Adopting Low-cost Alternative for Energy Saving
Case Study

This section deals with the compliance requirements for ECBC envelope.


Compliance for ECBC wall

ECBC Recommended Wall features in Warm & Humid climate:
The ECBC recommended walls has the following features
The maximum U-factor both in Day use building and 24-Hour building is 0.44 (W/m2-ºC)

Climate zone Maximum U-factor (24 Hour use building) (W/m2-ºC) Maximum U-factor (Day time use building) (W/m2-ºC)
Moderate 0.39 0.44
Table 2: ECBC recommended wall features for Moderate climate

U-factor :  When there is a temperature difference between inside and outside, heat is lost or gained through the window frame and glazing by the combined effects of conduction, convection, and long wave radiation. For example; opaque U-value refers to the amount of heat transferred (lost/gain), due to a temperature differential of 1°C between inside and outside, per square meter. Figure next illustrates the concept of U-factor.

Thickness R-Value R-Value
15mm (0.5”) 0.70 1.262
20mm (0.75”) 1.06 0.874
25mm (1.0”) 1.41 0.668
40mm (1.5”) 2.11 0.454
50mm (2.0”) 2.82 0.344
65mm (2.5”) 3.52 0.277
75mm (3.0”) 3.70 0.264

Table 3: U-values for different thickness of exterior insulation layers (source: ECBC user guide, BEE)

The below descriptions are ECBC recommended thermal mass materials/construction to achieve ECBC recommended U-factor in Moderate climate.

 
 

Mass Double Wall:

 

Material/Construction

U-factor (W/m2-ºC)

Double brick wall with extruded polystyrene 2.4”-32kg/m3

0.38

Double brick wall with extruded polystyrene 3”-32kg/m3

0.31

Double brick wall with expanded polystyrene (thermocol) 3”-24kg/m3

0.41

Double brick wall with phenolic foam 2.4”-32kg/m3

0.37

Double brick wall with phenolic foam 3”-32kg/m3

0.30

Double brick wall with Polyurethane 2.4”-32 +2 kg/m3

0.33

Double brick wall with Polyurethane 3”-32 +2 kg/m3

0.27

Double brick wall with Polyisocyanurate slab 2.4”-32 +2 kg/m3

0.33

Double brick wall with Polyisocyanurate slab 3”-32 +2 kg/m3

0.27

Double brick wall with Bonded Mineral Wool (Rock or glass wool)  2.4”-64 kg/m3

0.43

Double brick wall with Bonded Mineral Wool (Rock or glass wool)  3”-64 kg/m3

0.35


Table 4: ECBC recommended double wall constructions (source: ECBC stringency analysis, BEE)

   
   

Mass Single Wall:

 

Building Form: Thermal insulation plays an important role in reducing the conductance or U value (W//m2K) of walls. Insulation should always be placed on the external side of the surface. In moderate climate, the advantages of placing insulation on the external side of wall composition is that it does not allow the external heat gain or heat loss from the building enabling thermal management of the building. Air-conditioning costs are considerably higher than heating so external wall insulation works equally as well, saving energy costs to cool as well as

Material/Construction

U-factor (W/m2-ºC)

Initial rate (Rs/Sf)

Single brick wall with 2.4”extruded polystyrene insulation  between gypboard and external brick wall 32kg/m3

0.36

179

Single brick wall with 3”extruded polystyrene insulation  between gypboard and external brick wall 32kg/m3

0.30

205

Single brick wall with 2.4”phenolic foam insulation  between gypboard and external brick wall 32kg/m3

0.35

197

Single brick wall with 3”phenolic foam insulation  between gypboard and external brick wall 32kg/m3

0.32

229

Single brick wall with 2.4”Polyisocyanurate slab insulation  between gypboard and external brick wall 32 +2kg/m3

0.34

176

Single brick wall with 3”Polyisocyanurate slab insulation  between gypboard and external brick wall 32 +2kg/m3

0.28

201

Single brick wall with 2.4”Bonded Mineralwool (Rock wool or glass wool) insulation  between gypboard and external brick wall 64kg/m3

0.40

113

Single brick wall with 3” Mineralwool (Rock wool or glass wool) insulation  between gypboard and external brick wall 64kg/m3

0.34

117

Table 5: ECBC recommended single wall constructions (source: ECBC stringency analysis, BEE)

   

Impact of ECBC Wall:

Energy simulation engine was used to quantify energy saving potential from ECBC compliant wall in a daytime office building. It is observed that, ECBC compliant wall as an individual ECM has energy saving potential, only when WWR is less than 20%. The below graph the reduction in energy consumption in a day time building by ECBC wall as an individual ECM.

