Performance evaluation of a mechanically ventilated heat recovery (MVHR) system as part of a series of UK residential energy retrofit measures

This study involves a detailed analysis of a mechanically ventilated heat recovery (MVHR) system installed as a case study retrofit project in a UK test dwelling. Comparisons of predicted and in situ performance are made through the calculation of a theoretical and practical heat loss coefficient value (HLC). Analysis revealed underperformance in the installed MVHR system, as compared to predicted data. Issues were identified in the installation and function of the control unit and ductwork. Improvement work enabled the system to function more closely to optimum performance levels. However, discrepancies still existed between the predicted and actual HLC values, which were largely accounted for through theoretical heat loss calculations attributable to slight imbalances within the system supply and extract rates. When normalised, the data still showed an unaccounted heat loss of approximately 6 W/K in both MVHR tests. The study reinforces the need for high quality MVHR installation and commissioning work, which is critical to ensure that a system can perform to the optimum levels specified in manufacturer literature. Education and training throughout the supply chain is essential in achieving this, as system inefficiencies can lead to unnecessary heat losses resulting from increased levels of air infiltration or leakage

Improving the airtightness in an existing UK dwelling: the challenges, the measures and their effectiveness

Air infiltration, occurring through gaps in the building envelope, can contribute up to one third of total heat losses associated with older UK dwellings [1]. Therefore, reducing the rate of air leakage (i.e. improving air ‘tightness’) can have a positive effect in terms of decreasing space heating requirements. This study presents an investigation of the effectiveness of airtightness measures applied in a retrofit context to a UK dwelling. A phased programme of refurbishment work was undertaken to a test dwelling at the University of Nottingham campus, UK. Evaluation techniques, including building energy modelling (SAP 2009), air pressurisation tests and thermal imaging, were performed. The study demonstrates that the use of conventional draught-proofing measures can achieve a reduction in air permeability of over 30% when compared with the house base case value of 15.57 m3/(h.m2) @ 50 Pa. This reduction was only achievable with close attention to installation detail. Further measures of service penetration and floor sealing enabled the air permeability to be reduced to as low as 4.74 m3/(h m2) @ 50 Pa. Modelling of the test dwelling predicted an initial space heating supply energy requirement of 32,373 kWh, which was reduced to 23,197 kWh by a combination of the air tightness measures, insulation, and system (boiler and ventilation) improvements. Air tightness measures alone contributed to approximately 9% of the predicted total reduction, half of which was due to relatively straight-forward draught-proofing. Other more advanced air tightness measures were considerably more expensive, though cheaper approaches to their application could help reduce payback times

A domestic operational rating for UK homes: Concept, formulation and application

A Domestic Operational Rating (DOR) scheme is presented for assessing the energy performance of occupied dwellings. The DOR is complementary to the method used to generate the asset rating of UK dwellings: the Standard Assessment Procedure (SAP). The DOR is transparent, easy to calculate, based on readily available information, producible from daily smart meter data, calculable for any period on a rolling year basis and applicable across all UK homes.The DOR method was developed using a new primary data set collected from 114 homes as part of the DEFACTO project. All were semi-detached, gas centrally heated, privately owned and internet connected properties, located in the English Midlands. The mean daily energy demands are analysed alongside information gathered through an energy survey and household questionnaires. These data are presented and analysed for the first time in this paper.The DOR method, which is described in full, generates metrics that indicate the absolute and relative energy demands, greenhouse gas emissions and energy costs of homes. The DOR ratings for the D114 homes were stable from year to year. Comparing the DOR with homes’ asset (SAP) ratings, indicates that the SAP rating poorly reflects the inter-home variation of households’ actual energy demand. For the D114 homes, it was possible produce a reduced data Domestic Operational Rating, rdDOR, using the energy demands measured on only a few cold days.Although developed in the UK context, the DOR is generally applicable to national, regional or local housing stocks in which daily energy demand is metered. Potential improvements to the DOR, and the need for trials using smart meter data from diverse homes and locations, are discussed

Conventional roofs as collectors in a solar-assisted heat pump system

SIGLELD:D48712/84 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

In-Situ Measurements of the Performance of Thermosyphon Solar Water Heating Systems in Libya

