Notes on Airtightness
Build Tight, Ventilate Right!
- Lower heating bills due to less heat loss, with potentially smaller requirements for heating and cooling equipment capacities
- Better performing ventilation system
- Reduced chance of mould and rot because moisture is less likely to enter and become trapped in cavities
- Fewer draughts and thus increased thermal comfort
For best thermal performance, the application of Icynene is used to achieve very high levels of airtightness, minimising heat loss and eliminating random air infiltration. When the thermal envelope is being completed in this way then the quality of air within the building must be considered…in order to supply and condition the air we breathe, some form of mechanical ventilation must be considered. Traditionally this has been in the form of extractor fans in areas of high humidity, such as kitchens and bathrooms, and trickle vents in the windows. Whilst these methods are adequate for removing and replacing air, they do introduce pathways for random leakage and/or infiltration, thus reducing the thermal performance of the building.
A more efficient way of providing the air requirements in a new building is to install a mechanical ventilation heat recovery (MVHR) system to provide fresh, conditioned air. These systems operate to their maximum efficiency when within a closed system thus airtightness is of paramount importance.
Leakage typically occurs at the following locations on the building envelope:
- Junctions between walls and other walls or floors
- Junctions between window frames and walls
- Electrical equipment
- Access doors and other wall penetrations
Our installers are aware of these potential weakpoints in the building and will pay particular attention to these areas…however simple timber frame detailing can help address some issues:
- Fixing soleplates with expanding glue, airtight tapes or similar
- Layering duplex studs with expanding glue before nailing
- Allowing clear pathways in corner detailing for easy application of Icynene
- Oversizing openings to allow for foam fill to surrounds of windows and doors
- Ensuring that there are no gaps in the building envelope
- Minimising the ‘penny gap’ between sarking
Though it isn’t strictly necessary to achieve all these, it’s always best to consider airtightness and how best to achieve it at each stage of the building process.