1. Energy in Buildings Prof. Tânia Sousa taniasousa@ist.utl.pt
Energy Management: 2014/2015
Energy in Buildings
Prof. Tânia Sousa

2. Energy Consumption in Buildings
Buildings account for 31% of global final energy consumption (20 to 40%)
Energy Services?
66.96GJ
34.70GJ
16.45GJ
1MWh=3.6GJ

3. Energy Consumption in Buildings
Buildings account for 31% of global final energy consumption (20 to 40%)
Energy use in buildings: thermal confort, refrigeration, hygiene, nutrition, illumination, etc
66.96GJ
34.70GJ
16.45GJ
1MWh=3.6GJ

4. Energy Consumption in Buildings
Final Energy use in buildings by fuel in 2007 in EJ
Differences?
Residential
Commercial & Public

5. Energy Consumption in Buildings
Final Energy use in buildings by fuel in 2007 in EJ
Combustible and renewables is the most important fuel in residential buildings while electricity dominates comercial buildings
Residential
Commercial & Public

6. Energy Consumption in Buildings
What about Portugal?
In 2007 the final consumption of services + domestic sector represented 29% of the final energy consumption
In 2007 the final consumption per capita was GJ which is 61.5% of the EU-27
Electricity is 49% of the final energy used by buildings (68% in comercial and 36% in residential)

7. Energy Consumption in Buildings
What about Portugal?
In 2007 the final consumption of services + domestic sector represented 29% of the final energy consumption
In 2007 the final consumption per capita was GJ which is 61.5% of the EU-27
Electricity is 49% of the final energy used by buildings (68% in comercial and 36% in residential)
Do you think that the fraction of primary energy would be higher or lower?
Electricity is 22% of total final energy

8. Energy Consumption in Buildings
Most effective strategy to reduce energy use in buildings (Harvey, 2010):
Reduce heating and cooling loads through a high-performance envelope

9. Energy Consumption in Buildings
Most effective strategy to reduce energy use in buildings (Harvey, 2010):
Reduce heating and cooling loads through a high-performance envelope
Meet the reduced load as much as possible using passive solar heating, ventilation and cooling techniques while optimizing the use of daylight

10. Energy Consumption in Buildings
Most effective strategy to reduce energy use in buildings (Harvey, 2010):
Reduce heating and cooling loads through a high-performance envelope
Meet the reduced load as much as possible using passive solar heating, ventilation and cooling techniques while optimizing the use of daylight
Use the most efficient mechanical equipment to meet the remaining loads

11. Energy Consumption in Buildings
Most effective strategy to reduce energy use in buildings (Harvey, 2010):
Reduce heating and cooling loads through a high-performance envelope
Meet the reduced load as much as possible using passive solar heating, ventilation and cooling techniques while optimizing the use of daylight
Use the most efficient mechanical equipment to meet the remaining loads
Ensure that individual energy-using devices are as efficient as possible and properly sized
Efficiency label
Annual power consumption (kWh/year)

12. Energy Consumption in Buildings
How much energy reduction can we achieve?
Passive house standard: heating  15kWh/m2 per year cooling  15 kWh/m2 per year TPE  120 kWh/m2 per year n50 ≤ 0.6 / hour

13. Energy Consumption in Buildings
How much energy reduction can we achieve?
Triple-glazed windows with internal venetian blinds & mechanical ventilation with 82% heat recovery

14. Energy Consumption in Buildings
How much energy reduction can we achieve?
Heating needs decreased from 220 kWh/m2/year to 30 kWh/m2/year
Triple-glazed windows with internal venetian blinds & mechanical ventilation with 82% heat recovery

15. Energy Consumption in Buildings
How much energy reduction can we achieve?

16. Energy Consumption in Buildings
How much does it cost?

17. Buildings – High Performance Envelope
The effectiveness of the thermal envelope depends on insulation levels in the walls, ceiling and basement
Insulation levels control the heat flow by conduction & convection through the exterior and the interior

