ZEMedS: Case studies
Case study: ITC EINSTEIN High School, Ancona, Italy The sole responsibility for the content of this publication lies with the authors. It does not necessarily reflect the opinion of the European Union. Neither the EASME nor the European Commission are responsible for any use that may be made of the information contained therein. August 215
General data 3 Name of the School Type of school ITC EINSTEIN High School High School Number of students Owner 436 public Location Year of construction Municipality of Loreto, Italy 1966
General data ITC EINSTEIN High School, Municipality i of Loreto, Italy 4 Building typology Heated area (m 2 ) 4 floors building 2998 m 2 Site Urban Plain Heating degree days (base 18): 1897 Cooling degree days (base 26): 82
Current Situation 5 Renovation needs High Priority: energy efficiency and building facade safety. Building use Schedule for High school: Standard Use: From 9 th of September till 14 th of June Reduce Use: From 15 th of June till 12 th of August From 19 th of August till 6 th of September 2 nd, 3 rd, 4 th of January 12 th, 16 th of April 23 rd, 24 th, 27 th, 3 th, 31 st of December Standard Use: Monday till Thursday: 8: to 14: and Friday: 8: to 18: Reduce Use: Monday till Friday: 7: to 8: Wednesday: 14: to 18: Friday: 14: to 15:
Current Situation ITC EINSTEIN High School, Municipality i of Loreto, Italy 6 Building envelope: Walls Brickwall with wall cavity U = 1 W/m².K Building envelope: Roof Roof with insulation and waterproofing U =.4 W/m².K Building envelope: Groundfloor Ground floor consists of concrete U =.9 W/m².K Building envelope: Windows Single glazed windows with wooden frames Uw = 6 W/m².K
Current Situation 7 Airtightness: No measurements Heating/Cooling: 2 natural gas boilers (347 kw). A secondary system, fed by aseparated boiler (cargomax 31) placed on the terrace roof (first level) provide heating to the gymnasium, through two wall mounted air heaters. All the other spaces of the school are heated through radiators, fed by the two boilers placed in the thermal central. At the ground floor, the distribution is not embedded in the walls/floors as in the other floors, but pipes are hung to the ceiling, in the corridors and in the classrooms, often not insulated. Ventilation: No mechanical Ventilation Ventilation by opening windows
Current Situation 8 Lighting: Mainly, fluorescent tubes controlled by users Appliances: Lab: PC, Projector, Printer Office: PC, Printer, Copy Machine Gym: PC, Refrigerator, Dryer DHW: DHW is present just in the Gym, managed through the CARGOMAX 31 boiler Cooking: No cooking
Current Situation 9 Current final energy consumption kwh/m2 conditioned area (from bills, metering etc.): electricity kwh/m2 y; 12 natural gas kwh/m2 y; 193 Total of energy consumption (bills 21 213): 614,949 kwh/year, 25 kwh/year m2 conditioned area Running cost: electricit y /y ; 8148 natural gas /y ; 6522 Energy (bills 21 213): 65,22 /year (natural gas), 8,148 /year (electricity). VAT included. Water: no data Maintenance: no data
1 Design approach: Deep renovation towards ZEMedS nzeb Schools requeriments. ZEMedS Goals: Requeriment 1: C PE Prod RES Primary energy consumption yearly (heating, cooling, ventillation, DHW and lighting) is produced by local renewable energies. Requeriment 2: C FE 25kWh/m2y FE consumption yearly (heating, cooling, ventillation and lighting) per conditioned area Requeriment 3: Indoor air quality guaranteed (CO 2 1 ppm) and temperature above 28ºC 4 hours yearly during occupancy National factors for conversion in energy and CO 2 have been taken into account (data 214). Methodology in energy simulations: Steps considered: First step: 3 proposals (variant A, B and C) in envelope renovation: from less insulated to more insulated Second step: 2 proposals for each variant: Renovation in lighting gsystem Renovation in lighting system, heating and DHW system + installation of PV system+use of natural ventilation Renovation in lighting system, heating and DHW system + installation of PV system+use of mechanical ventilation without heat recovery Renovation in lighting system, heating and DHW system + installation of PV system+use of mechanical ventilation with heat recovery
