PowerPoint guidelines

»Classroom ventilation that performs well
RENEW Technical Workshop, Oslo
Christian Anker Hviid
Ass. Prof., senior engineer
2014-10-21
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»Agenda
• Air quality and performance
• Presentation of ventilation principles
• Results of analysis of the best ventilation systems in schools
• Energy
• User experiences
• Costs
• New state-of-the-art developments
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»Effect of more air supply to pupils
Rasmussen & Pedersen (2014). Effekten af en øget frisklufttilførsel indikeret ved en lavere CO2- koncentration på
børns præstationsevne ved skolearbejde, M.Sc. afhandling, IHA, AU
Ventilation supply was increased from 1,7 l/s pr person to 6,6 l/s pr person.
The pupil’s performance increased approx. 1 pctpoint, when air supply
was increased 1 l/s per person
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»Ventilation principles
Central balanced mechanical
• Dual-duct system with balanced inlet and extract flow rate
• System services multiple rooms.
Decentral balanced mechanical with compact room unit
• Compact air handling unit services one room
Mechanical exhaust
• One-duct system with intake through small façade openings
Mechanical exhaust with pre-heating in façade
• Recovers heat via heat pump from exhaust air to water-based heating coil in
façade
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»Ventilation principles
Manual window opening (airing)
• Cheap. Research show significant improvement with nudging actions
Automatic natural ventilation
• Optimized opening of windows with cross and/or stack ventilation
Fan-supported automatic natural ventilation
Hybrid ventilation
• Ventilation performed by separate systems: automatic window opening and
central balanced mechanical system
• System operation dependent on weather, temperatures and air quality
• Great potential, but not very mature in the low-budget market of schools
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»Demands for well-performing ventilation systems
Air quality
Temperature
Cooling via night
ventilation
Draught risk
Noise
mechanical/traffic
Aesthetics
Filters
Specific fan power
Heat recovery
Installation
Maintenance
Legi
slati
on
2014-04-09
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»Indoor air quality on 85 schools
2014-04-09
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»Air quality and year of construction
2014-04-09
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»Ventilation energy consumption
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»User experiences
Advantages
Disadvantages
Comments
Central mech.
Performs very well Complex system
when it is serviced Ducting really
only possible on
roof
Challenges aesth.
Service contract necessary
Sophisticated automatic
demand control
Special attention on fan
consumption
Decentral
mech.
Performs very
Challenges aesth.
Service intensive
well, plug’n’play
solution
Fire compartment.
Service contract by
manufacturer is cheap
Automatic failure
feedback necessary
Mech. exhaust
Simple
Cheap but uncontrollable
Airvents are closed by
users
Mech. exhaust
with pre-heat.
Induces draught
No heat rec.
Complex, induces Difficult to regulate
massive draught
Freezing2014-10-21
of façade coils
10
in comfort zone
»User experiences
Advantages
Disadvantages
Comments
Manual window
opening
Cheap
Aesthetics
Performs badly, air
quality, draught etc.
Nudging promises
value-for-money.
Automatic
natural vent.
Aesthetics
Free night
cooling
Creates draught
No heat recovery
Requires expert care
to operate properly
Fan-supported
Performs ok
auto natural vent.
Creates draught
No heat recovery
Requires expert care
to operate properly
Hybrid
Costs depends on
mech. system size
savings
External noise
Requires expert care
to operate properly
Product development
necessary
Low-energy
Free night
cooling
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Central
mech.
Decentral
mech.
Mech.
exhaust
Mech. exh.
w/HP
Manual
airing
Natural,
auto
Fansupported
nat. vent.
Hybrid,
nat+mech
Air quality
Temperature
Cooling via night ventilation
Draught risk
Noise mechanical/traffic
Aesthetics
Filters
Specific fan power
Heat recovery
Installation
Maintenance
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»Costs
What are the costs of retrofitting existing classrooms with ventilation?
• €0,08 pr pupil pr day for a ten year period
• The gain is one extra year of learning (over 10 years)
Barriers:
• Ambitions
• School owners seldom limits themselves to ventilation retrofit. Rather, school
retrofit often involves the ‘big package’ of remodelling, rebuilding, demolishing,
adding new buildings, reengineering etc.
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»Installation, service and maintenance 20 years
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»New developments
• Diffuse ceiling ventilation for draught-free ventilation supply
• Microunits for retrofit
• Dynamic reset of operation pressure to reflect actual airflow need
• Dropdampers
• Hybrid ventilation
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»Diffuse ceiling
ventilation
• Draught-free low
temperature air supply
• Longer free cooling periods
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»Microunits
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»Dynamic static pressure reset
• Conventionally the fan seeks to maintain a pressure setpoint somewhere in the
duct system. The dampers use this pressure to operate. Surplus pressure is lost
as noise and heat in the system
• The pressure setpoint is set (very conservatively) once-and-for-all, irrespective
of the actual need
• The DSPR method continuously resets the pressure setpoint based on feedback
from the dampers on their real needs
• Energy is saved because the fan pressure only meets actual need.
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»Drop dampers
• Aerodynamic dampers with linear control from 0-100% damper position (no scurve that limits the ‘good’ positions to 40-70%)
• Control of airflow at only 5 Pa pressure difference (typical 30-50 Pa)
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»Hybrid ventilation
Hybrid has potential, but also has issues:
• Recent sound attenuator design
- good for noise from outside
• Combinations with diffuse ceiling for better
distribution and no draught risk (work in
progress)
• Product development needed for better, lowbudget control integration that does not require
expert knowledge
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