Design and analysis of energy efficient indoor-climate control methods for historic buildings

Abstract

Indoor climate in historic buildings pose both practical and scientific challenges. Firstly, establishing a proper indoor climate with respect to both comfort and conservation. Secondly, achieving the desired indoor climate in a non-invasive, sustainable, and energy efficient way. This thesis aims to explore the link between technical equipment and target ranges for indoor climate, i.e. control strategies and algorithms based on the hypothesis that smarter and more effective control of the indoor climate, based on an understanding of the specific characteristics of the building in question can be a cost effective way to achieve a sustainable indoor climate. The first addressed method is intermittent heating of massive historic buildings. To control the change rate of relative humidity at a heat-up event, a simplified model for heat and moisture transfer together with a method to derive the hygrothermal parameters and the time constant of the building from measurements is presented and validated. The study considers a feedforward control algorithm that uses the model to predict and control the change rate of relative humidity during the heat-up event. The method has been validated on measurements and models of three historic churches. Unheated historic buildings often face problem with mould growth. Adaptive ventilation is a candidate for being an energy efficient method to decrease mould growth risk. The research questions are if the measure is sufficient to limit the risk, how it influences the stability in relative humidity, and if it is an energy efficient measure. The present research shows that adaptive ventilation significantly lowers the risk for mould growth on an annual basis, but there is still an increased mould growth risk during short periods when it´s not a sufficient measure. It also was shown that adaptive ventilation increases the risk of mechanical damage on objects due to increased fluctuations of relative humidity. Finally, in a three year study of Skokloster Castle, three climate control measures are compared: dehumidification, conservation heating, and adaptive ventilation. This comparison includes efficiency to prevent risk for mould growth, indoor climate stability, and energy efficiency. The investigation shows that dehumidification had the best result regarding all three criteria. However, the draught proofing of the rooms prior to the study improved the indoor climate significantly.

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