Best breather membrane- air and vapour permeable

[ab12]

I'm in the process of doing a full re-roof to replace old bitumen leaky felt. 

 

Would like to go with breather membrane that is air and vapour permeable. Any recommendations please.

 

Pitched roof will be finished off with fibre cement tiles with a dry ridge system and eaves ventilation.

 

It appears most of the membranes on the market are air tight and vapour permeable and a limited supply are both air and vapour permeable.

 

 

 

[JOE187]

https://klober.co.uk/membranes/roof-membranes/p/air-160       Tape all joints.

[G and J]

We used this

 

 Permavent APEX is a 3 layer breather membrane. APEX is both air and vapour permeable

[JohnMo]

We used proctor Roofshield, it's vapour and air open. 

[ab12]

On 17/05/2026 at 08:43, G and J said:

We used this

 

 Permavent APEX is a 3 layer breather membrane. APEX is both air and vapour permeable

Thank you everyone.

Had a look at the prices and SD values

 

Permavent £160 SD value 0.01

Roofshield £150 SD Value 0.013

and Klober £259 SD value 0.009

 

On paper Kolbre wins in terms of breathability but is there a bif difference between 0.009 and 0.1 SD value?

If not then I think either Permavent or Roofshield

 

Also I don't quite understand do these membranes to be taped or can they be used untaped.

Look at the brochure if taped for example Permavent require 100mm overlap and if untaped then 150 mm overlap.

 

In terms of tape- any specific type of tape ? or standard waterproof duck tape?

[ab12]

7 hours ago, JOE187 said:

https://klober.co.uk/membranes/roof-membranes/p/air-160       Tape all joints.

Which type of tape please?

[G and J]

4 hours ago, ab12 said:

Also I dont quite understand do thes emembranes to be taped or can they be used untaped.

We did not tape but used the 150mm overlap (permavent)

[JohnMo]

7 minutes ago, G and J said:

We did not tape but used the 150mm overlap (permavent)

Neither did we

[JOE187]

I taped the joints as a warm roof and just extra belt and braces for air testing .   https://klober.co.uk/membranes/a

[G and J]

22 minutes ago, JOE187 said:

warrm roof and just extra belt and braces

Good point, just for clarification ours is a cold roof

[ab12]

On 21/05/2026 at 07:13, JOE187 said:

I taped  the joints as a  warrm roof and just extra belt and braces for air testing .   https://klober.co.uk/membranes/a

So just to recap, no taping for cold roof but better to tape for warm roof?

[JohnMo]

8 hours ago, ab12 said:

So just to recap, no taping for cold roof but better to tape for warm roof?

Just follow manufacturers instructions of chosen membrane. If you need additional belts and braces for airtightness, your primary airtightness measures need to be looked at.

[ab12]

4 hours ago, JohnMo said:

Just follow manufacturers instructions of chosen membrane. If you need additional belts and braces for airtightness, your primary airtightness measures need to be looked at.

Probably a daft question but is there a need to use ventilated fibre cement tiles in places on a pitched roof if when using a  breather membrane. I suspect not but thought about belt and braces option.

My current roof has old bitumen felt under fibre cement tiles, is ventilated at eaves and has a few ventilated fibre cement slates in places for airflow.

Thing is old roofer actually cut thorugh the felt just under ventilated slates and this is allowing water ingress in places.

 

Also is there a need to leave an air gap between insulation and breather membrane when using an air and vapour open memrane?