Nearairtight

Nearairtight is a term used to describe a building enclosure that significantly reduces uncontrolled air leakage but is not necessarily as rigorously sealed as a completely airtight structure. It represents a level of performance that aims to minimize energy loss due to drafts and infiltration while often being more practical and cost-effective to achieve than extreme airtightness.

The concept of nearairtightness is often contrasted with older, less-sealed buildings, where air leakage can account for a substantial portion of heating and cooling energy consumption. Achieving nearairtightness typically involves a combination of careful construction detailing, the use of air barrier materials, and diligent sealing of joints, penetrations, and transitions in the building envelope. This can include taping sheathing seams, sealing around windows and doors, and managing penetrations for pipes and electrical conduits.

While true airtightness, often measured in air changes per hour (ACH) at a specific pressure differential, requires meticulous attention to detail and specialized testing, nearairtightness aims for a high level of performance without necessarily needing to meet the most stringent airtightness standards. The benefits include improved thermal comfort, reduced energy bills, better indoor air quality control through mechanical ventilation, and enhanced durability of the building structure by preventing moisture transport. It is a common goal in modern energy-efficient construction.