Thermal Mass the Key to Healthy and Sustainable New Housing

2 Nov 2018

The budget announced a further investment, creating a 5.5billion Housing Infrastructure Fund to support the building of 650,000 new homes. The Concrete Centre is calling for joined up thinking that responds to proven research from Government bodies and beyond to ensure that performance and quality are criteria for securing funding.
Government is keen to stimulate the housing market and regularly refers to the target of 300k new homes per year by 2025, but less has been written about the duty that Government and designers have to ensure that we build quality homes and do not pass a problem to occupants now and in the future.   

Andrew Minson, executive director, The Concrete Centre has examined the recent government’s response to Environment Audit Committee (EAC) report Heatwaves: adapting to climate change  (HC 826) that highlights the relevance of overheating and welcomes the promise of MHCLG’s research into overheating in new homes, but also highlights that many reputable studies are available to assist designers now (see listing).

Minson adds, “the EAC report was very timely during the hottest summer in England on record and the direction to Government was clear “the Government should stop directing financial support to modular housing from its Home Building Fund” - in recognition that modular housing is typically of lightweight construction and therefore does not have thermal mass. Together with natural ventilation and shading, utilisation of thermal mass is a recognised design strategy for minimising overheating”.   

The Government response published on October 25th reiterates the audit committee’s concerns relating to the risk of overheating on health and productivity and accepted recommendations such as: “The Department of Health and Social Care should provide guidance to the Care Quality Commission on how to inspect for overheating risk and ensure that overheating risk forms part of its inspection for safety and suitability of health and social care premises.”  

The government response also reported recent MHCLG research that “investigated the impacts of overheating in new homes on mortality and a loss of productivity due to sleep disruption.”  And that “this research will assist the Government in addressing the issues on overheating raised by the Committee in its forthcoming review of the energy efficiency standards in Building Regulations”

It is reassuring that finally we seem to be making progress in addressing overheating.  Thermal mass is a key benefit of concrete, so it is not surprising that it, and hence overheating, has formed a part of The Concrete Centre’s work for some time.  In 2005, we appointed Arup to study the performance of different house types over a 100-year study period to explore the whole-life carbon performance of housing.  It demonstrated that there is little difference in the embodied impact of a typical timber frame and masonry home– a finding confirmed later by the NHBC Foundation and that the small difference can be offset in only 11years. Hence a home that lasts more than 11 years can have a lower carbon footprint if it has thermal mass. Recently, data assumptions have changed and this could make the pay-back period even shorter, as European standards committees have recently confirmed that the carbon footprint of materials must take into account the whole-life, and that biogenic materials cannot be reported as being carbon sinks given that at end-of-life this carbon is released as CO2 or more harmful greenhouse gases such as methane. 

It is right to acknowledge that for a minority of buildings and for some occupancies, thermal mass may be ineffective or even adverse. A hotel room that has had summer solar gains throughout the day and no ventilation will feel hot, and if there is thermal mass this will radiate heat back into the space for some time.  This is not an issue of the thermal mass but of the management. Proper management would control solar gain and adequately ventilate during the day and the thermal mass would then act as a heat sink in the evening improving thermal comfort of the occupant.

We are confident that the MHCLG research will conclude that thermal mass has an important role to play in minimising risk of overheating and that this and change in regulations cannot come soon enough.   In many respects this government response is a missed opportunity to act now to protect housing associations and new home owners from buildings that will be built in the short term and will be more prone to overheating than need be. 
Notes to Editor:
  Operational and Embodied Carbon in New Build Housing: A Reappraisal”, NHBC Foundation, 2011
   Embodied and operational carbon dioxide emissions from housing: A case study on the effects of thermal mass and climate change, JN Hacker et al, Energy and Buildings, 2008 - Elsevier

Independent research on Overheating
There has been extensive work by many organisations to determine how to address overheating and included within this work is the positive role of thermal mass
•   CIBSE TM60: Good practice in the design of homes, 2018
•   The London Plan – cooling hierarchy, 2016
•   Zero Carbon Hub: Overheating in Homes – The Big Picture, 2015
•   Zero Carbon Hub: Solutions to Overheating in Homes, 2016
•   Building Research Establishment - Overheating in dwellings – guidance document, 2016
•   Good Homes Alliance: Preventing overheating, 2014
•   NHBC Foundation: Understanding overheating – where to start, 2012
•   Technology Strategy Board: Design for future climate, 2008
•   Energy Savings Trust – energy efficiency best practice in housing – reducing overheating a
     designer’s guide, 2005
•   Faber Maunsell: Control of overheating in future housing – design guidance for low energy
     strategies, 2003
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