Beyond recovery: Measuring ventilation strategies and their impact on energy

Working with a medium scale, research-focused architectural practice this paper measures the efficacy of balanced pressure heat recovery ventilation systems (BPHR systems) in the existing housing stock as a strategy to mitigate thermal heat loss when incorporating ventilation strategies in New Zealand. Current research indicates that BPHR systems boast an efficiency upwards of 80%. The aim of this research is to determine at what point do BPHR systems meet current claims of efficiency. An examination of the existing New Zealand housing stock identifies that 66% of all dwellings do not meet thermal performance requirements. This has been attributed, in part, to the governance of legislation of minimum performance, which did not exist until 1978. This paper, first, identifies building simulation measures and assumptions to accurately simulate BPHR systems in controlled conditions, which is quality assured against the expected performance of a conventional code minimum residential building and a range of models that represent a spectrum of building leakage for pre-legislation buildings. This paper then examines passive ventilation strategies in each model to identify the energy balance of using BPHR systems and the potential for heating energy loss when implementing simpler ventilation strategies. This study identifies that the efficiency of BPHR systems significantly differ in the pre-legislation building simulations. In these models, the building leakage alone renders heat recovery negligible in comparison to simple passive design and occupant-controlled measures thatm achieve a similar result for the indoor air quality.