Because air infiltration is uncontrolled, poor envelope airtightness may affect:
Indoor air quality: Some rooms may be largely under-ventilated (i.e. stuffy, high CO2 levels etc. ) while other are over-ventilated (draughty, cold etc.).
Energy use: Air leakage may inadequately increase the total ventilation airflow rate; or it may not allow sufficient heat recovery (in case of a systems with heat recovery devices, the unit will only recover heat on the airflow passing through it).
Building materials: Air leaking out of the envelope may cause condensation damage as its temperature drops below dew point.
Definition of terms used for tightening products –
Adhesive: Substance that holds one surface to another surface by attachment.
Adhesive membrane: Flexible film (generally made of polyethylene) associated with a no woven fabric used to seal joints between the peripheral of a window and a vapour barrier/retarder or a plaster.
Bond: Material used to tie or fasten things together.
Expanding foam: Expanding material (generally polyurethane-based) applied to fill gaps, to fix doors and to insulate connecting joints (especially between window frames and wall). Not considered long life airtight as the material can breakdown over time.
Fastener: Material used to bind things securely together.
Grommet: Material used to create an airtight seal around circular-section elements such as plumbing pipes, electrical conduits or cables as these pass through the airtight layer.
Joint: Location where several parts of the structure (building or ductwork) meet.
Sealant: A material that has the properties to join 2 surfaces together to prevent gases, liquids or solids from passing between these surfaces.
Mastic: Putty-like sealant.
Plasters: Fluid or paste-like mixtures made of cement, lime, or gypsum. These products are spread or projected on the surface.
Pre-compressed tapes: (also called pre-compressed foams) Rolls a few centimetres wide whose thickness is reduced when rolled-up and slowly get thicker when installed. They are made of polyurethane or polyester foams impregnated with a synthetic butyl or acrylic resin. The retarded decompression process allows the gaps to be filled while the foam was put without force into them.
Repair tape: Oversized tape roll or flat patch typically used to repair holes in films or holes made on purpose e.g., for blowing insulation.
Tape: An adhesive in the physical form of a tape, i.e., a narrow strip of material.
Vapour barriers or retarders: Membranes or films of large areas originally intended to limit or regulate vapour transfer within vertical walls and roofs. When properly installed and at the right location, they prevent interstitial condensation, in particular in the insulation layer. Their composition can be very diverse, e.g. they can be partly made of polyethylene, polyester, polyane, aluminium, etc. They are usually airtight unless perforated.