Effects of Floor Covering Resistance of a Radiant Floor on System Energy and Exergy Performances

Floor covering resistance (material and thickness) can be influenced by subjective choices (architectural design, interior design, texture, etc.) with significant effects on the performance of a radiant heating and cooling system. To study the effects of floor covering resistance on system performance, a water-based radiant floor heating and cooling system (dry, wooden construction) was considered to be coupled to an air-to-water heat pump, and the effects of varying floor covering resistances (0.05 m2K/W, 0.09 m2K/W and 0.15 m2K/W) on system performance were analyzed in terms of energy and exergy. In order to achieve the same heating and cooling outputs, higher average water temperatures are required in the heating mode (and lower temperatures in the cooling mode) with increasing floor covering resistance. These temperature requirements decrease the heat pump’s performance (lower coefficient of performance). This requires higher electricity input to the heat pump, corresponding to an increased exergy demand and consumption, to achieve the same space heating or cooling. The required exergy input to the system (power plant where the electricity is generated) increased by 14% and 5% for heating and cooling, respectively. Increased floor covering resistance has a similar effect to an increased space heating or cooling load, on the water side of the radiant system while in fact the space heating and cooling loads are not changing. The floor covering resistance should be kept to a minimum in order not to hinder the performance of the floor heating/cooling and the whole system and to benefit from the low temperature heating and high temperature cooling potential.