ISSUE: Petitioner
seeks a Relief from the provisions of Chapter 13 of the
Ms. Fiona Cousins of Arup USA, Inc. is designing the new
Miami Art Museum. The project is described as follows:
The new Miami Art Museum is a
four-story, 125,000 sq. ft. fine art museum to be located at Museum Park, 107
Biscayne Blvd. Approximately 40% of the building is preservation area dedicated
to displaying, conserving and storing high-value artwork. The remainder of the
building is comprised primarily of education, office, and mechanical spaces.
The mechanical design treats the preservation areas separately from the rest of
the building.
The HVAC systems for the
preservation areas are limited turn-down VAV with zone reheat and
humidification. The turn-down limitations are typical for systems serving
preservation areas and are described in more detail later. These systems must
maintain a space temperature of p72oF±2oF and space
relative humidity of 50%±5%, 24 hour per day, 7 days per week, 365 days per
year. These conditions are consistent with the most stringent class oaf control
defined in the Museums, Galleries, Archives and Libraries chapter of the ASHRAE
HVAC Applications 2007 Handbook.
Background:
1.
Section 13-101.1.5 of the code, Limited or special use
buildings, reads as follows: “Buildings determined by the Florida Building
Commission to have a limited energy use potential based on size, configuration
or time occupied, or to have a special use requirement shall be considered
limited or special use buildings and shall comply with the code by Method B of
Subchapter 13-4. Code compliance requirements shall be adjusted by the
Commission to handle such cases when warranted.”
2.
Section 13-400.0.B of the code, Method B, the Building
prescriptive method, reads as
follows: “This is a prescriptive
methodology that is allowed for shell building, renovations change of
occupancy, limited or special use buildings, and building system changeouts.
The building envelope complies with the standard if the proposed building meets
or exceeds the Mandatory Requirements and all relevant criteria on Form 400B or
the Energy Summit Fla/Com 2008 computer printout. Only the prescriptive
envelope measures of Method B are permitted for shell buildings.”
For museums, galleries, archives and libraries, the
ASHRAE HVAC Applications 2007 Handbook [S. 21.18] states that “air should be constantly
circulated at sufficient volume, regardless of tempering needs, to ensure good
circulation throughout the collection space…The type of HVAC system used is
critical to achieving project environmental goals. Proper airflow filters the
air, controls humidity, and suppresses mold growth. Minimum airflow criteria
vary from 6 to 8 air changes per hour…These needs are usually best met with a
constant-volume system.
Petitioner argues: Despite the recommendations in the ASHRAE
HVAC Applications 2007 Handbook, our prior experience designing, modeling and
commissioning museums and preservation areas has shown that VAV systems can be
used in lieu of constant volume systems when there is the potential for
turndown and energy savings. However, we have found that effective humidity
control can only be achieved when limited turn-down is implemented. In our
case, turndown is limited to the larger of 80% of the system’s peak airflow
rate or 6 ACH, the minimum airflow criteria listed in the ASHRAE HVAC
Applications 2007 Handbook.
In light of the discussion above,
the minimum airflow requirements stipulated by ASHRAE 90.1-2004 would be
inappropriate in a typical preservation area. In our case, neither the minimum
volume set point of 0.4 CFM/sq.ft. nor the minimum ventilation rate would
provide sufficient air circulation to maintain the required \space conditions.
For reference, the ceiling height of a typical gallery in our project is 16’6”.
At this height, 0.4 CFM/sq.ft. is equivalent to approximately 1.4 ach,
approximately 25% of the minimum airflow recommended by the ASHRAE HVAC
Applications 2007 Handbook.
a. The EnergyGauge Summit Fla/Com program has the
following limitations
b. Modifications to the baseline building cannot be made
by the user; FSEC can adjust the baseline as required.
c. The proposed design recovers heat from the chillers’
condenser bundles to reduce the amount of energy consumed for reheat, an
otherwise significant fraction of the Museum’s overall energy consumption.
