EUROPEAN MYTHOLOGY AND HELLENIC REALITY ABOUT ZERO ENERGY BUILDINGS Flourentzos Flourentzou Nov 2013 Flourentzos Flourentzou Estia SA Par Scientifique EPFL 1015 Lausanne, Switzerland flou@estia.ch 0
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 1
The little house in the prairie is a zero energy building 2
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/m 2 of primary energy for heating, cooling, ventilation, hot water. A zero-energy building is a passive building heated by renewable energy. 3
3 examples of Minergie Buildings A: Ecoquartier Les Fontenettes, Carouge (2012-2016) 7 multi-storey buildings GF+8 Minergie and Minergie-P 335 appartments, 30 000 m 2 for social housing Minergie GE-005-P B: Maison Villageoise à Corcelles (2011) Minergie refurbishment Minergie VD-626 C: Villa mitoyenne à Illkirch - France (2009) Minergie F-67-001-P New twin villas Minergie-P 4
3 examples of Minergie Buildings A 29 kwh/m 2 a 22 cm District heating Sewage heat recovery COP 4.5 Minergie GE-005-P B Minergie VD-626 56 kwh/m 2 a 8/16 cm 5.5 m 2 DCV 12 m 3 /y C Minergie F-67-001-P 25 kwh/m 2 a 38 +5 cm 7 m 2 80% HR COP 3.5 5
From Minergie to a zero energy building A + = 20 kwh/m 2 a 29 kwh/m 2 a 140m 2 Minergie GE-005-P B + = 0 kwh/m 2 a Minergie VD-626 47 kwh/m 2 a 48 m 2 C + = 0 kwh/m 2 a 25 kwh/m 2 a Minergie F-67-001-P 25 m 2 6
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? The building of the second half of hydrocarbon age should go beyong symbols and green communication Zero energy building cannot be an extrapolation of a zero energy single family house 7
Cold and hot climate European reality concerning energy demand Lefkosia Bern 192 (43) 192 (15) Lefkosia Bern In the first half of the «hydrocarbon age», European and Greek engineers and market have more or less the same problem to solve. 8
Energy demand after insulating and shading correctly a buillding 38 (4) 29 (7) 22 (20) 30 (28) Lefkosia Athina Bern Oslo After the first step towards low energy buildings, European and Greek market and engineers have a different problem to solve. 9
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/m 2 K 1.7 W/m 2 K Ventilation opening dimensions 1X1.8 1X1.8 Number of occupants 35 35 Ventilation airflow (30 m3/pers) 1050/120 m 3 /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 10
What ventilation system to reduce energy demand? 29 (7) 30 (28) Athina Oslo European mythology: air-tightness, ventilation control, heat recovery 11
Winter Summer F. Flourentzou European Mythology and Hellenic Reality about Zero Energy Buildings DIAL+ dynamic simulation of temperature difference Lefkosia Climate Bern climate In Bern there is a high winter recovery potential during day and night In Lefkosia there is a small recovery potential especially during day 12
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! 13
Heat and cooling demand and primary energy consumption Energy demand Primary energy consumption Heat recovery is more effective with polluting energies 14
Heat recovery: Environmental emissions and embodied energy Life span 25 years Heat recovery: 1.5 kwh/m 2 y, Simple ventilation: 0.64 kwh/m 2 y 15
7 kwh/m 2 y 1.5 kwh/m 2 y for 2 DC fans for grey energy F. Flourentzou European Mythology and Hellenic Reality about Zero Energy Buildings Heat recovery: Primary energy cost for fans (X 2.9) and grey energy Embodied energy is low but not negligible, fan energy is high 16
Primary energy cost and savings Fans & embodied primary energy cost Primary energy savings Heat recovery is a complex question in Switzerland Heat recovery is a simple question in Sweden, Greece and Cyprus 17
From mythology to reality in Europe Before refurbishment After refurbishment Spectacular reduction of envelope heat losses 18
Before and after reburbishment Spectacular but? 19
Window use Almost 1/3 of the windows are open after refurbishment with T ext - 4 C 20
And more windows 21
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 22
«mythological» and real user behaviour 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 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 23
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 24
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! 25
Ideal ventilation strategies for Hellenic zero energy buildings In winter, ventilation provides air quality: 30 m 3 /h per person during hours of use, minimum ventilation of 0.2 m 3 /m 2 h outside hours of use to save energy In summer, ventilation provides air quality: 30 m 3 /h per person during hours of use. In summer, ventilation provides night cooling: 2-4 air changes when T ext <T int 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. 26
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 27
Night cooling ventilation strategy for Lefkosia new Townhall Guarantee safety and provide large oppening possibilities. 28
natural ventilation design: user possibilities A window offers 30 to 366 m 3 /h stack effect airflow at ΔΤ 5 C 29
KWh/m2 F. Flourentzou European Mythology and Hellenic Reality about Zero Energy Buildings Use of ceiling fans to keep windows closed and rise set temperature 100 80 60 40 20 0 23-24 C 21-26 C 21-28 C 15 % rise of cooling energy per 1 C of set température decrease Ceiling fans may save 30% of cooling energy consumption 30
Passive Building Standard Building Heating and cooling system F. Flourentzou European Mythology and Hellenic Reality about Zero Energy Buildings 192 (43) 192 (15) Lefkosia Bern 38 (4) 29 (7) 22 (20) 30 (28) Lefkosia Athina Bern Oslo What energy system for Hellenic passive buildings? 31
Need of correct cooling load dimensionning 50 W/m 2 of simulated sensible cooling load according to ISO 15255 10 W/m 2 of simulated heating load according to ISO 15265 350 W/m 2 of total cooling initially proposed Static dimensionning 24-42 C is not adapted for low energy buildings 32
Technical installation sobriety F. Flourentzou European Mythology and Hellenic Reality about Zero Energy Buildings Lefkosia townhall passive building technical installations Installation of a High COP VRV, 135 W/m 2 33
COP according to demand F. Flourentzou European Mythology and Hellenic Reality about Zero Energy Buildings Oversising of heat pumps costs investment money but also energy We have to reinvent the job of the mechanical engineer 34
Heating and cooling emmition F. Flourentzou European Mythology and Hellenic Reality about Zero Energy Buildings Current machines are not adapted to distribute low intensity energy 220 fan electric Watts to distribute 2500 thermal Watts is to match 35
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/m 2 y 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 36