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Higher productivity and lower energy cost through better indoor climate and life cycle cost analysis
Dennis JohanssonForskning och utveckling – Swegon AB Byggnadsfysik/Installationsteknik – LTH [email protected]
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Content – Higher productivity and lower energy cost through better indoor climate and LCC analysis
• Introduction – how to solve both indoor climate and lower energy use
• Optimisation examples– Office– School– Dwelling
• Research on input data
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Background – energy use• Building sector uses 40% of the used energy
in Sweden– Like in Europe– Relevant to decrease the energy use in the sector– Goals are out regarding energy use and CO2 emissions– Examples are the Energy Directive and new Swedish
building code• Energy is used primarily for
– Space heating– Household electricty (heating?)– Common electricty, lighting– Cooling– Ventilation
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Indoor climate• We are approximately 90% indoors
– Temperature, ventilation, lighting
• Studies show for example that we– produce more at higher airflow rates and correct indoor
temperature – Tanabe, Wargocki, Fanger– reduce the level of sick leave with higher airflow rates – Milton,
Seppänen, Fisk– lower the prevalence of asthma and allergy - Bornehag, Hägerhed
Engman, Sundell– learn faster with higher airflow rate and
correct indoor temperature – Wyon, Wargocki
• Hypotheses– We are influenced by the indoor climate– There is a need for a system perspective
including the entire building and user
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Energy use and indoor climate• Often conflicts
– Indoor climate systems and lighting uses energy• What level is right?
– How to value the indoor climate?– How to value outdoor environmental load?– Detailed demands?– Functional demands?– Life cycle economics?
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Examples of optimisation• Assume that we can value the indoor climate
through productivity and health as a function of– outdoor airflow rate– indoor temperature
• Costs for indoor climate systems and the running costs including maintenance and energy can be calculated– Different systems can provide the indoor climate
• The sum of these costs can give optimal airflow rate and indoor temperature
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Content – Higher productivity and lower energy cost through better indoor climate and LCC analysis
• Introduction – how to solve both indoor climate and lower energy use
• Optimisation examples– Office– School– Dwelling
• Research on input data
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Office building - goals
• LCC for heating, cooling and ventilation systems
• Theoretical office building with one corridor and four storeys
• Including costs for productivity related to airflow rate and temperature respectively
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LCC - www.byfy.lth.se/Publikationer/1000pdf/TVBH-1014_web.pdf
• 40 year life span• Net present value discount interest rate
– 1% electricity, 2% heat, 3% other• Included costs
– Initial– Energy– Maintenance– Repair– Space loss– Cost to represent health and productivity
• ProLive computer program for LCC – 2005 • Salary cost 200 SEK/h
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Indoor climate systems• Default system
– Supply and exhaust ventilation with heat recovery, passive chilled beams and hydronic radiators
• Alternatives were– Occupancy controlled ventilation– Temperature controlled ventilation– Without cooling– Different duct system layout
• Airflow 0.35 l/(s·m²) + 7 l/person
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Productivity cost• Proposed equations:
Relative increase
-0.03
0
0.03
0.06
0 20 40 60q / (l/(s·person))
Relative loss
00.05
0.10.15
0.2
15 20 25 30 35Indoor temperature/°C
( )26.2100155.0 −⋅= roomt tPD
⎟⎟
⎠
⎞
⎜⎜
⎝
⎛−⋅=
⎟⎠⎞
⎜⎝⎛ −⋅− 1
5.6444.0
10571.0q
q ePI
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Result without productivity costCAV DCV
Life cycle cost / (SEK/m²)
0
1000
2000
3000
4000
5000
6000
7000
0 0.8 1.6 2.4 3.2 4
q / (l/(s·m²))
Life cycle cost / (SEK/m²)
0
1000
2000
3000
4000
5000
6000
7000
0 0.8 1.6 2.4 3.2 4
q / (l/(s·m²))
HeatChiller electricityFan energySpace lossRepairMaintenanceChillerDistrict heat exch.Air handling unitAdjustmentControlFire dampersPipes, coldChilled beamsPipes, heatRadiatorsDiffusersSilencersExhaust duct comp.Exhaust ductsSupply duct comp.Supply ducts
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Result with productivity cost related to airflow rate
LCC / (SEK/m²) Initial cost / (SEK/m²)
0
10000
20000
30000
40000
0 2 4 6 8 10 12q/(l/(s·m²))
0
500
1000
1500
2000
2500
3000
CAV - LCCDCV - LCCDCV - InitCAV - Init.
