Flat Roof Insulation Help

[Dave Jones]

They have done a nice job off the edpm in fairness it looks smart. How far under the tiles have they lapped it up and did they osb under the tiles ?

 

I think abutment vent's will be hard to get working right as they will push the bottom tiles up. Easiest and cheapest is to use some mushroom vents. I'd do 4 along either side of the lantern and 2 behind it They really easy to flash in with the edpm tape.

 

Lastly i also think you need more airflow in the pitched roof, assuming its not a warm roof. There doesn't appear to be any eaves vents where the 3 faces join the flat roof. You need air to flow up and over to take out the moisture that will inevitably collect in there when it gets cold. I would put in 9ish tile vents while you have niece easy access, they are cheap and you will have no worries come the winter.

 

https://www.roofingsuperstore.co.uk/browse/ventilation/flat-roof-vents-extraction/flat-roof-ventilation.html

 

[richo106]

Thanks Dave good ideas there!

 

I have attached some more photos of how it joins the pitched roof. As you can see there is a good gap through above the PIR in the pitched roof…if I kept a 50mm air gap on the flat roof would this give good enough ventilation you think?

 

I could install the 9 air tiles as you said?

[richo106]

[richo106]

Would my building inspector be able to advise on this?

[Dave Jones]

problem you have, how external air going to get to the bottom of those eaves ? They would normally be externally exposed so fresh air continually flows through.

 

[richo106]

I’m still going round in circles with this, my builders and a retired building inspector said as long as I leave an air gap above then that’s fine. I have my building inspector coming but still have no idea on how I am going to insulate this area🙈🙈

[Mike]

From where you are now, and from what you've posted, I'd with @Dave Jones's suggestion, though it will mean getting the roofers back:

 

On 30/05/2023 at 15:30, Dave Jones said:

I would put in 9ish tile vents while you have nice easy access, they are cheap and you will have no worries come the winter.

 

https://www.roofingsuperstore.co.uk/browse/ventilation/flat-roof-vents-extraction/flat-roof-ventilation.html

 

[richo106]

Hi @Mike

 

Yes I agree, I am going to take @Dave Jonesadvice/idea and install the mushroom vents.

 

I just need to decide the best way to insulate it now?

 

I have attached my buildup. I need to get my MVHR ducts and outlets in there, my outlets need to be at least 110mm below finished ceiling level

 

I also need to bring it down around 75-80mm to work with my frontage of the house so it flows through nicely