Possible UK residential demand-controlled ventilation assessment methodology

Demand controlled ventilation (DCV) can improve the energy performance of all kinds of ventilation systems, in residential and non-residential buildings and is already part of the European Lot 6 and Ecodesign regulations and standards. However, the lack of recognition of DCV in SAP (Standard Assessment Procedure) forms a great barrier for the use of this technology in the UK. A methodology was developed to prove the guarantee on good IAQ, with potential saving on heating and auxiliary energy by modulating ventilation rates based on actual demand.
It is generally accepted that a DCV system, with air flow rates lower than UK recommended values, can only be recognised provided that the IAQ is at least as good as the worst performing constant airflow ventilation system in the regulation. Therefore a model, based on UK reference dwellings and systems, was developed and particular attention was paid to dwellings with low air permeabilities.
A representative simulation model was established using the reliable multi-zone simulation tool Contam. Two different dwelling types, a detached house and a flat, were modelled. These dwelling types represent a large part of the UK housing stock.
Hypotheses concerning the dwelling characteristics (detached house and flat), the weather data, the location, the occupancy, the production of contaminants, the user behaviour and the ventilation components were made.
The IAQ achieved with a number of ventilation systems with or without DCV were assessed using (1) relative humidity (RH), (2) (total) volatile organic compounds ((T)VOC) and (3) carbon dioxide (CO2), after which the energy saving of hypothetical DCV systems were determined with respect to the four different reference system types in the regulation.
Each ventilation system was modelled at 5 building air permeabilities: 0.6; 2.5; 5; 7.5 and 10 (m³/h)/m² and for the 2 types of dwellings.
It is found that different configurations of DCV systems can comply with the 3 IAQ criteria, creating equally good or even better IAQ than the reference ventilation systems, while reducing energy consumption for heating and fan power consumption (average reduction factors of 0.83 and 0.93 respectively with the examples taken into account).