VLC where it shoud go?

[Tony C]

Hi, I have timber frame build up as :

(exterior)

12.5mm sheathing

120mm C24 frame with 120mm celotex

12mm ply

70mm C24 for service with 60mm celotex

VCL

12mm ply exposed interior

(interior)

 

Is this VCL location correct specified by architect?

When I see the construction picture on the website, it looks like it goes just after the main timber frame, then add service studs on the VCL layer.

 

 

 

Edited September 24, 2020 by Tony C

[BMcN]

Where achitect specified.  Normally it would be before service void but since your service void is filled with insulation it should go on the warm side of this.

 

Is the insulation to be checked out for services to run in? 

[Tony C]

  On 24/09/2020 at 16:57, BMcN said:

Where achitect specified.  Normally it would be before service void but since your service void is filled with insulation it should go on the warm side of this.

 

Is the insulation to be checked out for services to run in? 

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Thanks BMcN!

What do you mean by "checked out" ? Do you mean the insulation is suitable?

In this case VCL needs to be sealed with tapes the around the opening for the electric sockets and switches.

 

[BMcN]

You have a 70mm service void but it's filled with celotex - where are you putting the service in? Are you cutting grooves in the celotex?   Same goes for the electrical boxes. 

[ProDave]

I don't see that present 70mm as a service void, just an extra insulation later.

 

I would put VCL where architect says, all nicely taped, then 25mm battens for a true service void then plasterboard.

[A_L]

@Tony C, The VCL could be placed in either position. The deciding factor might be the number of penetrations of the VCL and the method of fixing the Celotex. Properly installed the foil surfaces of the Celotex have a greater vapour resistance than polythene vapour barriers with the usual penetrations and taped joints.

 

Section 7.3 and 7.5 here https://insulation-uk.com/assets/5405_dry-lining_bba-certificate_nov2018.pdf

Edited September 24, 2020 by A_L

[Tony C]

Thank you A_L for the useful info!

Between 120mm Structural studs would have tightly fitted celotex as it only has Rain water pipes in this void.

Between 70mm Service studs, there would be a little less celotex avoiding the area of mains cable, gas, water pipes etc. This gap area to be covered with sheep wool.

If I were to place VCL just after the 120mm Studs (the middle option), it will have less penetration. So this could be better option then?

 

 

 

 

 

[A_L]

  On 25/09/2020 at 09:44, Tony C said:

f I were to place VCL just after the 120mm Studs (the middle option), it will have less penetration. So this could be better option then?

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Whichever side of layer 15 (12mm ply) would give fewer penetrations.

[tonyshouse]

I don’t like 12mm ply, why is it there? 18 or not at all, 

 

I like vcl and air barrier combined and immediately behind the plasterboard 

 

Canada know how to do it right and inspect it before sheeting in 

[the_r_sole]

I know you didn't ask this, but what is the purpose of the inner 12mm plywood? Has the engineer asked for that?

 

[Tony C]

I

  On 25/09/2020 at 14:06, the_r_sole said:

I know you didn't ask this, but what is the purpose of the inner 12mm plywood? Has the engineer asked for that?

 

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I am not entirely sure. I assume the benefit will be having less cold bridging, enabling the studs to be offset each other.

 

[the_r_sole]

  On 25/09/2020 at 14:32, Tony C said:

I

I am not entirely sure. I assume the benefit will be having less cold bridging, enabling the studs to be offset each other.

 

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don't assume anything, ask whoever has designed it for you what the purpose of it is. (also 120mm isn't a common kit size, you would usually have 100 (89mm) or 150 (140mm))

Edited September 25, 2020 by the_r_sole

[ProDave]

Agreed this whole wall make up seems very strange.

 

You do not want to be trying to partly insulate a service void.  a service void should be there for services and does not need to be anything like 75mm.  25mm is plenty for cables and 45mm plenty for pipes.

 

All services in an ideal world would be inside the sealed envelope so no penetrations through VCL except where services run outside e.g. to outside lights, sockets or an outside tap and these would be sealed.  To even be thinking of sealing around switches etc is madness, you should not need to do that.

 

It seems like your basic frame structure is too thin. use something thicker to get all the insulation you need within the frame, then a thin service void.

 

the 12mm "ply" on the inside of the frame might be the racking layer in a case of externally clad timber frame.  Mine is like that, except because we are considered "exposed" the SE specified 2 layers of 12mm OSB3 as the racking layer with staggered joints.  Our VCL goes immediately over the racking layer, then the 25mm battens for the service void then the plasterboard.

[Tony C]

  On 25/09/2020 at 16:17, ProDave said:

Agreed this whole wall make up seems very strange.

 

You do not want to be trying to partly insulate a service void.  a service void should be there for services and does not need to be anything like 75mm.  25mm is plenty for cables and 45mm plenty for pipes.

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Hi ProDave, Thank you for the concern.

I understand that this is not conventional build-up. Its due to rather special design our achitect has worked on the timber frame.

no5. area in below 3D image has the build-up as I posted earlier. no4 (high area) is interesting open 70mm studs area. To align both area, the architect made service void 70mm.

I guess the Timber Frame could have been 170mm then you don't need to insulate this 70mm service void.

But the loss of 50mm of wall everywhere is not desired as I am building in London, the land size is limited!

Hope this make sense.

I will place VCL on interior side of number 15 (plywood 12mm).

 

 

 

[Tony C]

  On 25/09/2020 at 14:06, the_r_sole said:

I know you didn't ask this, but what is the purpose of the inner 12mm plywood? Has the engineer asked for that?

 

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I asked SE and architect and now I am omitting this 12mm plywood. Architect thought it might be useful for securing the plumbing pipes etc !?

[the_r_sole]

  On 27/09/2020 at 11:38, Tony C said:

Hi ProDave, Thank you for the concern.

I understand that this is not conventional build-up. Its due to rather special design our achitect has worked on the timber frame.

no5. area in below 3D image has the build-up as I posted earlier. no4 (high area) is interesting open 70mm studs area. To align both area, the architect made service void 70mm.

I guess the Timber Frame could have been 170mm then you don't need to insulate this 70mm service void.

But the loss of 50mm of wall everywhere is not desired as I am building in London, the land size is limited!

Hope this make sense.

I will place VCL on interior side of number 15 (plywood 12mm).

 

 

 

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Is that your house design? looks really sweet give us more!!