Reduction of heating energy demand by combining IR heaters and IR reflective walls: An experimental study

• Experiments in a climate chamber isolated the influence of IR heating power and surface emittance on thermal comfort. • Low surface emittance combined with IR heaters maximizes the use of thermal radiation and increases PMV. • High radiant temperatures achieved by low surface emittance allow for lower air temperatures and thus heating energy savings. • The response surface function from the experimental results can be used for IR heater control. In this study, we build upon previous simulation research that advocates the use of infrared (IR) heaters in conjunction with IR reflective interior walls to meet heating demand in buildings. This combination allows the walls to reflect the heat emitted by the IR heaters back to the occupants in a room, rather than absorbing the radiation. As a result, the radiant temperature increases and the air temperature can be lowered in order to maintain constant thermal comfort and to reduce heat loss through the building envelope. We conducted experiments in a climate chamber to isolate the effects of four factors on thermal comfort: the heating power of IR heaters, the IR emittance of the interior walls, the interior wall surface temperature, and the air temperature. The emittance was modified by applying an increasing number of adhesive aluminium foil stripes. Heat conduction through the wall to the outside is not part of this study. To minimize the number of required experiments, we employed a Central Composite Design, from which we derived a response surface function. The experimental results confirm a correlation between wall emittance and occupant thermal comfort in a room, particularly at higher IR heater power levels. The Predicted Mean Vote (PMV) value increases at lower wall emittance (corresponding to higher radiant temperatures), highlighting the potential for energy savings through reduced air temperatures. However, the observed impact of low emittance surfaces on the PMV is less pronounced than previously estimated in simulation studies.