Approved Document O: Overheating
Increased Ventilation Rates = Larger Ductwork
The control of overheating is detailed in Building Regulations (England & Wales) and the key requirements include;
• Design for comfort
• Limit solar gain
• Provide adequate ventilation
• Meet performance standards
Where the risk of overheating is identified, and a condition of planning, ventilation airflow rates are increased.
This can result in bigger and more powerful units (e.g. MVHR/purge rates) being required and therfore larger diameter ductwork to accomdate higher airflow requirements.
In practice however, it is not simple or cost-effective to just ‘increase the duct size’ due to ceiling void sizing in residential developments and running noise concerns