**1. Introduction**

The nearly zero-energy buildings (nZEB) requirements were introduced by the Energy Performance of Building Directive (recast) (EPBD recast) [1]. The EPBD supporting standards include the metrics and calculation procedures. The calculation starts with the determination of energy needs, followed by the determination of the required amounts of energy carriers produced on-site, nearby, or by distant systems.

The energy carriers should consist of a large share of renewable energies, which leads to lower primary energy needs. The directive explicitly requires that on the national level energy efficiency criteria must be set in a way to be cost-effective. Although the life cycle assessment (LCA) is voluntary, such approach can be very helpful in the decision-making process of building design. This challenging task should be performed in the early stage of the planning, requiring the relevant multidisciplinary knowledge [2]. A simplified computational tool can significantly help the implementation of EPBD in the planning process. Such a computer tool that enables building energy efficiency, the environmental impact of selected measures, and life cycle cost (LCC) assessment of new and renovated buildings was developed and is presented in this chapter.

## **2. Computer tool structure**

Computer tool consists of life cycle energy efficiency (LCEA), environment impact (LCIA), and life cycle cost assessment (LCCA) routine, divided into two calculation modules, building description unit (BDU) and LCA tool (Etool).

The BDU module enables the determination of:


The BDU is developed in a way that allows parallel analyses of two projects (for reference and designed buildings), allowing designers prompt and more convenient way for evaluation of proposed measures for increasing the energy efficiency of the designed building. For the same reason, designers could indicate separately which material, building structure, or building system will be included in the LCA. Such elements, marked as "LCA elements" are taken from the pre-designed database, but relevant data could be entered to form user-defined data.

After completing work in the BDU, data are automatically transferred into the second calculation module, the LCA evaluation module (Etool) in which end-LCA results are determined and displayed taking into account additional user-selected LCA data, for example, lifetime and discount rate and compared for reference and current designed building. The main reason that the evaluation tool is divided into two modules is to use an existing highly distributed tool used for obligatory EPBD evaluation and certification of the buildings with more than 5000 users in Slovenia. A tool, called KI Energija [3] was co-developed by the authors of the presented chapter. Besides that, the tool was developed for use in high-school and master education courses through wizarddesigned building service systems. The second module, Etool was developed in an MS Excel environment because of built-in statistical functions and the ability to display results. The structure of the LCA computer tool is presented in **Figure 1**. The monthly method is used for the determination of energy needs for heating and cooling (ISO EN 52016-1 Energy performance of buildings – Energy needs for heating and cooling, internal temperatures, and sensible and latent heat loads – Part 1: Calculation

*Evaluation of Energy Efficiency of Buildings Based on LCA and LCC Assessment… DOI: http://dx.doi.org/10.5772/intechopen.101820*

#### **Figure 1.**

*Structure and interactions between BDU (upgraded EPBD national certification tool KI Energija) and Etool (life cycle assessment tool).*

procedure) and other EPBD supporting standards were used for final energy determination. Yearly methods for determining non-energy-related variables (e.g. emissions of pollutant equivalents) are used in the evaluation procedure.
