What is the Energy Hierarchy?

Reduce first, then be efficient, then add renewables. The energy hierarchy is the logic behind Part L, planning policy, and every sensible low-energy design.

The principle

The energy hierarchy ranks the ways to cut a building’s carbon footprint, in order of preference:

  1. Reduce energy demand — fabric first: insulation (u-values), air tightness, minimised thermal bridging, good form and orientation.
  2. Use energy efficiently — efficient heating systems and controls, MVHR, LED lighting, waste water heat recovery.
  3. Supply from low-carbon and renewable sources — heat pumps, solar PV, solar hot water.

London plans phrase it as “be lean, be clean, be green” — and many Local Planning Authorities structure their energy statement requirements around exactly this logic, expecting demand reduction to be demonstrated before renewables are counted.

Why the order matters

A kilowatt-hour you never need is cheaper than one you generate. Fabric measures are permanent, maintenance-free and invisible to occupants; renewables degrade, need replacing, and underperform on poorly designed buildings. Part L embeds the same thinking through the fabric energy efficiency target, which renewables can’t satisfy.

It’s also why we push calculated junction Ψ-values so hard: they’re a step-1 improvement that costs nothing on site.

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