Originally the Guarajuba Ecohouse project [2], started with the idea of designing a zero cooling energy house for the tropics (Brazil), where the chosen location was the Northern beaches of the state of Bahia-Brazil. The development of this idea is now the BR ecoproject, in which alternative solutions to minimize energy needs are generated, along with possible applications of the proposed concepts to extended locations of equally or greater environmental importance within the area. The initial base case is maintained (warm-humid climate), but this research project aims to expand and establish a systematic process of designing/implementing demonstration houses, in which conservation of natural resources can be applied and its technical processes of implementation and use can be assessed and available to the community in general.

Design approach and features

A free running design should ensure that the indoor temperature does not rise higher than the outdoors, and an air-conditioned design should minimize cooling loads. The strategies to achieve these aims are different and depend on a wide variety of elements, but can overlap. The energy use and costs of a building depends on the complex interaction of many parameters and variables that can be effectively evaluated with hourly building energy simulation tools. Fabric, shape, openings, orientation, operation modes, control strategies, internal gains, each feature is part of an integrated design. No design feature can be added or deleted without affecting other elements of the whole-building package.

The dual mode project [3] was mounted to define the desirable attributes of both free-running and conditioned buildings, in order to find the extent and nature of such an overlap. The dynamic thermal simulation tool,

ESP-r, developed by the Energy Systems Research Unit (ESRU)

— University of Strathclyde, UK, had been used for the extensive parametric simulations. The performance of both conditioned and free running modes are presented. Conditioned results were measured in terms of energy requirements for (heating-cooling) and free

running results were measured in degree hours of overheating/underheating.

This extensive parametric study has led to a series of recommendations for conditioned/free running operation and dual mode operation (definitions of 5 use patterns), and a summary graph is shown (Figure 1).

As time of day and zoning could be defined as part of the brief of design, from the research results, the BR Ecohouse has tested through this project two of the 5 use patterns defined — patterns 4 and 5 (night time use of A/C in sleeping areas only and daytime use of A/C in living areas (office room only) in which it was possible to reduce cooling loads and improve thermal comfort levels.

Air conditioning could than be used in a more efficient and responsible manner and natural/mechanical ventilation could be effectively provided for most of the time.