Fla/Com cannot be used to model heat recovery chillers.
d. The proposed design includes air handlers with
face-and –bypass dampers. By recovering energy from the return air stream, the
face-and-bypass dampers limit the amount of reheat and humidification required
to maintain acceptable conditions in the preservation areas. Fla/Com cannot be
used to model air handlers with face-and-bypass dampers.
3.
Petitioners
states that Mr. Mangesh Basarkar of the Florida Solar Energy Center, proposed
the following walk-arounds:
a. The baseline can be adjusted per ASHRAE Addenda ac.
b. The energy savings associated with the Museum’s heat
recovery chillers can be claimed using an Exceptional Calculation Method per
ASHRAE 90.1-2004 Chapter 11. Using this approach, we would develop a method to
estimate the annual performance of the chillers outside of Fla/Com. The results
of this calculation would then be used to adjust Fla/Com’s outputs manually.
c. As with the heat recovery chiller, the energy savings
associated with the Museum’s face-and-bypass dampers can be claimed using an
Exceptional Calculation Method.
4.
Petitioner has
the following concerns with these proposals:
a. While any given modification to the baseline model may
be relatively straightforward to implement, the proposed and baseline building
models are linked.; modifications to the baseline may need to be updated
numerous times as the proposed building model is developed and refined.
Although we greatly appreciate Mr. Basarkar’s offer of assistance, we are
concerned that engaging FSEC each time the Fla/Com baseline requires adjustment
will add a significant amount of time to the modeling process and possibly
delay the Museum’s permitting process.
b. We agree that a calculation could be developed to
estimate the annual performance of the chillers. For this calculation to be
accurate, however, it would need to characterize all of the interactions
between the chiller, the Museum’s cooling load, and numerous pieces of
equipment in the Museum’s central plant, ;including the cooling towers,
condenser water pumps, heat recovery pumps and boilers. These calculations
would need to capture the performance of the chillers, the cooling towers, the
condenser water pumps, the heat recovery pumps and boiler under all part-load
conditions for every hour of the years. As such, the most appropriate way to
model the effectiveness of the heat recovery chiller is with an annual energy
simulation. We are concerned that the accuracy of the whole building model, and
in particular our ability to determine the energy savings associated with the
heat recovery chiller, will be limited if an Exceptional Calculation Method is
used.
c. Again, we agree that a calculation could be developed
to estimate the annual energy savings associated with the Museum’s face-and-bypass
dampers. This calculation would need to characterize the behavior of the
Museum’s entire mechanicalplant in response to the Museum’s changing thermal
and moisture loads. The calculation would need to be performed for every hour
of the year, under all part load conditions. As with the heat recovery chiller,
we believe that the most appropriate way to model the behavior of the Museum’s
plant is with an annual energy simulation. We are concerned that the accuracy
of the whole building model, and in particular, our ability to determine the
energy savings associated with the face-and-bypass dampers, will be limited if
an Exceptional Calculation method is used.
5.
Section 13-400.0.A, the Whole Building Performance
Method, “is a computer-based energy
code budget method which may be used for determining the compliance of all
proposed designs, except designs with no mechanical system. Under this method,
cost performance is calculated for the entire building based on the envelope
and major energy-consuming systems specified in the design and simultaneously
for a baseline building of the same configuration, but with baseline systems.
Compliance is met if the design energy cost does not exceed the energy cost
budget when calculated in accordance with this section; and the energy
efficiency level of components specified in the building design meet or exceed
the efficiency levels used to calculate the design energy cost. Compliance
calculations are those utilized in the EnergyGauge Summit-Fla/Com computer
program and are as described in Appendix 13-B. Basic prescriptive requirements
described in the sections called Mandatory Requirements shall also be
met.” The Method A energy cost budget is
based on criteria in Chapter 11 of ASHRAE Standard 90.1-2004, with a 0.85
multiplier applied to the calculation to make the code 15 percent more
stringent than ASHRAE 90.1-2004, not to Appendix G of ASHRAE 90.1-2004, which
is a building performance rating method. Standard 90.1-04 specifically states
that Appendix G does not offer an alternative compliance path for minimum
standard compliance.
