ICF'ers - Service void or no service void. That is the question....

[Mulberry View]

Our Architect drew a 50mm "Service Void". Now, I know it's not strictly needed with the ability to chase stuff in to the Polystyrene, but what have you done?

 

We have a Posi FF and roof, so plenty of service scope there.

 

I haven't got my mind off running an internal skin of PIR (25/50mm) instead in an attempt to lift the "weak" 0.24 u-value of the Nudura blocks, but I wouldn't do both the PIR and the void.

[Nickfromwales]

16 minutes ago, Mulberry View said:

Our Architect drew a 50mm "Service Void". Now, I know it's not strictly needed with the ability to chase stuff in to the Polystyrene, but what have you done?

 

We have a Posi FF and roof, so plenty of service scope there.

 

I haven't got my mind off running an internal skin of PIR (25/50mm) instead in an attempt to lift the "weak" 0.24 u-value of the Nudura blocks, but I wouldn't do both the PIR and the void.

Do you not have the XR35 block?

[Mulberry View]

5 minutes ago, Nickfromwales said:

Do you not have the XR35 block?

 

No, my build was spec'd in 2021 using their standard blocks. They advised us at the time not to bother with anything other than standard.

[Nickfromwales]

30 minutes ago, Mulberry View said:

 

No, my build was spec'd in 2021 using their standard blocks. They advised us at the time not to bother with anything other than standard.

Bum steer.....  

 

What's your AT score, or target AT score?

[Mulberry View]

27 minutes ago, Nickfromwales said:

Bum steer.....  

 

What's your AT score, or target AT score?

 

Not got it yet, but I really am hoping for 0.5.

 

The windows and most doors are Norrsken P31A which are capable of it apparently. The roof is a monopitch warm roof that has minimal opportunity for leakage. We'd said that if we don't hit our desired ACH that we'd consider Aerobarrier. I'm not planning to let that make me lazy though!

[Conor]

We fitted 100mm EPS on the outside to get our standard amvic blocks to 0.15. it's a LOT of work!!! But relatively easy. If you do PIR inside, you lose space and make fitting plasterboard more problematic - no guide lines for screws and screws will have to be something like 100mm+

 

We never did a service void, spark was happy to chase out with a hot wire cutter. Nothing else is really run in the external walls

 

[Nickfromwales]

2 hours ago, Mulberry View said:

 

Not got it yet, but I really am hoping for 0.5.

 

The windows and most doors are Norrsken P31A which are capable of it apparently. The roof is a monopitch warm roof that has minimal opportunity for leakage. We'd said that if we don't hit our desired ACH that we'd consider Aerobarrier. I'm not planning to let that make me lazy though!

Airtightness will trump insulation, and in winter, that, coupled with MVHR, will give you a plenty healthy-enough ROI on the house you've built, and then live in.

 

Adding IWI will be expensive, hard to execute perfectly (to achieve that 'goal'), and will impact on 2nd fix and GIA.

 

Leave it alone, you'll be spending a grand to save a hundred. Pointless (in actual, real life).

[Russell griffiths]

Forget fitting any additional insulation it is 100% not needed, forget the u value of nudura blocks for some reason it just looks poor on paper, they don’t add additional insulation in Canada you certainly won’t need it. 
 

you will wonder why you fitted a heating system at all once you move in, sort the airtightness and heating will be the least of your worries. 

[Russell griffiths]

We chased in and fitted conduit, loads of messy work, but I feel it makes the plasterboard feel more solid, by fitting the boards directly to the icf without a void. 
if you use sodal squirty foam behind the boards it bonds directly to the icf as well as screwing.