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CASE STUDY (HHHP System)
HHHP (Hybrid Hydronic Heat Pump)
Projects
Hôtel Place d’Armes (Montreal, QC)
5250 Décarie (Montreal, QC)
December 2006
efficiency without compromise
AIR
CUBE
INC
HHHP (Hybrid Hydronic Heat Pump) HVAC
System Exceeding Expected Performances.
it is difficult to be a pioneer in the introduction of new and avantgarde techniques, especially when the acquisition of the product
requires major investments. Whatever the product, the marketing
rules are the same for everyone. Time to adapt a new product
to the market can be long, in spite of some apparently obvious
advantages that one may have over its competitors. However,
tendencies of long-term transition are indicating, without the
slightest doubt, the direction of the product’s evolution and are
unveiling reasons for such orientation.
In the particular case of the HVAC techniques or equipment
transformation, the evolution is slower as the construction work
involved is important. For example, when it is a matter of choosing
the HVAC system for restoration or construction of high-rise
buildings, system choice justifications are often dictated by
capitalization cost and tested know-how prerogatives. Under
such market conditions, HVAC technical innovations have few
chances to appear unless particular circumstances justify a
different selection.
Here’s the case study of two projects of high-rise building
restoration including a major transformation of the HVAC
system, for which particular circumstances justified an
innovating approach. Surprisingly, the best qualities of these
two new systems were to have largely exceeded their owners’
expectations for comfort, energy performance, user friendly
maintenance and acquisition cost.
The nature of building restoration work has defined specific user
expectations which influenced the choice of HHHP HVAC system.
The planning stage of the work identified definite needs for
improvements to existing HVAC systems.
Specific Needs for Building 1 :
Hôtel Place d’Armes
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2-
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Select a HVAC system with failure events that would
not involve major building disruption, such as a defect
of air-conditioning affecting all or some of the hotel’s
guests.
Reduce hotel and room ventilation system noise levels.
Improve the hotel room HVAC system look and design,
to blend with the building’s architectural style.
Facilitate emergency maintenance work to minimize
repair operations in the rooms.
Ease to install new HVAC system in spite of physical
constraints inherent to an historical building built over
135 years ago.
Select a modular HVAC system allowing for adjustments
or future expansions.
Improve energy control efficiency compared to existing
HVAC system.
Choose a HVAC system for proven durability and
adaptability for future expansions.
Keep mechanical work budget within the industry
standard cost estimate margins.
Facilitate maintenance of regrouped modular
HVAC units for specific use in Isabella-Décarie
building.
Caracteristics of building 1,
Hôtel Place D’Armes
Usage :
Age of building :
Exterior walls :
Number of floors :
Location :
Energy source :
Hotel & commerce
135 years
Stone
7
Montreal
electricity & natural gas
Window surface :
approx. 22%
Specific Needs for Building 2 :
Isabella-Décarie
1-
Adapt the new HVAC system to limited space height
restrictions on each floor.
2- Reduce HVAC system energy related costs.
3- Improve mechanical room space use to facilitate
maintenance work.
4- Complete work in phases without disrupting business
activities in the building. This includes conducting HVAC
system modification with continuous ventilation service
to the building tenants.
5- Increase the comfort to users.
6- Choose a HVAC system for proven durability and
adaptability for future expansions.
7- Keep mechanical work budget within the industry
standard cost estimate margins.
Caracteristics of building 2,
Isabella-Décarie Building
Use :
Age of building :
Exterior walls :
Number of floors :
Location :
Energy source :
Window surface :
Office building
approx. 45 years
Concrete
7
Montreal
electricity & natural gas
approx. 55%
Case 1:
Hotel Place D’Armes.
Existing Conditions and Technical
Challenges.
The historical and patrimonial nature of the Hotel
Place d’Armes was certainly one of the most
important challenge on HVAC system scope of
work. Building’s wall integrity and architectural
conservation were adding to the already complex
constraints imposed to work and restorations in old
buildings.
The building’s renovation scope of work consisted
in expanding the hotel by integrating two adjacent
buildings. It was thus a major transformation to
building use, evolving from a business offices use,
to a luxury hotel.
The HVAC system was one of the owner’s major
concerns, since he already had to respond quickly
to major breakdowns having affected all of his
customers. Henceforth no HVAC failure should
compromise his hotel reputation.
The existing hotel thermal equipment was installed
with a four pipe central heating and cooling system.
It was certainly a HVAC system configuration
rejected by the owner for the expansion of his hotel.
The alternate HHHP HVAC system solution satisfied
the prime selection criteria based on reliability,
but analysis of other factors would determine its
selection.
