Passive house optimization for Southern Italy based on the “New Passivhaus Standard” Paolo Zangheri Lorenzo Pagliano (Director) Salvatore Carlucci end-use Efficiency Research Group, Dipartimento di Energia, Politecnico di Milano www.eerg.it
• The IEE Passive-On project has drafted a proposal to adapt the PassivHaus Standard to the conditions that characterize Southern Europe. • Can the revised PH Standard be met in the context of Southern Italy (e.g. Palermo) by simplifying the envelope specifications and adopting passive cooling strategies appropriately adjusted?
Passivhaus o Passive House? Un Sistema Passivo è un elemento tecnico o tecnologico di un edificio che fornisce un determinato servizio utilizzando solo i flussi di energia derivanti da fonti energetiche locali, senza impiegare macchinari ausiliari (ad esempio pompe, ventilatori,...). Per Progettazione Passiva (Passive Design) si intende un approccio progettuale basato sui Sistemi Passivi che permettono l’ingresso nella zona termica della luce diurna, del calore e dell’aria all’interno dell’edificio solo quando sono utili ed altrimenti di evitarli. Una Passive House (Casa Passiva) è un edificio realizzato conformemente ai principi della Progettazione Passiva in cui i servizi essenziali quali luce, calore, fresco e ventilazione sono forniti in maniera preferenziale con Sistemi Passivi. Tuttavia tale espressione non fornisce alcuna indicazione precisa in merito ai Sistemi Passivi implementati ne a quale fine. Una Passivhaus è un edificio che soddisfa i limiti e le prescrizioni dello Standard Passihaus .
Technical solutions
Original German Passivhaus Standard for Central European Countries: • energy need for space heating < 15 kWh/m ² y; • primary energy consumption for all energy services, < 120 kWh/m ² y;. • Air-tightness: pressurization test (at 50 Pa according to EN 13829) < 0,6 h-1. • Comfort winter: the operative room temperatures >= 20 °C;. • All energy demand values are calculated according to the Passive House Planning Package (PHPP) and refer to the treated floor area, e.g. the sum of the net floor areas of all habitable rooms, excluding e.g stairs.
O. Fanger on his model Expectancy factor: (0,5 to 1)
EN 15251 – Comfort categories • Non mechanically cooled buildings: Building Adaptive Category Range I ± 2°C Tc = 0.33Trm + 18.8 II ± 3°C III ± 4°C
EN15251: Temperature limits in Free Running Buildings Tc = 0.33Trm + 18.8
Comfort models use: ASHRAE • – “Spaces where the thermal conditions of the space are regulated primarily by the occupants through opening and closing of windows. There must be no mechanical cooling system for the space (e.g., refrigerated air conditioning, radiant cooling, or desiccant cooling). Mechanical ventilation with unconditioned air may be utilized, but opening and closing of windows must be the primary means of regulating the thermal conditions in the space.”
Allowance for air movement ASHRAE Standard 55, EN ISO 7730, then also in EN15251:
Proposed new Passivhaus Standard for Warm European Climates : • energy need for space heating < 15 kWh/m ² y; • sensible energy need for space cooling < 15 kWh/m ² y • primary energy consumption for all energy services, < 120 kWh/m ² y; • Air-tightness: if there is a mechanical ventilation system, pressurization test (50 Pa) < 0,6 h-1 according to EN 13829. For locations with winter design ambient temperatures above 0 °C, < 1,0 h-1 is usually sufficient; • Comfort winter: the operative room temperatures >= 20 °C; • Comfort summer: operative room temperatures within the comfort range defined in EN 15251. Furthermore, if an active cooling system is the major cooling device, the operative room temperature can be kept below 26 °C. • All energy demand values are calculated according to the updated Passive House Planning Package (PHPP)
• As a consequence, in the proposed revised Standard for Warm European Climates, homes must now meet the following requirements: • If cooling is provided by mainly passive means: • indoor comfort requirements: as defined by the adaptive model of the Annex A.2 (“Acceptable indoor temperatures for design of buildings without mechanical cooling systems”) of the EN 15251; • energy needs for heating and cooling shall be lower than 15 kWh/m2/ year • Total primary energy shall be lower than 120 kWh/m2/year; • If cooling is provided by active systems: • indoor comfort requirements: as defined by the Fanger’s model of the EN 15251; • energy need for heating shall be lower than 15 kWh/m2/year; • energy need for cooling: shall be lower than 15 kWh/m2/year (this value may be updated and possibly reduced based on field studies); • total primary energy shall be lower than 120 kWh/m2/year.
