The first step is to know what permeability the building envelope needs to achieve. It will be express in m3/h/m2, which is how many m3 of air will flow through a m2 of wall every hour at 50Pa. If you only pay attention to one number this is it, because if your building test over this number holes have to be found and the envelope has to be retested.
Apart from Green Star the highest permeability an envelope will be specified is 10m3/h/m3 and from past experience all well-constructed buildings should achieve this. The next level of air tightness will be a between 10 - 5m3/h/m2 something that the construction team need to actively manage during the project. When permeability’s are lower then 5, the team will need to dedicate more time into understanding what the air barrier is and might have to perform preliminary testing to ensure successful completion testing. Construction teams also must implement Inspection and Test Plans (ITPs) at critical stages to ensure each area is sealed before access is removed.
Step 2 - Define the Barrier
Its is an impossible task to build towards an air tightness target if you don’t know what building elements are to be air tight. Aerotight use our construction experience to document where the air barrier is on the documents before construction. This allows the team to identify complex sections that will need additional attention during construction.
Step 3 - Material performance
Materials selection for the air barrier is just as important as the water barrier on a building. The wrong material can be problematic, hard to seal retrospectively or impossible to make airtight at the end of a project making it critical that each element is identified for suitability before construction starts.
An example of an air barrier is plasterboard, glass, concrete, and cladding. Materials that are not airtight are grid ceilings, unpainted blockwork, any hole that is unknown, unsealed services penetrating through the air barrier.
Step 4 - Construction performance
All commercial projects are different and in most cases the air barrier is uniqe to that project. It is important the team breaks down the process of the air barrier to identify the correct check points in the program. We recommend using Inspection Test Points (ITP's) during the construction so that critical sealing is not missed.
Step 5 - Air Barrier Inspections
Before construction starts our team will identify check points in your construction program. Each site inspection will be at a critical stage of the project aiming to capture the continuity of the air barrier. During each inspection we walk the project with your team and identify areas that need more attention. The goal of the site inspection is to capture any problems while they are accessible and reasonable easy to correct. After each inspection a report is produced for the construction team detailing the identified leak points and locations.
Step 6 - Testing
Preliminary testing can be conducted on a project to indicate how well the building will perform in the final test. It is a analytical tool that will provide the envelope permeability and also identify leakage points before final testing. This allow the team to know how far the envelope is from the air tightness target and provides instant feedback on how much more work is needed.