The quiet and aesthetic aspect of HVAC the units
selected for the rooms met the owner’s requirements,
but three performance capabilities were decisive
aspects leading to his choice for the HHHP system.
1-
Modular HVAC unit malfunctions are
generally fixed in less than 30 minutes
by regular hotel mechanical maintenance
employees. Their intervention consists
in disconnecting the defective room unit
module and it with a functional one. No
mechanical repair is carried out directly
in the room. The repair of faulty units is
swift and clean. The defective units will
be repaired later in the machine shop and
stored ready to use.
2-
The physical system installation, whether for thermal piping
or ventilation ducting, allows simple adaptable characteristics
to suit the historical building of the hotel. The thermal piping
consists of two pipes instead of four. Their symmetrical
positioning in a vertical plane proves to be simple to adapt to
the architecture and does not require piping insulation. The
ventilation ducting is much less bulky than as needed for a
central HVAC system. These factors did make a considerable
difference in installation cost reduction.
3-
The modular flexibility for adaptation of the HVAC system
allows for expansions or local system shut down, without
affecting normal operation elsewhere in the building.
Although energy performance was an important issue in the equipment
selection, it was far down the owner’s priority list, but any equivalently
priced, efficient HVAC system solution was not to be excluded, if
such a system could be installed without a series of complicated or
dysfunctional gadgets.
Case 2 :
Isabella-Décarie Building.
Existing Conditions and Technical Challenges.
The Isabella-Décarie building is used for commercial and office
purposes. It was built in the 1960’s and its architecture is restraining
due to low headroom between the concrete floors. The available
height between the floors is less than 3 meters, which leaves little
technical ceiling space for lighting, fire protection and ventilation.
Air ducts on many stories reduced the available vertical space and
the mechanical rooms were so full, that maintenance task work
was always complex. The existing HVAC mechanical systems were
floor base central air handling units with DX coils or chiller. Some
modifications to the HVAC system had been made in the last few
years with the installation of a central chiller and cooling tower.
The renovation scope of work defined by the owners, included to
maintain the HVAC system functional at all times during all work
phases, for the comfort of the tenants. It was unthinkable to install
the same type of mechanical equipment due to the existing clutter
in the mechanical rooms, and the impossibility of increasing the
available space.
To adapt to this particular building constraint, modular HVAC units
were partly grouped in the same place on some stories and partly
distributed and incorporated to the floor layout on other stories.
Some of the existing office ventilation could not be modified during
previous HVAC building renovations and were then serviced by a
HVAC module located outside their existing office space.
The existing heating system included electric base board heaters
along the outside building walls. It was the second generation of
heating system since the original construction which was equipped
with hot water heating.
Easy maintenace access to decentralized HVAC units in a
office environment.
Mechanical HHHP System Design
Adated to Both Buildings.
No simultaneous heating and cooling in the same
sectors.
Internal Geothermal System
Simultaneous use of air conditioning and heating within the same
zone was common in the Isabella-Décarie building. The HHHP HVAC
system does not allow such an abuse of energy. There is no auxiliary
perimeter or air duct heating system, no electric base board heater
nor electric air duct reheat coils. A properly adapted zoning and
constant air flows, increased considerably the user’s comfort while
reducing energy consumed.
One of the driving principles of the HHHP HVAC
system design is to recuperate the air-conditioning
energy used to cool the central building’s inner
space and redirect it for heating the building
perimeter. This principle is applicable to many
high rise buildings when interior volumes require
year round air-conditioning whereas the perimeter
requires sometimes air-conditioning, sometimes
heating. The energy heat transfer of inner volume
air-conditioning towards outer building perimeter
heating may be compared to a form of internal
geothermal system.
Free cooling and costly heating - or
low cost air-conditioning and free
heating recovery
For conventional systems, thermal balance
calculation is relatively simple: air temperatures
in winter condition are about 15oC in the whole
building, when predominant air-conditioning signals
are driving the HVAC central control to satisfy inner
building volumes set points. Then, outer building
zones air volume has to be preheated by auxiliary
ventilation heating circuits or by base board
heaters. This is the free cooling mode with costly
heating.
For the HHHP HVAC systems the air temperatures
in winter condition are about 20oC throughout
the building and this set point is lowered by HVAC
modules to approximately 15oC when necessary
and only where required. The energy used for airconditioning will be recovered for building perimeter
heating. It is the low cost air-conditioning and free
heating recovery mode. For heating purposes during
the winter’s coldest time, high efficiency water
boilers supplement the heating energy needs.
Office space without visable heating system.
