If you have a metal roof chances are highly likely you have a condensation problem.
Ask yourself these questions?
One: Do you have a vapour barrier at all
Two: Is the vapour barrier sisalation foil.
If so – is the sisalation foil sagged at least 50mil between the rafters.
Or alternatively do you have a vapour barrier that incorporates sisalation foil and blanket combined.
Whether you have no vapour barrier, sisalation foil or sisalation blanket combo and you have no roofspace ventilation you will definitely have a a condensation problem this could be either mild or catastrophic depending on your own unique situation.
A lot of situations come into play when dealing with the problems of condensation, however when the heated air from inside your home permeates through the ceiling insulation to the roofspace it rises to meet whatever roof covering or underlay that is installed on your roof, at this point (pardon the pun) this is call the Dew Point when the outside temperature of the metal comes into contact with the trapped heated roofspace air it turns into moisture. No matter what vapour barrier that you may have there will be a certain amount of moisture obviously this is further exacerbated by the fact that this heated air is trapped between your ceiling insulation and the roof covering, with nowhere to go if you don’t have effective roofspace ventilation.
It could be raining in your roof if you do not have effective roof ventilation.
As previously mentioned there are many situations that come into play when dealing with condensation.
Some ideas for you to contemplate when building a new home if you don’t want to deal with condensation.
- 1. Don’t build using a flat roof – I would suggest anything below 15°c you could eventually have a substantial condensation problem, preferably 18°c is best practice.
- 2. If you are going to use sisalation foil make sure the foil is sagged between the rafters, so the foil does not come into contact with the roof sheeting.
- 3. Use timber battens rather than metal battens. Metal battens may help BHP get bigger but they are also a very good conductor for condensation.
- 4. No matter whether you use a vapour barrier or not, with a metal roof – roof ventilation should be one of the highest considerations if you want to be condensation free.
So get your effective roof ventilation installed when you are having your roof installed.