• Geometry, space disposition and use schedules of a typical terraced two floors house; • S/V Ratio of 0,9 m2/m3; • Medium-high thermal inertia of building components (450 kg/m2, according to ISO 13786 calculation method); • Low internal gains; • Low air permeability of building envelope (n50 = 0,6 h-1); • High insulated envelope (U-value of external wall, basement and roof equal to 0,135 W/m2K; U-value of windows equal to 0,7 W/m2K); • An air distribution system with 10 – 20 cm diameter ducts and two fans (around 40 W each) for the fresh air inlet and the exhausted air extraction (ach = 0,74 h-1);
• A air-air heat recovery exchanger with a 85% efficiency; • A heat pump of low power for the additional heating of air before immission in the rooms in winter. • Shading of windows on southern and eastern facades by means of the roof eaves and of the reflecting blinds controlled to block the direct solar radiation; • A hybrid nigh ventilation strategy realised by windows opening, (avoid discomfort conditions in the sleeping rooms of the building); • The use of an active cooling system capable to limit inside temperatures to 26°C and bound to intervene when the heat removal by night ventilation is not sufficient for this aim. This additional contribution could be given by a reversible heat pump with low power (the same is used during winter for heating purposes).
• optimization analysis to test, in a sequence of steps, reductions in requirements regarding t • he permeability and • the thermal resistance of the building envelope
An Italian Passivhaus – Climate Considered three locations: Milano, Rome, Palermo
Optimising air tightness Risultano come accettabili valori di n50 di: 1÷1.5 h-1 per Milano valori anche superiori per Roma e Palermo
Optimising air tightness
Optimising glazing • heating and cooling energy needs in Palermo. as a function of different glazing types: triple low-E (with U-value of 0,7 W/m2/K and solar factor of 0,5), double low-E (with U-value of 1,4 W/m2/K and solar factor of 0,6) and Standard double (with U-value of 2,7 W/m2/K and solar factor of 0,8
Envelope insulation scenarios
Optimising insulation levels Energy needs for heating and cooling in Palermo as functions of different combinations of thermal insulation of roof (T), external walls (P) and basement (B)
• The first model that meets these requirements is the one with • 5 cm insulation in the walls (U = 0,54 W/m2K), • 6 cm in the roof (U = 0,42 W/m2K) • non-insulated basement (U = 1,34 W/m2K ). • these results have been obtained considering buildings with a heat recovery strategy on exhaust air and they would not be valid without this strategy
indoor comfort conditions in free-floating mode for the climate of Palermo. The indoor operative temperatures are closer to the upper value of the adaptive limit (as defined by the EN 15251 norm) and often are higher (for the 15% of the summer period) than the Fanger’s limit, even using fans that increase the indoor air speed of 0,5 m/s .
if we increase to 25 cm the insulation levels of the perimeter walls and the building roof it is possible to reduce (of about 1 °C) the indoor temperature peaks
Modelli Ottimizzati • la permeabilità dell’involucro : a Milano il limite di n50 pari a 1 h-1 risulta accettabile, e probabilmente anche troppo conservativo per Roma e Palermo. • la trasmittanza delle superfici trasparenti : i tripli vetri normalmente impiegati nel centro Europa possono essere sostituiti da doppi vetri basso- emissivi. • l’isolamento delle superfici opache : mentre una tipica Passivhaus tedesca richiede 25-35 cm di isolante sulle pareti esterne e 30-40 cm sul tetto, a Milano è possibile soddisfare lo Standard con uno spessore degli strati isolanti di 25 cm e a Palermo si può ridurli a 5-6 cm (se si mantiene anche qui la ventilazione meccanica con recupero di calore) oppure si puo’ eliminare la ventilazione meccanica con recuperatore e potenziare l’isolamento.
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