Thread: Ventilation requirement

Inspected a commercial building today. My client wants to know (and so do I) how a building that is 576000 cu ft is ventilated by three 36" louvered fans with no make up air vents. Boy are the outside doors hard to open!! Where do I research the engineering charts to tell me what to tell him? The fans turn on when the lights are turned on. There is an A/C unit, but it only supplies conditioned air to office areas, not the open warehouse area. The intended use is for indoor soccer mini fields for practice and teaching, so a lot of little bodies will be in there at one time. My concern is that there is not enough air exchange. Any help is appreciated.
The other concern I had is this: There are at least 5 garage type forced air heaters hanging from the ceiling. Do I need to be concerned with CO detectors?

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Check Table 403.3 in the Mechanical Code for Ventilation Requirements For Different Buildings.

You might also want to verify that the unit heaters are OK in a soccer field environment. Some of those units have open flames and can't be use in some applications.

I'm not clear on your description but in general for every CFM of air introduced or exhausted you need virtually the same amount of exhaust or fresh air to balance it out. If the those are exhaust fans putting the entire building in negative pressure then none of the combustion appliances will exhaust and the fumes will be back drafting into the building.
Just from the sound of it, you have a problems that needs a HVAC engineer to design a repair.
Some positive pressure can be of benefit IF by design but it sounds like someone forgot to finish the equation.

There are a lot of issues here that your inspection report is unlikely to answer. In these types of assessments, I don't expect to give the client all the answers. I make it clear to the client that I can provide guidance on issues. The guidance and information provided will make what they have to do, faster and easier. Detailed answers will likely have to come from design engineers. Arch, SE, HVAC guy, etc.
You don't give any real details on the building or your location, so it's all sort of a guess. Was this an old warehouse? If so it may have been designed with passive air infiltration for make-up air. If it is an old warehouse those unit heaters typically weren't installed to 'heat' the place. They were generally just there to keep the space from getting 'too' cold. Chances are your client will need to install multiple RTU to heat and cool the place. A lot of kids running around will generate a lot of heat gain. Cooling will be needed.
It also sounds like your client will be changing the use classification of the building. If so, you can punt on the matter or, a better option, is to do some research with your local DOB. Your report could include info, pdf's and links on what the probable new use classification will be, general requirements, licensing req. and costs, etc.
For me at least, these types of reports/insp are more about counseling, holding hands, guidance. The client needs info and answers. The answers you can't really give them. The info to get the answers faster, easier and more reliably is what you can give them.
The HVAC needs a full load calc, can't do a load calc until you know the allowed occupancy, can't really know the allowed Occ., until someone talks with the Muni about requirements, etc,,
It's a long chain of info that has to come together.
And of course, there is also Zoning. If an old warehouse, is it located in an industrial zoning district or multi-use zone? Current zoning may not allow a bunch of little kids among trucks and hazardous materials. A zoning variance can take lots of time and money.

Thanks for the replys. I'm assuming that the locals are ok with what my client wants to do (I know what the word "assume" means). It is a baseball workout area now. Batting cages, pitching mounds, throwing areas, etc. It's a newer building (1997) and not in an industrial area. It's adjacent to and includes a full size ball field, tennis courts and some not used batting cages.

I don't have a copy of the Ventilation code that you reference. I am in agreement with "air in / air out" statement. Flue gasses will be sucked in the reverse direction if makeup air is not provided for. You can do that very same thing with a "whole house fan" in a residential setting.

I like the statement about guiding the client to a solution. I will relay some of the info in the inspection report and then refer him to a HVAC professional. Any other suggestions would be appreciated.

Not sure what other suggestions to give since I don't know the nature of the services you are providing for the client.
Off the top of my head though ...
- Sounds like usage is changing a bit from adult to child; will there be toilet facility changes needed
- Egress/panic door hardware
- Parking, loading, unloading, demarkation changes for better safety with kids running around
- Security camera issues for safety and privacy
- Installation of more automatic or timed controls to keep kids from messing with light switches
- Has your Muni adopted and ADA req since the last licensing of the facility? Was the last license and occupancy review done prior/with/without ADA in mind?

At the minimum there should be a gravity intake damper large enough to make up exhausted cfm.

I'm not an expert in this, but I have seen and been in many large warehouse type structures that have similar vent fans. In all cases the building had the same number of equally sized louvered intake vents on the opposite wall of the building.

The ceiling mounted furnaces are usually built like tanks. They should be vented to the exterior of the building. A common problem with this type of heater/furnace are the lack of maintenance. Out of sight and out of mind, so to speak. If they are over 15 years of age the odds of a cracked heat exchanger are pretty good.

Originally Posted by David Bell

At the minimum there should be a gravity intake damper large enough to make up exhausted cfm.

Yup. What he said.

Code varies but figure ventilation air at 20 CFM per occupant. If it were JUST a warehouse the ventialtion requirement is 0.05 CFM/SF.

Both of these figures are pretty low when it comes to ventilating the space for sports. I would size a system at around six air changes per hour if there were no conditioning taking place. 576,000 CF x 6 air changes per hour/60 min per hour = 57,600 CFM.

Truth is propeller fans CAN move a lot of air when there is very little pressure drop. If there are overhead doors to pull the make up thru you could be in the ballpark.