HELP - roof insulation disaster

LowOdour

I have just found that the rafters in my roof contain 100mm Thermafloor TF70 covered by 38mm insulated plasterboard underneath. How much trouble is this going to cause me? There are people to blame for this (myself included), but I really dont see me being able to redo the whole roof again

FesterBeatty

If you converted your attic you might fill the space between the rafters with rigid insulation, then you'd fit plasterboard to the underside of the rafters. I.e exactly what you have...

Am I missing something? What exactly are you concerned about?

LowOdour

its a new build and the thing im concerned about its thermafloor thats in the sloping rafters in the roof! I looked at kingspan website and cant see much difference between tf70 and tp10 (standard roof board). Is this correct?

DOCARCH

LowOdour wrote: »

Is this correct?

Probably very little difference, if any. I would not be worried but I would suggest you speak with Kingspan for your own peace of mind.

LowOdour

DOCARCH wrote: »

Probably very little difference, if any. I would not be worried but I would suggest you speak with Kingspan for your own peace of mind.

Spoke to Kingspan this morning....basically the TP10 and TF70 are pretty much the same material/product, expect the TP10 has a thicker gauge foil on it for extra vapour build up that would occur in a roof. He said he couldnt advise me on what to do as TF70 had not been tested on roofing structures. Is there any way to get that extra vapour control using a different material?

sinnerboy

Relax. The "thicker vapour control" foil is shot to pieces any way every time you cut the board to infill between the rafters anyway so I would be very skeptical about the benefit of the thicker foil in this application.

So you have a theortical less than optimum vapour control .

So re double your efforts to ensure that you ventilate correctly over the insulation.

Reminder
- min 50mm continuous clear space between to of insulation and underside of roofing membrane.
- Ensure positive ventilation routes at the roof overhangs - use continuous pvc vent strips 25mm- not 10mm
- 10mm vent strips at hips/ridges

Do not pay attention to advice that if you use a breather felt that you don't need to ventilate. I never accepted that personally.

sinnerboy

You can also help reduce vapour migration through the roof fabric by paying vigourous attention to all penetrations through the roof insulation - all power and lighting points , svp / extract ducts etc . Ensure they are well sealed.

LowOdour

sinnerboy wrote: »

Relax. The "thicker vapour control" foil is shot to pieces any way every time you cut the board to infill between the rafters anyway so I would be very skeptical about the benefit of the thicker foil in this application.

So you have a theortical less than optimum vapour control .

So re double your efforts to ensure that you ventilate correctly over the insulation.

Reminder
- min 50mm continuous clear space between to of insulation and underside of roofing membrane.
- Ensure positive ventilation routes at the roof overhangs - use continuous pvc vent strips 25mm- not 10mm
- 10mm vent strips at hips/ridges


Do not pay attention to advice that if you use a breather felt that you don't need to ventilate. I never accepted that personally.

Thats a relief....dont think Id have the heart to pull all that boarding and insulation down again. I will look at all ventilation to make sure its up to spec.

sinnerboy wrote: »

You can also help reduce vapour migration through the roof fabric by paying vigourous attention to all penetrations through the roof insulation - all power and lighting points , svp / extract ducts etc . Ensure they are well sealed.

Thanks, will certaintly keep a note of this.

Cheers Sinnerboy

Poor Uncle Tom

What depth of rafters have you on the roof?

LowOdour

Poor Uncle Tom wrote: »

What depth of rafters have you on the roof?

6 inch

Poor Uncle Tom

As sinnerboy said above if your insulation is against the bottom of the rafter leaving the 50mm air gap on the top side you should be fine.

No6

I couldnt disagree with that either!!