Francesco Leccese

On the optimization of building envelope thermal performance

The optimal sequence of resistive and capacitive layers within building envelope is determined, in order to minimize the air-conditioning plant intervention to keep the indoor air temperature constant against sinusoidal and impulsive external temperature variations. In the case of sinusoidal variations with angular frequency ω, the optimal structure of the building envelope is determined by the value of the dimensionless parameter σ = ωrc only, where rc is the wall thermal time constant. For σ < 18 the interventions of the air-conditioning plant are minimized if the whole heat capacity is lumped between two plane slabs with the same value of the thermal resistance (symmetrical three-layered wall); for σ > 18 symmetrical walls are still preferable, but with a number of layers increasing with σ (walls with more than three layers); for σ → ∞ the optimal structure is the one of a homogeneous wall. In the case of impulsive stresses, the wall which facilitates the plant intervention, is a symmetrical three-layered one, as the previous case for low values of σ.

Lighting of Indoor Work Places: Risk Assessment Procedure

In this paper the authors propose a procedure, based on in situ measurements, for risk assessment arising from lighting of indoor work places, paying particular attention to European technical legislation on lighting and standards on health and safety of workers.

Thermal analysis of the building envelope of lightweight temporary housing

In the last few years, to meet the need of build efficient homes in a short time and with maximum constructive simplification, lightweight prefabricated building systems have proved to be particularly suitable, especially in geographical areas which must deal with emergency situations (i.e., temporary housing). In this paper the winter and summer thermal performance of a building prototype, realised with modular steel framed elements, have been studied, in both winter and summer conditions. Special attention has been paid to the optimisation of the dynamic thermal performance of the multi-layered envelope structures. The dynamic thermal behaviour of the outer wall, analysed and discussed in details in the paper, shows that it is possible to improve the performance of lightweight walls by using an optimised stratigraphy characterised by an opportune sequence of resistive and capacitive layers. The influence of inner structures (partitions, floor and roof) on the building thermal behaviour has also analyzed trough the introduction of room performance indices appropriately defined. The results of the study have been discussed with special reference to the requirements fixed by the Energy Performance Buildings European Directive (EPBDs) and the resulting implementation in Italian Legislation.

Visual ergonomics of video-display-terminal workstations: Field measurements of luminance for various display settings

Abstract Electronic visual displays have shown a rapid technological evolution in the last two decades. With reference to the ergonomic requirements for video display terminal (VDT) workstations (ISO 9241), at an international level, attention is focused on the human–system interaction. With reference to visual ergonomics, the aim of this study is to assess luminance conditions through in-field measurements in order to evaluate: luminance and contrast ratios, luminance and contrast non-uniformities. The assessment was applied to widespread flat screen displays and repeated for fourteen combinations of Contrast–Brightness. The analysis carried out by the Authors shows the importance of realizing a simple and quick procedure to determine the performance levels of displays used in VDT workstations. The proposed assessment could be used as a practical tool for staff assigned to assess the risks arising from VDT use in the workplace within the Occupational Health and Safety Assessment Procedure.

Visual discomfort among university students who use CAD workstations.

BACKGROUND Extensive literature in ergonomics and optometry has indicated that computer use is closely associated with visual problems. Computer-Aided Design (CAD) requires a substantial effort on behalf of the visual system. The manifestations of visual fatigue phenomena may affect the working behavior and the human-system interaction. OBJECTIVE The aim of this survey is to identify the normal working conditions and how the eventual visual fatigue phenomena are able to influence the working behavior of CAD users. METHODS A questionnaire was created and submitted to a sample of 150 university students, who attend the Faculty of Engineering of the University of Pisa (Italy). RESULTS The questionnaire results show that university students spend on average 7 hours per day at the computer for CAD drafting. Most of the participants work in strongly lit environments, with high brightness screens and negative polarity. Such conditions cause high contrasts in luminance, especially between screen and surfaces that fall within the field of vision. The results show that 135 out of 150 students report visual fatigue during long CAD sessions, which in most cases leads to difficulty in continuing the activity and changing usual working behavior. CONCLUSIONS The results of the questionnaire show that the university students work in highly variable lighting conditions and with little attention on the luminance distribution on the field of view. This has highlighted the importance, for VDT workstations, of not limiting the risk analysis to the postural ergonomics (how usually occurs) but extend it to the workplace as a whole, analyzing also the ergonomics of vision, which involves different consideration on the natural and artificial lighting of the workplace and on the characteristics of the display.

Opportunities for energy savings with interventions on the lighting systems of historical buildings: The case of “Palazzo Medici” in Pisa, Italy

The energy audit for a building is a procedure designed mainly to obtain adequate knowledge of the energy consumption profile, identify and quantify opportunities for energy savings by a cost-benefit analysis and report, clearly and comprehensively, about the obtained results. If the audit is referred to a building with a significant historical and artistic value should be also developed a compatibility evaluation of the energy saving interventions with the architectural features. In this paper, discussing the energy audit carried out for the historical building named “Palazzo Medici” in Pisa (Italy), the Authors analyses, from a techno-economic standpoint, different possible interventions on the lighting systems aimed to obtain significant energy saving. The total of six interventions on indoor and outdoor lighting systems, analyzed in the paper, allow a reduction of about 35% of the electrical energy demands for the artificial lighting of indoor and outdoor spaces, with a very short payback times. From the results obtained by the Authors, it is possible to show that, for historical buildings used for public functions, interventions to improve energy efficiency of lighting systems may allow significant reductions in the electrical energy consumption, which, in some cases, may reach or exceed the 20% of the overall electrical energy consumption.

Risk assessment arising from exposure to artificial optical radiation: Results of an extensive evaluation campaign in the hospitals of Tuscany (Italy)

In this paper the Authors describe and discuss the results of an extensive evaluation campaign of optical radiation emitted by equipment provided with incoherent sources, commonly used in the hospitals of the Tuscany Region (Italy). The results of the evaluation campaign can be a useful database of technical information for the personnel involved in the risk assessment.

Energy saving exploiting light availability: a new method to evaluate daylight contribution

Rhinoceros and Grasshopper have the extensibility which makes architects able to study forms, structures, acoustic behaviour, energy consumption, etc. as well as daylight availability: the most important aspect in this study. The software described has been useful to evaluate running costs including heating, cooling, electrical devices and