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Result with productivity cost related to temperature
LCC / (SEK/m²)
0
5000
10000
15000
0 1 2 3 4 5
Temp span above and below 21.6°C/°C
CAV 200 SEK/hCAV 50 SEK/hCAV 0 SEK/h
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Conclusions and discussion• Old prices – electronics and motors cheaper today than 2005
– Demand controlled ventilation benefits easier– How to get correct prices on components?
• A possible and useful influence on the producitivty from airflow rate or temperature has high impact– Optimal airflow rates can be high– Cooling is beneficial,
temperature control also• Initial cost not negligible• With demand control, the
airflow rate can be increased with constant energy use
Optimal airflow rate / (l/(s·m²))
05
1015202530
0 250 500 750 1000Salary / (SEK/h)
CAVDCV
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School
• Indoor climate problems in schools – seems not to be taken seriously
• Normally no cooling• Higher people density than
offices
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Objectives• LCC for heating, cooling and ventilation
systems• Theoretical school building
– 2 storeys– 1200 m²– Stockholm, Sweden
• Including productivity related cost based on airflow and temperature according to recent studies
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LCC
• 40 year life span• Net present value discount interest rate
– 1% electricity, 2% heat, 3% other• Included costs
– Initial– Energy– Maintenance– Repair– Space loss– Airflow related cost to represent health and
productivity• ProLive computer program for LCC
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Ventilation systems• Supply and exhaust ventilation with heat
recovery– Constant airflow with timer– Constant airflow with chilled beams– Demand controlled airflow
• 0.35 l/(s·m²) + 7 l/(s·person)• Occupancy daytime 30%
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Productivity cost• Proposed equations:
Relative increase
-0.03
0
0.03
0.06
0 20 40 60q / (l/(s·person))
Relative loss
00.05
0.10.15
0.2
15 20 25 30 35Indoor temperature/°C
( )26.2100155.0 −⋅= roomt tPD
⎟⎟
⎠
⎞
⎜⎜
⎝
⎛−⋅=
⎟⎠⎞
⎜⎝⎛ −⋅− 1
5.6444.0
10571.0q
q ePI
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Result without productivity related cost
• Left– Constant
airflow with timer
• Right– Demand
controlled airflow
• X-axis– Airflow per area
Life cycle cost / (SEK/m²)
0
1000
2000
3000
4000
5000
6000
0 4 8 12
q / (l/(s·m²))
Heat
Fan energy
Space loss
Repair
Maintenance
District heat exch.
Air handling unit
Adjustment
Control
Fire dampers
Pipes, heat
Radiators
Diffusers
Silencers
Exhaust duct comp.
Exhaust ducts
Supply duct comp.
Supply ducts
Life cycle cost / (SEK/m²)
0
1000
2000
3000
4000
5000
6000
0 4 8 12
q / (l/(s·m²))
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Result without productivity related cost• Occupancy at daytime varied for
– normal airflow, 3.85 l/(s·m²)– higher airflow, 10 l/(s·m²)– constant airflow with timer versus demand controlled
airflow
• Higher LCC at higher airflow
• Break point higher at higher airflow
LCC / (SEK/m²)
0
1000
2000
3000
4000
5000
6000
7000
0 20 40 60 80 100Daytime occupancy/%
DCV 10 l/(s·m²)
CAV with timer10 l/(s·m²)
DCV 3.85l/(s·m²)
CAV with timer3.85 l/(s·m²)
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Result with productivity related cost• Value per hour of productivity due to airflow in
legend• Airflow per area on x-axis
(LCC - LCCmin) / (SEK/m²) Initial cost / (SEK/m²)
0
5000
10000
15000
20000
25000
0 5 10 15 20
q/(l/(s·m²))
0
500
1000
1500
LCC 8 SEK/hLCC 20 SEK/hLCC 50 SEK/hInitial
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Result with productivity related cost• Value per hour of productivity due to temperature
in legend• Constant airflow with timer
LCC / (SEK/m²)
0
5000
10000
15000
20000
25000
Los
Ang
eles
Par
is
Mal
mö
Frös
ön
Kar
asjo
k
No coolingCooling
• Productivity value of 50 SEK/h
• Cooling is expensive
• Summer vacation not taken into account
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Conclusions and discussion• High optimal airflow rates
– limited by other criteria• The method can be one tool to determine demands• Rather old component price database
– Price of control and motorized diffusers have decreased
• Long term effects?• How to value the work
of pupils?– Influences optimal
levels and use of cooling
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Dwellings• LCC for heating and ventilation systems• Theoretical detached house and
multifamily apartment building– Presentation focuses on detached house
• Including health related cost
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LCC• 40 year life span• Net present value discount interest rate
– 1% electricity, 2% heat, 3% other• Included costs
– Initial– Energy– Maintenance– Repair– Space loss– Airflow related cost to represent health and
