Introduction to basics of energy efficient building design

Transcription

1 Introduction to basics of energy efficient building design Pierre Jaboyedoff Seminar on Energy Efficient & Thermally Comfortable Buildings in Amravati For CRDA, Andhra Pradesh May 2 nd 2017 Indo-Swiss Building Energy Efficiency Project Project Management and Technical Unit (PMTU) 1 of 21

2 Factors influencing the Thermal Comfort of the human body Metabolic rate Air temperature Mean radiant temperature Short wave (solar radiation) Long wave (surface temperature) Personal Factors Thermal Comfort Environmental Factors Clothing Air velocity Relative humidity Source: ASHRAE Handbook _2009

3 Main factors influencing the comfort in a building Air temperature Inside the building Humidity Radiant temperature Surface temperature Air velocity Low velocity for «cold» air Higher velocity for «warm air» Solar radiation Direct on the body Diffuse or re-radiated Solar protection Daylighting Clothing Activities

4 Climate-Responsive Architecture? Environment (Climate)-responsive architecture can be defined as architecture aimed at: achieving occupant thermal and visual comfort with little or no recourse to non-renewable energy sources (Simos Yannas, 2003) Solar Radiation- Temperature Humidity Direct & Diffused Wind Rain

5 Click to edit Master title style BRIEF HISTORY OF THE DESIGN PRACTICES AND OF THE TECHNOLOGY PROGRESSES

6 Passive design of the building envelope versus time Ancient architecture (low window to wall ratio, natural ventilation, «modern» architecture % glazed, no natural ventilation, all air systems «sustainable» architecture, 25-40% window to wall ratio, natural ventilation, external movable solar protection Passive

7 Insulation of the walls Insulation did always exist Became an industrial product in the 1950 s Reduction of the heat (in/out) across the walls Typical values Brick 9 inch U~2 W/m^2- C 20 cm insulation U~0.2 W/m^2- C Reduction of the losses/gains of a factor ~10

8 Insulation characteristics of glazing systems have improved significantly in the Single glass U~6 W/m^2- C Triple glass with selective coating U~0.6 W/m^2- C Reduction of the losses by a factor 10 Partly solar protection by reduction of the solar radiation passing through by 60% Daylighting compromise by a reduction of the visual light transmission of ~30%

9 Heat gains by ventilation Infiltration Building tightness has improved during the last 40 years Reduction of the gains/losses by a factor ~5 Mechanical ventilation Reduction of the fresh air flow rate to the hygienic need Addition of heat and humidity recovery heat exchangers Reduction of the gains/losses by a factor 4-5

10 Click to edit Master title style CLIMATE ANALYSIS

11 Climate analysis Temperature evolution Dry bulb Wetbulb (humidity) Solar radiation Direct Diffuse Wind regime Velocity Direction Fluctuation (gust) Time analysis Over 24 hours Over seasons

12 Example: Wind on a specific site

13 Strategies for Climate Responsive Design

14 Click to edit Master title style CLIMATE RESPONSIVE BUILDING MASSING

15 Building Orientation and Massing Massing is the overall shape and size of the building Orientation is the direction the building faces N E W S Good building massing and orientation helps minimise external energy loads and harness solar and wind energy for human comfort

16 Solar Heat Gains North façade receives very little direct radiation. Only in summer mornings and evenings N Horizontal surface receives the greatest intensity Summer 21 st Jun Winter 21 st Dec E East and West façades receive high amount of radiation both in summer and winter South façade is highly exposed in winter, but less in summer. W S

17 Access to Daylight and Natural Ventilation Daylight Ventilation

18 Orientation: Effect on Cooling Load 4305 Total cooling load (kwh) on an intermediate Linear building form in which the longer sides oriented the floor north for and south will have less solar heat gains in summer. March to May (BELGAVI) %

19 Effect on Daylight Access < 100 lux Linear building form in which the longer sides oriented the north and south will have better daylight access. Shallow floor plate (14m 18m) deep allows maximum daylight penetration lux

20 Effect on Natural Ventilation Air velocity < 0.1 m/s Linear building form with a shallow floor plate (14m 18m) deep allows better natural ventilation potential. Air velocity < 0.1 m/s

21 Conclusions on Building Massing and Orientation Linear building form with shallow floor plates (14 18 m) and with the longest façades towards north and south preferable

22 Click to edit Master title style DESIGN OPENINGS FOR DAYLIGHT

23 Daylight Factor Illumination available inside I i Illumination available outside I o Daylight Factor= I i / I o

24 Daylight Autonomy Daylight Autonomy: Percentage of the time-in-use that the daylight levels exceed a specified target illuminance or lighting set-point. TIME-IN-USE: Time when building is being used. For e.g. 9 am to 6 pm TARGET ILLUMINANCE / LIGHTING SET POINT: Recommended illuminance (lux) levels. For e.g. lighting set-point for standard offices is lux. Daylight Autonomy: the percentage of time that an occupant can work through the use of just daylight without supplemental electric lighting

