EUROPEAN MYTHOLOGY AND HELLENIC REALITY ABOUT ZERO ENERGY

F. Flourentzou European Mythology and Hellenic Reality about Zero Energy Buildings

0 ASHRAE Greek Chapter, Energy and Buildings Nov. 2013

EUROPEAN MYTHOLOGY AND HELLENIC REALITY

ABOUT ZERO ENERGY BUILDINGS

Flourentzos Flourentzou

Nov 2013

Flourentzos Flourentzou

Estia SA

Par Scientifique EPFL

1015 Lausanne, Switzerland

[email protected]

mailto:[email protected]



Energy conservation in Europe is thougnt to conserve heat.

The symbol of a building is a single family house.

We can read contemporary mythology in the symbols



The little

house in

the prairie

is a zero

energy

building



• A passive building in cold Europe:

30 cm of thermal insulation, triple glazing low-e, no thermal bridges

High airtightness (0.5 h-1 at 50 Pa) and ventilation heat recovery unit 80%.

Solar collectors for hot water

A heat pump or wood boiler for heat production

A passive building consumes < 50 kWh/m2 of primary energy for

heating, cooling, ventilation, hot water.

A zero-energy building is a passive building heated by renewable

energy.



• 3 examples of Minergie Buildings

C: Villa mitoyenne à Illkirch - France (2009)

New twin villas Minergie-P

•Minergie GE-005-P

•Minergie VD-626

B: Maison Villageoise à Corcelles (2011)

Minergie refurbishment

A: Ecoquartier Les Fontenettes, Carouge (2012-2016)

7 multi-storey buildings GF+8 Minergie and Minergie-P

335 appartments, 30’000 m2 for social housing

•Minergie F-67-001-P



• 3 examples of Minergie Buildings


•Minergie VD-626


29 kWh/m2a 22 cm District heating Sewage heat recovery COP 4.5

56 kWh/m2a 8/16 cm 5.5 m2 DCV 12 m3/y

25 kWh/m2a 38 +5 cm 7 m2 80% HR COP 3.5

A

B

C



• From Minergie to a zero energy building


•Minergie VD-626


29 kWh/m2a

47 kWh/m2a

25 kWh/m2a

140m2

48 m2

25 m2

+

+

+

= 20 kWh/m2a

= 0 kWh/m2a

= 0 kWh/m2a

A

B

C



• From mythology to reality about zero energy buildings

Should we construct small buildings in order to have enough available surface

for solar collectors ?

In order to have energy produced in the building perimeter, should we promote

photovoltaic systems on façades with 30% losses instead of remote renewable

energy?

Why 0 and not -13, -25 or +12?

Zero energy building cannot be an extrapolation of a zero energy

single family house

The building of the second half of hydrocarbon age should go

beyong symbols and green communication



• Cold and hot climate European reality concerning energy demand

Bern Lefkosia

192 (43)

192 (15)

Bern Lefkosia

In the first half of the « hydrocarbon age », European and Greek

engineers and market have more or less the same problem to solve.



• Energy demand after insulating and shading correctly a buillding

After the first step towards low energy buildings, European and

Greek market and engineers have a different problem to solve.

38 (4)

29 (7)

Athina

22 (20)

Bern

30 (28)

Oslo Lefkosia



• technical characteristics of a passive office building

Cold climates Mild climates

Thermal insulation position Sandwich light wall Sandwich light wall

Wall/roof thermal insulation thickness 30 cm 10 cm

Glazing g value 0.6 0.4

Window U value 0.8 W/m2K 1.7 W/m

2K

Ventilation opening dimensions 1X1.8 1X1.8

Number of occupants 35 35

Ventilation airflow (30 m3/pers) 1050/120 m3/h 1050/120 m

3/h

Internal gains (7 W/m2) 3400W 3400W

Lighting power (15.9 W/m2) 7223W 7223W

Solar protection g value 0.15 0.15



• What ventilation system to reduce energy demand?

European mythology: air-tightness, ventilation control, heat recovery

29 (7)

Athina

30 (28)

Oslo



Lefkosia Climate Bern climate

Sum

mer

Win

ter

• DIAL+ dynamic simulation of temperature difference

In Bern there is a high winter recovery potential during day and night

In Lefkosia there is a small recovery potential especially during day



• Heat and cooling demand reduction by ventilation heat recovery

Heat recovery recudes by 45-47% energy demand in cold climates!

Heat recovery recudes by 10-14% energy demand in mild climates!



