Contents lists available at ScienceDirect Applied Thermal Engineering journal homepage: www.elsevier.com/locate/apthermeng The possibilities and limitations of using radiant wall cooling in new and retroftted existing buildings Michal Krajčík a, ⁎ , Ondřej Šikula b a Slovak University of Technology, Faculty of Civil Engineering, Radlinského 11, 81005 Bratislava, Slovakia b Brno University of Technology, Faculty of Civil Engineering, Veveří 331/95, 60200 Brno, Czechia HIGHLIGHTS • Possibilities and limitations of four wall cooling systems were explored. • A novel indicator to quantify the efciency of heat and cool transfer was defned. • Radiant wall cooling is applicable in both new and retroftted existing buildings. • Performance depends on requirements on installation, cool storage, thermal response. • In wall with pipes uncoupled from the core only pipe spacing afects the output. ARTICLE INFO Keywords: Radiant system Wall cooling Building retroft Heat transfer Thermal dynamics Thermally activated building systems (TABS) ABSTRACT The use of radiant wall cooling presents a potentially feasible solution to cover the cooling demand of buildings due to its suitability for combination with renewable energy sources at relatively high sensible cooling capacity. We defne and directly compare four types of wall cooling systems, from which three are potentially suitable for building retroft. Besides using established performance indicators, an indicator called heat transfer efciency is introduced to allow detecting diferences in the thermal dynamics of various systems even in cases when their response time, defned as τ 95 , is alike. Systems with pipes underneath the surface provide higher cooling output and are sensitive to pipe spacing. Systems with pipes embedded in the core allow thermal storage and are sensitive to insulation thickness. Thermal conductivity of the core material proved to be an important parameter to consider except for the system with the pipes separated from the core by thermal insulation. The systeḿs suitability depends on the requirements such as avoiding interventions in the interior, exploiting thermal storage, or providing fast thermal dynamics. It is shown how various confgurations of pipe location, material layers and thermal conductivity of the core allow compromising between the diferent performance indicators to design a system with the desired characteristics. 1. Introduction The growing trends in global temperature, population, urbanization, economic development and demands on thermal comfort have been causing a gradual increase in the energy consumption for space cooling of buildings. It is expected that the resulting increase in the number of space cooling systems and cooling capacity will put tremendous pressure on the energy infrastructure and severely increase the environmental impacts if the design of cooling systems is not optimized [1–4]. The installation of low-exergy water-based radiant systems can help alleviate these negative efects. This should be possible due to their suitability for combination with low-grade renewable energy sources such as ground-coupled heat pumps and solar collectors [5–8] at relatively high sensible cooling capacity [9], and the possibility to use the same system both for heating and cooling. In a moderate and dry climate and well thermally insulated buildings like, e.g., in Europe, only a fragment of the surface may be enough to create thermal comfort throughout the whole year [10–12]. This makes radiant walls poten- tially feasible systems for new and retroftted existing buildings, which could be preferable to the more common radiant foors and ceilings due to the following benefts: • Suitability for retroftted buildings. Additional installation of a ra- diant wall system does not reduce the story height. This can be useful in retroftted buildings, where radiant foor and ceiling systems di- minish the precious height, possibly beyond the acceptable limit. https://doi.org/10.1016/j.applthermaleng.2019.114490 Received 27 April 2019; Received in revised form 5 September 2019; Accepted 3 October 2019 ⁎ Corresponding author. E-mail address: michal.krajcik@stuba.sk (M. Krajčík). Applied Thermal Engineering 164 (2020) 114490 Available online 08 October 2019 1359-4311/ © 2019 Elsevier Ltd. All rights reserved. T