Insulation
Insulation is very important to the life span of shingles and your roof, as well as energy conservation. It is very important that a roof not be over insulated as well as not under insulated. Air flow is very important in any roof cavity. Improper air flow not only can damage the life expectancy of your shingles, but null and void the warranty from the majority of manufacturers.
A roof with improper air flow will also cause harmful bacteria or mould to accumulate in the roof, therefore creating a potential health hazard. It can also create ice formation on the underside of the plywood in the attic in the winter, and then create leaks when the weather gets warmer and the temperature changes. It will also deteriorate the plywood, and roofing materials, and lead to extensive cost replacement at some stage.
Examples of water and moisture damage from improper ventilation.
In the examples below, there was no ventilation between the insulation and the roof boards. This created a build up of moisture and caused mould to grow.
 |
 |
Bathroom Fan : Many houses have a bathroom fan installed like the one below, left. The arrow points to where the moist air comes out of the fan directly into the attic. A correct installation would have included an insulated flexible pipe from the fan to a "B" vent in the roof so that the moist air is expelled outside of the attic. The picture to the right shows the underside of the roofing plywood covered with mould.
 |
 |
Hole in the Vapour Barrier: When there is a hole in the vapour barrier, such as the one in the picture below left, this creates condensation and consequentially mould, harmful spores, and bacteria.
 |
 |
Inside moisture damage. When people see water damage like the examples below, they tend to think it is due to their roof. In these examples, the damage was caused from improper installation of the vapour barrier.
 |
 |