SHGC - Green Building, Glass

January 15, 2018 | Author: Anonymous | Category: Science, Health Science, Pediatrics
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Energy Efficient Glass Façade for building envelope

Sri Ram.N – IGBC AP; GRIHA Trainer Saint Gobain Glass India 15th June 2011

Glass for building envelope • Indispensible construction material • Freedom from conventional building shapes, with unmatched aesthetics.

• Transparent to visible light – daylighting of interiors • Blending of interiors with exteriors • Helps to maintain hygienic environment with easy

maintenance • Glass is 100% recyclable – Sustainable building envelope

Consumption Pattern Others Television 10%

Lighting 28%

4%

Refrigeration 13%

RESIDENTIAL Airconditioner 45%

Equipment 15%

Lighting 20%

Ventilation 5%

COMMERCIAL Source: Res :UNEP SBCI & TERI Study, Comm: IGDB Study

80 % of Building Energy Consumption

Airconditioner 60%

Key Performance Factors Lighting Energy • Light Transmission Cooling Energy • Total Heat Gain / Heat Transmission – SHGC or SF : Solar Heat Gain Coefficient or Solar Factor – U Value

Performance Parameter Light Factors

Visual Light Transmission (VLT) • Percentage of incident light transmitted • Percentage transmission depends Tint & Coating out

Light Transmitted

Factors affecting Visual Light Transmission (VLT)

Single Glazed Unit

Single Glazed Unit

Single Glazed Unit

Single Glazed

Single Glazed

Clear

Unit

Green tint

Unit

Blue Tint

VLT = 89%

Clear - Solar control

VLT = 73%

Green - Solar control

VLT = 57%

VLT = 67% – 7%

VLT = 54% – 6%

Energy Performance Factors Total Heat Gain / Heat Transferred -SHGC -U Value

Total Heat Gain Electromagnetic Spectrum at Terrestrial Level

TOTAL HEAT GAIN

Amount of heat Transferred due to temperature difference

Heat Gain due to direct solar radiation Near Infra Red

UV Visible .25 .38

.78

Far Infra Red 2.50

Wave Length

50 µ

Heat gain due to Direct solar radiation

directly + re-emitted energy = S F / SHGC 1#

2#

directly transmitted energy

reflected energy re-emitted energy

re-emitted energy

Factors affecting SOLAR FACTOR (SF) or Solar Heat Gain Coefficient (SHGC)

Single Glazed Unit

Single Glazed Unit

Clear

Green

SHGC = 0.84

SHGC = 0.56

Single Glazed Unit Blue SHGC = 0.56

Single Glazed Unit

Single Glazed Unit

Clear –solar control

Green–solar control

SHGC = 0.15 – 0.68

SHGC = 0.16– 0.47

Shading Coefficient Shading Coefficient (SC) = Solar factor of Glass Solar factor of 3.0mm Clear Glass (0.87)

• SC should be used if the solar value are through 3mm clear glass • SF or SHGC should be used if it is direct solar value from sun Eg: Weather Files

Amount of heat Transferred due to temperature difference

U Value

Area = 1 m2

U = 5.7 W/sqm K

T1 = 1 oC

T2 = 0 oC

Factors affecting U value Inert Gas

Single Glazed Unit

Double Glazed Unit

Double Glazed Unit

Double Glazed Unit

U value = 5.8W/SqmK

U value = 2.9W/SqmK

Low-e

Low-e + inert gas

U value = 1.4 to 2 W/SqmK

U value = 1.0 to 1.3 W/SqmK

ECBC – [Energy Conservation Building Code] Glazing Requirements for building envelope

ECBC Compliance Approach • Prescriptive: component based approach (specs given for each) – Low Flexibility – Easy Approach

• Trade Off: system based approach (trade off between performance of envelope) – Moderate Flexibility – Comparatively Tedious Approach

• Performance Method: Whole Building Design Analysis Approach (overall building energy efficiency) – High Flexibility – Tedious Approach – High Detailing

Prescriptive Compliance Approach

Climatic zone map of India

WWR: Window to wall ratio

Z

Case 1 : WWR = X / Y

Z

Case 2 : WWR = (X+Z) / Y

• WWR = Net Glazing area / Gross wall area – Net glazing area (window area minus mullions and framing) divided by – Gross exterior wall area (e.g., multiply width of the bay by floor-to-floor height)

