Commercial humidification in summer performing arts building (big)

kalink

I’ve taken over this building and have been told that the climate control strategy is to cool the air then reheat then humidify     

       Chilled water from remote plant as well as steam to hot water     

       The humidification is for $100 k of pianos and for performers voices 
     The 400 seat theatre is rarely used    

      Why would it be necessary to reheat the air before humidification     

     Seems like a huge waste of steam and chilled water especially with our chill plant struggling in the summer 

EBEBRATT-Ed

Thats the way it is. Warmer air absorbs more water than cooler air. If you humidify into cold air the water will condense and drop out.

Basically, you turn on the heat and the cooling and let them fight to control the room temp and humidity. It is an energy hog but there isn't much you can do about it. It is only allowed in labs, hospitals (in some locations) manufacturing (like clean rooms) etc etc.

There is some technology to spray moisture directly into the space and it also cools the space by adiabatic cooling which would save energy if it can be used in your application.

pecmsg

Download the Honeywell Gray Manual. 

A bible for commercial buildings. 

https://www.av8rdas.com/honeywell-gray-manual.html

bburd

The air coming off the cooling coil will be near saturation, almost 100% humidity. You cannot add moisture to that air without adding some heat as well, to evaporate it.

kalink

Thank you both
   I figured it had to do with moisture absorption     

     It’s just that I’ve been fighting moisture and heat all my life to make occupied spaces comfortable   
   To here 2 10” Spence valves roaring 
and a 14” chilled water main dropping 12 degrees on a mild day just confounds me

CLamb

I don't understand why there are three steps. I expect only two would be needed. I'm assuming that in the summer the ambient outside air would be both too hot and too humid. For other seasons the steps might be different.

1. Chill the air to condense out enough water to achieve the target absolute humidity. The target absolute humidity is the absolute humidity which would achieve the target relative humidity at the target temperature.
2. Heat the air to the target temperature.

Jamie Hall

The scheme which your building is using does seem wasteful, and in most cases the approach @CLamb mentioned works just fine.

However. If you are dealing with pianos (that's much more likely to be $100,000 and up for each piano, by the way) they are absurdly sensitive to humidity, both in terms of action and pitch. If the humidity can be controlled very precisely, they may need tuning only once a month or so (if you are lucky and they are good instruments). If the humidity varies, once a week is more like it in a setting like yours. And tuning a piano properly takes half a day and costs several hundred dollars.

Therefore it's almost certainly a good deal less expensive to use the scheme your building is using, which allows for much more precision in humidity control.

CLamb

Not just pianos but lots of musical instruments are environmentally sensitive this way. It doesn't just affect tuning but also long term preservation. Changes in humidity cause wood to swell and contract. This close control is also needed for museums and archives.

ratio

I wonder how they dealt with these issues a few hundred years ago.

Jamie Hall

ratio said:

I wonder how they dealt with these issues a few hundred years ago.

Good question. Not as well, but a partial answer (my experience is with pipe organs and pianos) is that if the relative humidity changes very slowly, then many of the problems go away (pitch problems in organs are also related to temperature, and simply can't be avoided). Thus an instrument in an environment with a reasonably constant relative humidity -- say around 60%, give or take, will stay happy even if the temperature is changing... SLOWLY. Example: one of my Steinways, an M, is in an unheated building which changes temperature slowly, but the relative humidity is remarkably constant. It does go slightly sharp as it gets cold, but it does it uniformly, and the action isn't affected. There is also a tracker (mechanical) action organ I play, and again it is in an environment with reasonably constant relative humidity. However, if either instrument has the humidity change significantly, either way, it becomes fractious.

I might also mention that it depends in the case of pianos (there is no such thing as a consumer grade organ!) on the quality of the piano. Curiously a top end piano is less likely to be damaged by low or rapidly changing humidity than a less expensive one.

Again, in the case of pianos, if you are faced with a situation where the relative humidity is going to drop much below 50%, as it may well do in a normally heated house in the winter, it is much better for the instrument to go cold than to dry out. Though the people playing it may complain...

Instruments in dry climates, such as the desert southwest, must, in my view, be in a space which has controlled added humidity.

None of these instruments will be happy, and indeed may be irreparably damaged, in an environment where the temperature is raised (and the relative humidity drops!) once a week, or something similar.

Edit: I might add that my practice piano -- a Steinway D concert grand -- is allowed to drop to 50 F in the winter, to keep the relative humidity up. I wear fingerless gloves, and I rather suspect most of the folks from years ago did too!

EBEBRATT-Ed

The problem is that only controlling the heating or cooling there is no guarantee that the humidity will "line up on the Psyc chart" In the summer you will likely have to overcool the air to get the humidity low enough then the room will be too cold so reheat is needed.

In the winter the opposite is true. The air is so dry it takes a lot of moisture to bring the humidity up and the air must be warm enough to absorb the moisture.


Humidity is harder to control than heating or cooling. These rooms are usually sealed with special paint to act as a vapor barrier and plastic coated ceiling tiles etc.

psb75

A building with real old-fashioned plastered walls will hold humidity better than modern construction (sheetrock/drywall). The many tons of lime-plaster absorbs and holds humidity and then gives it off when the interior air drys out. It's like an equalizing humidity "sponge". Now, lets talk about harpsichord, virginal, and clavichord keyboard instruments! Generally the players of these instruments tune their own.

Jamie Hall

psb75 said:

A building with real old-fashioned plastered walls will hold humidity better than modern construction (sheetrock/drywall). The many tons of lime-plaster absorbs and holds humidity and then gives it off when the interior air drys out. It's like an equalizing humidity "sponge". Now, lets talk about harpsichord, virginal, and clavichord keyboard instruments! Generally the players of these instruments tune their own.

Mostly because they have to! The wrist planks on those things won't hold tension for any length of time1 They also do it because some of what they play sounds better with alternate tunings...