ECBC Building Envelope - 2

1. Bu i l di n g E nve l o pe - 2
Submitted by : Kshitiz Bhardwaj
Lakshay Vashist
Priyansh Sharma
Rishit kumar

2. • The Building Envelope 2 (BE2) requirements in the Energy Conservation Building Code (ECBC) are related to the thermal
insulation of the building envelope components such as walls, roofs, and floors.
• The BE2 requirements specify the maximum U-value (thermal transmittance) for each component based on the climatic zone
of the building location. The U-value is a measure of the amount of heat that can pass through a material, and lower U-values
indicate better thermal insulation.
• The BE2 requirements are divided into three levels of compliance:
1. Prescriptive compliance: In this level, the U-values of the building envelope components are prescribed in the ECBC code, and
the building envelope must meet these values to comply with the code.
2. Trade-off compliance: In this level, the building envelope can have higher U-values than those prescribed in the code, but the
overall energy performance of the building must meet a specified target.
3.Whole building performance compliance: In this level, the building envelope and other building components are optimized for
energy performance using computer simulations, and the overall energy performance of the building must meet a specified target.
I n t r o d u c t i o n

3. • The useful daylight illuminance (UDI) area requirements listed in Table 4-1 for 90% of the potential daylit time in a year.
• Assembly buildings and other buildings where daylighting will interfere with the functions or processes of 50% (or more) of the building floor area, are exempted from
meeting the requirements listed in Table 4-1.
Daylighting
Building Envelope Sealing
Following areas of the building envelope, of all except naturally ventilated buildings or spaces,
shall be sealed, caulked, gasketed, or weather-stripped:
1. Joints around fenestration, skylights, and door frames
2. Openings between walls and foundations, and between walls and roof, and wall panels
3. Openings at penetrations of utility services through roofs, walls, and floors
4. Site-built fenestration and doors.
5. Building assemblies used as ducts or plenums
6. All other openings in the building envelope
7. Exhaust fans shall be fitted with a sealing device such as a self-closing damper
8. Operable fenestration should be constructed to eliminate air leakages from fenestration
frame and shutter frame.
Roofs shall comply with the maximum assembly U-factors in Table 4-4 through Table 4-6. The roof
insulation shall be applied externally as part of structural slab and not as a part of false ceiling.

4. Vegetated and Cool Roof
All roofs that are not covered by solar photovoltaics, or solar hot water, or any other renewable energy system, or utilities and services that render it unsuitable for
the purpose, shall be either cool roofs or vegetated roofs.
• For qualifying as a cool roof, roofs with slopes less than 20° shall have an initial solar reflectance of no less than 0.60 and an initial emittance no less than 0.90.
Solar reflectance shall be determined in accordance with ASTM E903-96 and emittance shall be determined in accordance with ASTM E408-71 (RA 1996).
• For qualifying as a vegetated roof, roof areas shall be covered by living vegetation
Opaque External Wall
Opaque above grade external walls shall comply with the maximum assembly U-factors in Table 4-7 through Table 4-9.
Vertical Fenestration
For all climatic zones, vertical fenestration compliance requirements for all three incremental energy efficiency levels, i.e. ECBC, ECBC+, and
SuperECBC, shall comply with the following:
1. Maximum allowable Window Wall Ratio (WWR) is 40%
2. Minimum allowable Visual Light Transmittance (VLT) is 0.27
3. Assembly U-factor includes both frame and glass area weighted U-factors
4. Assembly SHGC includes both frame and glass area weighted SHGC

5. U-factor Exception
Vertical fenestration on all unconditioned buildings or unconditioned spaces may have a maximum U-factor of 5 W/m2.K provided they comply with all
conditions mentioned in Table 4-14.
Skylights
Skylights shall comply with the maximum U-factor and maximum SHGC requirements of Table 4-15. Skylight roof ratio (SRR), defined
as the ratio of the total skylight area of the roof, measured to the outside of the frame, to the gross exterior roof area, is limited to a
maximum of 5% for ECBC Building, ECBC+ Building, and SuperECBC Building, when using the Prescriptive Method for compliance.