Powered roof vent - Warehouse

[GRB]

My warehouse has 60' of tall south facing wall that is baked by the hot SoCal sun all day. Since this is SoCal, it is cooked a good 300 days a year. It has two whirlybird vents that move some air most of the time. We might shut off the manual closure a couple weeks a year.

I'm planning to add a Lomanco 1/10HP fan blowing air out the vent under power. This could all be done from inside the building. Has anyone done something like this? Looks like dedicated power air extraction would be a huge amount more difficult with work on the roof, etc.

I see the problem as the whirlybirds don't move enough air when it is cool. Even in the hot summer, it is usually cool from midnight until 5-6AM. A timer on the fan that runs it at those times would seem to pull air after the dust stirred up by traffic and prevailing breeze in the afternoons is done. When we arrive at 5-6AM, we could make a decision on running the fan longer.

I do see that the dedicated extraction fans for this are much more powerful than this.

 

[James-W]

You need a motor and fan capable of moving a sufficient volume of air in order for this to be useful. I don't know how to calculate it but there must be a formula for figuring it out.

 

[The Cobbler]

I don't think a 1/10 hp fan is enough to do any good for your situation ,
you will need to move a lot of air to have any noticeable effect IMO.
by no means am I an expert in the field .

 

[Richard Cranium]

a ceiling fan might help also.

 

[GRB]

It does seem like 1/10 hp isn't much compared to the units specifically installed to vent a warehouse. This fan unit I bought is the same one installed in the attic of my house to vent the attic. It seems to move a lot of air but that one is blowing out a grille on the side of the attic, not through a whirlybird.
Those whirlybirds seem to run a fair amount even on cool days. Yesterday barely was warm enough to take off a jacket and the whirlybirds were spinning, meaning air was exiting the building.
I'm working on cutting down the heat that is added to the building. I'm insulating one 12x12' metal door as a test. Only so much you can do as the door people told me not to add more than 35 pounds or so. I'm using expanding foam to seal anywhere air can leak in and using the thin reflective insulation: https://www.lowes.com/pd/Reflectix-400-sq-ft-Reflective-Roll-Insulation-48-in-W-x-100-ft-L/3775465?cm_mmc=SCE_BINGPLA_ONLY-_-LumberAndBuildingMaterials-_-SosInsulation-_-3775465:Reflectix&CAWELAID=&kpid=3775465&CAGPSPN=pla{ifdyn:dyn}&k_clickID=172292dd-b569-4224-a3cd-93ff006468a6&msclkid=3d6305903bb017ba94b35f78497de567
I'm making sure to leave a dead air space between the metal and the insulation and may add a second solid foil paper insulation on the inside for a second air space. i know you can't add fiberglass due to the weight. I may try the rigid foam on the other door and see which one works better.
I may also try to figure out a way to put a banner hanging in front of each roll up door to catch the sun and let the hot air out from behind. That would be a pain as it will have to be move out of the way for forklift and box truck to go through door.

 

[HoosierBuddy]

I ordered a fan from these guys for a warehouse:

https://www.industrialfansdirect.com/

The model I ordered maxes out at about 3000 CFM (16-inch). We also got their hood kit and a variable speed fan control switch. Total was a little less than $500.

The fan has been in service for about 2 years. It never gets turned off. It hasn't caused any problems. The variable speed is nice, because I wasn't sure how big of fan we needed. Typically, it's set to minimum all the time, but can be cranked up as needed.

You could put the same fan on a timer or a t-stat if you wanted to. They also sell powered roof vents.

Our installation was really not for temperature control. It was to create some air flow out of the warehouse for air quality purposes. For it's size, that fan moves a lot of air. It is only 1/10 HP. They sell all sizes though.

Phil

 

[GRB]

I thought I would update this thread in case my experience helps others. I did a quick install of a Lomarco 1800 1/10hp extraction fan, primarily made for gable ends of house attics. It says it can be mounted horizontally or vertically. This is the same unit I have had installed in the East end of my house attic. It runs hard every summer and has been working well for 17 years.

Mounting the warehouse unit below the whirlybird with the attached brackets, it ended up 4" below the opening to the whirlybird. I thought that would be a start and I would check air flow to see if I needed to get it closer to the actual hole or seal it up. It works great and when it is on, it is actually pulling additional air up through the 4" gap and seems to be moving more air out than if I had sealed the fan against the opening. Seems to be working like the bypass on a jet engine. Since it was 120F+ near the ceiling when I mounted it one morning at 4am, I figured I would just get it going and test it out. Didn't expect it to move more air than if I had done a "better" job.

Mounting it with the gap also seems to allow more air flow when the thermostat turns the unit off and there is only the natural airflow thru the whirlybird. It also still gives access to the chain that can be used to close the damper even if that is something you would only want to do in this climate for a month or so and even then not every year.

Getting the night time cooler air in the building and out the vent really helps. We have recently had record temps, with 115F one day and it is cooler in the warehouse than it was before it went from 80-85F to 90-110F.

Really happy.