Most existing non-residential buildings have Constant Air Volume (CAV) ventilation leading to over-ventilation in periods with low or no occupancy. Demand controlled ventilation (DCV) can considerably reduce the ventilation airflow rate and energy use for fans, heating and cooling compared to constant air volume (CAV) ventilation. There is a potentially enormous upcoming marked for converting from CAV to efficient DCV in existing commercial buildings.
Conversion from CAV to DCV with reuse of existing ductworks, was one of several energy measures carried out in Solbraaveien 23, a Norwegian office building. The building was originally built in the early eighties and is considered to be representative for a large number of buildings in need for an upgrade. Total delivered energy use was reduced from 250 kWh/m2 to 80 kWh/m2, and the indoor environment was improved.
Reuse of existing ductworks was very profitable. The ductwork cost in Solbraaveien 23 was roughly cut in half compared to the alternative which was demolition and new ductwork installation.
Based on the experiences from Solbraaveien 23, it is specified a step by step procedure for reuse of existing ductwork that can be used in all projects where such reuse is considered.
The following success criteria are identified for the successful conversion from CAV to DCV with reuse of existing ductwork:
• Can the original system partition be reused?
• Do shafts have sufficient capacity and availability?
• Does the ductwork have sufficient access and quality?
• Are there any visible corrosion?
• Are there risks for any duct parts with asbestos?
• Is the ductwork sufficiently airtight?
• Are the drawings up to date and easily accessible?