Cuting pir advice

speccy · 19 Oct 2019

I want to make sure cold draft isnt blowing in over room so was thinking about blocking this area with old rockwool as the rest of the ceiling I am filling with pir board. As you can see not easy to cut in this area and easier to use rockwool.
Is this ok or am I disturbing airflow to loft space?

garyo · 19 Oct 2019

Yes that's a problem with that non breathable felt. Get some corrugated plastic spacers so that you can do what you want without blocking ventilation. Cheap as chips.

garyo · 19 Oct 2019

This stuff : https://www.roofingsuperstore.co.uk/product/timloc-eaves-vent-roll-out-rafter-tray-600mm-x-6m.html

speccy · 19 Oct 2019

Thankyou so much

^woody^ · 19 Oct 2019

It's a waste of time using corrugated vents if the eaves are not vented in the first place with a soffit vent.

speccy · 19 Oct 2019

Theres no soffit vents

^woody^ · 19 Oct 2019

Then what you've done is ok

Leofric · 19 Oct 2019

There are other types of eaves vents apart from soffit vents such as over fascia vents or vents that sit on top of a brick corbelled eaves.
When was the house built ? It would be unusual for a 'cold' roof not to be ventilated unless it was built a long time ago.

^woody^ · 21 Oct 2019

Leofric said:
There are other types of eaves vents apart from soffit vents such as over fascia vents or vents that sit on top of a brick corbelled eaves.
When was the house built ? It would be unusual for a 'cold' roof not to be ventilated unless it was built a long time ago.

Soffit venting is relatively modern concept. 70's onwards?

Roofs tend to get enough adventitious ventilation from the laps in the felt, and from gaps in the general construction. Sometimes laps can be stuck together from age, but if they were opened again then that is enough

Leofric · 21 Oct 2019

^woody^ said:
Roofs tend to get enough adventitious ventilation from the laps in the felt, and from gaps in the general construction. Sometimes laps can be stuck together from age, but if they were opened again then that is enough

Can these 'woody regulations ' be used to apply for a relaxation of the building regulations on ventilation of roofs

^woody^ · 21 Oct 2019

Leofric said:
Can these 'woody regulations ' be used to apply for a relaxation of the building regulations on ventilation of roofs

Of course. I'll print you a certificate, once you've transferred the funds.

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Cuting pir advice

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