OHL-D
Drainable Weather Louver

Holyoake’s OHL-D drainable blade louver offers excellent water penetration performance, which it achieves by draining water from each blade before discharging it at the bottom of the louver through vertical down pipes.
In a typical horizontal louver, where water cascades down the face, the water builds to a level where the pressure differential and the velocity of air over the louver is enough to carry over the water to the inside of the louver. By avoiding this cascade effect, OHL-D drainable horizontal louver delivers a higher effective velocity without compromising the water penetration performance.
The OHL-D achieves this using special gutters on either side of each blade selection. This means that there is the option of selecting an OHL-D louver at a higher effective velocity without compromising the water penetration performance. If a selection is made at a higher velocity the louver can then be smaller than a typical horizontal louver, giving a direct saving on the louver size and also providing a smaller penetration for the building.