Vítor Leal

Recent progress on net zero energy buildings

The concept of net zero energy building (NZEB) is relatively new, but its deployment in building design construction practice is occurring quickly, with many countries now promising to make it mandatory for new constructions in a few years. It is therefore important to determine the relationship between research and NZEBs, in a context in which the research questions regarding NZEBs may not be obvious. This chapter discusses the recent progress in NZEB research and practice, dividing the analysis into the following sections: definition of the concept of NZEB; policy instruments; demonstration buildings (residential and non-residential); design strategies; and technologies for NZEBs. It shows that the feasibility of NZEBs has been demonstrated widely, in particular in low-rise buildings. The NZEB-specific research effort seems now to be moving towards issues of methods to assist efficient design (as an evolution from effective design) and their efficient monitoring and operation. NZEBs continue to benefit from motivating research in the areas of energy efficiency and on-site renewable energy, which may apply to all buildings, whether an NZEB or not.

Smart Cities Initiative: how to foster a quick transition towards local sustainable energy systems

The European Commission has recently launched the Smart Cities Initiative to demonstrate and disseminate how to foster a quick transition towards local sustainable energy systems. Within this initiative, the three main challenges faced by pioneering cities, are to reduce or modify the demand for energy services, to improve the uptake of energy efficient technologies and to improve the uptake of renewables in the urban environment. We find that enough resources will need to be provided to a significant number of pioneering cities, and propose that the initiative would allocate these resources through project competition, rewarding innovation, ambition and performance, which have been ingredients of success at Member State level.

Occupants’ behaviour in energy simulation tools: lessons from a field monitoring campaign regarding lighting and shading control

Previous studies have shown that the choice of the behavioural model for the control of lighting and shading devices has important implications in the energy performance assessment of office buildings and directly influences the comparison of design alternatives for control systems as well as for the façades (shading or glazing). Since many behavioural models exist for the same purposes, and in most cases there is no consensus on which ones are more representative of the reality, it is important to perform more real-world observations and draw lessons from them. This study appears in this context and explores the results of a field campaign that continuously monitored occupants’ behaviour regarding manual control of electric lighting and shading devices of eight real-world single offices under normal operation. Detailed measurements and observations were performed over two months in each office with the aim of assessing the level of agreement between existing behavioural models and actual occupants’ behaviour. Findings from this study enabled refining the hypothesis regarding realistic modelling of occupants’ behaviour when considering currently available whole building simulation (BS) software; moreover, needed improvements to increase the reliability of the results in whole BS were identified.

Urban Form and Energy Demand: A Review of Energy-relevant Urban Attributes

The implications of urban form on energy have long been present in international debate, whether considering travel patterns or thermal comfort in buildings. The urban environment is a result of a set of intertwined attributes, the understanding of which is often unclear. The energy trade-offs between urban form attributes haven’t received proper attention. Research remains sectorial, considering buildings and transport in isolation. In order to allow for a comprehensive analysis of this relationship, this article reviews urban attributes with energy relevance. A collection of attributes and metrics is gathered from the literature for incorporating urban form in urban energy analysis.

Energy and economic analysis of building retrofit and energy offset scenarios for Net Zero Energy Buildings

The concept of Net Zero Energy Buildings is gaining momentum. However, the underlying idea of offsetting the energy drawn from the grids with local production is yet to be proven as economically efficient, namely when compared with alternatives such as district/neighbourhood-level facilities or adding more large-scale facilities to the national grid(s). This paper presents a study on strategies for making an existing neighbourhood becoming net zero energy, focusing on the level of retrofit to apply to the buildings, on the proximity of the offset and on the selected offset equipment. The following discretization was considered: three levels of energy efficiency (low, medium and high), four offset generation alternatives (building integrated photovoltaic (PV), off-site large-scale PV, off-site large-scale wind turbines and not offsetting) and two energy tariff types (subsidized and non-subsidized). The results have shown that, under the reference economic conditions considered, it is best to upgrade the energy efficiency up to the medium level, and then offset the demand with off-site large-scale wind turbine equipment. These suggest that reaching net zero balance through on-site generation is less efficient than doing it through large-scale facilities.