25 Designing for Good Daylight Keep Window-to-Wall Ratio (WWR) around 20% 30%. Keep most of the windows OR Design larger windows on the north and south faces Openings for daylight should be close to the ceiling The space depth should not generally exceed 2.5 times the floor to lintel height. Usually, daylight is available up to 6 or 8 metres from the window. For good daylight, the visual light transmittance (VLT) of the glazing should be high. In most cases, the VLT of clear float glass is high. A balance has to be made in the daylight and heat gain through windows. This can be further controlled by the use of external movable shading The room finishes should be white or in light shades Shallow floor plates are better for daylighting and natural ventilation

26 Placement & Area (Window-Wall-Ratio) Summer 21 st Jun North façade receives very little direct radiation. More windows here. N Winter 21 st Dec E East and West façades receive high amount of radiation. Difficult to shade. Hence less windows here. South façade is highly exposed in winter, but less in summer. Windows can be easily shaded here. W S

27 Windows closer to the Ceiling for daylight access Daylight penetrates into a room roughly 2.5 times the height of the top of the window from the ground. H 2.5 H 2.5 H Higher the window, deeper the daylight penetration in the room Usually, daylight penetration in the room is between 6m to 8m from the fenestration

28 Building Massing and Zoning for Daylight Shallow floor-plates provide daylight access to greater floor area Building spaces can be zoned to place areas requiring more daylight near the perimeter. Areas requiring less daylight placed in the centre of the floor-plate

29 Visible Light Transmission (VLT) of Glass VLT is the ratio of visible light that passes through a glazing unit to the total visible light incident on it. FACTORS INFLUENCING VLT: - Colour of glass - Tints & Coatings on the glazing - Number of glass panes

30 Design features for better daylight access Light shelves help better day light distribution while also providing shading Lighter colours on interior surfaces reflect light better. Helps in daylight distribution and reducing glare.

31 INFOSYS, HYDERABAD Very high daylight autonomy

32 Click to edit Master title style DESIGN FOR NATURAL VENTILATION

33 What is Natural Ventilation? Natural ventilation is the process of supplying and removing air through an indoor space without using mechanical systems. Wind driven natural ventilation Buoyancy driven natural ventilation

34 Purpose of Natural Ventilation To provide an acceptable indoor air quality (IAQ) To provide thermal comfort by providing a heat transport mechanism Cooling of indoor air by replacing or diluting it with outdoor air as long as outdoor temperatures are lower than the indoor temperatures. Cooling of the building structure i.e. Thermal mass of building. A direct cooling effect over the human body through convection and evaporation.

35 Natural Ventilation Potential (example in Karnataka) Semi arid climate: Vijayapura Nearly 40% of annual hours below 26 C

36 Natural Ventilation (example in Karnataka) Temperate climate: Bengaluru Nearly 65% of annual hours below 26 C

37 Wind Driven Natural Ventilation Single sided ventilation Cross ventilation When possible, cross ventilation is more efficient than single sided

38 Wind Driven Natural Ventilation Cross ventilation works well up to building depths of around 15 m and when the predominant wind direction is ± 60 from the axis perpendicular to the building façade

39 Wind Driven Natural Ventilation If the predominant air direction is parallel to the building façade, the use of deflectors is helpful in increasing the flow.

40 Stack Ventilation

41 Night Ventilation Night Ventilation keeps windows and other passive ventilation openings open at night to flush warm air out of the building and cool thermal mass for the next day. For night cooling to be efficient, it requires a building with large areas of exposed internal thermal mass

42 Click to edit Master title style CLIMATE-RESPONSIVE BUILDING ENVELOPE

43 Significance of building envelope The building envelope is the boundary between the conditioned interior of a building and the outdoors. The building envelope is first a protection and shelter. It should meet this need of the occupants while reducing energy consumption.

44 Energy Loads: Building Envelope Components Roof Wall Air leakage Fenestration Floor

45 Heat gains through building envelope components Heat gain from windows is much higher compared to the heat gained through walls Reducing heat gains from the roof and windows should be a priority Heat gain from the roof is highest Heat gain from windows is also significant

46 Recommended Roof Insulation as per ECBC Day-time use buildings & other building types Max U-value Min. R-value of insulation alone Envelope component Climate Zone W/(m²K) m² K/W Roofs All Over deck insulation, e.g., with 10 cm of extruded polystyrene or 7.5 cm of polyurethane foam, is a standard suitable solution for roof insulation

47 Wall Insulation as per ECBC The contribution of heat ingress from walls generally smaller than the contribution of solar energy through glazing Day-time use buildings & other building types Envelope component Walls Climate Zone Tropical wet, wet and dry, semi-arid, and temperate climates Max U-value W/(m²K) Min. R-value of insulation alone m² K/W

48 Heat transfer through Windows- Single Glazing Conducted Incident solar radiation Infiltration Reflected Re-emitted Transmitted Absorbed Re-emitted Convection Conducted

49 Design decisions for windows Placement and Area (Window-Wall-Ratio) Solar Protection Glazing and Frame Properties

50 Window Glazing & Frame Heat transfer through Conduction Heat transfer through Conduction Convection Radiation U factor SHGC Light VLT Solar radiation is the largest contribution to heat gains through windows and often of the total heat gains

