31/08/2023
WHY DO COLORBOND ROOFS GET A MOULDY SURFACE NEAR THE TOP RIDGE LINE?
I noticed a post by Daniel on the NSW Roofers page a week ago, asking the question below:
"Does anyone know what the black s**t is under the ridge caps I seen it a lot on roofs and have heard it’s from being close to roads ect ?"
We at THE ROOFING PORTAL, are always on the lookout for the difficult questions. And what may be the answers....
WE are sometimes completely WRONG.
But we are up to learning why we are wrong about things, Then we will ALL know better....
Anyway, our theory goes like this.....
1) Air is a good insulator and the temperature of the air gap between the underside of the colorbond roof sheet and the top of the anticon blanket changes slowly. But the temperature of the roof sheet changes rapidly.
2) This air gap slowly loses heat during the night and is coldest in early morning. That means it keeps the roof sheet cold. Warming moisture in the early morning hits the colder metal and forms condensation on the surface.
If you have two roofs side by side (one with anticon and the other without), you will see more moisture on the roof with anticon...
3) In the winter late afternoon, the air gap in the higher roof areas (ridges) loses heat slowly (it is also warmer that the lower section of the roof due to convection) and keeps the sheets warmer. This means a longer growth period for the mould spores (warm = faster and more growth). Mould like warmth and dampness.
4) The ridge zone is therefore the most friendly to surface mould for growth.
5) Why the CLEAN zone adjacent edge of the of the ridge capping?
There is a wide water collection surface on the ridge and this causes a cascade of water onto the roof at its edge. This tends to wash mould growth away with the higher velocity flow. This 'rolling mould' gathers more mould along its way and clumps together further down the roof sheet, clinging onto the entrenched mould in the 'forest'...
NOW, WE CAN BE COMPLETELY WRONG...
That is what science is all about. Putting up a theory, and hoping that others can prove it wrong.
ANY TAKERS?