11 First step: 3 proposals (variant A, B and C) in envelope renovation: from less insulated to more insulated. Variant A Variant B Variant C Step 1 Uwindows and exterior doors 1.8 1.5 1.4 Solar protection Interior Curtains Replacement of existing single glazing for: Variant A: low e double glazing, 16mm(air) and wooden frame (with thermal break). Ug=1.6 Uf=22 2.2 Variant B: low e double glazing, 16mm(argon) and wooden frame (with thermal break). Ug=1.3 Uf= 2.2 Variant C: low e double glazing, 16mm(argon) and wooden frame. Ug=1.3 Uf= 2.2 Uroof.3.22.15 Variant A: 3cm roof tiles with cool material coating and 4cm EPS attached Variant B: 3cm roof tiles with cool material coating and 7cm EPS attached Variant C 3cm roof tiles with cool material coating and 14cm EPS attached Uwall.4.3.2 Variant A: External wall insulation 5cm EPS & plaster with cool coating Variant B: External wall insulation 8cm EPS & plaster with cool coating Variant C: External wall insulation 13cm EPS & plaster with cool coating Ugroundfloor current
12 Second step: 3 proposals for each variant A, B and C: Step 2.1: Renovation of heating and DHW system + installation of PV system + use of natural ventilation Step 2.2: Renovation of heating and DHW system + installation of PV system + use of mechanical ventilation without heat recovery Step 23:Renovation 2.3: of heating and DHW system + installation of PV system +useofmechanical ventilation with heat recovery Step 2.1 Natural lventilation Windows open sceanrio (,8 8 m3/sec/person) / Heating system Condensing boilers Cooling system no cooling system PV system 448m 2 PV panels Step 2.2 Mechanical Ventilation Heating system Cooling system PV system Ventilation systems without heat recovery (control when occupancy) 6.5 l/s person Condensing boilers no cooling system 67m 2 PV panels Step 2.3 Mechanical Ventilation Heating system Cooling system PV system Ventilation systems without heat recovery (control when occupancy) 6.5 l/s person, 7% heat recovery Condensing boilers no cooling system 496m 2 PV panels
13 Italian Regulation:
14 VARIANT A FINAL ENERGY: kwh/m2 16 14 12 1 8 6 4 2 134 129 15 1 75 66 7 62 25 2 Total ZEMedS Heating, cooling & ventilation 5 5 5 5 Lighting 5 ZEMedS requirements (heating, cooling, vent. & lighting) National Regulation step 1 & step 2.1 step 1 & step 2.2 step 1 & step 2.3 step 1 & step 2.1 : 66 kwh/m² in final energy e Lighting; 5 Ventilatio n; Cooling; Heating; 62 step 1 & step 2.2 : 15 kwh/m² in final energy Lighting; 5 Heating; 1 Ventilatio n; Cooling; step 1 & step 2.3 : 75 kwh/m² in final energy Lighting; 5 Heating; 7 Ventilatio n; Cooling; PRIMARY ENERGY: 25 193 Primary energy of existing building kwhpe/m².y 2 (heating, lighting, i DHW, appliances) data from bills 118 86 79 88 79 119 87 38 57 42 15 1 5 5 1 15 ng Existing buildi step 1 step 1 & ste ep 2.1 step 1 & ste ep 2.2 step 1 & ste ep 2.3 Primary energy for non renewable energy consumption kwhpe/m².y (heating, ventilation, lighting and DHW) (data from simulation) Primary Energy predicted by RES kwh/m2 y covering heating, vent., lighting, DHW (data from simulation)
15 FINAL ENERGY: 16 14 12 1 8 6 4 2 134 129 14 1 74 65 69 6 VARIANT B 25 2 kwh/m2 Total ZEMedS Heating, cooling & ventilation 5 5 5 5 Lighting 5 ZEMedS requirements (heating, cooling, vent. & lighting) National Regulation step 1 & step 2.1 step 1 & step 2.2 step 1 & step 2.3 step 1 & step 2.1 : 65 kwh/m² in final energy Lighting; 5 Ventilatio n; Heating; 6Cooling; step 1 & step 2.2 : 14 kwh/m² in final energy Lighting; 5 Heating; 99 Ventilatio n; Cooling; step 1 & step 2.3 : 74 kwh/m² in final energy Lighting; 5 Heating; 69 Ventilatio n; Cooling; PRIMARY ENERGY: 25 193 Primary energy of existing building kwhpe/m².y 2 (heating, lighting, DHW, appliances) data from bills 15 117 84 78 87 1 5 77 37 117 56 87 42 Primary energy for non renewable energy consumption kwhpe/m².y (heating, ventilation, 5 lighting and DHW) (data from simulation) 1 15 Existing buildin ng step 1 ep step 1 & ste 2.1 ep step 1 & ste 2.2 ep step 1 & ste 2.3 Primary Energy predicted by RES kwh/m2 y covering heating, vent., lighting, DHW (data from simulation)
