Overview on life cycle methodologies and economic feasibility for nZEBs

Highlights

• A critical overview on life cycle methodologies is proposed in relation with NZEB.

• EPBD recast requests new target for buildings in term of energy consumptions.

• Life Cycle Methodologies (LCMs) might be important tasks in a future EPBD recast.

• The paper analyses this challenge in order to support the NZEB design.

• Research outcome is individuation of principles and limitations of LCMs for a NZEB.

Abstract

The recast Directive on the energy performance of buildings (EPBD) stipulates that by 2020 all new buildings constructed within the European Union after 2020 should reach nearly zero-energy levels. This means that in less than one decade, all new buildings will demonstrate very high energy performance and their reduced or very low energy needs will be significantly covered by renewable energy sources. Such change is affecting both the nature of the built environment as well the actual method of designing and constructing a facility. The economic feasibility to realize a sustainable construction need to have a clear support by adequate analyses connected to the energy consumption and consequently to the new target reductions in greenhouse gas emissions for buildings. Life Cycle Methodologies (LCMs) are currently not considered in details on the EPBD recast, but according also to recent researches, they might be important tasks in a future recast. The paper analyses this challenge providing an overview on the main LCMs to individuate principles, limitations and implications of these approaches to design a Nearly Zero Energy Building (nZEB).

Introduction

Buildings account for around 40% of total energy consumption and 36% of CO₂ emissions in Europe. Therefore, reduction of energy consumption and the use of energy from renewable sources in the buildings sector constitute important measures needed to reduce the European Union's energy dependency and greenhouse gas emissions [1]. The mitigation potential of emissions from buildings is important and as much as 80% of the operational costs of standard new buildings can be saved through integrated design principles.

Due to these increasing awareness of the contemporary development model on climate change effects and the growing international movement towards high performance buildings, the current paradigm of building is changing rapidly.

This newly emerging approach differs from established practice in the following important ways: by selecting project team members on the basis of their eco-efficient and sustainable building expertise; greater focus on global building performance than on building systems; a strong emphasis on environmental protection for the whole life-cycle of a building; careful consideration of worker health and occupant health and comfort throughout all phases; scrutiny of all decisions for their resource and life-cycle implications; the added requirement of building commissioning, and a real emphasis on reducing construction and demolition waste [2], [3]. In assessing the performance of buildings, the scope of environmental evaluation is widening, marking an evolution from a single criterion consideration, like the economic performance of buildings, towards a full integration of all aspects emerging during the lifetime of a building and its elements. Dimitris et al. [4] stated that “Sustainable Buildings” is a broad, multi-criteria subject related to three basic interlinked parameters: economics, environmental issues, and social parameters. Other researches [5], [6], [7], [8], [9], [10] remarked and demonstrated moreover the importance of the early design stage of the building itself to reach a responsible and saving energy use, which could be affected e.g., by the geometric form or the functional and aesthetic integration of renewable energy systems [11].

The economical analysis of a construction project allows the feasibility evaluation of the monetary resources being applied, in term of investment and/or future costs (operation, maintenance, etc.), considering equally technical liable options for construction. The analysis gives the investor a more realistic and comprehensive approach about the investment he is about to make and the results in terms of building use. The main objective of this paper is to understand how the zero energy concept for building design is interpreted into the economical field.

A research conducted by Ecofis on Nearly Zero Energy Buildings asserted that an LCA for nZEB is definitely far beyond the current intention of the EPBD, but might be in a future recast. The paper analyses this challenge providing an overview of the main Life Cycle Assessment (LCA) and Life Cycle Energy Analyses (LCEA) and their implications for the nZEB design.

The main life cycle methodologies and analyses are presented to understand how it is possible to limit construction costs still creating sustainable and nearly zero energy buildings and also to verify if the estimation of eco-costs against intended value is a useful way of evaluating ex ante the ecological impact of the building during the development design process.