18. Buildings – High Performance Envelope
The effectiveness of the thermal envelope depends on insulation levels in the walls, ceiling and basement
Insulation levels control the heat flow by conduction & convection through the exterior and the interior

19. Buildings – High Performance Envelope
The effectiveness of the thermal envelope depends on insulation levels in the walls, ceiling and basement
Insulation levels control the heat flow by conduction & convection through the exterior and the interior
U value (W/m2/K), the heat transfer coefficient, is equal to the heat flow per unit area and per degree of inside to outside temperature difference
The U value of a layer of insulation depends on its thickness l and type of material (conductivity – C)

20. Buildings – High Performance Envelope
The effectiveness of the thermal envelope depends on insulation levels in the walls, ceiling and basement
The most highly insulated houses have a heat transfer coefficient of U= W/m2/K
Blown-in cellulose insulation (fills the gaps)
Foam insulation
Vaccum insulation panels
Cork W/m/K

21. Evolution for the heat transfer coefficients in new buildings in Portugal
The most highly insulated houses have a heat transfer coefficient of U= W/m2/K

22. Buildings – High Performance Envelope
The effectiveness of the thermal envelope depends on the insulation levels of windows
Windows offer substantially less resistance to the loss of heat than insulated walls
Single glazed windows have a typical U-value of 5W/m2/K which can be reduced to to 2.5 and 1.65W/m2/K with double and triple glazing because of the additional layers of air
The U-value of 2.5W/m2/K of double glazed windows can be reduced to 2.4W/m2/K and 2.3W/m2/K with Argon and krypton
Double and triple glazing vaccum windows can reduce the U value to 1.2 and 0.2W/m2/K

23. Buildings – High Performance Envelope
The effectiveness of the thermal envelope depends on the gain/loss energy by radiation
Windows permit solar energy to enter and loss of infrared radiation
The solar heat gain coefficient, SHGC, is the fraction of solar radiation inicident on a window that passes through the window
Low emissivity coatings reduce the absorption of long-wave radiation, i.e., they can reduce loss of heat by infrared radiation in winter

24. Buildings – High Performance Envelope
The effectiveness of the thermal envelope depends on the air leakage
The net heat flow due to an air exchange at rate r is:

25. Buildings – High Performance Envelope
The effectiveness of the thermal envelope depends on the air leakage
The internal energy change due to an air exchange at rate r is:
The stack effect promotes air leakage
Warm air is lighter
Stack effect can account for up to 40% of heating requirements on cold climates
The wind effect

26. Buildings – High Performance Envelope
The effectiveness of the thermal envelope depends on the air leakage
Careful application of a continuous air barrier can reduces rates of air leakage by a factor of 5 to 10 compared to standard practice (enforcement of careful workmanship during construction)
Buildings with very low air leakage require mechanical ventilation (95% of the available heat in the warm exhaust air can be transfered to the incoming cold air) to keep indoor air quality

27. Energy Balance in Open Systems
Heat Exchangers:
Transfer energy between fluids at different temperatures
Nos três acetatos seguintes coloquei bonecos para poderes explicar melhor as leis da ternodinâmica
Counter-flow Heat exchanger

28. Buildings – The role of shape, form, orientation and glazed %
Building shape & form
Have significant impacts on heating and cooling loads and daylight because of the relation between surface area and volume
Which one minimizes heat transfer by conduction and convection?

29. Buildings – The role of shape, form, orientation and glazed %
Building orientation
For rectangular buildings the optimal orientation is with the long axis facing south
Why?

