PIR boards in cavity wall- should joints be taped?

[MG-FIDO]

Dear all,

We're due to start have Kingspan Kooltherm K108 PIR boards installed in the cavity walls of our extension. I don't think Kingspan mention taping along the joints but the boards don't seem to overlap and I wondered whether some sort of foil tape like Ultra tape Aluminium Foil Tape 75mm x 45m should be used along the joins between the sheets to reduce cold air movement?

Many thanks for any advice.

[119]

I would say yes, although a friend had an extension built and they had to use tongue and groove boards and taped.

Cost him a small fortune over standard boards!

[dickymint]

K8 and K8+ boards are overlapping but some say still needs taping! If your builder will/can do one skin first then it's a piece of cake otherwise it'll be a right pain in the arse! I don't think building regs require it taped but would say no gaps.

[blueg33]

When we use PIR in the factory (off site built homes) we do not tape.

[LooneyTunes]

What are you using for vapour control?

If relying on the foil, then yes they should really be taped. If there’s a separate vapour control membrane then no need to tape.

[blueg33]

LooneyTunes said:

What are you using for vapour control?

If relying on the foil, then yes they should really be taped. If there’s a separate vapour control membrane then no need to tape.

Good point. We produce closed panels with a vapour membrane and sheathing.

We have to use fireproof sheathing with PIR and some clients won’t let use it all

Edited by blueg33 on Sunday 21st July 13:09

[MG-FIDO]

Thanks for the comments so far guys. In terms of vapour control, I don't think we've got anything in terms of vapour barriers beyond the DPM, DPC and then this foil coated Kingspan with a gap to the outer stone blockwork.

Do I take it I should be getting some aluminium foil then to tape the joints as opposed to something breathable?

[LooneyTunes]

Tbh, I don't do much with newer houses (I've never had major work done on one with cavity walls) so my Kingspan use in walls has been in built-on-site timber frames or internal insulation where the approach has been to tape joints with aluminium tape.

For something new I'd be checking any building regs docs for the extension, seeing how Kingspan recommend installing, or asking whoever had designed it.

[Panamax]

Just bear in mind that all this sealing of walls and windows is precisely why modern homes have to be constructed with "vents". Seal one bit - then cut a hole in another to compensate. Pretty bonkers really.

[Aluminati]

blueg33 said:

When we use PIR in the factory (off site built homes) we do not tape.

Most accurate answer here .

[blueg33]

Panamax said:

Just bear in mind that all this sealing of walls and windows is precisely why modern homes have to be constructed with "vents". Seal one bit - then cut a hole in another to compensate. Pretty bonkers really.

Controlled rather than random ventilation.

If you have no ventilation, in th uk, you get massive condensation issues especially with a cold roof which is the norm.

[Snow and Rocks]

blueg33 said:

When we use PIR in the factory (off site built homes) we do not tape.

Out of interest, how do you seal the boards against the timber/each other? From experience, even taking a lot of care, there's always a gap.

[blueg33]

Snow and Rocks said:

Out of interest, how do you seal the boards against the timber/each other? From experience, even taking a lot of care, there's always a gap.

Cut using a cnc saw to less than 1mm tolerance. Frames are assembled using a cnc framing machine with similar tolerances.

[Snow and Rocks]

blueg33 said:

Cut using a cnc saw to less than 1mm tolerance. Frames are assembled using a cnc framing machine with similar tolerances.

Ah that's interesting, not really relevant to the OP's extension I suspect though, I would always tape for all the extra cost.

I'd also pay attention to whoever's doing the fitting - it needs quite a bit of care to do properly.

[blueg33]

Snow and Rocks said:

blueg33 said:

Cut using a cnc saw to less than 1mm tolerance. Frames are assembled using a cnc framing machine with similar tolerances.

Ah that's interesting, not really relevant to the OP's extension I suspect though, I would always tape for all the extra cost.

I'd also pay attention to whoever's doing the fitting - it needs quite a bit of care to do properly.

Agree, its not relevant as we have machines that you just don't have at home, the framing machines are nearly as big as a tennis court. I was discussing PIR insulation with the production director this morning. I was generous with the tolerance, its more like 0.25mm.

However, if the OP orders enough extensions, we can make them

Framing Machine

Edited by blueg33 on Monday 22 July 10:50

Edited by blueg33 on Monday 22 July 10:51