Abstract
Finding cost-optimal solutions towards nearly-zero energy buildings in accordance with the Energy Performance of Buildings Directive (EPBD) is a challenging task. In order to reach the 20-20-20 targets, EU energy policy has introduced new ambitious levels for the large-scale spread of nearly-zero energy buildings (nZEBs) and the concept of the cost-optimal level, defined as the energy performance level, which leads to the lowest cost during the estimated economic lifecycle of the building. Consequently, building design has begun a challenge involving both energy targets and economic concerns. The aim of this research is to analyze an example building of a new single family house, using the cost-optimal methodology, in order to define how energy and economic aspects influence the preliminary design phase of the project and, in particular, the choice of the performance features of some components of the project itself, such as envelope elements and systems. The impact on energy performances of different configurations for the building envelope and heating, ventilation and air conditioning (HVAC) systems was assessed with the dynamic simulation software EnergyPlus. Finally, the costs of the different design scenarios were estimated, according to the European Standard EN 15459:2007 to establish which of them had the lowest global cost and, consequently, represents the cost-optimal level for the design configurations analyzed. In order to test the stability of the results obtained, different sensitivity analyses were carried out.
Highlights
The future of any energy resource depends on the state of the art of the technology to harvest, convert and transport it and, on economic and political factors, which include the appropriate regulations.In the past century, there was a trade-off between energy engineering and economics, because, generally, a design that achieved high energy efficiency was costly, and this led to a high price per unit of energy.On the other hand, a low-cost design was often characterized by low efficiency, and the cost of energy was high because large amounts of primary energy resources were necessary
Step 1: Selection of the reference building that represents the basic design scenario [16]; Step 2: Definition of some alternative design scenarios that provide for different solutions in terms of building envelope thermal insulation for four specific heat transfer levels and HVAC systems; Step 3: Evaluation of the final and primary energy uses of the different design scenarios; Step 4: Economic evaluation of the hard costs due to construction; Step 5: Economic evaluation of the operational costs due to energy consumption; Step 6: Sensitivity analyses for the escalation of energy prices, variation of the calculation period and discount rate and the introduction of a tax credit
The recast of the Energy Performance of Buildings Directive [7] recommends evaluating at least ten different design scenarios to make sure that enough design options are analyzed and the choice of one of this is well-informed
Summary
The future of any energy resource depends on the state of the art of the technology to harvest, convert and transport it and, on economic and political factors, which include the appropriate regulations.In the past century, there was a trade-off between energy engineering and economics, because, generally, a design that achieved high energy efficiency was costly, and this led to a high price per unit of energy.On the other hand, a low-cost design was often characterized by low efficiency, and the cost of energy was high because large amounts of primary energy resources were necessary. Member States have committed to this, reducing greenhouse gas emissions by 20% compared to 1990 levels, increasing the share of renewable sources in the EU’s energy mix to 20% and achieving the 20% energy efficiency target by 2020 [5]. To reach these goals, European legislation set out a cross-sectional framework of ambitious targets to achieve high energy performances in buildings. Since the global cost value of Scenario 2c, which represented the optimum in all other previous analyses, lied close to those of the low energy performing scenario mentioned above, it is possible to declare that this sensitivity analysis confirmed the results
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