30. Buildings – The role of shape, form, orientation and glazed %
Glazing fractions
High glazing fractions increase energy requirements for heating and cooling
There is little additional daylighting benefit once the glazed fraction increases beyond 30-50% of the total façade area

31. Buildings – The role of house size
The living area per family member increased by a factor of 3 between 1950 and 2000 in the US

32. Buildings –Passive (almost) solar heating, ventilation & cooling
Evaporative Cooling:

33. Buildings –Passive (almost) solar heating, ventilation & cooling
Evaporative Cooling:

34. Buildings – Passive (almost) solar heating, ventilation & cooling
Thermal & wind induced ventilation & cooling:
Earth Pipe cooling

35. Buildings – Passive (almost) solar heating, ventilation & cooling
Thermal & wind induced ventilation & cooling:
Large Atria

36. Buildings – Passive (almost) solar heating, ventilation & cooling
Thermal & wind induced ventilation & cooling:

37. Buildings – Passive (almost) solar heating, ventilation & cooling
Thermal & wind induced ventilation & cooling:
Wind catcher

38. Buildings – Passive (almost) solar heating, ventilation & cooling
Passive Solar Heating & Lighting
Shading
Light tubes

39. Buildings – Passive (almost) solar heating, ventilation & cooling
Passive Solar Heating & Lighting
Trombe
Wall

41. Buildings: Mechanical Equipment
In evaluating the energy efficiency of Mechanical Equipment the overall efficiency from primary to useful energy should be taken into account
This is particularly important in the case of using Mechanical Equipments that use electricity (produced from fossil fuels)

42. Buildings: Mechanical Equipment for heating
Furnaces
heat air and distribute the heated air through the house using ducts;
are electric, gas-fired (including propane or natural gas), or oil-fired.
Efficiencies range from 60 to 92% (highest for condensing furnaces)
Boilers
heat water, and provide either hot water or steam for heating;
heat is produced from the combustion of such fuels as natural gas, fuel oil, coal or pellets.
Efficiencies range from 75% to 95% (highest for condensing boilers)

43. Buildings: Mechanical Equipment for heating & cooling
Electrical-resistance heating
Overall efficiency can be quite low (primary -> useful)
Heat-Pumps
Overall efficiency can be quite good
It decreases with T
Air-source and ground-source
For cooling & heating
District Heating/Colling
For heating & cooling
Users don’t need mechanical equipment

44. Buildings: Mechanical Equipment for cooling
Chillers
Produce cold water which is circulated through the building
Electric Chillers: use electricity, COP = (larger units have a higher COP)
Absorption chillers: use heat (can be waste heat from cogeneration) , COP =

45. Buildings: HVAC Systems
Ventilate and heat or cool big buildings
All air systems: air at a sufficient low (high) T and in sufficient volumes is circulated through the building to remove (add) heat loads
CAV: constant air volumes
VAV: variable air volumes
Air that is circulated in the supply ducts may be taken entirely from the outside and exhausted to the outside by the return ducts or a portion of the return air may be mixed with fresh air
Incoming air needs to be cooled and dehumidified in summer and heated and (sometimes) humidified in winter
Restrict air flow to ventilation needs and use additional systems for additional heating/cooling
Heat exchangers that transfer heat between outgoing and incoming air flows

46. Buildings: Mechanical Equipment for water heating
Electrical and natural gas heaters
Efficiency of natural gas heaters is 76-85%
Efficiency of oil heaters is 75-83%
There is heat loss from storage tanks
Point-of-use tankless heaters have losses associated with the pilot light
There are systems that recover heat from the warm wastewater with % efficiencies

47. European Directives
European Directives on the Energy Performance of Buildings
Directive 2002/91/EC of the European Parliament and Council (on the energy performance of buildings):
This was implemented by the Portuguese Legislation RCCTE and RCESE
Directive 2010/31/EU of the European Parliament and Council (on the energy performance of buildings)
This is implemented by the Portuguese Legislation DL 118/2013

48. Directive 2010/31/EU: Aims Reduction of energy consumption
Use of energy from renewable sources
Reduce greenhouse gas emissions
Reduce energy dependence
Promote security of energy supplies
Promote technological developments
Create opportunities for employment & regional development

49. Directive 2010/31/EU: Aims Reduction of energy consumption
Use of energy from renewable sources
Reduce greenhouse gas emissions
Reduce energy dependence
Promote security of energy supplies
Promote technological developments
Create opportunities for employment & regional development
Links with aims of SGCIE?