• Heat and cooling demand and primary energy consumption

Heat recovery is more effective with polluting energies

Energy demand

Primary energy consumption



• Heat recovery: Environmental emissions and embodied energy

Heat recovery: 1.5 kWh/m2y, Simple ventilation: 0.64 kWh/m2y

Life span 25 years



• Heat recovery: Primary energy cost for fans (X 2.9) and grey energy

Embodied energy is low but not negligible, fan energy is high

for

2 D

C f

an

s

for

gre

y e

ne

rgy

7 k

Wh

/m2y

1.5

kW

h/m

2y



• Primary energy cost and savings

Heat recovery is a simple question in Sweden, Greece and Cyprus

Fans & embodied primary energy cost

Primary energy savings

Heat recovery is a complex question in Switzerland



• From mythology to reality in Europe

Spectacular reduction of envelope heat losses

Before refurbishment After refurbishment



• Before and after reburbishment

Spectacular but?



• Window use

Almost 1/3 of the windows are open after refurbishment with Text -

4°C



And more windows



• A multistorey building is not an extrapolation of a single family house

According to code calculations, user behaviour is evacuated

Designers should take it into accound like real consumption does



• « mythological » and real user behaviour

Real consumption for lighting is higher, real solar gains in winter are

50-70% lower than calculated ones according to regulations standard

use, in summer 30-50% of glazed area is not shaded

Standard use

Blinds down in summer

Blinds up in winter

Blinds down when blinding

Real Use

50-70% shading summer

or winter indifferently

88-90% of users do not

use the blinds

1.3 to 2 average blind

movements per week



• Hellenic reality about ventilation

Fans & embodied primary energy cost

Primary energy savings

Heat recovery net saving potential (primary energy) is low and

sometimes negative in mild climates



• Heat and cooling demand reduction by night cooling

Night ventilative cooling in almost zero energy buildings in cold mild

climates is necessary, in mild climates essential!



• Ideal ventilation strategies for Hellenic zero energy buildings

In winter, ventilation provides air quality: 30 m3/h per person during hours of

use, minimum ventilation of 0.2 m3/m2h outside hours of use to save energy

In summer, ventilation provides air quality: 30 m3/h per person during hours of

use.

In summer, ventilation provides night cooling: 2-4 air changes when Text<Tint

In summer, when outside temperature is fresh ( <28°C), wind breeze is

cooling the user but when temperature rises ( > 26°C), wind breeze is heating

the building => cross ventilation should be reduced to provide only air quality.



• Possible strategies: Closed or open?

Install mechanical ventilation with low airflow (and heat recovery) for winter and

high airflow for summer night time ventilation

Or

Design natural ventilation able to be manually controlled, taking into account

user natural behaviour

Or

Design automatically controlled natural ventilation



• Night cooling ventilation strategy for Lefkosia new Townhall

Guarantee safety and provide large oppening possibilities.



• natural ventilation design: user possibilities

A window offers 30 to 366 m3/h stack effect

airflow at ΔΤ 5°C



• Use of ceiling fans to keep windows closed and rise set temperature

15 % rise of cooling energy per 1 °C of set température decrease

Ceiling fans may save 30% of cooling energy consumption

0

20

40

60

80

100

23-24°C 21-26°C 21-28°C

KW

h/m

2



• Heating and cooling system

What energy system for Hellenic passive buildings?

38 (4)

Pa

ss

ive

Bu

ild

ing

29 (7)

Athina

22 (20)

Bern

30 (28)

Oslo Lefkosia

192 (43)

Sta

nd

ard

Bu

ild

ing

192 (15)

Bern Lefkosia



• Need of correct cooling load dimensionning

350 W/m2 of total cooling initially proposed

Static dimensionning 24-42°C is not adapted for low energy

buildings

10 W/m2 of simulated heating load according to ISO 15265

50 W/m2 of simulated sensible cooling load according to ISO 15255



• Technical installation sobriety

Lefkosia townhall passive building technical installations

Installation of a High COP VRV, 135 W/m2



• COP according to demand

Oversising of heat pumps costs investment money but also energy

✖ ✓

We have to reinvent the job of the mechanical engineer



• Heating and cooling emmition

Current machines are not adapted to distribute low intensity energy

220 fan electric Watts to distribute 2500 thermal Watts is to match

✖ ✓



• European mythology and Hellenic reality about zero energy buildings

Hellenic zero energy energy engineers should invent their own mythology

The objective is the same: energy needs < 40 kWh/m2y for heating and cooling

and extensive use of renewable energy

A zero energy building is a completely different reality of the reality we know

We have to be open to revisit our rules of thumb

The good technical solutions of the Hellenic zero energy have to be invented,

they do not exist to be imported

EUROPEAN MYTHOLOGY AND HELLENIC REALITY ABOUT ZERO ENERGY

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