51 Solar Heat Gain Coefficient (SHGC) SHGC is the ratio of solar (radiant) heat gain that passes through the fenestration to the total incident solar radiation that falls on it. SHGC is a dimensionless number between 0 and 1. FACTORS INFLUENCING SHGC: - Solar protection or shading - Type of glass & number of panes - Tints & Coatings on the glazing - Gas fill between glazing layers

52 U Factor As with opaque envelope components, U-factors measure thermal conductivity through the window components. FACTORS INFLUENCING U FACTOR: - The size of the air gap between glass panes - Coatings on the glazing - Gas fill between glass panes - Frame construction

53 Visible Light Transmission (VLT) VLT is the ratio of visible light that passes through a glazing unit to the total visible light incident on it. FACTORS INFLUENCING VLT: - Colour of glass - Tints & Coatings on the glazing - Number of glass panes

54 Different Glazing Types Glazing type Glass pane thickness (mm) U factor W/(m²K) SHGC Single clear glazing Double glazing (clear) Double glazing (low-e) Triple glazing (clear) Double glazing, argon filled (low-e) Source: Whole Building Design Guide VLT Double glazing (low-e) SKN Envision Source: Saint Gobain

55 Click to edit Master title style SOLAR SHADING SOLUTIONS

56 Solar Protection Summer 21 st Jun N Winter 21 st Dec E W North-facing windows receive direct sunlight in summer mornings and evenings. Vertical fins can shade adequately S

57 Static Solar Protection Summer Winter Horizontal overhangs can effectively cut direct solar radiation on the south façade in summer but not the diffuse radiation

58 IRRAD, Gurgaon

59 Solar Protection Summer 21 st Jun N Winter 21 st Dec E Summer W Winter Low sun on east west facades Solar azimuth angle also changes Dynamic shading most effective on east west facades S

60 Interior Blinds SHGC > 40% Inside Outside

61 Exterior Blinds SHGC ~ 12%

62 External movable shades can reduce solar heat gains by 60 % - 80%

63 External Movable shades

64 External Movable shades

65 External Movable shades COMMUNICATION BUILDING, EPFL, LAUSANNE ROLEX LEARNING CENTRE, EPFL, LAUSANNE

66 External Movable shades: India GOLCONDE, PONDICHERRY

67 External Movable shades: India SABARMATI ASHRAM, AHMEDABAD

68 External Movable shades: India SAFAL PROFITAIRE, AHMEDABAD

69 External Movable shades: India SAFAL PROFITAIRE, AHMEDABAD

70 Click to edit Master title style RECAP

71 Recap 1 CLIMATE RESPONSIVE BUILDING MASSING Orient the building and organise the spaces and forms so as to minimise the heat gains from solar radiation, provide good daylight access, and facilitate natural ventilation. A linear building form with shallow floor plates (14 18 m) and with the longest façades towards north and south fulfills the 3 criteria mentioned above.

72 Recap 2 DESIGN OPENINGS FOR DAYLIGHT For a typical office building in Karnataka, WWR of 20% 30% is sufficient to provide good daylight (daylight autonomy of around 75%). To achieve good daylight, the building shape should be linear (14 18 m width) in which the longer sides are oriented towards the north and south and the windows are provided only on the north and south façades. Use of clear glass for best VLT in combination with adequate shading devices to cut off glare and heat and use of light-coloured finishes Zone building spaces to place areas needing daylight at the perimeter Place windows higher up on the wall, near the ceiling for better daylight distribution

73 Recap 3 DESIGN FOR NATURAL VENTILATION Cross ventilation works well up to building depths of around 15 m and when the predominant wind direction is ± 60 from the axis perpendicular to the building façade. If the predominant air direction is parallel to the building façade, the use of deflectors is helpful in increasing the flow. In certain cases, stack effect can be used to enhance natural ventilation. However, to be effective, due care should be exercised in designing the height and dimensions of the opening of the stack. Night ventilation takes advantage of lower night-time temperatures to flush heat out of the building and precool the building structure. For night cooling to be efficient, the thermal mass of the building structure needs to accessed by the air flowing through the building and thermally closed false ceilings should be avoided.

74 Recap of Passive Design Measures 4 CLIMATE RESPONSIVE BUILDING ENVELOPE Roof needs to be insulated and treated to reflect the solar radiation. The ECBC for Karnataka recommends roof insulation to reach U values of 0.4 W/m.K. Buildings should have an optimum WWR, which helps in admitting adequate daylight yet limits heat gain. WWR of around 20% 30% may be adequate. The U value of the windows should be low and a trade-off is to be made between SHGC (heat gains) and the VLT (for daylight).

75 Recap of Passive Design Measures 5 SOLAR SHADING SOLUTIONS The best solutions for solar shading are exterior dynamic shading solutions such as shutters or external movable blinds. The major advantage of such solutions are listed below: Flexibility of use according to weather conditions and seasons Provide good daylight, when opened Effectively cut 80% to 90% of the solar gains Can be applied on any façade, which gives more flexibility for the orientation of the building.

76 Click to edit Master title style THANK YOU