•For single-room ventilation, a novel rotary heat exchanger uses a low-cost plastic honeycomb.•Thermal design theory predicts 84% temperature efficiency for 8.2L/s with 6% bypass leakage.•Measured and modelled temperature efficiencies agree for 8L/s and 13L/s and disagree for 4L/s.•All leakages are slightly excessive and should be reduced with proper sealing. The existing building stock will likely undergo widespread energy renovations to meet future emissions targets. Single-room ventilation may enable the process due to its simple installation, low fan power, and potential for local heat recovery. A short plastic rotary heat exchanger is developed for single-room ventilation based on thermal design theory. Performance is predicted from correlations of dimensionless groups for regenerative heat exchangers, and this guides the selection of a polycarbonate honeycomb with small circular channels. Experiments quantify flows and determine temperature efficiencies at several ventilation rates while accounting for heat gains from motors and air leakage. The measured and modelled temperature efficiencies show adequate agreement and exceed 80% for a balanced nominal ventilation rate of 28m3/h. This result meets the development criteria but cannot validate the model due to the presence of unmeasurable bypass leakage. All leakages are slightly excessive and should be reduced with proper sealing. Experimental results demonstrate the potential to reduce heat recovery by slowing rotational speed, which is required to prevent frost accumulation. Overall, the development meets objectives and provides a novel and efficient option for ventilation heat recovery.