Testing the full cooling hierarchy through dynamic thermal modelling across current and future climate scenarios, showing which rooms cooling actually resolved and where it fell short.
Project Overview
- Client: Mimetico
- Sector: Private Residential – Retrofit & Existing Homes
- Location: Kensington & Chelsea and Knightsbridge, London
- Services Provided: CIBSE TM59 Dynamic Thermal Modelling, Part O Overheating Assessment
- Scale: Multiple individual London properties, each assessed separately across current and future climate scenarios
- Target: CIBSE TM59, Approved Document Part O (2021) and CIBSE Guide A (2015a) fixed/adaptive overheating criteria, per the London Plan’s cooling hierarchy.
The Challenge
London faces a genuine and worsening overheating problem; in response, the London Plan sets a clear cooling hierarchy: passive measures, then mechanical ventilation, must be shown insufficient before mechanical cooling is accepted – precisely to avoid active cooling compounding the very heat problem it’s meant to solve. That leaves homeowners and their architects caught between a real comfort problem and a planning system that expects every rung of that hierarchy to be tested, not assumed. Mimetico needed exactly this evidence across a series of projects on period and mews properties in Kensington & Chelsea and Knightsbridge.
The Solution
CIBSE TM59 Dynamic Thermal Modelling
For each property, we built a dynamic thermal model using DesignBuilder EnergyPlus under CIBSE TM59 and Approved Document Part O methodology, testing against current (2020) and future (2050, 2080) climate scenarios so any conclusion would hold up across the building’s expected lifetime. Each assessment worked through the cooling hierarchy in order rather than jumping straight to a cooling conclusion.
On one project – a mews property undergoing refurbishment – this staged approach was tested most thoroughly, and the constraints were real ones rather than assumptions. The property’s listed status ruled out altering the original single-glazed windows or adding external shading. Its proximity to a busy road also meant openable windows couldn’t be relied on for night-time ventilation, since Part O’s acoustic criteria effectively require windows to stay closed once external noise passes a set threshold during sleeping hours. Modelled with passive measures only, several rooms failed badly, with one study space showing overheating for over a third of occupied hours. Adding mechanical ventilation alone brought some improvement, but the same rooms still failed – the same acoustic and heritage constraints limiting how much ventilation could realistically achieve. Only once both stages had been tested and shown insufficient did the modelling turn to mechanical cooling (air conditioning) – at which point nearly every room passed, with only a slight residual risk remaining in one bedroom.
Elsewhere, the picture was more mixed. At one period flat, cooling applied to the worst-affected kitchen resolved that room under current conditions, but bedrooms continued to fail an entirely different criterion – night-time comfort – that kitchen cooling alone couldn’t touch. At a larger property nearby, this same night-time bedroom problem persisted even under future climate projections, with cooling reducing but not eliminating the risk in every case.
The Outcome
Mimetico came away with property-specific, quantified evidence for each assessment – not a generic assertion that a space needs cooling, but a genuine, staged test of the entire cooling hierarchy that planning policy expects to see. Critically, the modelling was honest wherever the picture was mixed: where cooling in one room didn’t resolve a different room’s night-time overheating, that was reported as clearly as the properties where the full hierarchy resolved every space. That kind of evidenced, non-uniform conclusion – showing passive measures and ventilation genuinely tested and found wanting, not assumed – is exactly what gives this modelling credibility as planning evidence.
Client Testimonial
We’ve have been working with Building Energy Experts for a number of years now in the preparation of our Part L1 and O compliance requirements for our central London residential projects. From their Dynamic Thermal Modelling TM59 reports to their Energy Statements, their team have always reacted quickly and provided clear professional information, which have been instrumental in supporting the provision of all LPA documentation, along with ensuring we have all the technical compliancy details for our Permanent Works Packs. They are our preferred Energy Consultants.
— Alex Keane, Managing Director, Mimetico
