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Rapid measurement of heat losses from walls

BRE is looking for new solutions to accurately and quickly measure the heat losses from solid walls.  Support up to the value of £50,000 is available to support further testing and development of working prototypes.

The solid wall challenge  | Accurate measurements  |  Seeking innovative solutions  |  Scope  |  Key dates  | Competition rules  |  Assessment Procedure FAQs


The solid wall challenge

Improving the energy efficiency of Britain’s housing stock forms a major part of the UK Government’s energy and climate change policy. Progress on insulating hot water cylinders, roofs and wall cavities has been significant however programmes will now have to start addressing some of the more challenging improvement measures if significant efficiency gains are to be made in the future.

Insulating the solid wall housing stock is one of the greatest challenges for energy efficiency policy. It also potentially offers some of the most significant savings, as there are more than 7 million solid wall dwellings in Great Britain. Policies to deliver this work, such as the Green Deal and ECO, rely on modelled estimates of savings from solid wall insulation. It is therefore essential that the models used to provide these estimates are based on robust, up to date and accurate data.

Questions exist around the assumptions used when predicting savings from solid wall insulation. In particular there is a gap between calculated predictions and actual realised energy savings following the application of this measure.

Accurate measurements

The current physical method for measuring/determining wall heat losses (U-values) usually takes up at least 10 days to collect reliable results. It is probable that any attempt to measure wall heat losses over a period of less than 14 days will encounter a trade-off between the speed of measurement and reliability of results.

BRE plans to collect & assess viable ideas for the development of rapid wall U-value assessment tools in order to help energy assessors determine the U-values of the solid walls in dwellings as part of their routine survey inspection.

Seeking innovative solutions

In order to consider the widest possible range of options for rapid wall U-value measurement tools, a competition is being run which will collect ideas that could be tested through the BRE solid wall research programme. There will be a prize for the best idea in the form of a package of support to take the tool onto the next stage of assessment and development.

The main aim of the competition is to identify a tool that can rapidly measure U-values, however we welcome entries that suggest alternative novel ways of assessing heat losses through walls.  The main determinant of a wall's U-value are the density and moisture content of the constituent materials and the thickness of the wall.  Any device that allows these to be determined rapidly and accurately will be considered a valid entry.

Please complete the online form to submit your proposed solution.


All entrants to the competition must fulfil the following criteria:

  • Accuracy of measurement – The tool must provide a U-value measurement (or other appropriate measurement) that is sufficiently accurate to make its use worthwhile.  Therefore should demonstrate an accuracy of at least +/- 15%
  • Speed of measurement – The tool must provide a reading within the time that an energy assessor would normally be at a dwelling i.e. not more than one hour
  • The simplicity of the device and its robustness in providing repeatable and consistent measurements, all else being equal.
  • Financial viability – The tool will need to be purchased by energy assessors and so a business model must be produced that is viable within this context.

Key dates:

  • Competition opens 16 March 2015
  • Q&A Webinar: 27 March 2015 - Your opportunity to find out more about the competition and ask your questions to the technical experts, whether it is right for you etc.
  • Competition closes: 15 May 2015
  • Winner announced: 15 July 2015
  • Testing: September to November 2015

Competition rules:

  • All entrants must submit, via the online form a description of their idea, with accompanying diagrams and other evidence.  Link: https://breinnovar.typeform.com/to/EPONfE
  • Existing prototypes may also be submitted
  • All ideas must be original, and must not infringe existing copyrights and patents in the EU.  Entrants from outside the EU will also be accepted.
  • BRE reserves the right not to award the prize in cases where it is considered that no acceptable ideas have been proposed.
  • BRE reserves the right to restrict the number of entrants and/or entries considered at the evaluation process.
  • For this project we are primarily interested in the measurement of un-insulated solid walls. However, we will consider tools that measure insulated solid and cavity walls where there is sufficient time and resource.
  • DECC, BRE and/or independent adjudicators will judge the entries.  The judges' decision is final and cannot be challenged.
  • Ownership of the ideas and tools:  All ideas will continue to be owned by the original proposer.
  • The competition owners retain the right to curtail or cancel the competition at any time.

Assessment Procedure

BRE will specify a repeatable process that can test the performance of any prototype tool for measuring the U-value of a solid wall (and other walls if applicable – e.g. cavity walls). It is proposed to have a two-stage process for testing prototype wall U-value measurement tools.

Stage 1: The tool will be tested in a hot-box under test conditions

BRE will use one or more test walls with established U-values to help determine the performance of the prototype tools. The test walls will be loaded into a hot-box, which will have temperatures on the hot and cold sides cycled to simulate typical conditions for housing in the UK. The hot-box can be operated under variable conditions within certain limits. The variable limits for the operation of the hot-box are:

Hot side - min: Lab temperature (~24°C), max: 28°C.