16 16 134 FINAL ENERGY: 14 129 12 1 8 6 4 2 14 99 73 64 68 59 VARIANT C 25 2 kwh/m2 Total ZEMedS Heating, cooling & ventilation 5 5 5 5 Lighting 5 ZEMedS requirements (heating, cooling, vent. & lighting) National Regulation step 1 & step 2.1 step 1 & step 2.2 step 1 & step 2.3 step 1 & step 2.1 : 64 kwh/m² in final energy Lighting; 5 Ventilatio n; Heating; Cooling; 59 step 1 & step 2.2 : 14 kwh/m² in final energy Lighting; 5 Ventilatio n; Heating; 99 Cooling; step 1 & step 2.3 : 73 kwh/m² in final energy Lighting; 5 Heating; 68 Ventilatio n; Cooling; PRIMARY ENERGY: 25 193 Primary energy of existing building kwhpe/m².y 2 (heating, lighting, DHW, appliances) data from bills 15 117 81 76 86 1 117 85 5 77 Primary energy for non renewable energy 37 56 41 consumption kwhpe/m².y (heating, ventilation, lighting and DHW) (data from simulation) 5 1 15 Existing building step 1 step 1 & step 2.1 step 1 & step 2.2 step 1 & step 2.3 Primary Energy predicted by RES kwh/m2 y covering heating, vent., lighting, DHW (data from simulation)
17 Global cost and paybacks for the renovation scenarios: Calculations based on: Average yearly increase in gas price*: 3.9 % (data from 23 to 214) Average yearly increase in electricity price**: 2.5 % (data from 23 to 214) Overall cost of gas: 65,22 /year (VAT included) Overall cost of electricity: 8,148 /year (VAT included) Considered an overall maintenance cost of the renovation scenarios (yearly percentage of the total cost of the renewals) in.5% (envelope measures), 2% (heating systems and PV) Replacement assumed in lighting (15 2 years lifetime) Average inflation considered in 1.8% (from 1 years average data) Overall maintenance yearly percentage of total cost of investment. All construction costs (prices at 214) in renovation scenarios include assembling, disassembling and daily amortization of scaffold are included. Sources for cost data are gathered from using of existing cost database which have been derived from market based data gathering, evaluating of recent projects, and analyzing of standard offers of construction companies. *Source: http://ec.europa.eu/eurostat/tgm/table.do?tab=table&init=1&language=en&pcode=ten117&plugin=1 ** Source: http://ec.europa.eu/eurostat/tgm/table.do?tab=table&init=1&plugin=1&language=en&pcode=ten118
18 Paybacks for the renovation implemented in steps (every 4 years): Expected savings in Expected savings in Overall cost of gas Overall cost of electricity Investment Overall maintenan ce Cost of replacemen Payback gas electrcicity /year /year in cost /year t in Items to be replaced (years) step 1 var A (windows & ext. doors & walls & roofs) 54% % 29.76 8.148 876.478 93 17 step 1 var B (windows & ext. doors & walls & roofs) 56% % 28.844 8.148 918.278 93 17 step 1 var C (windows & ext. doors & walls & roofs) 57% % 27.778 8.148 994.65 93 19 step 2.1 boiler + nat. vent. + PV gas boiler (15 years)/inversors 9% 33% 26.359 5.445 163.388 1.614 57.367 system (var A) PV 39 step 21 2.1 boiler + nat. vent. + PV gas boiler (15 years)/inversors 8% 33% 26.445 5.445 16.388 1.614 56.999 system (var B) PV 39 step 2.1 boiler + nat. vent. + PV gas boiler (15 years)/inversors 6% 33% 26.997 5.445 16.388 1.614 56.999 system (var C) PV 4 step 2.2 boiler + mechanical vent. + gas boiler (15 years)/inversors 43% 33% 41.211 5.445 352.93 3.59 64.911 PV system (var A) PV >5 step 22 2.2 boiler + mechanical vent. + gas boiler (15 years)/inversors 46% 33% 42.15 5.445 349.93 3.59 64.543 PV system (var B) PV >5 step 2.2 boiler + mechanical vent. + gas boiler (15 years)/inversors 51% 33% 43.54 5.445 349.93 3.59 64.543 PV system (var C) PV >5 step 2.3 boiler + MVHR + PV system gas boiler (15 years)/inversors 3% 33% 29.732 5.445 341.478 2.724 59.23 (var A) PV >5 step 23 2.3 boiler + MVHR + PV system gas boiler (15 years)/inversors 4% 33% 29.995 5.445 341.478 2.724 59.23 (var B) PV >5 step 2.3 boiler + MVHR + PV system (var C) 7% 33% 3.821 5.445 338.478 2.724 58.655 gas boiler (15 years)/inversors PV >5 Ttl Total payback in all variants is > 5 years, except for variants with natural ventilation. Overall maintenance yearly percentage of the total cost of the investment. All construction costs (prices at 214) in the renovation scenarios include assembling, disassembling and daily amortization of scaffold are included in wall insulation costs. VAT included.
