Quest Journals Journal of Architecture and Civil Engineering Volume 6 ~ Issue 2 (2021) pp: 08-19 www.questjournals.org *Corresponding Author: Daniel Kalús 8 | Page Department of Building Services Faculty of Civil Engineering, Slovak University of Technology in Bratislava Research Paper Combined Building-Energy Systems/Energy Roof/Calculation of Energy Efficiency Assoc. Prof. Ing. Daniel Kalús, PhD. 1 , Ing. Peter Janík, PhD., 2 Ing. Matej Kubica 1 1 (Department of Building Services Faculty of Civil Engineering, Slovak University of Technology in Bratislava) 2 (Engineer in the Field of Energy Efficiency of Buildings, Topolčianska 5,851 05 Br atislava) Corresponding Author: Daniel Kalús ABSTRACT: The use of combined building and energy systems is closely related to the use of renewable heat sources or waste heat. An energy roof is an alternative solution to solar thermal collectors. Research aimed at evaluating the energy efficiency of an energy roof was the subject of the dissertation of Ing. Peter Janík, PhD. entitled: "Optimization of energy systems with long-term heat accumulation." (supervisor: Kalús), and at the same time the subject of the research project HZ PG 73/2011 titled: "Experimental measurements, analysis, and determination of the optimal rate of use of renewable energy sources on a prototype of a family house EB2020 with nearly zero energy demand ”(responsible researcher: Kalús). Due to the fact that determining the efficiency of an energy roof is a relatively difficult matter, as it has differing geometry in enclosed space between the roofing and thermal insulation, this paper focuses on one of the possible calculation methods. KEYWORDS: combined building-energy systems, active thermal protection (ATP), thermal barrier, low- temperature radiant heating/high-temperature cooling, climate factors, energy roof, solar absorbers, solar thermic collectors, energy efficiency Received 23 Jan, 2021; Revised: 04 Feb, 2021; Accepted 07 Feb, 2021 © The author(s) 2021. Published with open access at www.questjournals.org I. INTRODUCTION A combined building and energy system with active thermal protection (ATP), an energy roof, and ground heat storage is based on the principle of active use of solar energy, long-term heat accumulation, and subsequent heat supply for ATP. Solar energy can be used by means of an energy roof, which is formed by an absorber located between the top layer of the roof structure and thermal insulation. The heat transfer medium is then conveyed to the heat storage. During the heating period, heat from the heat storage is supplied to the ATP formed by pipes in the peripheral structures. [2, 7, 8, 9, 10, 13, 20, 24] Depending on the temperature of the working medium in the ATP, building structures with an internal energy source have different functions, namely large-area wall (ceiling) heating (working medium temperature is higher than indoor air temperature), thermal barrier (working medium temperature is lower or equal the air temperature indoors) or are used for heat accumulation. In summer, they can be used for large-area wall (ceiling) cooling using a cooling circuit. II. PRINCIPLE OF COMBINED BUILDING-ENERGY SYSTEM WITH AN ENERGY ROOF An example of a schematic diagram of an energy system is shown in Fig. 1. Description of summer operation : A solar energy absorber, which is formed by a circulating liquid in a plastic pipe, is heated by solar radiation. The heated liquid then supplies heat to the ground heat storage. This part of the storage is formed by a plastic pipe in the foundation slab or under the foundation slab. With suitable solar radiation, the heat flux from the solar roof is also fed into an accumulation tank. Heat can be taken from the lower part of the storage to the accumulation tank, while in summer operation the inlet is closed of this heated liquid to the ATP distributor. During the warm period, liquid from the cooling circuit flows into the ATP distributor. The cooling circuit consists of a plastic pipe located at a non-freezing depth away from the heat storage. The temperature there should be approximately constant throughout the year. Using a cooling circuit, we cool building structures. Low temperature heating (floor, wall or ceiling) is not in operation.