productivity• ProLive computer program for LCC
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Ventilation systems• Exhaust ventilation
– Exhaust in bathrooms and kitchen– Supply from air valves at windows
• Exhaust ventilation with heat pump– Heat pump recovers heat to tap water and
heating• Supply and exhaust system with heat
recovery• Airflow 0.35 l/(s·m²) according to
Swedish building code
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Health cost• Proposed equation:
• Two examples, in SEK = 0.11€ = 0.14 US$, over the life cycle– Sick leave
• k1 = 774; k2 = 3.28• based on literature
– Asthma• k1 = 838; k2 = 2.23• based on the Värmland
study and a thesis regarding costs
qkhealth ekC ⋅−⋅= 2
1
Life cycle health related cost / SEK
0
200
400
600
800
1000
0 1 2Airflow / (l/(s·m²))
AsthmaSick leave
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Life cycle cost / SEK
0
400
800
1200
1600
0 0,4 0,8 1,2 1,6 2
q / (l/(s·m²))
Result without health related cost• E SEH EHP
ycle cost / SEK
0 0,4 0,8 1,2 1,6 2
q / (l/(s·m²)
ycle cost / SEK
0 0,4 0,8 1,2 1,6 2
q / (l/(s·m²))
HeatElectrical energySpace lossRepairMaintenanceDistrict heat exch.Air handling unitAdjustmentPipesRadiatorsDiffusersSilencersExhaust duct comp.Exhaust ductsSupply duct comp.Supply ducts
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Result with health related cost• E: exhaust ventilation• S: supply and exhaust ventilation• aa: asthma, sl: sick leave, co: both
(LCC+health related cost) / SEK
0
1000
2000
3000
4000
0 0.2 0.4 0.6 0.8 1q / (l/(s·m²))
E,coE,aaE,slE,no
(LCC+health related cost) / SEK
0
1000
2000
3000
4000
0 0.2 0.4 0.6 0.8 1q / (l/(s·m²))
S,coS,aaS,slS,no
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Conclusions and discussion• Supply and exhaust ventilation has lower LCC at
required airflow than exhuast• Exhaust with heat pump lowest at required airflow
– Not at higher airflow rates– Electricity price in future?
• Initial cost not negligible Optimal q / (l/(s·m²)
0
0.20.4
0.6
0.81
1.2
0 1000 2000 3000 4000 5000k1 / [k1]
SEHE
• Health is an issue– Reasonable airflow
• Should be combined with demand control
• Useful method?
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Dwellings – demand controlled ventilation
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Optimisation examples – conclusions• It is difficult to motivate low energy use if we
value the benefit– With higher energy prices, the optimal airflow rate
decrease and temperature limits changes– Initial cost increases with better indoor climate
• Indoor climate systems – Right choice can decrease energy use at the same
indoor climate– Initial cost is usually higher
at lower energy use• Who pays what?
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The building as a system• Risks
– To decrease the CO2 emissions (save the world) indoor climate is sacrificed
– The one paying the indoor climate system is stingy• Energy use
– The building survives energi supply systems – low use is more reliable than modern supply systems
– Windows – increase cooling and heating• Moisture design
– Moisture problems can result in increased energy use and bad indoor climate
– Does not need to increase energy use– Air tight buildings is necessary
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General conclusions• A moisture safe building with good materials
constructed for low energy use– Low emissions– Options for good ventilation and indoor temperature
• Demand controlled indoor climate– Good when needed – low energy use other times– System choice– Occupancy levels important as parameter
• Heat recovery• Initial cost increases but not life cycle costs• Need for better requirements and functions
through research and system approach
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Ongoing research• Measurements in dwellings
• Household electricity• Common electricity• Presence of people (or pets)• Domestic hot water• Relative humidity• Moisture supply• Moisture production• Ventilation airflow rate• Carbon dioxide concentration• Outdoor climate
• For about 15 multi family dwellings including about 300 apartments
• Spread over a few locations in Sweden
• Hourly• During at least a year• In central exhaust air of
multi family dwellings
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Ongoing research• Measurements in other buildings• A number of buildings of different kinds each
15 min during a year with the software in GOLD– Temperature, vapour contents, specific fan power,
airflow rates, occupancy, pressure, heat recovery– Sweden, Norway and occasionally other locations
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Ongoing research
• Other issues• Life cycle cost
simulations, energy calculations– Softwares for
system comparisons
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Thanks for your attention!