Insulation of Tricky Voids?

[Duncan62]

Hello all, we have cripple studs in our TF IBEAM design.

My question: how best to get insulation into these?

I'm don't want to reinvent the wheel, so please chime in with how it's done!

 

The plan is for woodfibre/cellulose blown insulation in the main voids.

 

Here is the cross section

 

FIRST idea is to make holes either side, with an adjacent hole on the inside air tightness board, and feed the pipe through the first void into this difficult one. Fill. Repeat up the wall.

 

SECOND idea is to fill with 100mm Rockwool in the 88mm void - As it is being constructed. The Rockwool will friction fit on one side as the second is positioned and fixed into place.

 

Thank you!

 

[IanR]

47 minutes ago, Duncan62 said:

I'm don't want to reinvent the wheel, so please chime in with how it's done!

 

Insulated I-Joists

 

Edited August 2, 2024 by IanR

[joe90]

Either will work but the advantage of no 2 is you know there is no voids

[Alan Ambrose]

+1 keep it simple

[IanR]

4 hours ago, Duncan62 said:

in the 88mm void

 

What's making you go with a 97mm flange width? I have 47mm on my walls. I only went to 72mm of the roof as JJ didn't do a 47mm or 63mm on a 350mm deep I-Joist 

[Duncan62]

3 hours ago, IanR said:

 

Insulated I-Joists

 

What type of insulation are you using here?

[IanR]

3 minutes ago, Duncan62 said:

What type of insulation are you using here?

 

They're delivered pre insulated (at request), using a fibre board type insulation.

[Duncan62]

19 minutes ago, IanR said:

 

What's making you go with a 97mm flange width? I have 47mm on my walls. I only went to 72mm of the roof as JJ didn't do a 47mm or 63mm on a 350mm deep I-Joist 

 

Two letters: 

 

SE

[Duncan62]

26 minutes ago, Alan Ambrose said:

+1 keep it simple

 

3 hours ago, joe90 said:

Either will work but the advantage of no 2 is you know there is no voids

 

Great. I thought so. I'll get rockwool slabs to fill them.

[IanR]

12 minutes ago, Duncan62 said:

 

Two letters: 

 

SE

 

I'd challenge that. Unless it's allowing you to go 600mm centres, it's going to cost you quite a bit extra.

[Duncan62]

37 minutes ago, IanR said:

 

I'd challenge that. Unless it's allowing you to go 600mm centres, it's going to cost you quite a bit extra.

It is. Fortunately.

[Duncan62]

The I-Beam flange depth is 210mm.

 

If I cut in HALF 455mm NyRock® Cavity Slab 032 (or similar)

 

455mm / 2 = 227mm

 

Will this friction fit nicely?

Or is 17mm excess not enough for a nice friction fit?

[scottishjohn]

slight change of subject 

there are some new houses near me that they built the TF then fixed 12" slabs of polystreyne  insulation to exterior then rendered  it

so no messing with voids and tricky bits 

thought it was quite clever

[markocosic]

Hope they're airtight internally...

[Iceverge]

On 05/08/2024 at 23:09, scottishjohn said:

slight change of subject 

there are some new houses near me that they built the TF then fixed 12" slabs of polystreyne  insulation to exterior then rendered  it

so no messing with voids and tricky bits 

thought it was quite clever

 

Caution with this approach, @ProDavehad a few issues with EWI straight onto insulation. I believe it's no longer accepted as durable enough in Norway with similar amounts of driving rain so I'd steer clear of it personally. 

 

However a good layer of EWI on any structure, espically timber frame can only be a good thing in my opinion.  You get excellent thermal bridging numbers and total continuity of insulation. 

 

Moreover it'll keep the timber itself at a really consistent temperature, well above the dew point so it should last forever if no bulk water gets in. 

 

 

 

[Iceverge]

On 11/08/2024 at 13:40, markocosic said:

Hope they're airtight internally...

 

Not a huge issue with all the insulation outboard as the dew point will never be near the timber structure. 

 

The only consideration I would be worried about from that point of view is that the insulation boards are fitted with all joints staggered in 2 layers with a good quality low expansion foam between all joints. 

 

Otherwise you might get moist internal air escaping through the gaps and condensation at the render/insulation interface causing render failure. 

 

Better in any case to have a ventilated rainscreen in my opinion. 

Edited August 14, 2024 by Iceverge

[ADLIan]

Render direct onto insulation direct onto timber frame is not accepted practice - see Building Regs and any good guidance on the design of TF. I believe this is a result of failures observed in the USA and Canada that took many years to become apparent. Should be a rainscreen system using render board with ventilated cavity behind. Not sure I’d want polystyrene in this system however due to fire risk.

[scottishjohn]

5 hours ago, ADLIan said:

Render direct onto insulation direct onto timber frame is not accepted practice - see Building Regs and any good guidance on the design of TF. I believe this is a result of failures observed in the USA and Canada that took many years to become apparent. Should be a rainscreen system using render board with ventilated cavity behind. Not sure I’d want polystyrene in this system however due to fire risk.

Ok then 

attach cement board to insulation ,then render

I was only commenting on what I saw locally on some new houses 

 maybe they sheeted them and rendered so quickly I never saw what was done when passing them 

 

[markocosic]

9 hours ago, Iceverge said:

 

Not a huge issue with all the insulation outboard as the dew point will never be near the timber structure. 

 

Assuming continuous heating in winter; no cooling in summer?

 

Enough air leakage condensed water can eventually run back towards the wood?

 

Doesn't need much ventilation/drainage layer to avoid issues.

[Iceverge]

12 hours ago, markocosic said:

Enough air leakage condensed water can eventually run back towards the wood?

 

Where is this water condensing exactly?

[markocosic]

Back of the render; edges of render?

[Duncan62]

Thank you all.

Following up: how is best to ensure insulation stays in place during construction?

 

Will use Rockwool RW3 60kg/m3 insulation, in 100mm/50mm/25mm depths as required.

600mm wide, 1.2m long.

This is cut into 240mm/240mm/120mm strips, 1.2m long.

This will nicely fit the 220mm void. (doubled up when using 120mm width strips, obviously)

 

Shall I simply apply wood glue to the inside of the I Beam, then lay the cut Rockwool strips - and wait for it to stick?