Download “Common ventilation system”.

Proposed Modification to the Florida Building Code
Modification #:
Section 553.73, Fla Stat
Name: Guy Van Meulebrouck PE
Address: 1660 Trade Center Way
E-mail:
[email protected]
Phone:
(239) 597-7544
Fax
(239) 597-6363
Code:
mechanical
Section #: 403.3.2
Text of Modification [additions underlined; deletions stricken]:
403.3.2 Common ventilation system. This section deleted in it’s entirety.
Replace with:
403.3.2 Intermittent Occupancies: Where individual rooms within a building are
typically used for periods of 3 hours or less in any given 8 hour period, the
required ventilation air for that space can be reduced by up to half depending on
ratio of hours in use over a three hour period divided by three.
Fiscal Impact Statement [Provide documentation of the costs and benefits of the
proposed modifications to the code for each of the following entities. Cost data
should be accompanied by a list of assumptions and supporting documentation.
Explain expected benefits.]:
A. Impact to local entity relative to enforcement of code:
this change makes review of drawings easier. This change basically codifies common
practice of design and operation of buildings, in other words, no longer makes it
necessary to lie in order to design a proper building in Florida.
B.
Impact to building and property owners relative to cost of compliance with
code:
This change reduces owner’s risk of moldy buildings and high energy bills while still
maintaining a proven adequate ventilation to buildings. There will be no negative cost
impacts due to adoption of this change.
C.
Impact to industry relative to cost of compliance with code: Because some
buildings are currently providing more expensive systems than is necessary, the
dollar volume of mechanical air conditioning products sold will show a small
decrease-
Rationale [Provide an explanation of why you would like this Proposed
Modification to the Florida Building Code.]:
This multi space calculation is not correct. As can be readily seen, it only considers the
quantity of fresh air coming out of a worst case air device, in the first minute of operation.
Official Form 9B-3.047-2004
565342104
It fails to acknowledge the amount of fresh air that is naturally occurring in a building due
to infiltration overnight (at one half air change per hour, the air inside any building
naturally replenishes itself during unoccupied nights.).
This multispace calculation fails to represent the amount of fresh air that recirculates
unused. This is no small mistake. Conscientious use of the multispace calculation can
actually double the outside air into buildings. Even in lesser cases, say a 10% increase to
outside air, this amount of air is always unused and therefore re-enters the system on a
minute by minute basis.
This multispace calculation also fails to acknowledge infiltration during occupied times
and fails to acknowledge short duration occupancies.
This calculation further assumes that gases do not readily disburse evenly throughout a
space within a reasonable amount of time (say 10 minutes). To my knowledge, this has
never been shown to be true and in fact violates Dalton’s Law of Partial Pressures.
The ASHRAE committee who promotes this equation has been challenged on this issue
by people on and off of the committee.
Detailed Testing and Observation of any 10 random buildings in Florida should prove that
many of Florida’s buildings that work (no mold and no complaints) have either ignored the
multispace calculation or the owner/contractor has reset the ventilation rates to below
what the multispace calculation requires.
Additionally, this calculation assumes that long crowded meetings do not or will not adjorn
for breaks nor open the door for better air circulation. Neither of these assumptions
warrant forcing building owner’s into risk of molding buildings.
Please explain how the proposed modification meets the following requirements:
1. Has a reasonable and substantial connection with the health, safety, and
welfare of the general public: once air conditioning equipment exceeds 20%
outside air, specialized equipment is required to handle the humidity in
Florida. Common commercial duty air conditioning equipment IS NOT
DESIGNED FOR MUGGY AIR. Restaurants, Assembly occupancies and
schools provide high levels of outside air and specialized equipment
regardless of the multispace calculations. The only effect this calculation has
is to force occupancies that do not require dehumidification into using
dehumidification.
2.
Strengthens or improves the code, and provides equivalent or better
products, methods, or systems of construction: many buildings were
successful at the oldest 5 cfm ventilation rate as long as there was no
smoking and no VAV. Since then this ventilation rate has been boosted to
typically 4 times the previous. Modern VAV ventilation controls are adequate
to keep the ventilation rate entering the building. This multispace calculation
is not needed to promote healthy buildings and in fact endangers typical
offices with mold and excessive energy use.
Official Form 9B-3.047-2004
565342104
3.
Does not discriminate against materials, products, methods, or systems of
construction of demonstrated capabilities:
While the code allows for alternative methods outlined in ASHRAE, design
engineers are not paid enough fees to address this in such a fashion, as can
be evidenced by the statewide lack of such things.
4. Does not degrade the effectiveness of the code: Enforcement of the
multispace calc in the field is difficult if not impossible to test and document.
Also, this code changes frees up building officials all over florida from having
to take the time to review alternative systems.
Form No. 2000-01 Effective date: 11/28/00
Section for DCA Only
Committee Action:
Committee Reason:
Commission Action:
Commission Reason:
Official Form 9B-3.047-2004
565342104