WoodFibre & Air Tightness

Foe those of you putting woodfibre over the rafters, did you all use a an tightness membrane above it ?

If so did you also tape it ?

Thanks

Calahonda52

Follow the details for the product, such as what is detailed here
http://www.ecologicalbuildingsystems.com/Ireland
of nearer to you http://www.partel.ie

and forgot about what anyone else did unless they did as required!

This is strictly table d'hote and not al a carte

Calahonda52

Calahonda52 wrote: »

Follow the details for the product, such as what is detailed here
http://www.ecologicalbuildingsystems.com/Ireland
of nearer to you http://www.partel.ie

and forgot about what anyone else did unless they did as required!

This is strictly table d'hote and not al a carte

I have actually done the air tightness course with both companies, the instructors in the same companies differ on opinion.

Some say you should use the air tightness membrane and tape it, others say it is over the top as you would already be making the woodfibre layer air tight.

To confuse me even more the manufacturers have images of it done both ways. It would make more sense to me to make the woodfibre layer airtight but i was told by an instructor that not all the tongue and groove boards are airtight when fitted. This would then mean using vana tape on the valleys for the wood fibre layer, and then doing it again for the wind tightness layer.

I suppose im looking for practical advice on those who have already done this ?? My engineer is absolutely clueless, it feels more like im teaching him as we go along, so i have stopped asking him any questions as he doesn't know. He has never even seen a warm roof in his life. Hence why im trying to educate myself, very very disappointed in the so called building professionals so far. Of the ones that i have so far met, there lack of knowledge, research, professionalism and courtesy would not be acceptable in any other industry.

My roof build up is
1) Plaster
2) 50mm cavity with metac
3) Intello plus
4) 180mm metac in a 175mm rafter
5) 24mm steico board
6) counterbatten
7) Slate

Calahonda52

Best to keep emotions and other non tech stuff out of the posts: we deal best just with facts here

So you are mixing and matching!

What is the business case for intello plus? which is a super premium product?

What is the vapour resistance of the steico board?

In any event the layer in question now that you have clarified the issue a little is the (exterior) wind tightness layer as opposed to the (interior) airtightness layer. so maybe edit the title

Post the images you mention and lets see.

In addition have you no slating lathes?

Calahonda52

Calahonda52 wrote: »

Best to keep emotions and other non tech stuff out of the posts: we deal best just with facts here

So you are mixing and matching!

What is the business case for intello plus? which is a super premium product?

What is the vapour resistance of the steico board?

In any event the layer in question now that you have clarified the issue a little is the (exterior) wind tightness layer as opposed to the (interior) airtightness layer. so maybe edit the title

Post the images you mention and lets see.

In addition have you no slating lathes?

Yip, forgot to add the slating laths to the list.

The Intello plus was recommended by Ecological building systems as a airtight/ partial vapor barrier,

The Steico board is fully water vapor open
http://www.ecomerchant.co.uk/steico-universal-wood-fibre-insulation-sarking-board.html

This is Solitex over woodfibre, edit its actually under the woodfibre here. But its the same point, is there need for both ?



Here there is only solitex where its needed, assuming that the woodfibre is airtight.

Calahonda52

Yep, I thought you would post these!

look closely at the first picture, this is showing two different setups so it is not correct, imo, to say that the solitex is under the wf.

The one here is better
http://www.ecologicalbuildingsystems.com/Ireland/Products/Gutex/Roof

The question is whether GUTEX Multiplex-Top which is used in the second image, or the the sheating on left in first image is the same performance wise as your Steico board, which in the link shows some sort of membrane under it.

The overtop sheating is primarily a thermal bridging consideration when using the more solid woodfibre stuff in-between the rafters..
Did you tell ebs that you were using metac when they speced the intello plus?

I don't see the value in it with metac because metac cannot absorb the moisture the way the wf does.

I am assuming metac isa glass fibre product so the gf fibres will not act like the wood fibres.
The make up has to as I said already one system and not mix and match and the science is importnat.

IMO a option is to use the solitex outside and maybe use a less expensive airtightness layer in side because your big threat is heatloss through the metac by negative pressure on the roof when windy.

re the gaps in the T&G, you can caulk them as per the ebs website