50. Directive 2010/31/EU: Principles
The establishment of a common methodology to compute Energy Performace
including thermal characteristics, heating and air conditioning instalations, renewable energies, passive heating and cooling, shading, natural light and design

51. Directive 2010/31/EU: Principles
Set Minimum Energy Performance Requirements
Requirements should take into account climatic and local conditions and cost-effectiveness

52. Directive 2010/31/EU: Principles
Energy Performance Requirements should be applied to new buildings & buildings going through major renovations

53. Directive 2010/31/EU: Principles
Set System Requirements for: energy performance, appropriate dimensioning, control and adjustment for Technical Building Systems in existing and new buildings

54. Directive 2010/31/EU: Principles
Increase the number of nearly zero energy buildings

56. Directive 2010/31/EU: Principles
Establish a system of Energy performace certificates.
Energy Performance certificates must be issued for constructed, sold or rented to new tenants
Buildings occupied by public authorities should set na example (ECO.AP in 300 public buildings in Portugal)

57. Directive 2010/31/EU: Principles
Regular maintenance of air conditioning and heating systems
Independent experts

58. Implementation of the directives
Directive 2002/91/EC was implemented with:
Directive 2010/31/EU was implemented with:
DL 118/2013 (SCE, REH e RECS)
DL 78/2006, the National Energy Certification and Indoor Air Quality in Buildings (SCE).
DL 79/2006, Regulation of HVAC Systems of Buildings (RSECE).
DL 80/2006, Regulation of the Characteristics of Thermal Performance of Buildings (RCCTE).

59. Legislative Framework
Decreto-Lei n.º 118/2013
SCE – Buildings Energy Certificate System
REH – Residential Buildings Energy Performance Regulation
RECS – Commerce and Services Buildings Energy Performance Regulation
Lei n.º 58/2013
Defines rules for SCE technicians
Legislative framework is complemented by:
5 portarias
10 despachos
Despachos
15793-C/2013
Pre-certificates and Certificates templates
15793-D/2013
Conversion factors
15793-E/2013
Computation simplification rules
15793-F/2013
Climatic data
15793-G/2013
Testing and maintenance plan
15793-H/2013
Renewable energies
15793-I/2013
Energy demand calculation
15793-J/2013
Energy classification rules
15793-K/2013
Thermal parameters
15793-L/2013
Economic analysis methodology of energy efficiency measures
Portarias
349-A/2013
Role of SCE managing entity
349-B/2013
Methodology and requirements to classify residential buildings’ energy performance (REH)
349-C/2013
Permitting procedures and usage authorization of urban buildings
349-D/2013
Methodology and requirements to classify commerce and service buildings’ energy performance (RECS)
353-A/2013
Indoor air quality
1/17/2014
Doctoral Program and Executive Master in Sustainable Energy Systems Energy Management – 4th Group Work

60. SCE – Domain of Application
RCCTE – Domain of application
Buildings that SCE applies to:
Edifícios ou fracções novos ou sujeitos a grande intervenção
Edifícios área útil > 1000m2 ou > 500m2
Edifícios ou fracções a partir do momento da sua venda 60

61. SCE – Fiscalização e Gestão
Obrigações Proprietários

62. SCE – Edifícios ZEB

63. REH
Objectivos:
Requisitos mínimos para edifícios de habitação novos ou sujeitos a grandes alterações
Metodologia de caracterização do desempenho energético em condições nominais
Metodologia de desempenho dos sistemas técnicos

64. REH and RECS RCCTE - Outdoor conditions Reference Indoor conditions
I3 (higher heating needs) and V3 (higher colling needs)
18ºC in heating season
25ºC in the cooling season
Consumption of 40 liters of water at T+35ºC/occupant . day
Reference Outdoor conditions:
Portugal is divided in winter and summer climatic zones 64

