Building envelope and solar energy optimization: a new “wizard” for architects

When designing a project, architects are facing more and more constraints on the building’s energy efficiency. Tougher values on insulation and energy consumption are now often combined with compulsory implementation of active solar systems - photovoltaics or solar thermal. With natural lighting, passive and active solar all competing for envelope areas, comparing results of architectural variants becomes more important and at the same time more complex. To help overcome this situation, a renowned “energy balance calculation/certification” software tool has been improved and adapted, proposing a wizard developed to meet a growing demand: obtain a quick feedback on building envelope, energy efficiency and solar strategies, especially in the early design stage, when strategies are defined. The wizard helps fulfilling various norms of different European countries, allowing architects to compare variants during this crucial phase. By simplifying data entry using smart default values derived from appropriate general choices, and by presenting a clear and intuitive user’s interface, this new tool offers practicing architects an easy access to building envelope and solar energy use optimization.

Energetic, Visual and Non-Visual Aspects of Office Lighting

Friedrich Linhart

Light has important visual and non-visual effects on humans and high-quality light should therefore be supplied inside buildings in sufficient quantities. On the other hand, artificial lighting is responsible for a large part of an office building's electricity needs. It is thus important to take into account at the same time visual comfort, non-visual effects of light and energy-efficiency when designing lighting systems for office buildings. The general objective of this doctoral thesis was to combine knowledge from several scientific fields (e.g. daylighting technology, artificial lighting technology, lighting simulation and chronobiology) to discuss how sustainable lighting solutions (i.e. lighting solutions that are optimized in terms of energy-efficiency, visual comfort and performance as well as non-visual aspects of lighting) can be achieved in office rooms. A research strategy that used a test office room equipped with an Anidolic Daylighting System (ADS) as a starting point has been followed. This ADS was shown to be well-accepted by office occupants and to be able to supply sufficient daylight flux during large parts of most working days. Based on this ADS, a highly energy-efficient electric lighting system for complementary artificial lighting was developed and tested in a visual comfort and performance study with human subjects. In addition to that, the chronobiological properties of the test office room were assessed. It was shown that the ADS-equipped room performs extremely well under daylighting conditions in terms of non-visual aspects of office lighting. For the rare times when this is not the case, a back-up system for chronobiological lighting based on blue Light Emitting Diodes was developed. In order to get a deeper insight into chronobiological aspects of office lighting, a first applied chronobiological study at the Solar Energy and Building Physics Laboratory was initiated. Furthermore, possibilities to apply the concepts developed during this doctoral thesis to other types of buildings and other geographic regions were discussed. In conclusion, this doctoral thesis successfully demonstrated that it is possible to achieve sustainable lighting scenarios that are optimized in terms of energy-efficiency, visual comfort and performance as well as non-visual aspects by combining day- and electric lighting technologies in an appropriate way.

EPFL2010

Compact cities in a sustainable manner

Raphaël Compagnon, Marylène Montavon

Densification is generally assumed to exert negative impacts on urban daylight and solar potential, however, this paper demonstrates the possibilities to increase usable floor area and plot ratio without undermining the opportunities of daylight and solar applications. The paper investigates the diverse influences of built density on daylight access and the potential of two solar systems. The findings suggest that plot ratio is influential to quantities such as daylight factor, sky view factor and the potential of solar thermal and photovoltaic applications on roof, whilst the potential of solar thermal and photovoltaic applications on building facades are more dependent on site coverage and the extent of horizontal obstruction.

2006

Criteria and policies to master the visual impact of solar systems in urban environments: The LESO-QSV method

Maria Cristina Munari Probst, Christian Roecker

Increased use of solar collectors in buildings is necessary but poses major challenges in existing built environ ments, especially where architectural quality is an issue. The large size of solar systems at the building scale requires careful planning, as they may easily end up compromising the aesthetics of buildings, threatening the identity of entire contexts. A new method named LESO-QSV(for Laboratoire d'Energie SOlaire - Qualite Sensibilite-Visibilite) has been developed to help authorities promote solar energy use while preserving the quality of pre-existing urban areas. The vision underlining the approach is that solar integration is possible also in delicate contexts, if appropriate design efforts and adequate cost investments are made. The issue is then no longer to be in favour or against the use of solar systems in cities, but rather to define appropriate local levels of integration quality, and to identify the factors needed to initiate smart solar energy policies able to preserve the quality of pre-existing urban contexts while promoting solar energy use. The LESO-QSV method helps tackle these issues with clear and objective proposals: First it clarifies the notion of architectural integration quality and proposes a simple evaluation method, based on a set of criteria derived from pre-existing literature. Then it helps authorities set and implement local acceptability requirements, introducing the notion of architectural "criticity" of city surfaces (LESO-QSV acceptability). The concept of "criticity", at the basis of the whole approach, is defined by the Sensitivity of the urban context where the solar system is planned, combined with its Visibility (close and remote) from the public domain. The more sensitive the urban area and the more visible the system (high "criticity"), the higher the need for integration quality. In practice, authorities will be in charge to set the desired integration quality levels for each of the defined "criticity" situations, considering local specificities (energy context, available energy sources, political and social considerations, city identity and topography, among others). To help authorities set these quality expectations, the software LESO-QSV Grid has been developed. It illustrates the acceptance impact of pre-defined sets of quality requirements, using a large number of integration examples (150 emblematic cases). These detailed examples are provided to show authorities how to objectively evaluate integration quality, but they also constitute a large set of learning examples, good and bad, for architects, installers and building owners. Finally the method proposes a way to tailor solar energy policies to local urban specificities by mapping the architectural "criticity" of city buildings surfaces, and crossing this information with a city solar irradiation map (LESO-QSV crossmapping), hence completing the characterization of the building surfaces with the potentially required effort of integration.