District Geometry Simulation: A Study for the Optimization of Solar Façades in Urban Canopy Layers

open4This paper shows the results of a research aimed at assessing the amount of energy that can be produced by solar envelopes (facades and roofs) in urban contexts.A preliminary set of simulations was carried out, through dynamic yearly analyses on a sample building, to identify the main parameters influencing the availability of solar radiation and to optimize the building's shape. The general target is to maximise solar radiation available on the external building envelope, in order to exploit it through building integrated solar systems.Furthermore, the effect of reflected solar radiation has been analysed by simulating different finishing materials (green façades, glazed façades, concrete façades and aluminium façades) on the neighbouring buildings.G. Lobaccaro; F. Fiorito; G. Masera; T. PoliLobaccaro, Gabriele; F., Fiorito; Masera, Gabriele; Poli, Tizian

The Effect of Water Spray Systems on Thermal and Solar Performance of an ETFE Panel for Building Envelope

ETFE membranes are generally used in architecture for large roofing and façade systems, because of their transparency and lightness compared to glass alternatives. Multilayer ETFE panels are used to improve single membrane systems performances, reducing thermal losses, by the use of an air gap between two or more ETFE foils, generally serigraphed or surface treated to reduce solar gains. Surface temperatures and global solar radiation strongly affects mean radiant temperature (MRT), and comfort perceived by a user facing a transparent envelope as well as solar gains strongly influences primary energy use for cooling in summer conditions. In the following paper an alternative dynamic solar gains mitigation strategy is presented and applied to a double layer, non-cushions, ETFE panel for façades. We measured the effectiveness of a water spray system located in the air-gap between the parallel ETFE foils and used to reduce surface temperatures and solar access depending on different summer solar radiation values and outdoor/indoor air temperature conditions. Systems alternative with different in nozzle dimension, water spray geometry and water consumption were already tested to evaluate the best compromise between solar gains reduction and water use. The results are preliminary but we noticed that a reduction up to the 10% of the total solar gains could be achieved as well as a reduction of 10 °C of surface temperature. Comfort evaluation for a standard indoor space were already done

Spectral Light Transmission Measure of Metal Screens for Glass Façades and Assessment of their Shading Potential

Abstract Metal mesh grids and perforated screens are used in new and renovated buildings as an external second skin for the building envelope; to enhance architecture design, to filter daylight and to reduce solar gains. Their effectiveness as shading devices depends on their geometry, texture and application. In the first part of the paper six types of shadings with similar transparencies, depending on geometry and openness factor of metal mesh grid and perforated screen, were investigated. Integrating sphere measurements were collected to obtain spectral optical properties of the shading devices. The optical properties were measured for incidence angles between normal and 60°with a step of 15°. The data collected were integrated to obtain visible and solar transmittance values in accordance with ISO 9050. In the second part of the paper a parametric study on spacing and thread dimension of metal mesh grids was done using Window 6.2 models to evaluate their shading potential, defining annual different shading profiles depending on shading geometry, latitude and orientation. A conventional office unit with a curtain wall facade with a metal mesh grid shading system was modeled in TRNSYS to evaluate the solar gain profiles and their effects on the energy balance of the office unit, under different weather conditions

Spectral Light Transmission Measure and Radiance Model Validation of an innovative Transparent Concrete Panel for Façades

Abstract This paper presents an approach to measure, characterize and simulate photometric performances of light transmission efficiency of an innovative transparent concrete panel for facades. The transparency was obtained by a texture of PMMA resin insertions in the fiber reinforced concrete panel. In the first part of the paper integrating sphere measurements were collected to derive spectral optical properties of the panel. The optical properties of a specimen were measured for incidence angles between normal and 60° and the spectral results were reported. The data collected during the measures were used to: create and validate a simplified Radiance model of the panel and to optimize simulation parameters to estimate properly the total internal reflections effects thought the PMMA resin insertions

assessment of thermal stress in a street canyon in pedestrian area with or without canopy shading

Abstract Urban areas are characterized by a plurality of microclimates given by the diversity of morphologies, optical and radiative properties, solar access and air circulation in different street canyons. For these reasons, beyond strategies at urban scale, mitigation needs to be addressed at district or even at urban canyon scale, just like the design of buildings. Among different options, canopy shading has been proposed in several urban contexts, and to assess the impact of this mitigation technique on air temperature and outdoor thermal comfort conditions we performed numerical simulations for a north-south oriented urban canyon with high solar access (height to width ratio equal to 0.18) in the climate context of Milano (Italy)

A Novel Approach to Shape Memory Alloys Applied to Passive Adaptive Shading Systems

