Requirement for Outdoor Air Dispute
Requirement for Outdoor Air Dispute
(OP)
I completed the HVAC design for a church in my area a while back. Currently there is a disagreement over the neccessity for outdoor (ventilation) air. I'm in FL and the current Florida code is based upon the 2003 IMC.
Section 403.3 of the 2004 Florida Mechanical Code states, “Ventilation systems for other than Group R-3 (one- and two-family dwellings), shall be designed to have the capacity to supply the minimum outdoor airflow rate determined in accordance with Table 403.3 based on the occupancy of the space and the occupant load or other parameter as stated therein. The occupant load utilized for design of the ventilation system shall not be less than the number determined from the estimated maximum occupant load rate indicated in Table 403.3. Ventilation rates for occupancies not represented in Table 403.3 shall be determined by an approved engineering analysis. . .”
The mechanical contractor on this project has convinced the owner that because Table 403.3 does not explicity list churches, they are exempt from vetilation air requirements. I pointed out to the owner that the table does not list everything and that the paragraph states "Ventilation rates for occupancies not represented in Table 403.3 shall be determined by an approved engineering analysis" which I did. The owner countered that some county official has sided with the contractor in this case.
I believe that counties and municipalities can have their own requirements independent of the state, but this doesn't seem right at all. I have asked the owner to secure a letter from the county office which states that ventilation air is not required. If they are able to get this letter, I will then ask the owner for a letter stating that they have asked me to not include ventilation air in the design and recognize the health risks associated with this decision. At that point, I suppose I will remove the outside air and resize the equipment. Can anybody offer any advice on this situation?
Let me add that I have emailed the state Building Codes and Standards Office looking for their input as well.
Section 403.3 of the 2004 Florida Mechanical Code states, “Ventilation systems for other than Group R-3 (one- and two-family dwellings), shall be designed to have the capacity to supply the minimum outdoor airflow rate determined in accordance with Table 403.3 based on the occupancy of the space and the occupant load or other parameter as stated therein. The occupant load utilized for design of the ventilation system shall not be less than the number determined from the estimated maximum occupant load rate indicated in Table 403.3. Ventilation rates for occupancies not represented in Table 403.3 shall be determined by an approved engineering analysis. . .”
The mechanical contractor on this project has convinced the owner that because Table 403.3 does not explicity list churches, they are exempt from vetilation air requirements. I pointed out to the owner that the table does not list everything and that the paragraph states "Ventilation rates for occupancies not represented in Table 403.3 shall be determined by an approved engineering analysis" which I did. The owner countered that some county official has sided with the contractor in this case.
I believe that counties and municipalities can have their own requirements independent of the state, but this doesn't seem right at all. I have asked the owner to secure a letter from the county office which states that ventilation air is not required. If they are able to get this letter, I will then ask the owner for a letter stating that they have asked me to not include ventilation air in the design and recognize the health risks associated with this decision. At that point, I suppose I will remove the outside air and resize the equipment. Can anybody offer any advice on this situation?
Let me add that I have emailed the state Building Codes and Standards Office looking for their input as well.





RE: Requirement for Outdoor Air Dispute
Couple thoughts... What is driving the contractor and owner's to NOT provide ventilation? Is their motivation just the operating cost? If so, you could tell them they can shut the OA dampers down after install if they want.
Another angle would be to inform them ASHRAE is the leading HVACR industry organization that writes the majority of the standards the codes adopt. The "Applications" handbook Chapter 4 "Places of Assembly" states that OA for Places of Assembly should be provided per ASHRAE 62. ASHRAE 62 doesn't specifically list churches either BUT! It does say in the bottom of Table 6.1 (General Note #6)
Unlisted Occupancies: If the occupancy category for a proposed space or zone is not listed, the requirements for the listed occupancy category that is most similar in terms of occupant density, activities, and building construction shall be used."
This clearly states that at least SOME kind of ventilation is required.
