Insulation in a slab

[Gaz1892a]

Thanks for the reply guys, 

 

Is there a special tape for taping it?

 

Good tip with the 100 and 50, makes life easier 🙂

 

What about the weep vents below DPC in the engineering bricks?

 

 

[Chanmenie]

17 minutes ago, Gaz1892a said:

Thanks for the reply guys, 

 

Is there a special tape for taping it?

 

Good tip with the 100 and 50, makes life easier 🙂

 

What about the weep vents below DPC in the engineering bricks?

 

 

Foil tape 

https://www.toolstation.com/aluminium-foil-tape/p81953
 

[saveasteading]

8 hours ago, G and J said:

Just looked that up.  Is it just for the ends of PIR sheets

Me too. For all 4 sides.

£3/m, so for a 2.4 x 0.6 board,  add £18. = £1.20/m2.

The site I found doesn't show the tech info esp u value.

Clever. It wouldn't do for wonky old rafters though.

[G and J]

So does gapotape then expand to fill any gaps round the PIR?

[saveasteading]

10 hours ago, G and J said:

does gapotape then expand

Ig looks to me that it is soft foam, so it squeezes inoto place.

Between rafters, better than expanding foam.

No need under floors except maybe on the final board cut.

[G and J]

44 minutes ago, saveasteading said:

Ig looks to me that it is soft foam, so it squeezes inoto place.

Between rafters, better than expanding foam.

No need under floors except maybe on the final board cut.

So it’s ‘squeeze-o-tape’.  Invented by Wallace one assumes!

[Dave Jones]

23 hours ago, G and J said:

Just looked that up.  Is it just for the ends of PIR sheets?

 

it gives an interference airtight fit as timber is rarely dead straight.

[G and J]

So, a sheet of 140mm PIR costs about £53.

 

Gapotape to line it costs £36.

 

Ouch.  That means I’ll spend about £2.5k on gapotape on our build on just the walls.  That’s a lot of Smarties.  

 

I think I need to research alternatives, I’ll start a new thread if I can’t find it covered elsewhere.  

 

 

[saveasteading]

Our solution was twofold. Nb this is for 100 year old rafters, so much twisted.

1. Instead of 100mm pir , use 2 x 50mm. That way it is easier to press them in.

2. After the first 50mm in in place, instead use mineral wool. It fits of course, and covers all the perimeter gaps.

 

Obv the wool isn't such good insulation, but the figures are OK, and the practicality makes up for it.