Using future weather files to tackle overheating in London’s buildings

By Colin Rees on Thursday 21 April 2016

The recent COP21 summit in Paris again threw into focus the challenge of climate change, with urban development being confronted to reduce their energy usage. Simultaneously there is a growing concern on how overheating is severely impacting building performance and occupant comfort. With rising global temperatures being experienced now and significant increases expected over the short to medium term, overheating is a key issue that needs to be addressed. Occupant comfort is still a major concern, as is energy use, and they are both intrinsically linked.

Modern buildings are well sealed and insulated and in London where outside temperatures are higher than average this can lead to an enhanced need for cooling during the summer both in Residential and Non-Residential properties.

A historic design response to avoid overheating would have been to introduce comfort cooling measures but this brings additional energy and carbon use as well as higher running and maintenance cost. However, contemporary design approaches more frequently look to tackle solar and internal loads through passive design methods that minimise their impact without retrospective cooling measures being required, or where necessary allow ventilation approaches with mechanical cooling capacity to offset the peak cooling load.

Developing a response to climate change has led London to introduce a chapter specific to this in its London Plan. Policy 5.9 seeks to adapt to climate change by directly addressing the overheating and cooling conundrum. As London suffers from the urban heat island effect, retrofit and new build need to prioritise the opportunities available to reduce the cooling load and remove the potential for space overheating.

To further investigate the impact and mitigation of overheating, a new dataset of weather files has been released by CIBSE to dynamically simulate against the 2020’s, 2050’s and 2080’s. These files for London and other UK locations will offer climate change scenarios to benchmark the projected building performance. Additionally, London has a TM49 dataset representing three summers with different types of hot events.

Dynamic simulation can present fast yet detailed parametric datasets offering the ability to compare design options and drive the optimisation of the most beneficial design solutions such as shading, glass type, window-to-wall ratio, mixed mode ventilation, thermal mass, etc. The Greater London Authority have rightly identified an expectation for dynamic simulation to be used to demonstrate overheating performance. Without a robust analysis you can’t rely on the results and lack of good data leads to plant oversizing and operational inefficiencies.

IES Consulting have the experience to help investigate and interpret the impact on your building design by employing these new datasets for retrofit or new design through a parametric modelling approach where a large number of options can be run in parallel to optimise decision making. IES work with you from the concept stage to build a scope of design options and then provide detailed feedback on the best value opportunities. By generating reliable data we help project teams design with confidence, sizing plant correctly to operate at optimal efficiency and minimise their capital costs without compromising on comfort.