19 Paybacks for the renovation implemented in steps (every 4 years): Values in m2 conditioned area Expected savings in gas Expected savings in electrcicity Overall cost of gas /year m2 Overall cost of electricity Investment /year m2 in /m2 Overall maintenanc e cost /year m2 Cost of replacemen t in /m2 Items to be replaced step 1 var A( (windows & ext. doors & walls & roofs) 54% % 1 3 292 17 step 1 var B (windows & ext. doors & walls & roofs) 56% % 1 3 36 17 step 1 var C (windows & ext. doors & walls & roofs) 57% % 9 3 332 19 step 21 2.1 boiler + nat. vent. +PV 9% 33% 9 2 54 1 19 system (var A) step 2.1 boiler + nat. vent. + PV 8% 33% 9 2 53 1 19 system (var B) step 2.1 boiler + nat. vent. + PV 6% 33% 9 2 53 1 19 system (var C) step 2.2 2 boiler + mechanical vent. 43% 33% 14 2 118 1 22 + PV system (var A) step 2.2 boiler + mechanical vent. 46% 33% 14 2 117 1 22 + PV system (var B) step 2.2 boiler + mechanical vent. 51% 33% 15 2 117 1 22 + PV system (var C) step 23 2.3 boiler + MVHR + PV 3% 33% 1 2 114 1 2 system (var A) step 2.3 boiler + MVHR + PV 4% 33% 1 2 114 1 2 system (var B) step 2.3 boiler + MVHR + PV 7% 33% 1 2 113 1 2 system (var C) Total payback in all variants is > 5 years, except for variants with natural ventilation. Overall maintenance yearly percentage of the total cost of the investment. All construction costs (prices at 214) in the renovation scenarios include assembling, disassembling and daily amortization of scaffold are included in wall insulation costs. VAT included. Payback (years) 39 39 4 >5 >5 >5 >5 >5 >5
2 In graphics, global cost of step 1: Global costs en /m² 5 4 3 2 1 Existing building step 1 var A (windows & ext. doors & walls & roofs) step 1 var B (windows & ext. doors & walls & roofs) step 1 var C (windows & ext. doors & walls & roofs) 5 1 15 2 25 3 35 4 Confort Maintenance costs /m2 year Energy price (electricity) /m2 year Energy price (diesel) /m2 year Cost of replacement /m2 Investment /m2 Confort (numbers of hours > 28ºC) Number of hours of overheating over 28ºC for renovated buildings are expected to be zero.
21 In graphics, global cost of step 2.1: Global costs en /m² 2 15 1 5 Existing building step 2.1 boiler + nat. vent. + PV system (var A) step 2.1 boiler + nat. vent. + PV system (var B) step 2.1 boiler + nat. vent. + PV system (var C) 5 1 15 2 25 3 35 4 Comfort Maintenance costs /m2 year Energy price (electricity) /m2 year Energy price (diesel) /m2 year Cost of replacement /m2 Investment /m2 Comfort (numbers of hours > 28ºC) Number of hours of overheating over 28ºC for renovated buildings are expected to be zero. The replacement of the gas boilers have been considered in the cost of replacement of the existing building. There is no information of the costs in maintenance concerning the existing building.
