Energy demand with natural ventilation in unheated bedrooms, combined with balanced ventilation

Abstract

In Norway, many detached houses are renovated without mechanical ventilation being installed. Many occupants prefer or accept low temperatures in bedrooms and ventilate with regular window openings all year round. In this context, a hybrid ventilation strategy combining ordinary balanced ventilation in warm zones, and natural ventilation in cooler bedrooms, could be appropriate Such a hybrid ventilation strategy might be most relevant for renovation projects where introducing ventilation ducts can be complicated and costly. The aim of this work is to investigate the energy performance using this hybrid strategy when implemented in a detached Norwegian wooden house. Detailed dynamic simulations of a case house are performed using the simulation software IDA-ICE for 2 insulation levels, and 6 different occupant behaviours. In order to reduce the uncertainty of airflow rates through open windows, simulations are done in 3 different simulation modes. Three natural ventilation strategies for bedrooms are compared to the reference with standard balanced mechanical ventilation with heat recovery. Results show that the energy performance of the investigated hybrid ventilation strategies is strongly influenced by occupant behaviour. Given an energy-conscious occupant behaviour (e.g., regarding thermal zoning), it seems possible to achieve a low energy use with natural ventilation in bedrooms. Low temperatures are frequently applied in Norwegian bedrooms so the proposed hybrid ventilation strategies could be applied to a significant share of the renovation market. However, temperature in bedrooms is strongly related to habits and culture. Therefore, the potential of hybrid ventilation can be different for other countries. With the proposed hybrid ventilation strategy, it is possible to create a night setback in the unoccupied zones with mechanical ventilation. This is a technically cheap and simple way to decrease energy use and could be investigated in further research.