Hope that helps,
RDmac
RE: Requirement for Outdoor Air Dispute
Take the "V" out of HVAC and you are left with a HAC(k) job.
RE: Requirement for Outdoor Air Dispute
Don Phillips
http://worthingtonengineering.com
RE: Requirement for Outdoor Air Dispute
I was taken aback by the code officials leaning this way - especially in the State of Florida. I do tons of work there and if anything, they interpret the codes more stringent than others.
Andy W.
RE: Requirement for Outdoor Air Dispute
It is common knowledge, good practice and a code requirement that assembly spaces be ventilated.
If there's controversy, you're the man......
RE: Requirement for Outdoor Air Dispute
Throughout the building, there are a few operable windows, but not nearly enough to do away with mechanical ventilation.
Andy (Wareagle) - I'm in the rural panhandle - things are typically alot less stringent up here than in the peninsula. ALOT less. But I think this is taking things too far.
RE: Requirement for Outdoor Air Dispute
Take the "V" out of HVAC and you are left with a HAC(k) job.
RE: Requirement for Outdoor Air Dispute
Take the "V" out of HVAC and you are left with a HAC(k) job.
RE: Requirement for Outdoor Air Dispute
The owner has been told that this will save money and won't make any difference, by the mech contractor.
The owner twists/makes up the story about the code official and only hears what he wants to hear.
Tell the owner that if he pre-cools his Mary and leaves her near a window, not only will she cry a few tears, she will sweat a baptismal font.
RE: Requirement for Outdoor Air Dispute
I challenge you to find a condominium in FLA that is not ventilated with windows.
No, I Would Never recommend to a commercial client to ventilate in this manner. I'm just making a speculation on the contractor's thought pattern.
PatBethea - I've also done a far amount work in the panhandle - mostly the Destin & P.C. area.
Andy W.
RE: Requirement for Outdoor Air Dispute
Take the "V" out of HVAC and you are left with a HAC(k) job.
RE: Requirement for Outdoor Air Dispute
And again - I would never do it.
Andy W.
RE: Requirement for Outdoor Air Dispute
I passed all of this along to my clinet who indicated they would be in touch after talking to the local officials. That was three or four days ago. Hopefully the issue is closed.
RE: Requirement for Outdoor Air Dispute
Don Phillips
http://worthingtonengineering.com
RE: Requirement for Outdoor Air Dispute
Outdoor air ventilation cooling load can be mitigated by using air to air heat exchangers. Also your utility may have off peak ice storage or chilled water storage rebates.
You may need to look at the block load for that short time period when the main sanctuary is occupied, try running the load calcs and allow some deviations from ideal conditions. For a few hours/week this is not eschatological. Also try a pre occupancy cooldown cycle with next to zero outside air. Most dampers leak 5% even when shut. You can measure the CO2 or O2 with a sensor and get by with no extra OA.
Another strategy for churches is to use chilled water, size the sanctuary and fellowship hall air handlers for their respective loads, however the chiller that serves both AHU's will see a load that is less than the sum, because the occupants don't occupy both spaces simultaneously.
There are some legitimate means of reducing the tonnage on a church HVAC system. Eliminating OA ventilation is not one of them. SARs, tuberculosis, influenza B, other airborne infectious diseases make an expenditure for ventilation very necessary.
RE: Requirement for Outdoor Air Dispute
Especially when ventilated to an excessive code which anything based on the current ICC code set would be.
Perhaps it is not a Pentacostal Church, those are always as tough as doing a gym :)
Take the "V" out of HVAC and you are left with a HAC(k) job.
RE: Requirement for Outdoor Air Dispute
Maybe an ERV preconditions and then feeds the AC with air
Take the "V" out of HVAC and you are left with a HAC(k) job.
RE: Requirement for Outdoor Air Dispute
RE: Requirement for Outdoor Air Dispute
You might tell the Church that if the CO2 levels are not controlled, the entire congregation may get sleepy during the service. Of course, that could be caused by CO2 or a boring sermon!!