Maintaining air tightness with downlighter

[Annker]

In summary I am fitting an intello plus AVCL to 1st floor ceiling joists, these rooms will have downlights fitted in the ceiling which are about 120mm in length.

I cannot create a service void below the AVCL to accommodate the downlights, therefore they will be located within the ceiling joist void, hence above the level of the AVCL.

 

There is an off the shelf solution like these however I do not see any mention of them being used by builders on this forum.

I am a carpenter so I could make plywood boxes into which the AVCL is folded up into.

 

I'm sure this must be a common detail but I can't find much detail on solutions so keen to hear what others have done to maintain the air tight layer in this situation.

 

 

Edited 3 hours ago by Annker

[JohnMo]

18 minutes ago, Annker said:

these rooms will have downlights fitted in the ceiling which are about 120mm in length

Change the design of down lighters, you can get them sub 20mm if you want. Make life simple and not complex

[Iceverge]

I had to recess the mounts for my MVHR terminals.

 

I just ran a piece of OSB between the joists on battens. The bottom face of it was about 50mm above the lower face of the joists. I folded my airtight membrane up and taped it to the OSB .

[ProDave]

What stage of the build are you?

 

Why not put the VCL across the top of the joists?

 

Or as above slim downlights.  Some will literally fit in the thickness of plasterboard.

[Annker]

4 minutes ago, JohnMo said:

Change the design of down lighters, you can get them sub 20mm if you want. Make life simple and not complex

Have you a link to lights that small, sounds like a great option if required.

 

I'm afraid shallowest light I'm using is ~90mm

 

[Annker]

8 minutes ago, Iceverge said:

I had to recess the mounts for my MVHR terminals.

 

I just ran a piece of OSB between the joists on battens. The bottom face of it was about 50mm above the lower face of the joists. I folded my airtight membrane up and taped it to the OSB .

Yes this is a good solution for me, fully constructed boxes probably aren't necessary just need some bit of background to taped the vcl to

[Annker]

9 minutes ago, ProDave said:

What stage of the build are you?

 

Why not put the VCL across the top of the joists?

 

Or as above slim downlights.  Some will literally fit in the thickness of plasterboard.

Its a retro fit/renovation.

I think it would be near impossible to seal the perimeter of the VCL if it was fitted above the joists, and also more difficulty to fit the insulation to be laid between the joists.

 

Photo below for reference, as you can see its very easy for me to fit the vcl from below.

I have a thread going on IWI, my design was largely gathered from very useful info received on the forum and I will updated it once that phase of works is complete  

 

[Nickfromwales]

For a clients build which had some deep lights and mist heads, I just used an off-cut of duct (125mm for mist heads iirc) and some AVCL to create ‘top hats’, and then taped these into cutouts.

 

 

These were done after the cellulose had been blown in, but wasn’t too difficult or messy as I could push back and compress it enough for it to stay in place for cutting the membrane.

 

A bit of cellulose fell out, but prob not equal to what I needed to remove to create some clear area for the recess, so all good. 
 

Doubt you could do this approach before insulation gets blown in, unless you somehow support these when the cellulose gets pressure filled; otherwise your inny’s would become outy’s. 

[JohnMo]

35 minutes ago, Annker said:

Have you a link to lights that small

The first I found - 17mm deep, there are loads on the market. The bigger dia ones are way better than a 101 small ones doted about everywhere. 

https://www.simplelighting.co.uk/6w-circular-led-panel-120mm-diameter-warm-natural-cool-white-led/

[Annker]

30 minutes ago, JohnMo said:

The first I found - 17mm deep, there are loads on the market. The bigger dia ones are way better than a 101 small ones doted about everywhere. 

https://www.simplelighting.co.uk/6w-circular-led-panel-120mm-diameter-warm-natural-cool-white-led/

Interesting, I wasn't aware such slim lights were available.

 

I should have clearer that I have a somewhat specific light design intent, wrt downlighters I want trimless, small diameter and in some instances directional.

For what I have seen ticking them boxes means a fitting with a min depth of ~90mm 

 

As aside on a previous project I worked with John Cullen Lighting, they were client appointed and initially I thought Lighting design was a makey uppy discipline to extract money out of wealthy home builders but I learnt a lot from them and a good lighting design certainly elevates a project to the high end.

   

 

[Russell griffiths]

In that case you will need a full depth of joist box all taped up. 
make them bigger than needed.