Another Insulation / Ventilation Question

[rjb]

Hi,

I'm currently having a double garage (workshop / store) built with a second floor above within a pitched tiled roof. I've asked the builders to properly insulate this so I can control the temperature and humidity consistently. The gable walls are timber studwork and they have filled these with rockwool before cladding with ply which I think is ok. On the main roof area they have fixed multi-layer foil insulation to the rafters then fixed horizontal 1" battens across and then clad with ply. My concern is that around the edges of the roof there is no seal between the cold air outside and the edge of the insulation so cold air can circulate freely to both sides. Also there are some small gaps around the edges of the ply lining and the area around these appeared slightly damp today - possibly due to condensation?

I have mentioned my concern about this to the builder and he said it's important to allow the air to circulate to avoid condensation, but I don't see how the insulation will work effectively if cold air can circulate on both sides. I would appreciate some advice on this.

Thanks

Richard.

 

[Rob Platt]

Ideally the vertical insulation should link to the roof insulation in a continuous line. This will of course be interupted by the timber head in the studwork. That will not matter and is an unavoidable design problem however a gap in this area is likely to cause a condensation problem as a result of a cold spot with mould as a problem. Ideally the roof insulation should provide a remedy to this by filling that void and continue up and over the roof with ventilation above the insulation. I would have a look at the drawings that were approved by building control and get it sorted before it gets too far down the line.
Your area building control officer should be able to provide a satisfactory solution to this as it is his responsibility to sign off the build.
All the best
rob

 

[rjb]

Thanks Rob, I hadn't thought about the building control officer ..that's another option if the builder doesn't sort it out.

Thanks,

Richard.