Staff
Analysis for Declaratory Statement Request
DS2014-135
Issue:
Petitioner requests a declaratory statement concerning applicable nature
of FBC, Building 2010 – Section 423.15.5
Ventilation air make-up for HVAC systems,
in relation to the FBC, Mechanical. Petitioner seeks a decision concerning
the use of an Exemption listed under Section
403.2, FBC, Mechanical 2010
through Section 423.15.5, FBC, Building 2010. In addition,
Petitioners seeks clarification on ventilation mandated in occupied spaces.
Background:
FBC 423.15.5 is
based on ASHRAE 62-1999 and earlier editions for Variable and Intermittent Use Occupancies.
An Educational Facility is a Constant and Continuous Use Occupancy, and FBC
423.15.5 should not be considered applicable.
ASHRAE 62.1-2001 and later
editions were revised to remove the wording of FBC 423.15.5 because it was
being used incorrectly to reduce the Ventilation (Outside) air make-up below
the requirements of ASHRAE 62.1 Ventilation (Outside) Air Tables, FMC 403.3 and
FMC Table 403.3. The wording of FBC
423.15.5 was included in FMC-2001-403.3.
The Florida
Building Code caught up with ASHRAE. 62.1 and removed the wording of FBC
423.15.5 from 403.3 in the 2004 and subsequent Editions. The wording of FBC.
423:15.5 was added in FBC 2007 (in 2007 it was FBC 423.15.6) even though this
same wording was removed from FMC 403.3-2004 and subsequent editions. Due to
revisions of ASHRAE 62.1 and FMC 403.3, FBC 423.15.5 no longer has any basis of
support.
For an Example of
the misuse of FBC 423.1 5.5, please see the attached Outside Air Ventilation
Rates Table from a specific Florida School District Construction Standards
Section 15100.
In addition, the
wording of FBC 423.15.5 which states in part " ... for the duration of
operation of the air 'conditioning system ... " is requiring the
operation of the Ventilation (Outside) Air Systems and associated Exhaust
System even when spaces are unoccupied.
For a large School District the operating cost of Ventilation (Outside)
Air Systems and associated and associate Exhaust Systems is approximately
$500,000 per hour per year District wide.
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SECTION 102, FBC, Building 2010
APPLICABILITY
102.1 General.
Where there is a conflict between a general requirement and a specific
requirement, the specific requirement shall be applicable. Where, in any
specific case, different sections of this code specify different materials,
methods of construction or other requirements, the most restrictive shall
govern.
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423.15.5
Ventilation air make-up for HVAC systems. - FBC,
Building 2010
Where peak occupancies of less than 3 hours duration occur, the outdoor
air flow may be determined on the basis of average occupancy for school
buildings for the duration of operation of the air-conditioning system, provided
the average occupancy used is not less than one-half the maximum.
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403.2 Outdoor air
required. - FBC, Mechanical 2010
The minimum outdoor airflow rate shall be determined in accordance with
Section 403.3. Ventilation supply systems shall be designed to deliver the
required rate of outdoor airflow to the breathing zone within each occupiable
space.
Exception: Where the
registered design professional demonstrates that an engineered ventilation
system design will prevent the maximum concentration of contaminants from
exceeding that obtainable by the rate of outdoor air ventilation determined in
accordance with Section 403.3, the minimum required rate of outdoor air shall
be reduced in accordance with such engineered system design.
403.2.1
Recirculation of air.
The outdoor air required by Section 403.3
shall not be recirculated. Air in excess of that required by Section 403.3
shall not be prohibited from being recirculated as a component of supply air to
building spaces, except that:
1.
Ventilation air shall not be recirculated from one
dwelling to another or to dissimilar occupancies.
2.
Supply air to a swimming pool and associated deck
areas shall not be recirculated unless such air is dehumidified to maintain the
relative humidity of the area at 60 percent or less. Air from this area shall
not be recirculated to other spaces where more than 10 percent of the resulting
supply airstream consists of air recirculated from these spaces.
3.
Where mechanical exhaust is required by Note b in
Table 403.3, recirculation of air from such spaces shall be prohibited. All air
supplied to such spaces shall be exhausted, including any air in excess of that
required by Table 403.3.
4.
Where mechanical exhaust is required by Note g in
Table 403.3, mechanical exhaust is required and recirculation is prohibited
where more than 10 percent of the resulting supply airstream consists of air
recirculated from these spaces.
403.2.2
Transfer air.
Except where recirculation from such spaces
is prohibited by Table 403.3, air transferred from occupiable spaces is not
prohibited from serving as makeup air for required exhaust systems in such
spaces as kitchens, baths, toilet rooms, elevators and smoking lounges. The
amount of transfer air and exhaust air shall be sufficient to provide the flow
rates as specified in Section 403.3. The required outdoor airflow rates
specified in Table 403.3 shall be introduced directly into such spaces or into
the occupied spaces from which air is transferred or a combination of both.
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403.3 Outdoor airflow
rate - FBC, Mechanical 2010
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 this section. 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 those for a listed occupancy classification that is most similar in
terms of occupant density, activities and building construction; or shall be
determined by an approved engineering analysis. The ventilation system shall be
designed to supply the required rate of ventilation air continuously during the
period the building is occupied, except as otherwise stated in other provisions
of the code.
