homes.  Are you kidding me?  I said, “No way man.”  I want that thing ducted out of the house.  The excess moisture has to be removed.  Unlike San Diego, especially this year when it seems the temperature has rarely been above zero, condensation problems will cause serious damage, especially with windows if we don’t purge moisture; and the stove is a major source of moisture whether cooking vegetables, roasting a hunk of T-Rex, or baking cookies.

For commercial buildings, my concern would be that exhaust fans are forgotten.  People focus on widgets – heating and cooling equipment, light bulbs, and stupid stuff like cable TV boxes, and Xboxes.  Even controls geniuses may forget the importance of exhaust fan maintenance and control.  Ah, it’s just one stupid control point and the condition is energized or de-energized.

Let me tell you about problems of exhaust fans gone wild.  They can cause a boat load of damage and/or cost facility owners / tenants a small treasure every year.

I affectionately refer to some retrocommissioning (RCx) providers as one-trick ponies.  One breed of such ponies finds operating schedules that are way beyond the bounds of occupied hours, or even 24/7.  “Well jeez; schedule the equipment for occupancy only”, thinks the simpleton.  Slam dunk.

Hold on.  Even ignorant people are not so stupid as to run things 24/7 for no apparent reason.  Why are things running 24/7?  Or 12/7?  A stage 5 RCx guru will ask, what is the reason for this?  Reasons may include the space otherwise stinks, the temperature cannot be maintained, heating coils froze, pipes froze, etc.  Well, gee.  What are the exhaust fans doing?  Running all the time sucking in sub-zero air wherever it can and wreaking havoc.

And get this:  we conducted an energy study for a well known maker of delicious sugar-bomb cereals, and found that in the humid summertime, they shut down the supply of outdoor air to their air handlers to save energy.  Whoops!  What about the exhaust fans?  Running wild.  The result: warm and excessively moist air flooding the manufacturing area.  News: sugar, flour, corn meal, and such don’t handle very well in these conditions.

Exhaust and exhaust control are absolutely critical for all types of spaces.

[1] I just made this up – but it means very nice but not quite “luxurious” maybe.

Jeff Ihnen

Author Jeff Ihnen

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