Creating an airtight home is a fundamental part of modern building design, supporting energy efficiency and building performance, from meeting regulatory requirements through to high-performance standards such as Passive House. An airtight home eliminates leaks in the building envelope that should not exist. This is crucial for maintaining indoor temperatures, reducing heating demands and minimising energy consumption. Airtightness not only enhances energy efficiency but, with correct detailing, the use of appropriate materials and controlled indoor ventilation, also supports moisture control.
There are several ways to ensure airtightness. Building designers should identify areas where air leakage could possibly occur at the design stage. This includes service penetrations (ie, electrical wiring or plumbing connections), openings such as windows and doors, and structural junctions like the interface between walls, roof and floors, or a combination of these. By proactively addressing and sealing these critical points with products like Pro Clima Aerosana Visconn airtight liquid membrane or Pro Clima Airtightness tapes, a continuous and reliable air barrier can be created.
Airtightness must be combined with moisture control via the incorporation of an airtight membrane into the build – one that responds accordingly to humidity. Vapour control membranes, such as Pro Clima Intello Plus, offer a tried and trusted solution. Intello Plus allows up to 100 times more vapour to pass through when exposed to a humid environment compared to being exposed to a low humidity environment. In the colder months, when internal humidity is lower, the membrane behaves as a vapour control layer (high moisture vapour diffusion resistance). In the summer, when internal humidity is higher, the membrane becomes more vapour open and allows any moisture to harmlessly diffuse back to the room internally. This ensures moisture content in the building envelope insulation zone never reaches critical levels.
Finally, high-quality air barrier tapes and sealants are essential for ensuring airtightness at joints, seams and penetrations. These products are designed to withstand movement, temperature fluctuations and exposure to moisture, providing long-lasting airtightness.
QUALITY CONTROL
Implementing stringent quality control measures is crucial for maintaining airtightness throughout the construction process. This includes verifying that all materials used for airtightness carry appropriate certifications from recognised bodies, such as the Passivhaus Institute.
Airtightness testing is typically carried out using a blower door test, which quantifies the air exchange rate through the building envelope under controlled pressure. This provides a clear assessment of the building’s airtightness performance and demonstrates compliance with energy efficiency requirements. Carrying out intermediate tests during the construction phase also enables targeted remediation of leakage paths, minimising the risk of defects and avoiding the need for extensive corrective work once the building is complete.
MOISTURE MANAGEMENT
Airtightness must be balanced with effective moisture management to prevent interstitial condensation and maintain indoor air quality. Understanding how moisture vapour moves through different building materials can help to manage it effectively and maintain the integrity of the building envelope.
A careful balance needs to be struck between the moisture loading of materials and ensuring sufficient drying reserves. If the moisture loading of a build exceeds the drying reserves, structural damage can occur due to an uncontrolled build-up of moisture in the insulation zone of the building envelope. Building in adequate drying reserves is essential to prevent long-term issues such as moisture-induced mould.
Internal membranes like Pro Clima Intello Plus, used on internal walls and ceilings, and Pro Clima Dasatop, used in lofts and roofs applications, provide airtightness while managing vapour diffusion by adjusting to changes in humidity. They create a smart vapour control layer that reduces the risk of condensation and supports safe drying in constructions that involve wet materials, such as plasters or screeds. These membranes are often referred to as ‘intelligent’.
AIRTIGHTNESS IN PRACTICE
To ensure the airtightness of a building, effective coordination between all parties involved in the construction process is essential. Clear detailing, shared understanding on site and careful sequencing of works all play a critical role in achieving a continuous airtight layer.
Achieving effective airtightness together with appropriate vapour management is essential for delivering a high performing modern home which is energy efficient, comfortable and has good indoor air quality. By integrating airtightness at the design stage, building designers can limit unintended air leakage and support consistent long-term performance throughout the life of the building. www.ecologicalbuildingsystems. com.com