22 In graphics, global cost of step 2.2: Global costs en /m² 3 25 2 15 1 5 Existing building step 2.2 boiler + mechanical vent. + PV system (var A) step 2.2 boiler + mechanical vent. + PV system (var B) step 2.2 boiler + mechanical vent. + PV system (var C) 5 1 15 2 25 3 35 4 t Comfort Maintenance costs /m2 year Energy price (electricity) /m2 year Energy price (diesel) /m2 year Cost of replacement /m2 Investment /m2 Confort (numbers of hours > 28ºC) Number of hours of overheating over 28ºC for renovated buildings are expected to be zero. The replacement of the gas boilers have been considered in the cost of replacement of the existing building. There is no information of the costs in maintenance concerning the existing building.
23 In graphics, global cost of step 2.3: Global costs en /m² 3 25 2 15 1 5 Existing building step 2.3 boiler + MVHR + PV system (var A) step 2.3 boiler + MVHR step 2.3 boiler + MVHR + PV system (var B) + PV system (var C) 5 1 15 2 25 3 35 4 Confort Maintenance costs /m2 year Energy price (electricity) /m2 year Energy price (diesel) /m2 year Cost of replacement /m2 Investment t / /m2 Confort (numbers of hours > 28ºC) Number of hours of overheating over 28ºC for renovated buildings are expected to be zero. The replacement of the gas boilers have been considered in the cost of replacement of the existing building. There is no information of the costs in maintenance concerning the existing building.
24 Paybacks for the renovation implemented all at once (step 1 + steps 2): Expected Expected Overall cost Overall cost Overall maintenanc Cost of savings in savings in of gas of electricity Investment e replacement gas electrcicity /year /year in cost /year in Items to be replaced step 1+ step 2.1 (var A) 58% 33% 27.147 5.445 1.39.867 5.455 152.75 step 1+ step 2.1 (var B) 59% 33% 26.445 5.445 1.78.666 5.455 152.41 step 1+ step 2.1 (var C) 6% 33% 25.999 5.445 1.154.453 5.455 152.41 Payback (years) 22 22 23 step 1+ step 2.2 2 (var A) 35% 33% 42.443443 5.445 1.229.381 6.43 159.72 36 step 1+ step 2.2 (var B) 35% 33% 42.15 5.445 1.268.181 6.43 159.38 step 1+ step 2.2 (var C) 36% 33% 41.896 5.445 1.343.967 6.43 159.38 step 1+ step 2.3 (var A) 53% 33% 3.621 5.445 1.217.957 6.35 154.28 step 1+ step 2.3 (var B) 54% 33% 29.995 5.445 1.259.756 6.35 154.28 step 1+ step 2.3 (var C) 54% 33% 29.681 5.445 1.332.543 6.35 153.94 36 37 26 26 27 Total paybacks in variants with natural ventilation is expected in 22 23 years. Total paybacks in variants with mechanical ventilation is expected in 36 37 years. Total paybacks in variants with mechanical ventilation with heat recovery is expected in 26 27 years. Overall maintenance yearly percentage of the total cost of the investment. All construction costs (prices at 214) in the renovation scenarios include assembling, disassembling and daily amortization of scaffold are included in wall insulation costs. VAT included.
25 Paybacks for the renovation implemented all at once (step 1 + steps 2): Values in m2 conditioned area Expected savings in gas Expected savings in electrcicity Overall cost of gas /m2 year Overall cost of electricity /m2 year Investment in /m2 Overall maintenanc e cost /m2 year Cost of replacement in /m2 step 1+ step 2.1 (var A) 58% 33% 9,1 1,8 347 2 51 step 1+ step 2.1 (var B) 59% 33% 8,8 1,8 36 2 51 step 1+ step 2.1 (var C) 6% 33% 8,7 1,8 385 2 51 step 1+ step 2.2 (var A) 35% 33% 14,2 1,8 41 2 53 step 1+ step 2.2 (var B) 35% 33% 14, 1,8 423 2 53 step 1+ step 2.2 (var C) 36% 33% 14, 1,8 448 2 53 step 1+ step 2.3 (var A) 53% 33% 1,2 1,8 46 2 51 step 1+ step 2.3 (var B) 54% 33% 1, 1,8 42 2 51 step 1+ step 2.3 (var C) 54% 33% 9,99 1,8 444 2 51 Items to be replaced Payback (years) 22 22 23 36 36 37 26 26 27 Total paybacks in variants with natural ventilation is expected in 22 23 years. Total paybacks in variants with mechanical ventilation is expected in 36 37 years. Total paybacks in variants with mechanical ventilation with heat recovery is expected in 26 27 years. Overall maintenance yearly percentage of the total cost of the investment. All construction costs (prices at 214) in the renovation scenarios include assembling, disassembling and daily amortization of scaffold are included in wall insulation costs. VAT included.
