Sustainability
Net zero and energy strategy
Energy strategy for planning and for real performance — the hierarchy, the options appraisal, and the gap between the compliance model and the meter.
- Discipline
- Sustainability
WHAT IT IS
An energy strategy sets out how a building will meet its energy and carbon obligations, in the order the decisions have to be made: reduce demand, then supply it efficiently, then supply what remains from low carbon sources, then verify the result.
For most projects it is a planning document before it is an engineering one. Local plan policy, and in London the energy and cooling hierarchies, require the strategy to be submitted with the application — which means it is written early, and then commits the detailed design that follows.
The part that is usually missing is the last one. A compliance model is not a prediction of energy use, and a strategy built only on compliance modelling tells a client nothing about what the building will cost to run.
WHEN YOU NEED IT
Before the planning application, and before any carbon or running-cost target is committed to contractually.
Also whenever an existing estate needs a decarbonisation plan: what to replace, in what order, and what has to be done to the building before the plant change is worth making.
OUR PROCESS
Demand first
Fabric, glazing, shading, ventilation strategy and controls, because every kilowatt removed here is a kilowatt of plant, plant space and electrical capacity that does not have to be provided or paid for.
Then supply
Options appraised on capital cost, running cost, carbon and space — all four, stated separately, rather than collapsed into a single recommendation.
Then verification
Predicted operational energy to CIBSE TM54 alongside the compliance figure, with the difference between them explained rather than hidden. Metering strategy designed so the prediction can actually be tested once the building is in use.
DELIVERABLES
What you receive
- Energy strategy report for planning
- Options appraisal with capital, running cost, carbon and space stated separately
- Operational energy prediction to TM54
- Heat decarbonisation plan for existing buildings
- Embodied carbon assessment of the services installation to TM65
- Metering strategy so the prediction can be verified in use
STANDARDS
Standards applied
The editions in force at the time of design. Where a standard is amended mid-project we confirm which edition the appointment is based on.
- CIBSE TM54Evaluating operational energy use at the design stageCIBSE
- CIBSE TM65Embodied carbon in building servicesCIBSE
- CIBSE TM39Building energy meteringCIBSE
- The London PlanEnergy and cooling hierarchiesGreater London Authority
- PAS 2038Retrofitting non-domestic buildings for improved energy efficiencyBSI
QUESTIONS
Common questions
What does net zero mean for building services design?
In practice it means three separate things that are often conflated: eliminating fossil fuel combustion in the building, reducing the electrical demand that replaces it far enough that the grid can carry it, and accounting for the carbon embodied in the plant and pipework itself. A building with a heat pump and an unreduced demand is not a net zero building; it is the same building with a different fuel.
Why does the predicted energy use differ from the compliance figure?
Because they answer different questions. Compliance modelling uses standardised occupancy, operating hours, internal gains and control assumptions so that buildings can be compared on a common basis, and it excludes unregulated loads such as equipment and catering entirely. An operational prediction to CIBSE TM54 uses the building’s actual intended use and includes those loads. The difference is routinely a factor rather than a percentage.
What does the London Plan require of an energy strategy?
The London Plan sets an energy hierarchy — be lean, be clean, be green, be seen — and a cooling hierarchy requiring passive measures to be demonstrated before mechanical cooling is accepted. Boroughs apply both through planning conditions, so the energy statement submitted with the application effectively commits the detailed design that follows it.