Airtightness in masonry construction is widely considered much more difficult to achieve than in the timber frame.
However, masonry construction can achieve excellent levels of airtightness if designed and constructed correctly. With a timber frame construction, a continuous AVCL (Airtight vapour control membrane) is applied to the warm side of the insulation, creating a highly air impermeable layer. The membrane is sealed to the openings, wrapped around the intermediate floor if present, taped to the ground floor airtight layer (concrete slab or screed) and to the ceiling AVCL membrane.
A very similar approach is used with masonry construction. However, rather than a membrane used as the airtight layer for the walls, a wet plaster finish is used. Plaster is inherently airtight, as is concrete. All that is required is to connect these airtight layers together to create a continuous and effective airtight layer.
Chasing of blockwork for services will damage the airtightness layer. This can be remedied by using an airtightness paint.
Insulated plasterboard is often used in masonry construction. In situations like this or where plasterboard is battened out from the masonry in order to create a service cavity, a sand and cement parge coat can be applied to the block to create an airtight layer.
Passive House Systems supply the appropriate airtight materials for achieving complete airtightness in masonry construction. We have non-woven fabric airtight tapes specifically designed to adhere to masonry or similar rough/porous surfaces and take a plaster finish. We also supply the appropriate sealants and primers to achieve a lifetime airtight bond.
We’re very proud of the quality of our services and our technical support is consistent with BS 9250 (Code of practice for design of airtightness) & DIN 4108-7 (Airtightness of buildings – requirements, recommendations and examples). We’re able to supply materials and provide technical support for airtightness regardless of the type of construction.