Cold side -  min: 8°C, max:16°C

In preparation for the test the hot-box will run for two days on a typical winter climate cy-cle. After two days the prototype will be used to measure the wall U-value for a period of one hour between the hours of 9am and 5pm (the likely time that any energy assessor would visit a dwelling to complete a survey). The test will then be repeated two further times at different times during the day. 

Stage 2: The tool will be tested in the field against the existing heat flux plate methodology

Once laboratory tests have been completed, the prototypes will be taken out into the field to be tested on real dwellings. The existing heat flux plate methodology will be used in parallel to compare the results. The prototype will again be tested for three one hour periods in order to assess its ability to measure wall U-values under typical energy survey conditions.


  1. Do I need to have an in-depth knowledge of the housing sector?
    No, we are encouraging novel ideas from come from outside the sector.  We are actively seeking technology transfer based on best practice from other sectors.  BRE staff are experts in the sector and will help achieve market understanding.
  2. How far from market can my technology be?
    We don’t anticipate that there will be an off the shelf product that meets all aspects of the specification.  We anticipate that the solution will either be at concept stage or come from adapting a solution from another sector such as geotechnical, structural monitoring etc.
  3. What is the scale of the opportunity?
    This tool is primarily intended for use by energy assessors in the UK.  Details of the number of Green Deal and ECO assessements that are currently undertaken are available from the DECC website.
    It is reasonable to expect that a successful tool would be equally desirable in other European markets where there is an obligation to produce energy performance certificates under the Energy Performance of Buildings Directive (EPBD).
  4. Do I have to be based in the UK?
    There is no requirement to be based in the UK however we do anticipate that the UK will be the initial market for the technology.  The challenges of rapid U-value measurements extend to many countries, especially across Europe and therefore the size of the market opportunity for the successful company is significant.
  5. What do you mean by performance gap?
    Primarily this refers to the gap between the savings from installing solid wall insulation predicted by modelling and the actual savings observed by the householder once the insulation has been installed.  A secondary meaning is the gap between the assumed performance (U-value) of a wall and the actual performance measured.
  6. Are academic institutions eligible to enter the competition?
    Yes, we know that a lot of leading research has been carried out by academics in this space, applying measurement technologies on research projects.  We anticipate that some concepts will come from the academic sector and provided there is a potential route to market, academics are encouraged to enter. 
  7. What form will the prize take?
    The nature of the prize will vary depending on factors including but not limited to the approach taken by the winning entry, the stage of the development of the winning entry and the number of winning entries.  For example, the prize for an existing prototype measurement tool will take the form of testing and verification using BRE's renowned facilities and experts.  
  8. How do I participate?
    Please complete the online questionnaire to submit your innovation to the competition.  Link: https://breinnovar.typeform.com/to/EPONfE

Questions from Webinar 27 March 2015

  1. Do you anticipate splitting the prize and having multiple winners?
    It is certainly possible, depending on what entries the competition receives, but if there is more than one viable entry it is certainly something that can be considered.
  2. Does the competition entry involve provision of an actual device?
    The competition is calling for a device to enable more accurate measurement of heat losses.  If it is a prototype device that has been produced already then that is fine, if it were to win the prize would be to test that device and take it to the next stage of development.  Concepts are equally valid.
  3. Do you have any ideas at the moment  of when to measure . e.g heating on/off?
    The existing methodology requires a large temperature difference between the inside and the outside of the property.  Therefore it has to be done when the heating is on.  There is no requirement for the competition entrants to have heating on or heating off.  The aim of this competition is find a device that can be used throughout the year by EPC assessors or energy assessors who need to be able to carry out assessments throughout the year.  If your proposed device requires a temperature difference that is OK, however a device that doesn’t require a temperature difference is advantageous.
  4. Do you recommend a price for the device, a maximum price?
    Pricing is for the entrants to decide, based on market analysis.
  5. Will a future software model take into account time of year i.e. will the data from the device be used to inform the software models?
    The current RD SAP software is the methodology that is used for government approved energy calculations in existing dwellings such as EPCs, Green Deal Assessments etc.  Therefore the RDSAP software is the target of the competition.  Any software model outside of the SAP/RDSAP methodology is outside of the scope of the project.   SAP calculates energy use for an entire year, including heating season and non-heating season in its calculations.  Wall U-values are the same regardless of the time of year (subject to changing conditions such as moisture content), it is just a question of the temperature differentials required when you try to measure it.