Rokia Raslan

Solid-wall U-values: heat flux measurements compared with standard assumptions

The assumed U-values of solid walls represent a significant source of uncertainty when estimating the energy performance of dwellings. The typical U-value for UK solid walls used for stock-level energy demand estimates and energy certification is 2.1 Wm−2 K−1. A re-analysis (based on 40 brick solid walls and 18 stone walls) using a lumped thermal mass and inverse parameter estimation technique gives a mean value of 1.3 ± 0.4 Wm−2 K−1 for both solid wall types. Among the many implications for policy, this suggests that standard UK solid-wall U-values may be inappropriate for energy certification or for evaluating the investment economics of solid-wall insulation. For stock-level energy modelling, changing the assumed U-value for solid walls reduces the estimated mean annual space heating demand by 16%, and causes a proportion of the stock to change Energy Performance Certification (EPC) band. The analysis shows that the diversity of energy use in domestic buildings may be as much influenced by heterogeneity in the physical characteristics of individual building components as it is by variation in occupant behaviour. Policy assessment and guidance material needs to acknowledge and account for this variation in physical building characteristics through regular grounding in empirical field data.

Results variability in accredited building energy performance compliance demonstration software in the UK: an inter-model comparative study

In the context of performance-based building regulations, the benefits provided by building energy performance prediction tools in facilitating the exploration of innovative approaches to achieving performance requirements has been recognized. In accordance with the Directive on Energy Performance of Buildings (EPBD), the UK has introduced a methodology that allows the use of accredited third-party software for demonstrating compliance with energy performance criteria outlined in the relevant technical guidance for the non-domestic sector. This study investigates the issue of predictive inconsistencies between accredited tools available at the time of writing and presents the final results of an inter-model comparative analysis that examines the extent of variability in key compliance outputs. An overview of tool applicability limitations and issues associated with results variability are presented. Implications concerning the credibility of the methodology and recommendations to address current shortcomings are noted.

An analysis of industry capability for the implementation of a software-based compliance approach for the UK Building Regulations 2006

In support of the movement towards the integration of modelling in the building design process, a unified software-based methodology for the demonstration of compliance with energy performance standards was introduced in the UK Building and Approved Inspectors (Amendment) Regulations 2006 (England and Wales). This paper reports the conclusions drawn from a longitudinal two-stage industry survey undertaken at key implementation stages of the methodology to gauge industry adaptability in accommodating the new requirements followed by subsequent in-depth interviews with relevant professionals to explore the challenges associated with application and enforcement. Key findings include shortcomings in the technical capabilities of accredited software, the quantification of the effect of their shortcomings on user assessment of the methodology and the lack of clarity and consistency of enforcement. Practical application: This work provides an analysis of the adaptive capability of the UK construction industry in accommodating integrated energy performance modelling as a legislative requirement associated with performance based standards. The analysis of firsthand feedback from practitioners involved in the implementation of the new regulatory requirements provides both an overview of key industry indicators and detailed insights into the practical implementation and enforcement of the methodology, the feedback of which is used to establish future priorities and improvements for future regulatory revisions.

Retrofit solutions for solid wall dwellings in England: The impact of uncertainty upon the energy performance gap

This study seeks to evaluate the impact of uncertainty in the pre-retrofit thermal performance of solid walls of English dwellings on post-retrofit energy use. Five dwelling archetypes, broadly representative of English solid wall properties, were modelled pre- and post-retrofit, under different wall insulation scenarios, using dynamic thermal simulation. Findings indicate that whilst solid wall insulation could result in a significant reduction of space heating demand, uncertainties in the pre-retrofit solid wall U-value could lead to a gap between the anticipated and actual energy performance. Specifically, results show that if the current U-value assumption of 2.1 W/m2K is indeed an overestimation of the in-situ U-value of solid walls, then the anticipated carbon savings could be significantly reduced by up to 65%. Practical application: The performance gap observed in this study revealed that the actual carbon savings arising from the retrofit of solid wall properties could be significantly lower than predicted. This will not only affect UK Government carbon reduction targets but it can also result in a lack of confidence amongst stakeholders who may consequently doubt the effectiveness of energy retrofit measures, thus reducing their uptake. Uncertainties regarding solid wall U-values may necessitate the re-examination of the carbon targets set for the retrofit of solid wall dwellings and the exploration of alternative ways to further reduce their carbon emissions, e.g. by specifying higher insulation thicknesses.

