Pandraud, G., & Fitton, R. (2014). QUB: Validation of a Rapid Energy Diagnosis Method for Buildings. In International Energy Agency Annexe 58 (pp. 1–6). International Energy Agency.
Introduction
The aim of this paper was to produce a peer reviewed paper to present to the International Energy Agency Annexe 58 members. The paper presents a unique and patented method for measuring the whole house heat loss of a building, in an accelerated way. Currently, these measurements are carried out use the Whole House Heat Loss Methodology, created by Leeds Becket University (LBU) (Johnston et al. 2012). This is known colloquially as the coheating method. This test, although well validated and backed up with extensive field trials take around two weeks to complete and requires a vacant property. The QUB methodology can be completed in two days.
Main Outcomes
The researchers at Saint Gobain Recherché (SGR), developed and patented the QUB method in 2012.(Mangematin et al. 2012) It aims to measure the whole house heat loss of a single building in 48 hours or less. Following a field trail by SGR in France, it was deemed necessary to validate the method under controlled conditions, and also make a comparison to
Page 45 of 85 the most commonly used existing method developed by LBU. The main outcomes of this work were:
• Prior to this experiment LBU had carried out a quasi-steady state coheating test of the building and the results were made available. A close match was found between the two methods.
• Two test sessions were carried out to obtain the repeatability which was found to be ~4% in terms of variance. The HLC found was to be in agreement with the LBU value within ±7%
• There was a significantly reduced timescale when compared to coheating ~48 hours, reflecting two nights testing, dusk till dawn.
• The tests can be carried out with lower temperature differentials between internal and external temperatures,
• The temperatures involved are not excessive, the testing temperature is ~19-20 degrees Celsius. This avoids risks to newly constructed dwellings
• The level of uncertainty is ~10-15%, which is comparable to the LBU methodology.
• The QUB test can give other outputs aside from the HLC such as the capacity of the structure and information regarding time constants of the building
• The faster method allows for more tests to be carried out in quick succession, to reduce error and also to measure retrofit interventions at staged points
Work is still underway to estimate the uncertainty of the QUB method, but given the above results and work that SGR have carried out in the field, the uncertainty is likely to be ± 10- 15%
Limitations
It should also be considered that a sample of one building does not give solid evidence that a test method is valid or accurate, however the SGR team are currently trialling this method in the field in a larger sample of different buildings to add to their research data.
Research Updates
The majority of research around whole house heat loss testing has two strands, cost effectiveness/ease of use and test duration. Stamp concludes that the standard coheating
Page 46 of 85 method, given the correct analysis and favourable conditions can be reduced to 3 days in total (Stamp 2016). The ISABELLE methodology claims to be able to shorten the duration of testing between 5-15 days, as the test is dependant on the weather conditions (Brun et al. 2014). Research carried out by Farmer identifies alternate methods to reach the whole house loss figure, where the central heating system is fitted with a heat meter to give an energy input figure, so the home’s central heating system is used rather than additional apparatus. This gives comparable results of the standard LBU methodology, with the added advantage of providing data on the performance and set up of the heating system itself, which may prove useful. However, Farmer does not appear to investigate the shortening the duration of the test, and it is assumed that due to the uplifted temperature of 25 degrees Celsius that the building should be unoccupied (Farmer et al. 2016)
Summary
This research illustrates that, under controlled conditions, short terms tests are possible to measure the heat loss characteristics of a dwelling. The accuracies and repeatability are within acceptable boundaries of other types of measurement in this field. Additional work to validate the accuracy and to carry out sensitivity analyses, will help to gain further information on the limitations of the test method, such as times of year when it can be performed. A significant finding of this research is that if a building can be tested in 48 hours then more tests can be conducted along the process of a retrofit and, as such, this could take the part of a stage-based quality approach, checking the retrofit as it is being completed. This was carried out in Publication S1 where the Energy House was retrofitted in 6 different scenarios and QUB/coheating was used to measure the results. There are also drawbacks with the QUB method; where coheating heats the building for approximately 2 weeks, this gives the researchers time to carry out heat flux and u-value measurements, the QUB does not. Also the equipment used for the QUB is not significantly less in size or cost than that used in the coheating method.
Section Conclusion
This section opened with a discussion around the numbers of studies currently taking place in the UK, and the fact that this figure is growing all time, next Publication 6 gave an insight into the day to day issues encountered by these individuals, suggestions were made on how
Page 47 of 85 BPE could be improved. Publication 7 is also aimed toward the practitioner who is embarking on a monitoring or testing regime, in particular retrofit projects to dwelling. This chapter contains evidence and practical guidance for these individuals, before this chapter was written it is believed that all of this advice had not been gathered together into one publication, and certainly not one that was up to date.
The ZCH Performance Gap Report Publication A4 then highlighted the significant gaps in knowledge behind new build performance measurement and stated that new technologies were required to assist with this problem, as well as further research into accuracy of these methods and new methodologies in order to discover where the performance gap was originating, and thus minimise it. In response to this, several new testing/measurement techniques are discussed; the new testing methodology for reflective foils (Publication A1),
which previously did not have a standard, the new u-value sensor (Publication A2) co- developed by the author which aims to make the process of u-value measurement easier, more accurate and more accessible. The QUB method (Publication 8) offers a quick, convenient and accurate method to measure the whole house performance of new buildings and retrofit scenarios.
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