The Impacts of a Building’s Thermal Mass on the Cooling Load of a Radiant System under Various Typical Climates

Rong Hu,Jianlei Niu,Gang Liu

doi:10.3390/en13061356

Abstract

Cooling load is difficult to predict for a radiant system, because the interaction between a building’s thermal mass and radiation heat gain has not been well defined in a zone with a cooling surface. This study aims to reveal the effect of thermal mass in an external wall on the transmission load in a space with an active cooling surface. We investigated the thermal performances in a typical office building under various weather conditions by dynamic simulation with Energy-Plus. It was found that the thermal mass in the inside concrete layer had positives in terms of indoor temperature performance and energy conservation. The peak cooling load of the hydronic system decreases 28% in the proper operating state, taking into account the effect of the thermal mass in an external wall. Compared to the performances in zones with equivalent convective air systems (CASs), the peak cooling load and the accumulated load of the combined system (radiant system coupled by fresh air system) are higher by 9%–11% and 3%–4%, respectively. The effect of thermal mass is evident in a transient season with mild weather, when the relative effects are about 45% and 60%, respectively, for a building with radiant systems and a building with equivalent CASs.

Highlights

The energy consumption of space heating and cooling has attracted attention, and thermal transmittance (U-value) must be limited to maximum acceptable values for commercial and residential buildings according to construction regulations and related energy efficiency standards [1,2,3]
The results showed that the position of a massive layer strongly influences the transient heat transfer through the structure, but that it has no effect on the heat flux in the time-average quasi steady-state; and they confirmed that the thermal insulation performs better when located at the inside in an intermittently conditioned room
The second reason can be illustrated by Figure 7; only a very narrow gap in accumulated transmission load exists between the structures of (a)light weight and of heavy weight when the same cooling system applied to maintain an identical indoor thermal environment

Summary

Introduction

The energy consumption of space heating and cooling has attracted attention, and thermal transmittance (U-value) must be limited to maximum acceptable values for commercial and residential buildings according to construction regulations and related energy efficiency standards [1,2,3]. Increasing the normal thermal resistance (R-value in steady state) of a building envelope is the main measure used to protect the indoor environment from extreme external conditions and reduce the energy consumption on space heating and cooling. These factors are not sufficient to characterize the dynamic thermal behavior. Optimizing the thermal mass has been regarded as an important measure for passive heating/cooling strategies and for designing low-energy buildings [5,6,7]. The phase change materials (PCMs) embedded in a building

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