The Rytons Periscope Underfloor Ventilator is usually a cranked z-shape underfloor ventilator capable of extending vertically through two-five brick courses as just one unit. The external Multifix Air Brick features one among the highest airflows that you can buy at 7750mm² per device which, unrestricted because of the Periscope sleeve, http://roof-ventilation19641.designertoblog.com/12967508/an-unbiased-view-of-sub-floor-ventilation-products