With the exception of smoking lounges, the ventilation rates in Table
403.3 are based on the absence of smoking in occupiable spaces. Where smoking
is anticipated in a space other than a smoking lounge, the ventilation system
serving the space shall be designed to provide ventilation over and above that
required by Table 403.3 in accordance with accepted engineering practice.
Exception: The occupant load
is not required to be determined based on the estimated maximum occupant load
rate indicated in Table 403.3 where approved statistical data document the
accuracy of an alternate anticipated occupant density.
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403.5 System operation.
- FBC, Mechanical 2010
The minimum flow rate of outdoor air that the ventilation system must be
capable of supplying during its operation shall be permitted to be based on the
rate per person indicated in Table 403.3 and the actual number of occupants
present.
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401.3 When
required. - FBC, Mechanical 2010
Ventilation shall be provided during the periods that the room or space
is occupied.
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Table 403.3 FMC.
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FMC
403.4-2007.
403.4 ASHRAE 62 Alternative.
In lieu of compliance with Section 403.1 through Section 403.3,
mechanical ventilation may be implemented in compliance with ASHRAE 62
including approved addenda
[Note: Red to Indicate outdated code]
Staff analysis: (Note: staff
response is only applicable to future projects)
Questions:
1) Question:
Does FMC 403 supersede FBC 423.15.5?
Answer: No, with regard to the project in
question and as per Section 102.1 of the 2010 Florida Building Code, Building,
the requirements of Section 423.15.5 are more specific to educational facilities
and for that it supersedes the relevant requirements of Section 403 of the
Florida Building Code, Mechanical.
2) Question: The School District is using FBC
423.15.5 to comply with FNC 403.2-Exception.
Since the working of FBC 423.15.5 was removed from ASHRAE 62.1, FMC
403.3-2004, FMC 403.3-2007, and FMC 403.3-2010, FBC 423.15.4 has no basis of
support and it does not make sense that FBC 423.15.5 should be allowed for
compliance with FMC 403.2-Exception. Can
FBC 423.15.5 be used to comply with FMC 403.2-Exception?
Answer: See answer
to Question #1.
Question: FMC
403.4-2007 states "ASHRAE 62 Alternative. In lieu of compliance with
Section 403.1 through Section 403.3, mechanical ventilation may be implemented
in compliance with ASHRAE 62 including approved addenda". FMC 403.4-2007
was removed in FMC 403-2010. In addition, FMC 403.2-Exception was added in FMC
403-2007 and FMC 403-20 l 0 and with no basis of compliance. Does the Analysis
and/or Demonstration required for compliance with FBC 403.2-Exception have to
have an ASHRAE 62.1 basis?
Answer: No, as per section 403.2, Exception, of the 2010 FBC, Mechanical, an engineered
ventilation system is permitted as designed by the engineer of record and
approved by the local authority having jurisdiction. There is no reference to ASHRAE 62.1 in the
said exception.
3) Question: FMC 403.5-2010 states "The
minimum airflow rate of Outside Air that the Ventilation System must be capable
of supplying during its operation shall be permitted to be based on the rate
per-person indicated in Table 403.3 and the actual number of occupants
present". FMC 403.3-200 l,
403.3-2004, FMC 403.3-2007 all state in part "Ventilations Systems shall
be designed to supply the minimum outdoor air flow rate determined in
accordance with Table 403.3 based on the occupancy of the space and the
occupant load or other parameter stated therein." For a large School
District the operating cost of Ventilation (Outside) Air Systems and associated
Exhaust Systems is approximately $500,000 per hour per year District wide.
Basing the design of Ventilation (Outside) Air Systems on the first column of
Table 403.3 (similar to FMC 403.3-2001, FMC 403.3-2004 and FMC 403.3-2007) will
minimize the operating costs of the Outside Air Systems and associated Exhaust
Systems and minimize the Outside Air and associated Exhaust Equipment size and
cost. Based on 30 years of experience, Ventilation (Outside) Air Systems
designed based on the air flow rates or other parameter listed in the first
column of Table 403.3 will provide adequate outside air for the space. Based on the above, is the minimum
acceptable design for a Ventilation (Outside) Air System based on the air flow
rate determined in accordance with Table 403.3 based on the occupancy of the space
and the occupant load or other parameter listed in the first column of Table
403.3?
Answer: See answer to Question #1.
4) Question: FMC 403.3-2010 states in part: "
... the Ventilation (Outside) Air System shall be designed to supply the
required rate of Ventilation (Outside) Air continuously for the period the
building is occupied ... "
FBC
423.15.5 states in part"… for the duration of operation of the air
conditioning system ...”
The
intent of FMC 403 and FBC 423.15.5 is for all occupied spaces to be supplied with
Ventilation (Outside) Air. In order to
reduce operating cost and comply with FMC 403 and/or FHC 423.15.5, if the
Building and Space Air Conditioning Systems are required to run as well as
Outside (Ventilation) Air and Exhaust Systems for spaces that are occupied., is
it acceptable to turn off the respective Ventilation (Outside) Air Systems
(Units) and associated Exhaust Systems (Fans) that serve unoccupied spaces?
Answer: See answer to Question #1.
5) Question: With regard to the specific issues
of FBC 423.15.5 and FMC 403, does the "Authority Having Jurisdiction"
(in this case the School District) have a legal obligation to enforce the
Florida Building Codes correctly and in accordance with the Florida Building
Code Commission Declaratory Statement pursuant to this Declaratory Petition'?
Answer: Answer is not possible. The subject matter raised by the question
falls outside the scope of the Declaratory Statement request.