PLEA 2011 - 27 th Conference on Passive and Low Energy Architecture, Louvain-la-Neuve, Belgium, 13-15 July 2011. DESIGN TOOLS AND METHODS 59 Solar radiation and architectural design in Barcelona Reconciling protection in summer and gain in winter Alexis AGUILAR 1 Carlos ALONSO 1 Helena COCH 1 Rafael SERRA 1 1 $UFKLWHFWXUH(QHUJ\DQG(QYLURQPHQW*URXS6FKRRORI$UFKLWHFWXUHRI%DUFHORQD83&%DUFHORQD6SDLQ ABSTRACT: The principles of the passive solar house were defined in the 1970s. Since that time, strategies have been conceptualized and tested with different examples built in the USA and in Europe. Models directly related to the Mediterranean climate are rare in this context. They will be the subject of the present study. In these cases, the main issue is to reconcile solar gain in winter and solar shading protection in summer. In addition, summer heat can be lost through natural ventilation. The research will focus on aspects of architectural design to implement alternatives for optimizing control of radiation. The Heliodon 2TM computer software will be used to establish evaluation methods for certifying the energy efficiency of the solutions under study. Keywords: solar radiation, Mediterranean climate, architecture 1. INTRODUCTION When addressing the issue of solar radiation in DUFKLWHFWXUH D VHSDUDWLRQ EHWZHHQ VWUDWHJLHV IRU VXPPHU DQG ZLQWHU DUH FRPPRQO\ HVWDEOLVKHG >@ ZKLFK a priori DUH FRQWUDGLFWRU\ JDLQ DQG SURWHFWLRQ 7KLV DUWLFOH RQ WKH RWKHU KDQG KDV QRW chosen this dichotomy. Except in particular cases that are architecturally designed for summer [2] or ZLQWHU XVH GHVLJQV DUH XVXDOO\ FRQFHLYHG IRU JRRG air conditioning throughout WKH \HDU 7KHUHIRUH LQ WKLV DUWLFOH ZH WUDFH GLIIHUHQW DUFKLWHFWXUDO DVSHFWV and jointly assess their impact in summer and winter. The objective is to identify compromise solutions that give a good response for both summer and winter. 2. METHODOLOGY The sun’s path follows a daily and seasonal pattern. That path is closel\ OLQNHG WR ODWLWXGH WKXV an architectural form experiences different degrees of exposure to radiation. ,QFRQWUDVWRQO\DSSUR[LPDWLRQVPD\EHRIIHUHGLI an attempt is made to quantify the annual radiation received by each architectural surface using theoretical model calculations. The radiation reaching the earth's surface must pass through the atmosphere [3] and cloudiness is a variable that is XQSUHGLFWDEOH E\ D PRGHO 7KHUHIRUH RQO\ approximations of absolute values are valid. In FRQWUDVW ZKHQ H[SRVXUH LV HTXDO EHWZHHQ VXUIDFHV ZLWK GLIIHUHQW RULHQWDWLRQV RU LQFOLQDWLRQV WKHLU comparative relations will be correct. In thLVFDVHWKH relationships that differentiate one area from another are invariable because they are due to purely positional geometric relations of a flat surface with regard to solar radiation. These relationships will be explored later on in this paper as they relate to the latitude of Barcelona LWVHOI 1 DV D representative of the Mediterranean climate. The computer software tool XVHG LV +HOLRGRQ 70 >@ GHVLJQHG E\ %HQRLW Beckers & Luc Masset [5]. The program performs FDOFXODWLRQV LQ WKHRUHWLFDO FORXGOHVV FRQGLWLRQV >@ without taking into account either the diffuse radiation emitted by the sky [7] or the radiation reflected by nearby surfaces. This method of calculation is not a drawback because its purpose is not to determine precisely the absolute value of radiation received. As LQGLFDWHG DERYH WKH DLP LV WR HVWDEOLVK FRPSDUDWLYH relationships between the gain of some surfaces and others. The 2TM Heliodon program is highly useful for this in that it also performs the calculations for the desired time period. ,Q WKLV VWXG\ ZH V\VWHPDWLFDOO\ DVVHVV WKH radiation accumulated during winter (21-Dec to 21- 0DU DQG VXPPHU -XQ WR 6HS NQRZLQJ WKDW LQ ZLQWHU WKH UDGLDWLRQ ZLOO EH GHVLUHG ZKHUHDV LQ summer it will not be. The study establishes an assessment procedure that is justified as follows: Phase 1: design aspects are not incorporated Compares radiation received by the same VXUIDFH DW GLIIHUHQW RULHQWDWLRQV 7R GR VR D FXEH form aligned with the cardinal points is used. Phase 2: design aspects are incorporated Knowing the different exposures of a surface in terms of its orientation raises design aspects that improve the performance of a project in regard to radiation. Each aspect provides design alternatives with different impact in terms of radiation. In each FDVH LW LV SRVVLEOH WR GHWHUPLQH WKH DOWHUQDWLYH WKDW provides the best response to radiation and reconciles the situations of winter and summer. The following table sets out the aspects and alternatives considered: Table 1: Aspects and design alternatives ASPECTS ALTERNATIVES 1- Proportion of the rectangular layout Analysis of various proportions of the layout