The London Plan cooling hierarchy: when London planners accept air conditioning

What does London Plan Policy SI 4 say?

Policy SI 4, Managing heat risk, has two parts in the London Plan 2021. Part A asks development proposals to minimise adverse impacts on the urban heat island through design, layout, orientation, materials and green infrastructure. Part B says major development proposals should demonstrate through an energy strategy how they will reduce the potential for internal overheating and reliance on air conditioning systems, in accordance with a cooling hierarchy.

Step	The plan's wording
1	Reduce the amount of heat entering a building through orientation, shading, high albedo materials, fenestration, insulation and the provision of green infrastructure
2	Minimise internal heat generation through energy efficient design
3	Manage the heat within the building through exposed internal thermal mass and high ceilings
4	Provide passive ventilation
5	Provide mechanical ventilation
6	Provide active cooling systems

The order matters. The 2016 plan's Policy 5.9 began with minimising internal heat generation and ended with active cooling systems "ensuring they are the lowest carbon options". A guide that lists a different first step may be quoting the older plan.

Does the policy ban air conditioning?

No, but it puts it last. The supporting text says the increased use of air conditioning is not desirable because these systems have significant energy requirements and, under conventional operation, expel hot air that adds to the urban heat island effect. It says passive ventilation should be prioritised, taking account of external noise and air quality. If active cooling is unavoidable, it should be designed to reuse the waste heat it produces.

Who has to follow the hierarchy?

The policy is aimed at major development proposals, though the plan adds that its principles can also be applied to minor development. A plant change to an existing building is a different question: whether it needs permission at all is covered in the planning permission guide, and noise on adjoining premises is covered in the air conditioning noise guide.

What does a compliant submission look like?

1. Passive measures first. Orientation, shading, glazing, thermal mass and ventilation strategy are shown working through steps 1 to 4.
2. Modelling to the plan's named methods. The plan says CIBSE TM 52 should be used for non-domestic developments, and TM 49 guidance and datasets should be used so the design suits the climate it will experience over its design life.
3. Evidence of the order. The strategy shows the steps were taken in sequence, so that mechanical ventilation or active cooling appears only as the remaining step.
4. Efficient active cooling where it remains. The plan says unavoidable systems should be designed to reuse the waste heat they produce.

A hypothetical illustration: a 6,000 square metre speculative office with a largely glazed south front. Its energy strategy would show external shading and a glazing specification (step 1), efficient lighting and equipment loads (step 2), exposed concrete soffits (step 3), openable windows or mechanical ventilation (steps 4 and 5), and only then cooling plant sized to the load that remains. A planning officer reads the order of the argument, not just the final plant schedule.

The GLA's energy planning guidance page states that all major development proposals must be accompanied by a detailed energy assessment, and links the current assessment guidance.

How do boroughs apply it?

Boroughs add their own local plan policies. Camden's sustainability guidance page names Local Plan Policy CC2, Adapting to Climate Change, as its main planning policy, covering the cooling hierarchy and overheating. The Local Plan was adopted by the council on 3 July 2017. Other boroughs word theirs differently, so the borough's adopted plan and any supplementary guidance are the documents to read for a specific site.

Which London Plan applies now?

On 22 October 2026 the 2021 plan is the adopted plan. The GLA says it was published in 2021 and runs on a five-year cycle. A new draft is moving through the process: consultation ran from 16 July to 15 October 2026, with an independent examination before adoption expected in early 2028. The draft is a proposal, and the 2021 wording above stands until it is replaced.

	Adopted 2021, Policy SI 4	Draft 2026, Policy GHR4 (proposal)
Structure	Six-step cooling hierarchy	Three measures for major development: limiting solar gains, removing excess heat, minimising the need for active cooling
Air conditioning	Increased use "not desirable"	Not prevented; likely to be needed in hospitals, care homes and schools
Modelling	CIBSE TM 52 and TM 49	Dynamic overheating modelling, TM 52 for non-domestic

The draft also says active cooling should be considered after passive measures, once need is shown using CIBSE overheating assessments, and that systems should avoid purging hot air close to homes and amenity spaces. It is a consultation draft: wording may change before examination.

Why does a planning policy cover overheating in offices?

The draft London Plan's rationale sets out the logic, and it is a proposal rather than adopted policy. It says the policy applies to all building uses because current Building Regulations on overheating only apply to residential uses. It adds that addressing overheating at the planning stage allows building design to be adjusted more effectively to maximise passive measures, whereas leaving it to the building control stage limits the available solutions because the design is largely fixed by then. It also asks for London's particular characteristics to be considered, including density, building types, and noise and air quality constraints. The 2021 plan makes the same link: passive ventilation is to be prioritised, taking external noise and air quality into account.

Does this apply outside London?

No. The cooling hierarchy is the Mayor's policy for Greater London, and other authorities set their own. Readers with a London building can find the capital's plant and market context on the commercial HVAC in London page, and can send an enquiry through the site's form from there.

Sources

• London Plan 2021, Chapter 9 Sustainable Infrastructure: Policy SI 4 Managing heat risk, Greater London Authority, checked 22 October 2026
• London Plan 2016, Policy 5.9 Overheating and cooling, Greater London Authority, checked 22 October 2026
• The next London Plan, Greater London Authority, checked 22 October 2026
• Draft London Plan consultation, Greater London Authority, checked 22 October 2026
• Mayor publishes streamlined draft London Plan, Greater London Authority, checked 22 October 2026
• Draft London Plan, chapter 5: Creating a greener, healthier and resilient city (GHR4 Heat risk), Greater London Authority, checked 22 October 2026
• Energy planning guidance, Greater London Authority, checked 22 October 2026
• Sustainability and energy policy and planning guidance, Camden Council, checked 22 October 2026
• Camden Local Plan, Camden Council, checked 22 October 2026

Common questions

Does the cooling hierarchy apply to a small office refit in London?

The plan says the hierarchy applies to major developments and that its principles can also be applied to minor development. A small refit is judged against the borough's own policies and the normal planning tests, so the borough's planning team is the place to ask.

Which overheating method does the plan name for offices?

CIBSE TM 52 for non-domestic developments, with TM 49 guidance and datasets so that the design suits the climate it will experience over its design life. TM 59 is the method named for domestic developments.

Does the draft London Plan change the rules now?

No. It is a draft: consultation closed on 15 October 2026 and examination comes before adoption, which the Mayor expects in early 2028. Until then Policy SI 4 in the 2021 plan is the policy in force.

Is active cooling accepted for hospitals and schools?

The draft says air conditioning is likely to be needed in heat-sensitive uses such as hospitals, care homes and schools. That is a proposal. The adopted plan simply puts active cooling last and asks for it to reuse waste heat where it is unavoidable.

Related guides

• Can air conditioning spread legionella?
• Air conditioning in listed buildings and conservation areas
• Commercial air conditioning noise: limits, assessments and complaints
• Do you need planning permission for commercial air conditioning?