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

[ozzmosiz]

Hi all,

We just had our dormer bungalow roof replaced. It had red concrete tiles before on the slope and on the dormer front and sides, but we replaced with natural slate and the dormer face with slate effect cladding. The dormer and roof were reinsulated as the previous insulation was quite pathetic.

Today the temperature is 22c outside. I opened the eaves door hatch and a waft of very hot air came out.
I put my greenhouse Govee temperature gauge in the eaves just by the door hatch and shut it.

Currently it is logging the temperature as 50.2c (and it seems to be rising) with 18.8% humidity - that it VERY hot! nearly 30c hotter than outside.

We have the electric cables and water pipes for radiators run along the inside of these eaves.

I am worried we've made a mistake with the roof choice (in very quick hindsight) or the roofers have missed something?


Any advice please?

 

[freddiemercurystwin]

Wow, 50°C is pretty intense! Is this the temperature inside the loft room itself or the sloping voids spaces under the roof at the edges? What is the make-up of the new construction types?

 

[ozzmosiz]

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:

 

[Vinty]

Did the roofers put vents in the roof to allow air to circulate.

 

[ozzmosiz]

No vents were installed

 

[Vinty]

No vents were installed

Most new roofs have vents installed to allow air to flow through.
Old slate roofs didn't have vents because there was no underlay underneath and air just flowed through under the slates.

 

[ozzmosiz]

I know in the ridge tiles they have vents usually, but what about in an eaves that is outside of the dormer? Would you put a vent on the sloped part of the roof?

 

[Vinty]

Slate vents help regulate the temperature in the roofspace.
You can also fit vents at the eaves.
Hope this helps.

What is a Slate Tile Vent?

A slate tile vent adds modern roofing technology into the traditional style and design of slate tile roofs to provide effective ventilation of your roof space. Find Out More!

beddoesproducts.com

 

[ozzmosiz]

Slate vents help regulate the temperature in the roofspace.
You can also fit vents at the eaves.
Hope this helps.

What is a Slate Tile Vent?

A slate tile vent adds modern roofing technology into the traditional style and design of slate tile roofs to provide effective ventilation of your roof space. Find Out More!

beddoesproducts.com

What sort of vents?
Do they stop rain getting in? These weren't mentioned by the roofer.

 

[Vinty]

What sort of vents?
Do they stop rain getting in? These weren't mentioned by the roofer.

Yes they are watertight, these days houses have a lot more insulation and require ventilation, most new roofs have vents installed to allow air to circulate in them.

 

[jj4091]

What sort of vents?
Do they stop rain getting in? These weren't mentioned by the roofer.

Google Search

installed in the soffits

 

[ozzmosiz]

JJ thanks. There are no vents in the soffits at all. How would this extract hot air as it would be the lowest point and outside the top of the eaves is flashing covering the tiles and joining to the cladding that covers the dormer

 

[freddiemercurystwin]

Do you have a photo of the outside?

 

[ozzmosiz]

First photo is stood under the soffit facia facing up
Second is where the tile ends on the slope
Third shows the flashing at the top of the eaves to the dormer

 

[jj4091]

Instalation

Google Search

difficult to tell which type to use and how to instal them from your pics so have a search.