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In a changing climate there is increasing concern about the risk of overheating in UK buildings, particularly those with a low-carbon footprint which cannot rely on mechanical cooling. This gives rise to concern among building professionals about how overheating risk can best be assessed. Current Chartered Institution of Building Services Engineers (CIBSE) guidance uses a simple definition of overheating as the exceedance of 288 8 8 8 8C for more than 1% of occupied hours, based on simulations using weather files from a 'design summer year' (DSY). There is increasing evidence that this criterion is both insensitive and open to abuse. This paper uses field surveys of thermal (dis)comfort and the adaptive thinking behind the British and European Standard BS EN15251 to propose a new approach. It takes account of the effect of indoor and outdoor climate on the dissatisfaction of building occupants. An alternative definition of overheating in buildings is proposed, along with an approach to predicting the magnitude and/or frequency of occurrence of overheating in buildings.Keywords: adaptive thermal comfort, comfort, design summer year (DSY), discomfort, overheating, standards Dans un climat en évolution, il existe une préoccupation croissante à l'égard du risque de surchauffe dans les immeubles du Royaume-Uni, en particulier ceux qui ont une empreinte carbone faible et ne peuvent pas compter sur un refroidissement mécanique. Cela amène les professionnels du bâ timent à se préoccuper de la manière dont le risque de surchauffe peut être le mieux évalué. Les informations actuellement fournies à titre indicatif par le CIBSE (Chartered Institution of Building Services Engineers) utilisent une définition simple de la surchauffe comme étant des températures dépassant 288C pendant plus de 1% des heures d'occupation, sur la base de simulations utilisant les fichiers météorologiques de l'indice DSY (« Design Summer Year ») correspondant à une année à été chaud moyenne. Il est de plus en plus manifeste que ce critère n'a pas la sensibilité nécessaire et incite aux abus. Cet article utilise des enquêtes de terrain portant sur le confort ou l'inconfort thermique et les idées d'adaptation qui sous-tendent la norme britannique et européenne BS EN15251 afin de proposer une approche nouvelle. Il prend en compte l'effet du climat intérieur et extérieur sur l'inconfort des occupants de l'immeuble. Une autre définition de la surchauffe dans les immeubles est proposée, ainsi qu'une approche permettant de prévoir l'ampleur et/ou la fréquence de l'apparition de cette surchauffe dans les immeubles.

A theory is developed for the speed and structure of steady-state non-dissipative gravity currents in rotating channels. The theory is an extension of that of Benjamin (1968) for non-rotating gravity currents, and in a similar way makes use of the steady-state and perfect-fluid (incompressible, inviscid and immiscible) approximations, and supposes the existence of a hydrostatic ‘control point’ in the current some distance away from the nose. The model allows for fully non-hydrostatic and ageostrophic motion in a control volume V ahead of the control point, with the solution being determined by the requirements, consistent with the perfect-fluid approximation, of energy and momentum conservation in V, as expressed by Bernoulli's theorem and a generalized flow-force balance. The governing parameter in the problem, which expresses the strength of the background rotation, is the ratio W = B/R, where B is the channel width and R = (g′H)1/2/f is the internal Rossby radius of deformation based on the total depth of the ambient fluid H. Analytic solutions are determined for the particular case of zero front-relative flow within the gravity current. For each value of W there is a unique non-dissipative two-layer solution, and a non-dissipative one-layer solution which is specified by the value of the wall-depth h0. In the two-layer case, the non-dimensional propagation speed c = cf(g′H)−1/2 increases smoothly from the non-rotating value of 0.5 as W increases, asymptoting to unity for W → ∞. The gravity current separates from the left-hand wall of the channel at W = 0.67 and thereafter has decreasing width. The depth of the current at the right-hand wall, h0, increases, reaching the full depth at W = 1.90, after which point the interface outcrops on both the upper and lower boundaries, with the distance over which the interface slopes being 0.881R. In the one-layer case, the wall-depth based propagation speed Froude number c0 = cf(g′h0)−1/2 = 21/2, as in the non-rotating one-layer case. The current separates from the left-hand wall of the channel at W0 ≡ B/R0 = 2−1/2, and thereafter has width 2−1/2R0, where R0 = (g′h0)1/2/f is the wall-depth based deformation radius.

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