A Framework To Evaluate The Energy Efficiency Potential Of Kuwaiti Homes

© 2014 WIT Press. Energy demand and consumption rates in Kuwait are amongst the highest in the world. This is largely due to a substantial amount of waste and overconsumption of energy in the residential building sector which accounts for almost 60% of Kuwait’s national electrical power generated. In spite of the existence of an Energy Conservation Code of Practice for Buildings, homes in Kuwait continue to be designed and built with little consideration to their climate, consuming significant amounts of electricity. There is a universal dependence among households on air conditioning systems, artificial lighting, and electrical appliances. Rapidly rising consumption rates by this sector are presenting an increasingly critical challenge for the Kuwaiti government, which is struggling to satisfy existing power demands. This paper reviews and discusses the key characteristics of Kuwait’s residential sector, and proposes a framework to evaluate the energy efficiency potential of Kuwaiti homes in order to inform policy developments in this field. As there is a significant lack of data about the Kuwaiti housing stock (its building fabric, energy consuming equipment, and occupants’ demand for services), the proposed framework suggests that energy use in a number of Kuwaiti homes is first examined, via an investigative case study strategy, before developing a residential building stock model to evaluate the impact and potential of different efficiency measures.

Can the choice of building performance simulation tool significantly alter the level of predicted indoor overheating risk in London flats

The accurate prediction of building indoor overheating risk is critical in order to mitigate its possible consequences on occupant health and wellbeing. The Chartered Institution of Building Services Engineers issued Technical Memorandum 59 (TM59) with the aim of achieving consistency in the modelling processes followed for the prediction of overheating risk in new dwellings. However, as each tool’s prediction may depend on its inherent assumptions, an inter-model comparison procedure was used to assess whether the choice of building performance simulation tool influences the overheating assessment. The predictions of two popular tools, IES VE and EnergyPlus, were compared for nine variations of a naturally ventilated, purpose built, London flat archetype, modelled under the default algorithm options. EnergyPlus predicted a high overheating risk according to TM59 criteria in seven out of the nine model variants, contrary to the low risk of all the IES VE variants. Analysis of heat transfer processes revealed that wind-driven ventilation and surface convection algorithms were the main sources of the observed discrepancies. The choice of simulation tool could thus influence the overheating risk assessment in flats, while the observed discrepancies in the simulation of air and heat transfer could have implications on other modelling applications. Practical application: Technical Memorandum 59 issued by the Chartered Institution of Building Services Engineers may be widely adopted within the industry to assist the prediction of overheating risk in new dwellings. This work suggests that the choice of building performance simulation tool can greatly influence the predicted overheating risk. Furthermore, the differences identified in the modelling of heat transfer processes could also impact other modelling applications. Following these results, the need for detailed empirical validation studies of naturally ventilated homes has been highlighted.

Small power and lighting load time series data for 27 departments across 8 UK hospitals

The electricity consumption of 27 departments was measured across 8 medium to large General Acute hospitals in England (largely by the authors, some data was donated and authorised for publication by the respective hospitals). The departments fall into 6 different categories which have been selected due to their prevalence in General Acute Hospitals (wards), their high energy intensities (theatres, laboratories, imaging and radiotherapy) or their distinct operating hours (day clinics). This data article provides floor areas and the time series of departmental power loads, mostly encompassing lighting and small power (but excluding central electricity use for ventilation, pumping and medical gas services). Comparative interpretations of the data are published in doi: 10.1016/j.enbuild.2016.02.052 [1].