1. Assessment of the Energy Savings Potential of Daylight Utilization and its Impact on a Building Energy Performance
Hermano Bernardo
Vienna, 2010

2. Energy efficiency in buildings – some challanges
Reducing energy consumption and greenhouse gases emissions
Optimizing Heating, Ventilation and Air Conditioning (HVAC) systems
Optimizing artificial lighting systems:
Maximizing the use of natural lighting

3. Energy efficiency in buildings – some challanges
Ensuring good indoor air quality (IAQ):
Adequate ventilation with filtration
Thermal comfort
Evaluating the energy performance:
Determining the energy efficiency classification 3 3

4. Buildings: 29% of final energy Buildings: 62% of electricity
Portuguese energy outlook
Buildings: % of final energy
Buildings: % of electricity
Source: DGEG, 2006

5. Legal impositions
European Directive 2002/91/EC: Energy Performance of Buildings (EPBD)
SCE - Sistema Nacional de Certificação Energética e da Qualidade do Ar Interior nos Edifícios (Decreto-Lei n.º 78/2006)
RSECE - Regulamento dos Sistemas Energéticos de Climatização em Edifícios (Decreto-Lei n.º 79/2006)
RCCTE - Regulamento das Características de Comportamento Térmico dos Edifícios (Decreto-Lei n.º 80/2006)

6. Portuguese regulations – application
RCCTE
Residential buildings;
Small services buildings without central HVAC systems, or P ≤ 25 kW;
Basis for the simplified methodology – certification of existing buildings.
RSECE
Services buildings:
Large (>1000 m2 or 500 m2);
Small with HVAC (P > 25kW).
Residential buildings with HVAC systems, P > 25kW

7. Case study – Canteen Building
Location: Leiria
Climate zone: I2V1Norte
Main façade: SE
Year of construction: 2005
Element
U [W/m2.ºC]
External wall
0,50
Ground floor
2,50
Flat roof
1,60
Pitched roof
0,85
Glazing description
U [W/m2.ºC]
Double glazed aluminum window (6+10+4) mm
3,74

8. Methodology Development of a computational model of the building
Model calibration
Full energy audit
Detailed characterization of the actual operating conditions of the building
e.g. Occupation, equipments, lighting, temperature regulation...
Simulation of nominal consumptions
Using reference patterns, rather than actual occupation, equipments and lighting profiles and densities
A climate data file is needed
Determination of the Ieenom index and assignment of the Energy Class

9. Calculation of IEE index
IEE – Energy efficiency index [kgoe/m2];
FCI – Correction factor for heating;
FCV – Correction factor for cooling;
Qaq – Energy used for heating [kgoe/year];
Qarr – Energy used for cooling [kgoe/year];
Qout – Energy used for other purposes [kgoe/ano];
Ap – Net floor surface [m2].

10. Building energy simulation
Set of parameters has to be defined:
e.g. working hours diagrams for lighting, occupation, equipments, air changes, ventilation equipments, heating and cooling temperatures
Confort conditions:
Heating season: air temperature of 20ºC
Cooling season : 25ºC with 50% relative humidity
Primary energy conversion factors
0,290 kgoe/kWh for electricity
0,086 kgoe/kWh for natural gas

11. Building energy simulation
Simulation tool – DesignBuilder for EnergyPlus:
Climatic data;
Definition of the geometry and thermal zones to be included in simulation;
Building envelope characterization;
Internal loads definition;
Parameters of infiltration and ventilation systems;
Environmental control definitions. 11

12. Construction surface [m2]
Building model
Floor
Construction surface [m2]
Net surface
[m2]
1.074
854 1
894
633
Total
1.968
1.487

13. Simulated consumption
Model calibration
Comparison between annual energy consumptions
Energy type
Measured consumption
Simulated consumption
Deviation
[kgoe]
[%]
Electricity
57.982
52.942
-8,7%
Natural gas
23.205
24.455
+5,4%
TOTAL
81.187
77.397
-4,7%

14. Base case simulation Energy usage Electricity Thermal energy Total
[kWh]
[kgoe]
Lighting
31.355
9.093
Equipments
54.177
46.510
Heating
55.587
4.780
Others
6.888
17.013
TOTAL
77.397

15. Lighting systems optimization simulation
Energy usage
Electricity
Thermal energy
Total
[kWh]
[kgoe]
Lighting
23.494
6.813
Equipments
54.177
46.510
Heating
57.851
4.975
Others
6.888
17.013
TOTAL
75.312

16. Lighting optimization
Comparison of results – primary energy
Energy usage
Base case
Lighting optimization
Reduction
[kgoe]
[%]
Lighting
9.093
6.813
25,1
Equipments
46.510
0,0
Heating
4.780
4.975
-4,1
Others
17.013
TOTAL
77.397
75.312
2,7
Energy for lighting systems reduced in 25% but, due thermal load reduction, energy for heating increased in 4%.

17. Annual energy savings potential
Cost reduction
Investment
Pay-back time
[kgoe]
[€]
[years]
Repercussion on electricity consumption
2.280
708
~3.000 ~5
Repercussion on natural gas consumption
-195
-121
Globally, there is an energy saving potential of 2.085kgoe, which means a total cost reduction of 587€ and a reduction in CO2 emissions of kgCO2e.

18. Energy labelling of the case study building
Full simulations were performed under two scenarios:
Reference case;
Maximization the use of natural lighting.
Energy Class
Limits A+
IEEnom
95,25 A
103,5 B
111,75 B-
120 C
136,5 D
153 E
169,5 F
186 G

19. Energy consumption [kgoe]
Reference case - with nominal profiles
Heating
Cooling
Others
Energy consumption [kgoe]
35.217
20.078
IEE = 104,89 kgoe/m2
Class B

20. Energy consumption [kgoe]
Maximization of the use of natural lighting
Heating
Cooling
Others
Energy consumption [kgoe]
36.049
19.737
IEE = 100,59 kgoe/m2
Class A

21. Conclusions
A lighting control system that maximizes the use of natural lighting leads to a considerable reduction of the IEEnom index and the building becomes a Class A building.
During the winter, artificial lighting systems can be beneficial and should always be taken into account when performing simulations and sizing HVAC systems, as they represent a thermal load which contributes to the building’s heating.
During the summer, lighting systems should also be considered, this time because they represent an extra load that must be removed by the cooling system, in case of its existence.
Computational simulation enables the comparison beforehand, in terms of energy performance and thermal comfort, of different alternatives.