Airflow appreciates that once you have a hole in the wall the natural process and character of the flow of air would mean that the colder outside air will be able to enter the building. The purpose of a ventilator is to protect from rain, vermin etc. enteFeatures:Meets all BS5440..
Features: Easy fit products Even standard models give greater draught resistance to strong winds than most other vents on the market All meet (and exceed) relevant British/Scottish Gas Services Standards, BS5440 Pt2. 2000 and BS493 1995 The only plastic ventilation ma..