Underfloor heating A guide for house builders Guide NF71 NHBC Guide to Underfloor Heating 2nd draft RH.indd 2 08/08/2016 16:50:21 NHBC Foundation NHBC House Davy Avenue Knowlhill Milton Keynes MK5 8FP Tel: 0344 633 1000 Email: [email protected] Web: www.nhbcfoundation.org Twitter: @nhbcfoundation Acknowledgments This guide was written and published for the NHBC Foundation by David Bleicher and Saryu Vatal of BSRIA. Photograph credits: Page 1 SAV Systems Page 17 & 21 Warmafloor Page 25 Emmeti Page 26 Testo © NHBC Foundation. September 2016 NF71 Published by BSRIA on behalf of the NHBC Foundation ISBN 978-0-9930691-8-5 NHBC Guide to Underfloor Heating 2nd draft RH.indd 3 08/08/2016 16:50:21 Underfloor heating A guide for house builders September 2016 NF71 NHBC Guide to Underfloor Heating 2nd draft RH.indd 4 08/08/2016 16:50:22 The NHBC Foundation The NHBC Foundation Expert Panel The NHBC Foundation’s research programme is guided by the following panel of senior representatives from government and industry: The NHBC Foundation, established in 2006, provides high- quality research and practical guidance to support the house- building industry as it addresses the challenges of delivering Rt. Hon. Nick Raynsford Michael Finn Geoff Pearce Chairman of the NHBC Design and Technical Director, Executive Director of 21st-century new homes. To date, it has published more than 70 Foundation and Expert Panel Barratt Developments plc Regeneration and reports on a wide variety of topics, including the sustainability Development, Swan Housing Association agenda, homeowner issues and risk management. Jane Briginshaw Cliff Fudge Design and Sustainability Technical Director, H+H UK Ltd Mike Quinton The NHBC Foundation is also involved in a programme of Consultant, Jane Briginshaw and Associates Chief Executive, NHBC positive engagement with the government, academics and Richard Hardy Managing Director, BRE Global other key stakeholders, focusing on the current and pressing Andrew Burke Helen Saunders issues relevant to house building. Associate, Rickaby Thompson Group Marketing Director, Associates Richard Harral Crest Nicholson plc Head of Technical Policy, Building To find out more about the NHBC Foundation, please Regulation and Standards Division, Richard Cook Department for Communities Steve Turner visit www.nhbcfoundation.org. If you have feedback or Head of Residential and Local Government Head of Communications, suggestions for new areas of research, please contact Development, Lend Lease Home Builders Federation [email protected]. Richard Hill Claire Curtis-Thomas Chief Executive, Andy von Bradsky NHBC is the standard-setting body and leading warranty Chief Executive, Spectrum Housing Group Consultant, PRP and Chairman, and insurance provider for new homes in the UK, providing British Board of Agrément The Housing Forum risk management services to the house-building and wider Neil Jefferson Hywel Davies Director, NHBC Karl Whiteman construction industry. All profits are reinvested in research Technical Director, Divisional Managing Director, and work to improve the construction standard of new homes Chartered Institution of Building Rod MacEachrane Berkeley Homes for the benefit of homeowners. NHBC is independent of the Services Engineers (CIBSE) Director, NHBC (retired) Tony Woodward government and house builders. To find out more about the Andrew Day Robin Nicholson CBE Managing Director, NHBC, please visit www.nhbc.co.uk. Director, Architecture, Design Kingerlee Homes & Sustainability - New Homes Senior Partner, Cullinan Studio and Communities, Countryside Properties (UK) Ltd Tadj Oreszczyn Neil Smith Director, The Bartlett School Head of Research and Russell Denness of Environment, Energy and Innovation, NHBC, and Group Chief Executive, Resources Secretary to the Expert Panel Croudace Homes Group ii NHBC Foundation Underfloor heating NHBC Guide to Underfloor Heating 2nd draft RH.indd 2 08/08/2016 16:50:22 Contents Foreword v 1 Introduction 1 2 Key considerations 5 3 Main heat source 7 4 System distribution 9 5 The floor as a heat emitter 15 6 Installing underfloor heating 18 7 Programmers and controls 24 8 Testing 26 9 Commissioning and maintenance 27 10 Handover 28 References 29 NHBC Foundation iii NHBC Guide to Underfloor Heating 2nd draft RH.indd 3 08/08/2016 16:50:22 iv NHBC Foundation Underfloor heating NHBC Guide to Underfloor Heating 2nd draft RH.indd 4 08/08/2016 16:50:22 Foreword The number of new homes with underfloor heating has It is equally important that homeowners and residents are increased in recent years. This is not surprising as underfloor inducted into the use of their particular system and understand heating brings several advantages. It frees up wall space, how to get the best from it. It is likely that it will need to be allowing more flexibility in furniture layouts, which is operated in a different way from other heating systems to particularly useful in smaller apartments. Equally it has which they have become accustomed in the past. Settings may advantages in housing for