New slate roof and dormer eaves is running VERY hot - have we made a big mistake???

[noseall]

Thanks Freddy, the dormer itself is a wooden framed dormer. The cladding is cedral click cladding, which is a fibre cement cladding.

The roofers supplied a breathable felt and counter batten to allow airflow. I recall them putting the polystyrene type insulation with foil backing on against the dormer too. The bedrooms, whilst warm, are not stupidly hot, just the eaves, so the heat from the tiles are warming the eaves up.

The tiles are natural slate and have new 25x50 battens 25x50 treated counter battens over a modern high performance breathable felt.
It doesn't seem to be very breathable as the temp hit 50.3c

I am worried what will happen when we hit temperatures in the mid to high 30s and whether that will be safe with such high temperatures.

The eaves has new fluffy insulation laying on it, which they added as the previous insulation was quite pathetic.


I took a photo inside the eaves. There is nothing between the breathable felt and the air in the eaves as seen:

View attachment 380368

Breathable (membrane) means it will let water vapor escape. It is not a protection from the sun. Nor does it insulate form the sun.

You may benefit from some through ventilation i.e. OFV's and vented ridge etc.

 

[ozzmosiz]

Thanks noseall. No idea if those were fitted at all

 

[freddiemercurystwin]

You can see they weren't, too late now, some soffit vents and some slate vents are all you can do now, assuming a clear ventilation path can be achieved between the soffits and the void. I'm gonna hazard there's no ventilation behind that cladding either.

 

[ozzmosiz]

You can see they weren't, too late now, some soffit vents and some slate vents are all you can do now, assuming a clear ventilation path can be achieved between the soffits and the void. I'm gonna hazard there's no ventilation behind that cladding either.

How would you ventilate behind the cladding?
With battens? If so there were battens

 

[freddiemercurystwin]

The battens are fine, you would normally have a gap at the bottom between the cladding and the lead and at the top between the top of the cladding and the soffit.

 

[ozzmosiz]

Thank you for the advice

I think there was a gap at the top of the cladding to the soffit and at the bottom (the lead is under the cladding) but the lead from tiles to cladding at the bottom is tight with no gaps. Presume that is normal, but no idea.

I've not had much luck with communication with the roofer owner as he's so busy.

Got to 27c today. The eaves peaked at 48.9c today. Surprised about that as it was 22c yesterday and 50.3c

Would adding inlet vents in the bottom soffit work now as it's already fitted. I guess I need an out vent near the peak of the eaves, like a tile vent or whirlybird so the hot air can escape and the lower inlet can suck air from outside in?

 

[ozzmosiz]

Today it's a cool 16c outside and the thermometer is registering the eaves at 39.6c
I expect heat with the tile colour we have (of course they will get hot) but did expect the eaves to be able to vent the build up.


Does 39.6c seem excessive in the eaves for an outside temp of 16c?
I'm not concerned with that temp, but am concerned when we get temps of 30c+ it will be really bad!

 

[freddiemercurystwin]

Loft spaces are typically roasting and uncomfortable places in the warmer weather but your figures do seem a bit excessive.

 

[Mottie]

Loft spaces are typically roasting and uncomfortable places in the warmer weather but your figures do seem a bit excessive.

3/10

 

[ozzmosiz]

3/10

Can you elaborate?

 

[Mottie]

Can you elaborate?

Yes. The tw@t is trolling me in one of my threads so I’m doing the same to him.

 

[Mottie]

.