PROVISIONS WHICH APPLY GENERALLY TO J COMBUSTION INSTALLATIONS O N L I N E V E R S I O N J 1.15 Grilles or meshes protecting air vents from the entry of animals or birds should have aperture dimensions no smaller than 5mm. Provisions complying with both Part F and Part J 1.16 Discomfort from cold draughts can be avoided by supplying air directly to appliances, locating vents close to appliances (for example by using floor vents), by drawing air from intermediate spaces such as hallways or by ensuring good mixing of incoming cold air by placing external air vents close to ceilings (see Diagrams 10 and 11).
In noisy areas it may be necessary to install noise-attenuated ventilators to limit the entry of noise into the building. Transfer or connecting ventilation should be at low level to reduce the transfer of smoke in the event of a fire and otherwise meet the guidance given in Approved Document B. 1.18 Rooms or spaces intended to contain open-flued combustion appliances may need permanent ventilation to comply with Part J and adjustable ventilation to comply with Part F. Permanently open air vents for combustion appliances can be accepted in place of some or all of the adjustable background ventilation for health, dependent upon opening area and location.
However adjustable vents installed to meet the requirements of Part F cannot be used as substitutes for the ventilation openings needed to comply with Part J unless they are fixed permanently open. 1.19 Rooms or spaces intended to contain flueless appliances may need: permanent ventilation and purge ventilation (such as openable windows) to comply with Part J; and adjustable ventilation and rapid ventilation to comply with Part F. Permanent ventilation provisions to comply with Part J may be acceptable in place of adjustable ventilation provisions for Part F subject to the limitations described in Paragraph 1.18.
Openable elements installed for the rapid ventilation of rooms and other provisions made for the rapid ventilation of kitchens, in order to comply with Part F, may be acceptable in place of openable elements for the rapid ventilation of rooms or spaces containing flueless appliances . 1.17 Buildings may have air-tight membranes in their floors to isolate them from the ground below. Ventilation ducts or vents installed to supply air to combustion appliances should not penetrate these membranes in a way that will render them ineffective.
Such membranes (including radon- proof membranes) are described in BRE Report BR 414 (2001) and BRE Report BR 211 (2007), which give guidance when service penetrations are necessary. Diagram 10 Location of permanent air vent openings, some examples Well- Well- 20 Combustion appliances and fuel storage systems Approved Document J O N L I N E V E R S I O N