Is my VCL Pointless?

[Onoff]

Photo heavy, but please bear with me!

 

I gutted the bathroom as many know (and are possibly trying to forget!  ). This meant digging up the concrete floor down to a depth of nearly 18". The ceiling joists doubled as a flat roof originally so were about 6" higher one end. These I ditched, built up the wall level in shuttered concrete and put new joists in. The roof space above is one of the uninsulated hip ends used just for a bit of storage.

 

 

The joists btw are 145mm deep.

 

I then insulated between the joists with 100mm of PIR:

 

 

 

The intent is to add another 50mm of PIR.

 

Here it is "finished" with foil tape over the joists too:

 

 

The five openings you can see are for 4 spots (over wc, basin, shower and bath). The BFO cut out is for a ceiling mounted body dryer.

 

I then put up a continuous, VCL against the foil face and moisture resistant plasterboards over the top:

 

 

 

Of course, above I've 5 uninsulated "pockets".

 

Been putting the lights / dryer off over the issue of puncturing my lovely draught free VCL!

 

Now thinking of lighting on the back of that flat panel thread the other day  I just had it originally in my head to fit Aurora downlights that have always been my go to. I've done them for myself and elsewhere and simply fitted a fire hood under the fluffy, roll type insulation. I'll openly admit where I've come across PIR between joists before I've just cut a chunk out fitted a hood. Never given it much thought...until now. But this is my house now and I've a better understanding thanks to here that that creates an obvious cold spot.

 

Is it a goer albeit a long winded one to:

 

- Cut the membrane in the pockets above the plasterboard. Lap the membrane up the sides of the PIR.

- Line the sides of the 5 pockets with fire resistant plasterboard. Tape, extra VCL etc.

- Cap the pocket off with a sheet of fire resistant plasterboard.

- Continue the VCL over the top of the plasterboard

- Lay 6" slabs of PIR above this extending say 6" all around the edge of the pocket. 

 

The VCL will be as continuous as I can get it. The 6" insulation will be staggered for want of a better word.

 

I'll then have in effect 6" deep pockets for the downlighters and body dryer.

 

Cable/conduit entries into the pockets will be siliconed. 

 

The body dryer basically just takes in cold air from the room, runs it over an element and pumps back out into the room.

 

It's the only way I can think of keeping the VCL continuous and maintaining the insulation depth.

 

Cheers

 

 

[Crofter]

Could you fit a fire hood, tape the VCL to that, and just fill the space above/around it with expanding foam? Would save a lot of faffing around building little boxes from PB.

[Nickfromwales]

What do the MI's for the drier say regarding it being boxed above ?

[Onoff]

6 hours ago, Nickfromwales said:

What do the MI's for the drier say regarding it being boxed above ?

 

They don't per se give clearance dimensions:

 

Important:  Loft  insulation  that  occupies the  space  required  for  the  dryer  should  be removed  or  rolled  back.  The  unit  must  be installed  on  flat  surfaces  both  above  and below  the  ceiling  otherwise  difficulty  may  be encountered  when  fitting  the  ceiling  cowling and  subsequent  operation  of  the  unit  may  be impaired. E B D Perforated  line B A E B C B Key Fig. Fig. a.   Air intake. B.   bolt hole for solid ceiling. C.    Communications cable hole. D.  Water drainage. E.    Exhaust nozzle. C note:  To  install  the  body  Dryer  to  a  concrete ceiling  with  an  additional  suspended  ceiling  or a  bathroom  with  a  timber  flat  roof  construction you  will  need  to  use  an  optional  fitting  kit  (not supplied).  Contact  Triton  Customer  Service  for further  details. Once  installed,  care  should  be  taken  to  ensure the  immediate  area  around  the  body  dryer unit  within  the  loft  space  remains  a  clear  of  of obstructions  and  that  other  items  are  not  placed against  the  unit  or  in  close  proximity

[Nickfromwales]

Where does it get the air intake from? 

[Temp]

Could you fit flat panel LED lights instead? Then only the wires have to puncture the VCL and you can seal those. Most other lights need some ventilation.

[Crofter]

15 minutes ago, Temp said:

Could you fit flat panel LED lights instead? Then only the wires have to puncture the VCL and you can seal those. Most other lights need some ventilation.

 

That crossed my mind too. The ones that @Stones posted about in his blog are only 15mm deep. I haven't checked to see if there are IP rated versions, though.

[PeterW]

The ones he used are IP25 according to the information on the website but are classed as SELV as they have a transformer in the roofspace. 

 

Whilst only 15mm they need a hole through the board so the VCL would need to be able to flex above them.  

[Onoff]

Cheers all.

 

Those 15mm flat panel ones; I'd be cutting out from below so there's no way I wouldn't accidentally puncture the VCL. Then even they have heatsinks on I think don't they? I don't fancy that against the VCL.

 

One compounding factor that might actually assist is that I'm running all the new cables in galv tube back to the cu. (Rat/squirrel paranoia).

 

Large, galv, upturned adaptable boxes might be the way to go for the lights (even if flat panel) as nice and square to then VCL over the top and tape to the stuff above the plasterboard. A nice mechanically protected pocket then!

 

 

 

Edited May 23, 2017 by Onoff

[Onoff]

Here's the body dryer:

 

 

Two elements, above the ceiling and below:

 

 

Air is drawn in through the circular intake, it passes over the 4.5 / 9kW heating element and vents downwards via the rectangular exhaust with has a fancy baffle to "swirl" the warm air curtain in a sort of vortex: