Low energy housing retrofit in North England: Overheating risks and possible mitigation strategies

In the drive to reduce space-heating demand and associated CO2 emissions as well as tackle fuel poverty, dwelling overheating and summer-time occupant thermal discomfort might be the unintended consequences of low-energy building retrofits. This paper presents the findings of a steady-state modelled low energy retrofit dwelling in northern England and its potential current and future climate overheating risks using UK Climate Projections 2009 (UKCP09) scenarios (2050 and 2080 High Emission Scenarios). Predictive findings highlight that retrofitting to low energy standards increases overheating risk over time, unless passive prevention measures are included in the retrofit design. In addition, the steady-state nature of the model might not fully capture the occupants’ exposure to actual future overheating risks. Among the most effective individual passive overheating mitigation strategies are temporary internal shading, permanent external shading, and night-time ventilation. Most effective is a combination of these adaptation measures, so that predictive overheating is minimised in a future changing climate, reducing the uptake of active cooling in retrofitted dwellings. Practical applications: Much research focuses on building overheating risks in the warmer South-east of England. However, this paper highlights how dwelling retrofit in north England (Sheffield) also can lead to increased dwelling overheating risk, unless passive design measures are included in the retrofit design. Among the most effective individual passive overheating mitigation strategies are solar shading devices and increased night-time ventilation, though ideally different measures are combined. Using future climate scenarios highlights that retrofits designed today might not be able to provide occupant thermal comfort in a future warming world

Assessment and mitigation strategies to counteract overheating in urban historical areas in Rome

As urban overheating is increasing, there is a strong public interest towards mitigation strategies to enhance comfortable urban spaces, for their role in supporting urban metabolism and social life. The study presents an assessment of the existing thermal comfort and usage of San Silvestro Square in Rome during the summer, and performs the simulation of cooling strategies scenarios, to understand their mitigation potential for renovation projects. The first stage concerns a field analysis of the thermal and radiative environment on the 1st and 2nd of August 2014, including meteorological measurements and unobtrusive observations, to understand how people experience and respond to extreme microclimate conditions. In the second stage, the research proposes scenario simulations on the same day to examine the influence of cool colored materials, trees and vegetative surfaces on thermal comfort. The thermal comfort assessment was based on Physiologically Equivalent Temperature (PET), whereas microclimatic simulations were conducted with CFD calculations (ENVImet v.4.3.1). The first stage shows a strong relationship between lower PET values and attendance rate, depending on daily shading patterns. The second stage shows a relevant improvement of thermal comfort, with PET values of 12 °C comparing to the no-intervention scenario, associated with a combination of cool materials and trees

Regulations and robust low-carbon buildings

Building regulations and associated calculation methods have been rapidly evolving, driven in Europe by the European Union Energy Performance of Buildings Directive. As an example, the current UK regulations are explored in relation to buildings that are naturally ventilated, mechanically ventilated, or mechanically ventilated and cooled. The UK regulatory energy and carbon calculation methods are investigated using a standard office design with typical, best practice, and advanced building fabric and systems applied. The criteria and calculations for demonstrating avoidance of excessive temperatures in buildings that have no mechanical cooling are also explored. Observations are made on how the regulations may influence future adoption of mechanical cooling. Current regulatory methods can be subjective and limited in scope. For example, they do not include adaptive comfort criteria or uncertainties in parameters such as occupant behaviour, climate, internal gains from equipment, etc. A design methodology is proposed that addresses these issues and provides a capability parameter to quantify robustness. This capability parameter allows comparison of design options and provides an indication to building users of the limitations to a building's use beyond which mitigating action would have to be taken for performance to be maintained

Towards an overheating risk tool for building design

PurposeThe work set out to design and develop an overheating risk tool using the UKCP09 climate projections that is compatible with building performance simulation software. The aim of the tool is to exploit the Weather Generator and give a reasonably accurate assessment of a building's performance in future climates, without adding significant time, cost or complexity to the design team's work.Methodology/approachBecause simulating every possible future climate is impracticable, the approach adopted was to use principal component analysis to give a statistically rigorous simplification of the climate projections. The perceptions and requirements of potential users were assessed through surveys, interviews and focus groups.FindingsIt is possible to convert a single dynamic simulation output into many hundreds of simulation results at hourly resolution for equally probable climates, giving a population of outcomes for the performance of a specific building in a future climate, thus helping the user choose adaptations that might reduce the risk of overheating. The tool outputs can be delivered as a probabilistic overheating curve and feed into a risk management matrix. Professionals recognized the need to quantify overheating risk, particularly for non‐domestic buildings, and were concerned about the ease of incorporating the UKCP09 projections into this process. The new tool has the potential to meet these concerns.Originality/valueThe paper is the first attempt to link UKCP09 climate projections and building performance simulation software in this way and the work offers the potential for design practitioners to use the tool to quickly assess the risk of overheating in their designs and adapt them accordingly.</jats:sec

Thermal comfort in the historical urban canyon: the effect of innovative materials

Urban heat island (UHI) can considerably affect the thermal quality of the urban environment, especially within urban canyons, that have typically low sky view factor and limited surface heat re-emission capability. A huge research effort has been registered to develop mitigation solutions for UHI, such as cool materials and greenery. Nevertheless, it is not always possible to apply such strategies in historical urban environments due to constrains for the preservation of their cultural value that do not allow to modify the exterior architectural appearance of heritage buildings. In this scenario, the present paper deals with the analysis of the potential of innovative cool materials characterized by the same appearance of historical ones in mitigating the UHI occurring in the context of a historical urban canyon located in central Italy selected as pilot case study. To this purpose, a preliminary experimental characterization of such innovative highly reflective materials has been performed. Afterwards, an experimental continuous monitoring campaign of the main outdoor microclimate parameters and a numerical modelling of the canyon have been carried out to evaluate the local mitigation capability of such materials when applied over the vertical and horizontal surfaces of the historical canyon. The results show the huge potential of the proposed innovative cool materials in mitigating the local microclimate of the historical urban canyon. In fact, a MOCI reduction up to 0.15 and 0.30 is detected by applying cool red envelope materials and cool red envelope materials plus cool grey paving materials, respectively, on the canyon surfaces

A failure recovery planning prototype for Space Station Freedom

NASA is investigating the use of advanced automation to enhance crew productivity for Space Station Freedom in numerous areas, including failure management. A prototype is described that uses various advanced automation techniques to generate courses of action whose intents are to recover from a diagnosed failure, and to do so within the constraints levied by the failure and by Freedom's configuration and operating conditions

Atmospheric impacts on daytime urban heat island

Daytime urban heat island effects can be weak compared to night time and even reversed (as in the case of cool islands, where urban locations display lower temperatures than at a rural site), mostly due to shading effects from buildings, vegetation, and other possible obstructions. The study of the relationship between the sky-view factor, an indicator of urban geometry in terms of sky openness, and urban heat island intensity generally focus on night time periods; only a few report on the daytime effect of the SVF. Such effect will also vary according to background atmospheric conditions of the period of measurements. This article is a commentary on a recent publication by the authors on a study of diurnal intra-urban temperature differences in a location with Koeppen’s Cfb climate

Economic impacts of climate change on cities: A survey of the existing literature

This paper attempts a survey of the existing literature on the direct market impacts of climate change on urban centers. In the first chapter, the argument for the importance of cities as case studies for research on the impacts of climate change is established using current population data and future projections. In the second chapter, a brief overview of how we can go from the global level to the regional level, when we consider the impacts of climate change, is given. In the third chapter, we examine the models and their estimates for the sea level rise impacts on cities. In the fourth chapter, we summarize the impacts of increasing temperature. In the last two chapters, we elaborate on the current limitations and we present some conclusions. --