Humidity Control - Large Millwork Warehouse

[Designer_82]

Owner for a large warehouse, roughly 42,000 sq.ft., needs the humidity controlled to 30%-45% @ 60°f-80°f.

From what I understand, that is a pretty tight range. Would the equipment required be extremely expensive and is any such equipment even available?


Thanks

 

[EnergyProfessional]

it is doable... museums and other places do it. you need good control of infiltration... it will be expensive. Climate will matter.

 

[Designer_82]

Any examples of equipment that can do this?

 

[EnergyProfessional]

Most commercial AHU could be built with various cooling, heating coils and possibly latent energy wheels to accomplish what you want. The details depend on the climate and other factors impacting sensible and latent load.

I would ask the owner what the requirement is based on so they understand what it may mean cost-wise. Also find out how tolerant the goods in there are to occasional exceeding those values.

This isn't an engineering problem, it is an economics problem.

 

[MedicineEng]

Also, you can consider if you need all the warehouse with such tight requirements or just a specific area where a particular type of wood is more sensitive to humidity.

If you can reduce the area to be subject to the tighter requirements, that would also reduce your investment.

But as EnergyProfessional mentioned, this is a economics problem, not an engineering one.
Technically it is feasible, now it all depends on how much is the owner willing to invest.

 

[LittleInch]

Square area is only one part. What's the height/cubic area?

Outside temp and RH?

Will probably need substantial insulation to reduce cost.

Not a particularly tight range, but would need "airlock" type entry systems.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Designer_82]

It is located in Wareham, MA. The structure is insulated sheet metal wall with interior gyp. board. Warehouse stuff.

So to achieve the tight humidity range, you just provide AHU's with more capacity for heating/cooling?
Is that how it is accomplished?
No special free standing commercial humidity units?

Thanks again

 

[LittleInch]

Humidty units tend to be self contained in terms of cooling to remove the water then reheating to get it back to more or less the same temperature plus the heat of the unit itself.

Insulated with what?

More importantly how air tight / leaky is is?

How many times are the doors opened, etc etc

Your questions cannot be answered here but needs someone to properly design it. Yes it can be done, but controlling the air temp and humidity of large open spaces is not cheap. A lot depends on your specification and requirements for how the building is laid out, insulation of walls, floor and roof, what obstructions there are to the air flow, sun load, wind load, snow load, internal heat load, door size .... I think you get the drift.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[nuuvox000]

First thing to do is find your ASHRAE design conditions to see how much water you need to remove (or add). I'm in Utah so when there are humidity requirements we typically are only worried about adding water.

In a humidity-controlled environment I typically like to keep the space slightly pressurized to keep outside air out of the building. You'll need to do a tightness calculation for this to see how much outside air you'll need for pressurization.

I'm not exactly sure of your humidity in that location but east coast seems to be humid so you'll likely need some dehumidifiers. Anyone who has purchased these before can tell you that they are incredibly expensive. If the owner is on budget you'll have to push them to see if you can push their requirements to a smaller area or to less-expensive constraints.

What happens if the building air goes out of line with these requirements? Is all of their millions of dollars worth of product immediately ruined? Or is that just the optimal humidity and temperature for storage of something?

I guess what I'm trying to say is the owner probably thinks you just have to change a setting on the existing RTU's to make this happen, they really aren't aware of the $$$ involved typically.

 

[Designer_82]

Thanks, that's very informative.

I was randomly browsing and saw some 200 pound units at around 5-10k in price. Is that what we're talking about when we say "expensive" 10k?

Lastly, about maintaining minimum humidity, how do you add water to increase humidity?

Thanks again

 

[LittleInch]

200 lb what. Per min, hr or day and assume you mean water removal amount.

How many do you need though?

To increase humidity you add water to a porous membrane and blow air through it.

https://www.temperaturemonitoringua...easing-humidity/humidifier-working-principle/

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[nuuvox000]

I'm not sure what you saw but any dehumidifiers I have installed are always in the 100's of thousands of dollars, Munters or Bry-air are manufacturers we'll use. We typically add water through ducted water dispersion units, something like Nortec GS series.

 

[MedicineEng]

Don't forget that dehumidifiers are not cheap to run, so it is not the initial investment but also the permanent running costs on dehumidifiers.

On humidifiers, be very, very attentive to Legionella. Humidifiers are a boon for Legionella so a very strict Legionella control program must be put in place.

 

[CCPudge]

This is my first time using this site, it was recommended by a friend.....I have a customer that needs 2 humidity controlled rooms added inside their warehouse. They only care that the humidity stays at 50% (+-5%). We are proposing to construct the room out of 2" foam panel walls with sealed doors.....I want to try to handle the humidity with just dehumidifiers, no cooling. The air around the rooms will be worst case 95 / 90% RH....Im trying to determine how many gallons of water that need to be removed every 24 hrs......Cu ft in each is 8,150 and 10,080.......

 

[LittleInch]

CC pudge.

Welcome, but the way it works here is that you don't hijack other peoples threads.

Please start your own thread and supply all info you can otherwise you'll just be asked for it.

SO e.g. in your post I guess people would like to know max / min temperature of your rooms and what the assumption is for amount / inlet of outside air in 24 hours, both as lumps when you do open the door and natural leakage. If you're not cooling, why the foam walls?

This will make a huge difference to the answer.

If you mean you keep the temperature the same then that's clear, but a stand alone dehumidifier will slowly add heat due to the power it consumes.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[zldh]

To OP:
I would recommend doing the following:
1) Plot your desired space condition ranges on a psychrometric chart for your elevation

2) Plot your location's summer/winter design conditions (probably ASHRAE climate data in your case or use your company's design day specifications if that is more stringent than ASHRAE)

3) Draw out the process lines required to get from your climate design condition to your desired condition. For example, if I have a -5F winter design day condition, I will first need to preheat say 75F to allow for evaporative cooling to add the required humidity and then re-heat to your desired final dry bulb temp of 70F. This is by no means the only way of doing this process nor does it take into account all the factors that should be considered (equipment overshoot/undershoot/leakage/internal loads/etc) but it at least gives you a mental picture.

To put it in perspective, one of my recent projects was to put a 100% OSA makeup air handler into a cleanroom with a semiconductor industry "standard" of 70F +/-1F, 45% +/-5%RH (note: my application was for 100% OSA, not internal recirc ventilation/cooling). The above thought process allowed me to do ROM calculations on the makeup air handler pre-heat coil, sensible coil, latent coil, humidifier and reheat coil that got me to within 5-10% of the final submittal capacity from our vendor from an afternoon of looking at a psych chart and a little bit of Excel for both the winter/summer design day conditions.

I know the above seems overly simplistic but getting your head wrapped around the situation can do wonders in focusing your research, calculations and vendor info requests on the economics of the equipment that could be applied. In the end, you will likely have vastly different equipment than my example, but the thought process will still be applicable.