6.
Conceptually, a
building designed to be compliant with Method A of the code using the EnergyGauge
Summit computer program could be used as a baseline building by another
computer program to establish an energy cost budget. If energy costs for the
actual building being evaluated can be determined to come in under the energy cost
budget established for the baseline building, equivalence to a compliant
building could be determined.
Petitioner’s Proposed
Methodology:
In her Request for Relief dated August 6, 2010, Petitioner
makes the following request:
Given the Museum’s 24 hour operation and strict environmental control
criteria, we are requesting that the building be granted special-use status
under Section 13-101.1.5, and propose the following three Code adjustments:
1.
FBC 13-400.0.A Method A, the Whole Building
Performance Method: VAV Turndown
Requirement. The recommendations
described in the ASHRAE HVAC Applications 007 Handbook should act as the
baseline in cases where the Whole Building Performance Method does not
adequately describe systems used to condition a typical preservation area.
Specifically, when modeling a VAV system serving a preservation area, the
minimum volume setpoint in the baseline model should equal the minimum volume
setpoint in the proposed model. Note that the minimum volume setpoint in the
proposed model will be consistent with the ASHRAE’s design guideline of 6 to 8
air changes per hour.
2.
Develop
both the proposed and baseline building models (per ASHRAE 90.1-2004 Chapter
11) in Trane TRACE in lieu of FLA/COM. Trane TRACE includes an explicit method
for modeling heat recovery chillers and air handlers with face-and-bypass
dampers. Trane TRACE also satisfies the requirements given in ASHRAE 90.1-2004,
Section 11.2;, Simulation General Requirements.” Further, Trane TRACE is recognized by the
Local Authority as an approved simulation program since its outputs may be
submitted as part of the permitting process to demonstrate adherence to correct
system-sizing methods. To demonstrate compliance with the Florida State Energy
Code, we will submit documentation showing that the Museum’s whole building
annual energy cost is at least % less than the adjusted baseline’s whole
building annual energy cost. In addition, we will submit a comprehensive set of
input and output reports for review.
3.
Utilize
Addendum ac to ASHRAE 90.1-2004 as follows:
a.
Use
ASHRAE 90.1-2004 Addendum ac to demonstrate compliance with the fan power
limitation described in Section 13-410.AB.1.1.1 of the Florida energy code. For
consistency, and because ASHRAE 90.1-2004 Addendum ac provides an improved
method to calculate the fan power limitation, we propose using Addendum ac for
all of the building’s systems, including those which do not serve galleries or
preservation areas.
b.
Use
ASHRAE 90.1-2004 Addendum ac to calculate the fan power of the baseline
building for use in the Whole Building Performance Method for all the building
systems, including those which do not serve galleries or preservation areas.
Staff Recommendations: Based on the
above facts and circumstances, staff provides the following recommendations as
answers to proponent’s request:
To the petitioner’s request, that the Miami Art Museum be
granted Special Use status as allowed by Section 13-101.1.5 of the Florida
Building Code, Building, and that Petitioner be allowed to demonstrate
compliance with Chapter 13 of the Florida Building Code, Building, using a hybrid method for calculating the Museum’s
energy usage [as shown above],
the answer is
Option 1: that the Commission allow determination of code compliance by
Petitioner’s proposed methodology.
Option 2: that the Commission allow determination of code compliance by
Petitioner’s proposed methodology if a version of the building determined to be
compliant with Section 13-400.0.A of the Florida Building Code is used in Petitioner’s computer
program (utilizing Chapter 11 of ASHRAE 90.1-2004) to determine an Annual Whole
Building Energy Cost Savings budget for the building and the building complies
with said budget using Petitioner’s program.