Many architects still design for ECBC 2017 and ENS 2018. Both have been superseded at the national level, and the newer codes ask for more than energy. Water, embodied carbon and EV readiness are now in the frame. The catch is that your state decides which version binds your project, so the first design task is a notification check, not a drawing.
Where the codes stand today
The Bureau of Energy Efficiency (BEE) now publishes the Energy Conservation and Sustainable Building Code (ECSBC) 2024 for commercial buildings and ECO-Niwas Samhita (ENS) 2024 for homes. ECSBC and ENS were published for states to adopt, and they bind a project only when a state or union territory writes them into its building regulations.
Enforcement still lags the paperwork. By December 2024, 25 states and union territories had notified the older ECBC, and 13 had put it into municipal bye-laws covering about 476 urban local bodies. A 2026 NITI Aayog assessment found ECSBC 2024 had not yet been adopted by any state or union territory. Some states have moved on their own paper, though. Kerala’s energy agency lists Kerala Energy Conservation and Sustainable Building Code Rules, 2025 alongside the national text, and Gujarat runs a dedicated platform for its adoption of ENS 2024. For a live project today, you will most likely be checked against your state’s notified ECBC version.
What ECSBC 2024 requires
ECSBC 2024 applies to commercial or office buildings and complexes with a connected load of 100 kW or more, or a contract demand of 120 kVA or more, and a state may set a lower threshold. Residential buildings sit outside it.
It has three tiers: ECSBC Compliant, ECSBC Plus and Super ECSBC, and the baseline tier is mandatory. The higher tiers are voluntary, but developers use them to chase incentives such as extra floor area or tax rebates where a city offers them.
The headline change is scope. The code now covers sustainability, water conservation, EV charging readiness and embodied carbon, on top of operational energy. Two points are worth knowing:
- Embodied carbon: reporting carbon from material extraction and manufacturing (stages A1 to A3) is optional. Our guide on what architects should measure for embodied carbon shows where to start.
- Systems: lighting, HVAC equipment, pumps, controls, energy monitoring and renewable systems all carry requirements. Your engineers own most of these, but your envelope and glazing choices set their loads.
What ENS asks for in homes
ENS Part I (2018) caps the Residential Envelope Transmittance Value at 15 W/m² for the vertical envelope in hot and temperate zones, and the roof at 1.2 W/m²K. A second part, added in 2021, covers building services and renewable energy. ENS 2024 consolidates both and adds site, water, waste and indoor environment considerations. The 2024 text may change the limits and the applicability threshold, so read it before calculating. Under the 2018 code, projects on plots of 500 m² or more were covered.
Five early design moves that decide compliance
Most of these moves come straight from passive design strategies, which cost far less to apply at sketch stage than to retrofit later.
- Orientation and massing. Keep long facades facing north and south. East and west fronts need deep shading from the first sketch.
- Window-to-wall ratio. It is the biggest lever on both codes. Every extra square metre of glass raises envelope heat gain and cooling load.
- External shading. Overhangs and fins earn credit in ENS and cut glare. They cost less than upgrading the glass.
- Roof and wall build-up. Decide insulation, cool-roof finish and wall system before the slab and waterproofing details are drawn.
- Glazing data. Get U-value, SHGC and visible light transmittance in writing. A “low-E” label alone proves nothing.
Add two items the new code makes relevant: a parking layout that leaves room for EV charging load and a rainwater and water-efficiency plan from day one.
A simple workflow
At concept stage, confirm which code version your state has notified and from what date. At schematic stage, fix orientation, glazing ratio and shading, then run a first envelope check. At design development, put U-values and SHGC on the drawings. Before tender, carry those values into the bill of quantities so what gets built matches what got checked. Keep material EPDs from the start, even though reporting is optional.
FAQs
Is ECBC still valid, or has ECSBC replaced it?
ECSBC 2024 is the latest national code, but it binds only where a state has adopted it. Most states still enforce their notified ECBC version. Check your state notification.
What is the difference between ECBC and ECSBC?
ECBC 2017 focused on operational energy. ECSBC 2024 keeps the energy rules and adds water efficiency, EV charging readiness and optional embodied carbon reporting.
Does the code apply to my building?
For commercial or office buildings, the national threshold is 100 kW connected load or 120 kVA contract demand, and a state may lower it. Homes fall under ENS, whose threshold depends on the version and the state.
Is ECO-Niwas Samhita mandatory?
Only where a state or local body has adopted it into its bye-laws. Several states have not.
Is embodied carbon reporting mandatory under ECSBC 2024?
No. The 2024 code makes reporting of stages A1 to A3 optional.
What is RETV?
RETV is the Residential Envelope Transmittance Value, a single number for heat gain through walls and windows excluding the roof. ENS 2018 capped it at 15 W/m² in hot and temperate zones.
Does an IGBC, GRIHA or LEED rating mean I comply with the code?
No. The content overlaps, and designing to ECSBC puts you in a good position for many rating credits, but one does not discharge the other. Code compliance is a legal approval matter, and a rating is voluntary.
Where can I check my state’s current rules?
Start with your state designated agency or energy conservation cell, your urban local body’s bye-laws and the BEE website. The state gazette notification shows the version and the effective date.