65. REH and RECS RCCTE - Outdoor conditions
Reference Winter Outdoor conditions: 65

66. Heating Degree Days Climate Heating Degree-days are: Where:
Tb is the desired indoor temperature (18ºC)
Tj is the temperature outside the hours j
The Degree-days are calculated for an entire year
For example, to Lisbon, for Tb = 18 º C, heating degree days are 1071 º C. day. Knowing the heating season is 5.3 months (160 days), the average daily GD (GDI) will be 6.7 º C. 66

67. Heating Degree Days – a comparison

68. REH and RECS RCCTE - Outdoor conditions
Reference Summer Outdoor conditions: 68

69. REH – Minimum requirements
RCCTE – Indices e parameters
Heat transfer coefficient:
Factores solares
more demanding for harsher winters U
Heat transfer coefficients of walls
Umax
The corresponding maximum permissible
more demanding for harsher summers
Solar factor of fenestration (for windows not facing NE-NW with area > 5%) Fs
Fsmax
The corresponding maximum permissible 69

70. REH – Thermal Behaviour
RCCTE – Indices e parameters
Annual useful energy needs for cooling and heating in new buildings:
Annual total primary energy in new buildings:
Nic
Nominal Annual Needs of Useful Energy for Heating Ni
The corresponding maximum permissible
Nic ≤ Ni
Nvc
Nominal Annual Needs of Useful Energy for Cooling Nv
The corresponding maximum permissible
Nvc ≤ Nv 70

71. REH - Heating Heating Nic < Ni
Heating: Maximum Useful Nominal Needs (Ni) [kWh / (m2.year)]
Nic < Ni
Heating: Useful Nominal Needs (Nic) [kWh / (m2.year)] 71

72. REH - Heating Heating Nic < Ni Corrected if there is heat recovery
Heating: Maximum Useful Nominal Needs (Ni) [kWh / (m2.year)]
Nic < Ni
Heating: Useful Nominal Needs (Nic) [kWh / (m2.year)]
Nic = (Qtr,i + Qve,i – Qgu,i) / Ap
Qt = x GD x  (A x U)
Qv = 0,024 (0,34 x R x Ap x Pd) x GD
Qt: heat loss by conduction & convection through the surrounding
Qv: heat losses resulting from air exchange
Qgu: solar gain and internal load
Corrected if there is heat recovery 72

73. Current average residential heating energy use (Harvey, 2010)
kWh/m2/yr for new residential buildings in Switzerland and Germany
220 kWh/m2/yr average of existing buildings in Germany
kWh/m2/yr for existing buildings in central and eastern Europe
Passive house standard: 15 kWh/m2/yr

74. REH: Cooling Cooling Nvc < Nv
Cooling: Maximum Useful Nominal Needs (Nv) [kWh/(m2.year)]
Nvc < Nv
Cooling: Useful Nominal Needs (Nvc) [kWh / (m2.year)]
Nvc = Qg * (1 - ) / Ap (kWh/m2year)
Qg : Total gross load (internal + walls + solar + air renewal)
 : Load Factor 74

75. REH: Total Primary Energy
Cooling
TPE: Maximum Nominal Needs (Nt) [kgep/(m2.year)]
Ntc < Nt
TPE: Nominal Needs (Nvc) (Ntc) [kgep/(m2.year)] 75

76. REH: Conversion to Primary Energy
Comparação com SGCIE - 1MWh needs toe?

77. REH – Equipment Energy Efficieny
Os equipamentos de aquecimento e arrefecimento ambiente e de aquecimento de águas devem cumprir requisitos de eficiência
A instalação de equipamento solar térmico para AQS (ou de outras renováveis) é obrigatória desde que a exposição solar seja adequada

78. REH – Thermal Behaviour
RCCTE – Indices e parameters
Valor mínimo de renovação de ar de 0.4 por hora 78

79. Energy Performance Certificate
Energy label
Energy Performance Certificate
Energy Labelling:
R = Ntc / Nt R
A A+
New buildings
B B 1 C D 2 E F 3 G 79

80. https://meocloud.pt/link/34d44317-19bb-467b-915e-78588c145383/Novo_CE_720p.mp4/