elderly people where there is a need need to be different, and the heating may need to come on to maintain constant warm temperatures. It also works well earlier and run for a longer period, albeit using less power than with energy efficient condensing boilers and heat pumps. But, other systems. Clearly the objective must be an effective and as with any unfamiliar technology, some problems have been economic heating system that delivers trouble-free warmth encountered as plumbers and house builders have begun and comfort for years to come. installing underfloor heating for the first time. Hopefully, house builders and their contractors will derive This guide has been prepared to help in particular smaller benefit from this guidance, and it will help to improve the companies who have not yet developed great experience of quality of underfloor heating installations, as well as the installing underfloor heating systems. It draws on the design satisfaction of the residents. expertise of BSRIA, for which the NHBC Foundation is very grateful, as well as NHBC’s practical experience of underfloor heating systems installed in new homes. The resulting good Rt Hon Nick Raynsford practice guidance is presented simply and clearly with helpful Chairman, NHBC Foundation illustrations. What are the key lessons? Obviously good design and installation are essential, but it is just as important to ensure that underfloor heating systems are properly commissioned. As we have found through NHBC Foundation research and guidance on other energy-related technologies, meticulous care and attention during commissioning is vital if systems are to work efficiently and deliver the intended benefits without unwelcome problems occurring. NHBC Foundation Underfloor heating v NHBC Guide to Underfloor Heating 2nd draft RH.indd 5 08/08/2016 16:50:22 vi NHBC Foundation Underfloor heating NHBC Guide to Underfloor Heating 2nd draft RH.indd 6 08/08/2016 16:50:22 1 Introduction The energy efficiency of new homes in the UK has steadily improved over the last 40 years, to meet the challenging standards set in Building Regulations. This has been achieved by a combination of improved levels of insulation and more airtight construction to minimise heat losses, and passive design measures such as large south- facing windows to maximise heat gains. Alongside these changes, central heating has become universal, allowing people to maintain their homes at warmer temperatures. The requirement to reduce the CO2 emissions that arise Figure 1 Underfloor heating loops laid out uniformly over an from the use of gas, electricity and other fuels in homes has insulation layer also led to the development of new fuel-efficient systems and technologies for space heating and domestic hot water (DHW) systems. All gas and oil boilers in new homes are of the condensing type, and heat pumps are increasingly being What is underfloor heating? specified. These are both low temperature heat sources. Underfloor heating uses the floor surface within a home as a The combination of lower demand for space heating and heat emitter, and is an alternative to the use of conventional greater fuel efficiency of low temperature heat sources has radiators. Hot water pipework loops are embedded into the led to the development of lower temperature heat emitter floor construction as part of the ‘wet’ central heating system. systems. One such system is underfloor heating, which can be To limit discomfort to residents, and to protect floor finishes installed with a wide range of floor constructions, finishes and from damage, BS EN1264-2[1] limits the maximum temperature heating sources. of the floor surface to 29°C. It should be noted that lower Underfloor heating is, however, a relatively new technology maximum temperatures are required for certain flooring and several factors must be considered when specifying and materials. incorporating this within the design of a home. With the entire floor area being used as the heat emitter, the This publication provides guidance for designers and house relatively low temperature of the floor is sufficient to provide builders on the design, installation and commissioning of as much heat output as smaller radiators with much higher underfloor heating systems. surface temperatures. NHBC Foundation Underfloor heating 1 NHBC Guide to Underfloor Heating 2nd draft RH.indd 1 08/08/2016 16:50:23 Introduction Underfloor heating is especially suited to applications where More than 50% of the heat emitted by underfloor heating is the demand for space heating is low and constant, such as in radiant. Radiant heat is transmitted directly to objects (and retirement housing. It may be less well suited for homes that people) from the emitter and not by first warming the air in the are only occupied intermittently, for example when residents room. Radiators, despite their name, emit most of their heat are not normally home during working hours. through convection – they heat the surrounding air which then rises, drawing in cooler air from lower down in the room.