A liquid constant temperature heat transfer
network
A heat transfer system between any building zones was thus
essential to elaborate such a principle of energy recuperation. If
this system would necessitate the design of complex gadgets, one
should think twice before getting into such a HVAC installation
adventure for his building. However, the energy heat transfer system
is of remarkable simplicity: it’s a non insulated twin pipe glycol and
water circuit. The water pipe network connects all HVAC modular
units of the building. The water temperature set point is adjusted
according to the seasons and will vary within approximately 15oC
in summer and approximately 45oC in winter. The temperature set
point follows outside temperature fluctuations in order to adjust
to the necessary heating level or in order to reduce necessary
energy in air-conditioning mode.
Small power modular HVAC nonreversible units
The small power modular HVAC units are the decentralized elements
of the complete building air network. Their most important feature
is non reversibility. They are thus not heat pumps with reversible
cycles, but hermetic water-cooled compressor air-conditioning
units with hot water heating coils. When alternating between
heating and air-conditioning, these units use either air-condition
hermetic compressor mode or passive heating coil mode. Their
mechanical design is a progression towards simplicity compared
to the reversible heat pump type units. The thermal efficiency of
these HVAC units is proportional to the heat transfer temperature
difference between the condenser and the thermal fluid. In the
particular case of the HHHP system, the condensers are subjected
to lower heat exchange temperatures difference in summer than
in winter. This condition would increase the durability of the
compressor because they are subjected to less important loads
during the most demanding season.
Caloporter system to simplify mechanical room in
Isabella-Décarie Building.
A simplified air duct installation
The air ducting distribution network of the HHHP
system is by far less bulky and less complex than
the network of a conventional HVAC system. The
air distribution architecture is decentralized, since
each modular unit is connected to its own local air
duct network whose dimensions are much lower than
the ones needed for conventional air distribution
architectures networks. This functionality allows
an installation of interior space with more vertical
headroom for the building users. In the cases of the
buildings Hotel Place d’Armes and Isabella-Décarie,
this characteristic proved to be a major advantage
for quality improvement or quality improvement for
headroom available space because of the reduced
size of ventilation ducts.
Increased reliability by modular
adjustable mechanical elements of
HHHP HVAC system
The various system’s modular mechanical elements
installed in the two buildings are increasing
reliability of the whole HVAC network and providing
a great flexibility for the needs for expansion or
retrofitting. In both cases, network modification
can be completed without affecting the use of the
existing system elements.
Thermal heat transfer bypass circuits allow for
modification or piping refitting without affecting
the whole water circuit.
While expanding the HVAC system, the cooling
heat transfer capacity of the water network can
be increased, if necessary, by adding modular
cooling water units or energy recovery units to
heat domestic water. In the case of hotel buildings,
the domestic water demand being very important,
the HVAC heat transfer system may serve as heat
source for water heating. This configuration of heat
transfer system increases the efficiency of HVAC
units air-conditioning in summer as it lowers heat
rejects to the environment. This recovery would not
be easily done with a conventional central HVAC air
handling unit.
The reliability of the HVAC system being an essential
characteristic, it is important to note that failure of
a mechanical module does not trigger a general
system breakdown.
High efficiency natural gas modular heating system.
HHHP system performance.
In summer, the air-conditioning thermal performances of the HHHP
systems may compare to similar systems used under the same
work conditions. However not all HVAC systems may benefit from
high performance conditions using water cooled condensers.
There are multiple technical advantages using HHHP, but this
HVAC system appears, from those cases, to be well adapted to
the winter energy demanding conditions. Moreover, the building’s
energy costs are mainly generated by the heating loads for which
the HHHP system excels to reduce.
The designers of this system managed to rethink the technical
energy control design approach by using a simplified mechanical
architecture. With this technical orientation, they were able to
propose mechanical HVAC modular solutions adaptable to the
user’s needs without involving complex gadget or economic energy
saving to justify an investment. The HHHP systems simply deliver
the goods as expected with an added bonus in energy savings.
The HHHP system heating energy performances vary for
each building and are proportional to air-conditioning used in
winter versus cost reduction for air reheating. The natural gas
consumption for the heating loads of the Isabella-Décarie building
was reduced by about 70%.
Beyond this exceptional energy performance, the user’s comfort
was largely increased following the installation of the HHHP HVAC
system. The constancy in air volumes and fresh air, contributed
to the pleasant feeling and comfort, described by the majority of
users.
Central distribution of glycole water circut with easy
access to mechanical rooms Isabella-Décarie building.
AIR
CUBE
INC
338 rue St-Antoine Est, Bureau 205
Montréal (Québec) CANADA, H2Y 1A3
T•514•954•1414
F•514•954•1410
www.aircubeinc.com