26 In graphics, global cost of renovation all at once for step 1+ step 2.1: Glob bal costs en /m m² 1 8 6 4 2 Existing building step 1+ step 2.1 (var A) step 1+ step 2.1 (var B) step 1+ step 2.1 (var C) 5 1 15 2 25 3 35 4 Confort Maintenance costs /m2 year Energy price (electricity) /m2 year Energy price (diesel) /m2 year Cost of replacement /m2 Investment /m2 Confort (numbers of hours > 28ºC) Number of hours of overheating over 28ºC for renovated buildings are expected to be zero. The replacement of the gas boilers have been considered in the cost of replacement of the existing building. There is no information of the costs in maintenance concerning the existing building.
27 In graphics, global cost of renovation all at once for step 1+ step 2.2: Gl lobal costs en / /m² 1 8 6 4 2 Existing building step 1+ step 2.2 (var A) step 1+ step 2.2 (var B) step 1+ step 2.2 (var C) 5 1 15 2 25 3 35 4 Confort Maintenance costs /m2 year Energy price (electricity) /m2 year Energy price (diesel) /m2 year Cost of replacement /m2 Investment /m2 Confort (numbers of hours > 28ºC) Number of hours of overheating over 28ºC for renovated buildings are expected to be zero. The replacement of the gas boilers have been considered in the cost of replacement of the existing building. There is no information of the costs in maintenance concerning the existing building.
28 In graphics, global cost of renovation all at once for step 1+ step 2.1: Glob bal costs en /m m² 1 8 6 4 2 Existing building step 1+ step 2.1 (var A) step 1+ step 2.1 (var B) step 1+ step 2.1 (var C) 5 1 15 2 25 3 35 4 Confort Maintenance costs /m2 year Energy price (electricity) /m2 year Energy price (diesel) /m2 year Cost of replacement /m2 Investment /m2 Confort (numbers of hours > 28ºC) Number of hours of overheating over 28ºC for renovated buildings are expected to be zero. The replacement of the gas boilers have been considered in the cost of replacement of the existing building. There is no information of the costs in maintenance concerning the existing building.
29 Current situation: gas electricity consumption (kwh) Ratio (kwh/m2) consumption (kwh) Ratio (kwh/m2) Real (bills) 578614 193 36335 12 Simulation (Open studio+energyplus) 495343 165 43755 15 Results of nzeb renovation under ZEMedS goals: Renovation implemented with energy efficiency measures in result 1 result 2 result 3 envelope + ventilation with natural ventilation + heating system (condensing boiler)+ PV system covering (heating, lighting, ventilation) envelope + ventilation with mechanical ventilation + heating system (condensing boiler)+ PV system covering (heating, lighting, ventilation) envelope + ventilation with mechanical ventilation with heat recovery + heating system (condensing boiler)+ PV system covering (heating, lighting, ventilation) Energy balance in PE (kwh/m2 y) (heating, cooling, vent., Var A 113924/38 17886/57 1 125916/42 DHW & lighting) and RES production (kwh and kwh/m2 Var B 1 11926/37 1 167888/56 1 125916/42 conditioned area) (ZEMedS requirement 1) (simulations) Var C 1 11926/37 167888/56 122918/41 Energy result in FE (kwh/m2 y) (heating, cooling, vent. & Var A 66 15 75 lighting) per conditioned area (ZEMedS requirement 2) Var B 65 14 74 (simulations) Var C 64 14 73 Goal of (ZEMedS requirement 3) natural ventilation by opening windows (no indoor quality guaranteed) predicted temperatures above 28ºC in less than 4 hours/year indoor quality guaranteed by mechanical ventilation predicted temperatures above 28ºC in less than 4 hours/year indoor quality guaranteed by mechanical ventilation predicted temperatures above 28ºC in less than 4 hours/year Paybacks (years) step by step implementation >5 (except for natural ventilation) Paybacks (years) all at once implementation 22 23 36 37 26 27