A shading device for façade application was developed by combining twisting cylindrical shading elements with the smart use of shape-memory alloy (SMA) components. These allow a dynamic behaviour of a shading device, which does not require electrical motors or manual activation, nor sophisticated electronic controls. The technical development of the system involved research of cylindrical shading geometries, which can transition from straight to hourglass configuration, given a 180° rotation, with limited mechanical movement. This is induced by the stroke of a SMA spring, which functions as both actuator and sensor. Its design is tailored to achieve a passive adaptive component that can be activated under set temperature stimuli, caused by incident solar radiation on a façade. A combination of computer simulations and physical tests were carried out to assess the optimal conditions of the SMA spring activation in a temperate climate condition (Cfa to the Koppen-Geiger classification), correlating transition temperature (50°C), incident solar radiation (>300W/m2 ) and the forces required to operate the cylinders. In parallel, an experimental apparatus was developed to validate the concept on a geometrical point of view, and to ensure its constraints were compatible with a SMA spring control system

La protezione solare degli edifici: dalla forma alla prestazione integrata

Nell’architettura contemporanea si assiste a una sempre più crescente smaterializzazione del muro: le superfici opache lasciano spazio alle superfici trasparenti. Questa trasformazione, evidente soprattutto per alcune specifiche destinazioni d’uso, ha portato a una continua evoluzione delle prestazioni dei vetri (sempre più performanti dal punto di vista termico ed energetico) e, più in generale, del sistema vetrazione unita alle schermature solari (interne e/o esterne). Vari sono gli obiettivi progettuali, ma le richieste del progettista all’ involucro edilizio riguardano la capacità di fornire prestazioni in grado di: 1. limitare le dispersioni incrementando al tempo gli apporti solari gratuiti (soprattutto durante il periodo invernale) al fine di limitare il fabbisogno di energia per il riscaldamento; 2. evitare o ridurre efficacemente gli apporti solari gratuiti durante il periodo estivo per ridurre il consumo energetico per il raffrescamento; e 3. favorire l’utilizzo e modulare la presenza di luce naturale in ambiente confinato (incrementando il daylighting autonomy). Nel seguente articolo è valuata l' efficienza energetica delle schermature solari nel contesto italiano, tramite l'uso di un caso di studio costituito da un ambiente ad uso ufficio, valutando le prestazioni sia di sistemi tradizionali, che le prestazioni di sistemi schermanti alternativi

Transparent Multilayer ETFE Panels for Building Envelope: Thermal Transmittance Evaluation and Assessment of Optical and Solar Performance Decay due to Soiling

AbstractThis paper is divided in two sections. The first section present the measurement and evaluation of soiling effects of spectral light and solar transmittance decay of Ethylene Tetrafluoroethylene Copolymer (ETFE) membranes after three and six months of exposure in Milano city outdoor urban conditions, with different tilt and orientation. The obtained values where use to compute thermal and solar properties of a multilayer ETFE panel.The second section presents the results of an experimental campaign for measuring thermal transmittance of a non-pneumatic and non-cushion shape double layer ETFE sample panel realized with two membranes parallel to each other and tensioned on a frame. The thermal transmittance measurement reflects ISO 9869 measurement approach combined with the use of a thermographic camera to evaluate surface temperatures over the sample panel

Color heterogeneity of building surfaces: lean image processing approach for visible reflectance characterization performance

Daylighting availability and uniformity depend on the interior surface reflectance (). Currently, is obtained through suggested reference values (Illuminating Engineering Society 2012; CIBSE 2015; CIBSE/SLL 2011; CIBSE/SLL 2005), laboratory tests (ASTM E 903 (2012) describes a standardized procedure requiring a calibrated instrument and an as-built surface sample), or by on-site measures (based on luminance and illuminance differences). Novel methodologies compute it by integrating image processing and/or photometry, applied on false colour or HDR images. A simple procedure is needed for accurately assess, even in preliminary design phases, the reflectance of heterogeneous surface areas for new and historical buildings. In fact, heterogeneous surfaces (colour, texture, composition, ageing) difficult the accurate estimation of a representative reflectance value (̅) for building simulation, leading to daylighting performance deviation. This work presents a methodology, based on a per-pixel colour reflectivity () evaluation, to easily acquire an approximate value of the surface visible reflectance (̅). This approach gives a more global ̅ of all surface components, aiming to improve the accuracy of the modelled daylighting analysis. Additionally, the procedure is experimented over a sample reference test room

Transparent multilayer ETFE panels for building envelope : thermal transmittance evaluation and assessment of optical and solar performance decay due to soiling.

Abstract This paper is divided in two sections. The first section present the measurement and evaluation of soiling effects of spectral light and solar transmittance decay of Ethylene Tetrafluoroethylene Copolymer (ETFE) membranes after three and six months of exposure in Milano city outdoor urban conditions, with different tilt and orientation. The obtained values where use to compute thermal and solar properties of a multilayer ETFE panel. The second section presents the results of an experimental campaign for measuring thermal transmittance of a non-pneumatic and non-cushion shape double layer ETFE sample panel realized with two membranes parallel to each other and tensioned on a frame. The thermal transmittance measurement reflects ISO 9869 measurement approach combined with the use of a thermographic camera to evaluate surface temperatures over the sample panel