Higher productivity and lower energy cost through better indoor climate and life cycle cost analysis

Dennis JohanssonForskning och utveckling – Swegon AB Byggnadsfysik/Installationsteknik – LTH dennis.johansson@swegon.se

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

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

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

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?

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

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

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

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

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

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

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

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.

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

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

School

• Indoor climate problems in schools – seems not to be taken seriously

• Normally no cooling• Higher people density than

offices

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

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

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%

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

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))

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)

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

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

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

Dwellings• LCC for heating and ventilation systems• Theoretical detached house and

multifamily apartment building– Presentation focuses on detached house

• Including health related cost

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

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

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

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

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

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?

Dwellings – demand controlled ventilation

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?

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

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

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

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

Ongoing research

• Other issues• Life cycle cost

simulations, energy calculations– Softwares for

system comparisons

Thanks for your attention!