• Spandrel Glass & Glass in front of dead wall are not considered as glass area

Prescriptive Requirements Light Transmission

SHGC / U value

ECBC Prescriptive requirements

Glass Performance Light transmission Solar Control U Value

89%

73%

Greater than 20%

0.84

0.55

Less than 0.25

5.7 W/SqmK

5.7 W/SqmK

Clear Glass

Tinted Glass

Less than 3.3 W/SqmK ECBC Requirements

Coated Glass with Solar / Thermal Insulation

Coating Technology - Glass Conforming to ECBC Compliance

C O A T I N G

Online Coating

T E C N O L O G Y

Offline Coating

CVD Coating Manufactured during manufacturing of glass it self. Process of manufacturing known as pyrolysis

Manufactured in a separate process (offline) by Magnetron sputtering on to raw glass

Choosing “Correct” Glass Energy Efficiency

Daylighting

Daylighting

Daylight Integration Sunlight aids in, – Reduction of Artificial lighting – Increasing Vitamin D level – Alleviate depression &anxiety – Eliminates Claustrophobic effect Glass, – Allows abundant natural sunlight – When compared to conventional brick-mortar building, daylight integration saves about 40 to 60% of the energy used for lighting – For a fixed lumen requirement, sunlight generates lesser heat in comparison to artificial lighting – reduce the A/C bill Light Heat ratio

Heat Built up lumen

watts

Lumen / watts Hr

Indian Annual average

33330

364

91

Retrofits spiral CFLs T5 luminaries

400

7 8 25 40 8

18 30 3 3 24

incandecent lamp LED Lights

750 230 415 600

Clear Glass

Light Transmission

Average Lux Level Peak Lux level Outdoor Lux level : 9000Lux

Solar Control Coated Glass

89%

430 lux 1680 lux Room Size : 4m X 5m

Light Transmission

Average Lux Level Peak Lux level

30%

220 lux 670 lux

Window Size: 1.0mX 2.4m (WWR:20%)

Energy Efficiency

Air conditioned Spaces

Energy Analysis of air conditioned space CASE

Solar Factor

U Value Light W/m2K Transmis sion

HVAC Consumpt ion kWh

Lighting Consumpt ion kWh

Total kWh

Savings / Year kWh

1. Single Clear

0.83

5.7

89%

9574

551

10125

Base

3. Solar Control

0.30

5.7

30%

7017

595

7612

2513

Glass Performance on cooling & Lighting load • Lower Solar Heat Gain coefficient significantly reduces the cooling •Optimized light transmission of glass reduces lighting energy during daytime operation Location: Mumbai

Floor area : 12000 Sqft WWR – 20%

Non - Air conditioned Spaces

Temperature Distribution •



Case 1: Double Glazed Unit – Clear Glass – Solar Factor – U value

Case 2: Double Glazed Unit – Single silver Low-e Glass – Solar Factor – U value



: 0.71 : 2.8W/SqmK

: 0.54 : 1.8W/SqmK

Case 3: Double Glazed Unit –Double silver Low-e Glass – Solar Factor – U value

: 0.32 : 1.6W/SqmK

• • • • • • •

Location : Room Size : Glass Direction : Glass Size : Over hang : Simulation : Simulation hours :

Mumbai 4m X 5m South 1.9m X 4.6m 1.0m Ecotect 8760 Hrs

Temperature Distribution Duration Comfort Temperature Range

Double Glazed Unit Clear Glass

Double Double Glazed Unit Glazed Unit Single silvered Double low-e silvered low-e

Temperature Range 20˚ – 30˚C Hours

7457

7579

7756

%

86%

87.4%

88.5%

Increase in comfort hours

Base

122 Hrs

299 Hrs

Temperature 32˚C

Discomfort Temperature Range

Hours

1021

1007

957

%

11.7%

11.6%

10.9%

Temperature Range 34˚ – 36˚ C Hours

282

174

47

%

3.25%

2.0%

0.53%

Go Green • Do your little bit to the planet ! •

Every reduction in Unit of electricity (KwHr) means

1.4 kg (CO2e) per kWh* • Every reduction in a single KWH, 1.4 Kg of CO2 emission is prevented • Conversion factor includes GHG emission for handling, generation & transportation loss

*Source: DEFRA – Dept of energy & climatic change

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