Energy Saving Potential with ECBC recommended U-value with various WWR

Alternative

Saving potential w.r.t corresponding WWR base case

Saving potential w.r.t base case (WWR 0.6)

Base case (wwr 0.6)

-0.31

 -0.31

ECBC wall (WWR 0.6)

Base case (wwr 0.5)

-0.26

1.31

ECBC wall (WWR 0.5)

Base case (wwr 0.4)

-0.15

2.88

ECBC wall (WWR 0.4)

Base case (wwr 0.3)

-0.33

4.60

ECBC wall (WWR 0.3)

Base case (wwr 0.2)

-0.31

6.53

ECBC wall (WWR 0.2)

Base case (wwr 0.1)

0.74

8.69

ECBC wall (WWR 0.1)


Table 6: ECBC recommended single wall constructions (source: ECBC stringency analysis, BEE)


Fig 5: Energy Saving Potential with ECBC wall against Base case/conventional building
     

Compliance for ECBC window

Details of ECBC Recommendations:

 

The ECBC limits the area of vertical fenestration, under the perspective approach to a maximum of 60% of the gross wall area.
The ECBC addresses energy losses through fenestration by specifying the following requirements: maximum U-factor (or thermal transmittance) and maximum SHGC, for the following window to wall ratio (WWR):

  • WWR up to 40% and
  • WWR in the range of more than 40% and up to 60%

Vertical fenestrations should meet the requirements for maximum are weighted U-factor and maximum area weighted SHGC.
Vertical Fenestration U-factor (W/m2.K) and SHGC requirements details in Warm & Humid climate

Climate

Maximum U-factor

WWR 40%

40%<WWR 60%

 

 

Maximum SHGC

Maximum SHGC

Temperate

6.9

0.4

0.3


Table 8: ECBC recommended features for ECBC window

Impact of ECBC fenestration for various WWR:

Details of ECBC Recommendations:

 

According to ECBC, if WWR<=40% then SHGC required is 0.25, for higher WWR the SHGC requirement becomes more stringent. Thus, when 40%<WWR<=60%, SHGC required is 0.20. Using similar glass configuration from WWR 10% to 40%, as specified in ECBC, energy consumption for WWR 40% is highest; therefore LCCA for WWR 40% with conventional window (Base case) and ECBC recommended window is carried out. The below graph shows the reduction of energy consumption for ECBC window (WWR 40%) against Base case



Fig 12: Energy consumption for Base case and ECBC Window Case (WWR 40%)

Alternative

Saving potential w.r.t corresponding WWR base case

Saving potential w.r.t base case (WWR 0.6)

Base case (wwr 0.6)

8.12

8.12

ECBC wall (WWR 0.6)

Base case (wwr 0.5)

7.00

8.46

ECBC wall (WWR 0.5)

Base case (wwr 0.4)

5.91

8.75

ECBC wall (WWR 0.4)

Base case (wwr 0.3)

4.69

9.05

ECBC wall (WWR 0.3)

Base case (wwr 0.2)

3.22

9.26

ECBC wall (WWR 0.2)

Base case (wwr 0.1)

1.68

9.55

ECBC wall (WWR 0.1)


Table 9: Energy saving potential w.r.t various WWR

Compliance for ECBC Roof

ECBC Recommended Roof Measures:

 

In roofs, the U-factor for the overall assemblies or minimum R-values for the insulation must be complied with the provisions of the Code.
Exterior roofs can meet the prescriptive requirements in one of the two ways:

  • Use the required R-value of the insulation (this R-value does not apply to building materials or air film.It should be referred exclusively for insulation), or
  • Use a roof assembly U-factor that meets the maximum U-factor criterion for thermal performance (see ECBC Table 4.3.1). The U-factor takes into account all elements or layers in the construction assembly, including the sheathing, interior finishes, and air gaps, as well as exterior and interior air films.

As per the Code:
The roof insulation shall not be located on a suspended ceiling with removable ceiling panels.
The maximum U-factor in Day use building is 0.409 (W/m2-ºC) and 24-Hour building is 0.261 (W/m2-ºC) respectively for Warm & Humid climate.

 

Climate zone

Maximum U-factor (24 Hour use building) (W/m2-ºC)

Maximum U-factor (Day time use building) (W/m2-ºC)

Warm & Humid

0.409

0.409


Table 9: ECBC recommended features for roof

Roof Construction categories complying with ECBC in Moderate climate:
The type of materials and construction that comply with ECBC can be selected for different kind of use from the list below:

Material/Construction

U-factor (W/m2-ºC)

Foam concrete or perilite instead of mud phuska

0.069

RCC slab with extruded polystyrene 2.4”-36kg/m3

0.380

RCC slab with extruded polystyrene 3”-36kg/m3

0.312

RCC slab with expanded polystyrene (thermocol) 3”-24kg/m3

0.409

RCC slab with Phenolic foam 2.4”-32kg/m3

0.363

RCC slab with Phenolic foam 3”-32kg/m3

0.301

RCC slab with Polyurethane  spray 2.4”-42 ± 2kg/m3

0.319

RCC slab with Polyisocyanurate spray 2.4”-42 ± 2kg/m3

0.329

RCC slab with Polyisocyanurate spray 3”-42 ± 2kg/m3

0.267


Table 10: Roof constructions complying with ECBC recommended U-factor
 
opyright 2010. All rights reserved by HPCB Privacy Policy