This paper reports on a project carried out by the Centre for Solar Energy Research and Studies (CSERS) to familiarize Libyan people with solar water heating technologies. Around 100 solar water heaters have been installed in the domestic sector and selected systems were equipped with monitoring instruments required to evaluate thermal performance. The paper presents the results of data collected over a one year period from a system installed in a family residence situated in a village located 90 km south of Tripoli (Libyan capital). The results showed that the system solar fraction was 55.8% of the average amount of daily hot water withdrawn (144 litres) at an average withdrawal temperature of 46.6 °C. The total energy withdrawn during the whole year was 1557 kWh. It is concluded that such a system is not adequate in terms of cost effectiveness for the current installed situation. It is recommended that the annual solar fraction for any solar water heating system should be over 70% in order to achieve cost—effectiveness and to help wide spread take—up of this technology

Vulnerability of the economy and guardianship

AbstractImproving the energy performance of existing building refurbishment has been identified as one of the key measures to reduce greenhouse gases (GHGs) emissions and combat climate change. However, little has been done to uncover how human behaviours would affect the selection of refurbishment solutions selection. The problem is particularly obvious for high-rise residential buildings as they are owned and/or occupied by different peoples with idiosyncratic behaviour and preference. In this research, 46 potential methods commonly used for major sustainable building refurbishment in high-rise residential buildings located in cities with sub-tropical climate like Hong Kong were identified through literature review. These sustainable building refurbishment methods are classified under five groups namely energy user pattern, domestic, high-rise building, climate feature and other building characteristics. A questionnaire survey was conducted to examine the feasibility of the identified refurbishment methods based on the perception of owners and occupants. The results show that those methods classified under building services category such as lighting, appliance, ventilation and lift received greater support from owners and occupants. It is interesting to note that owners and occupants did not favour those sustainable refurbishment options which are related to the building envelop when it comes to major building refurbishment. As for the renewable energy refurbishment methods, their acceptability was moderate indicating that there is huge potential for being incorporated into the major building refurbishment. This paper should help improve our understanding on what factors contribute to the satisfaction of owners and occupants of high-rise residential building in a major sustainable refurbishment scheme

Intelligence in buildings: the potential of advanced modelling

Intelligence in buildings usually implies facilities management via building automation systems (BAS). However, present-day commercial BAS adopt a rudimentary approach to data handling, control and fault detection, and there is much scope for improvement. This paper describes a model-based technique for raising the level of sophistication at which BAS currently operate. Using stochastic multivariable identification, models are derived which describe the behaviour of air temperature and relative humidity in a full-scale office zone equipped with a dedicated heating, ventilating and air-conditioning (HVAC) plant. The models are of good quality, giving prediction accuracies of • ± 0.25• °C in 19.2• °C and of • ± 0.6% rh in 53% rh when forecasting up to 15 minutes ahead. For forecasts up to 3 days ahead, accuracies are • ± 0.65• °C and • ± 1.25% rh, respectively.  The utility of the models for facilities management is investigated. The “temperature modeli was employed within a predictive on/off control strategy for the office zone, and was shown to substantially improve temperature regulation and to reduce energy consumption in comparison with conventional on/off control. Comparison of prediction accuracies for two different situations, that is, the office with and without furniture plus carpet, showed that some level of furnishing is essential during the commissioning phase if model-based control of relative humidity is contemplated. The prospects are assessed for wide-scale replication of the model-based technique, and it is shown that deterministic simulation has potential to be used as a means of initialising a model structure and hence of selecting the sensors for a BAS for any building at the design stage. It is concluded that advanced model-based methods offer significant promise for improving BAS performance, and that proving trials in full-scale everyday situations are now needed prior to commercial development and installation.

Equilibrium thermal characteristics of a building integrated photovoltaic tiled roof

Photovoltaic (PV) modules attain high temperatures when exposed to a combination of high radiation levels and elevated ambient temperatures. The temperature rise can be particularly problematic for fully building integrated PV (BIPV) roof tile systems if back ventilation is restricted. PV laminates could suffer yield degradation and accelerated aging in these conditions. This paper presents a laboratory based experimental investigation undertaken to determine the potential for high temperature operation in such a BIPV installation. This is achieved by ascertaining the dependence of the PV roof tile temperature on incident radiation and ambient temperature. A theory based correction was developed to account for the unrealistic sky temperature of the solar simulator used in the experiments. The particular PV roof tiles used are warranted up to an operational temperature of 85 °C, anything above this temperature will void the warranty because of potential damage to the integrity of the encapsulation. As a guide for installers, a map of southern Europe has been generated indicating locations where excessive module temperatures might be expected and thus where installation is inadvisable

Operation of a new large scale solar simulator for testing the thermal performance of building components with particular attention to ventilated facade elements

This paper looks at the operation of a new large scale solar simulator for testing the thermal performance of building components with particular attention to ventilated facade element