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  1. #1
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    Warehouse Ventilation Questions

    Hi,
    I would like to install exhaust and supply fans in our 450,000 cubic foot warehouse (30' ceiling) to keep it cool during the summer. I was thinking that these would be mainly stay on during the night to bring cold air into the warehouse.

    Some questions:

    1) Most sites list warehouses to require a minimum of 3 air exchanges per hour. This seems like a lot if i'm just trying to bring cooler air by running these fans all night long. If I run these for 8 hours at night time, and I exchange the air once per hour i'm still exchanging the air 8 times. Won't that be enough?

    2) Some places recommend ceiling fans, but that seems like it would only push the hot air that stays near the roof down to the work place. Everyone at the facility works at the ground level.

    3) I'd like to install the supply and exhaust fans by replacing windows near the ceiling. Should I run the exhaust fans during the day as well to remove the hot air that's stuck near the ceiling? If it's 100F outside wouldn't I want to avoid bringing hot air in? What would be a good schedule to activate the supply and exhaust fans?

    I'm an electrical engineer so any advice is helpful. Appreciate it in advance.
    Thanks,
    Omer

  2. #2
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    Quote Originally Posted by opeleg View Post
    Hi,
    I would like to install exhaust and supply fans in our 450,000 cubic foot warehouse (30' ceiling) to keep it cool during the summer. I was thinking that these would be mainly stay on during the night to bring cold air into the warehouse.

    Some questions:

    1) Most sites list warehouses to require a minimum of 3 air exchanges per hour. This seems like a lot if i'm just trying to bring cooler air by running these fans all night long. If I run these for 8 hours at night time, and I exchange the air once per hour i'm still exchanging the air 8 times. Won't that be enough?

    2) Some places recommend ceiling fans, but that seems like it would only push the hot air that stays near the roof down to the work place. Everyone at the facility works at the ground level.

    3) I'd like to install the supply and exhaust fans by replacing windows near the ceiling. Should I run the exhaust fans during the day as well to remove the hot air that's stuck near the ceiling? If it's 100F outside wouldn't I want to avoid bringing hot air in? What would be a good schedule to activate the supply and exhaust fans?

    I'm an electrical engineer so any advice is helpful. Appreciate it in advance.
    Thanks,
    Omer
    Where in God"s green earth are you located.
    Ventilating over night will in most cases raise the indoor dew point to outside levels. This may cause mold and other problems with materials in the warehouse.
    Keep us posted.
    Regards Teddy Bear
    Bear Rules: Keep our home <50% RH summer, controls mites/mold and very comfortable.
    Provide 60-100 cfm of fresh air when occupied to purge indoor pollutants and keep window dry during cold weather. T-stat setup/setback +8 hrs. saves energy
    Use +Merv 10 air filter. -Don't forget the "Golden Rule"

  3. #3
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    Quote Originally Posted by teddy bear View Post
    Where in God"s green earth are you located.
    Ventilating over night will in most cases raise the indoor dew point to outside levels. This may cause mold and other problems with materials in the warehouse.
    Keep us posted.
    Regards Teddy Bear
    We are located in Northern New Jersey. A few days out of the year it will reach 90-100F, but it's usually 80-85F and there is a 20-30F drop at night time. I didn't think about the dew point but I will have to do some more research on that.

    Omer

  4. #4
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    I have worked in factories that had the HUGE ceiling fans made by the 'Big ass fan' company. Yes that really is their name. They do a remarkable job. They really move a lot of air. And make a huge difference.
    "If you can’t describe what you are doing as a process, you don’t know what you are doing." ~ W. Edwards Deming

    All those who wander..are not lost.

    Do NOT..mistake my kindness for weakness.

    The early bird may get the worm..but the second mouse gets the cheese.

  5. #5
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    "If you can’t describe what you are doing as a process, you don’t know what you are doing." ~ W. Edwards Deming

    All those who wander..are not lost.

    Do NOT..mistake my kindness for weakness.

    The early bird may get the worm..but the second mouse gets the cheese.

  6. #6
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    May 2016
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    That's a pretty expensive solution for ceiling fans. I was hoping someone could get into the differences between exhaust ventilation and ceiling fans. It seems like the ceiling fans would just move the hot air near the ceiling down towards the work place. I understand there's a breeze but we have floor fans that point horizontally and I feel like that would be better.

  7. #7
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    I believe store rooms require 3 changes per hr. Occupied spaces (warehouses) 6 - 8 changes per hr.

  8. #8
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    The cooler air from night ventilation probably won't affect much if there is no way to store it. Many warehouses have little in terms of storage except for concrete floors.
    In the SW , swamp coolers are usually used but they wouldn't work in NJ.
    Often the approach is to keep the heat out through added insulation and reflective roofs but that's often also an expensive choice. Warehouses are usually not known for insulation. but that's often also an expensive choice.

    Any air you exhaust will be replaced by outside air. In NJ humidity could have a negative effect. Humidity has a negative effect on comfort.
    Air in a space, if not disturbed, will have a stacking effect where the warmer air will collect in the higher places. With fans blowing it will mix and might be a bigger problem. This was discovered in supermarkets years ago when the practice was to condition the entire space. The studies found they only had to condition the space where the occupants were.
    Fans blowing at ground level might help if the warmer air up higher wasn't disturbed.
    Some simply have vents up high to relieve warm air. You might ask around to see if other similar buildings have had luck with.
    I should have played the g'tar on the MTV. MK

    You can be anything you want......As long as you don't suck at it.

    SMW Lu49

  9. #9
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    I'm not sure you what you mean by storage. Are you referring to insulation? There's a lot of equipment and framing inside. We've turned on big fans at the loading doors in the early mornings and within 1-2 hours the entire warehouse cools down.

  10. #10
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    Quote Originally Posted by opeleg View Post
    I'm not sure you what you mean by storage. Are you referring to insulation? There's a lot of equipment and framing inside. We've turned on big fans at the loading doors in the early mornings and within 1-2 hours the entire warehouse cools down.

    Storage is the ability for a structure to absorb the cooling (or heat in other cases). The air has little capacity because of density. Framing won't store much. The concrete floors will do the most but often if it's not insulated slab-on-grade the ground temperature is the average of summer/winter. Where you're at probably around 55 DegF.
    Your big fans cool the air because of rapid exchanges and blowing air on people helps comfort as long the air is cooler than they are. It is dependent on out side air temps.

    To actually cool a space usually requires throwing a lot of cold air at it. Ventilation helps some but it's not a complete solution except in certain seasons.
    I should have played the g'tar on the MTV. MK

    You can be anything you want......As long as you don't suck at it.

    SMW Lu49

  11. #11
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    Quote Originally Posted by pecmsg View Post
    I believe store rooms require 3 changes per hr. Occupied spaces (warehouses) 6 - 8 changes per hr.
    The only requirement is a fresh air CFM exchange calculated from the people and the area of the room/building right? Or is there something that states a minimum exchange requirement?

  12. #12
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    Quote Originally Posted by vhdblood View Post
    The only requirement is a fresh air CFM exchange calculated from the people and the area of the room/building right? Or is there something that states a minimum exchange requirement?

    I'd check code requirements as most warehouses leak like a sieve. here the only requirement is combustion air venting. It's been awhile so I'd have to check.
    I should have played the g'tar on the MTV. MK

    You can be anything you want......As long as you don't suck at it.

    SMW Lu49

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