Insulating the fascia of a warm flat roof and VCL / VCB?

T

TofuSpaceship

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Unfortunately we are already amidst our renovation job, which includes also the redoing of a flat roof and upgrading it to a warm roof and I have a question regarding the insulation of the fascia, I find shocking that there isn't really much material on the web about it!
The new joists have been installed today and the more I look at the configuration, the more I get perplexed.
If we look at the diagram below

warm-roof.jpg


then two questions come to my mind:

1. how do you prevent for the end of the joists (just behind the fascia) to become cold themselves? Shouldn't you cap them with some insulation? Above they are all nice and warm but then the bits touching the fascia are going to become cold!
2. how do you lay the VCL if you are to insulate the end of the joists? Something like the below?:

image.png


But then how do you actually physically lay insulation and VCL in this funny shape? And most importantly, how do you fix the fascia?

Also, what do people mostly use as VCL, simple plastic sheeting?

Thanks
 
tofu, why not put up photos of above and below whats existin at your eaves.
joists typic run through and pick up the fascia.
having a soffit can change how the insulation is done at the eaves and at the verges.
 
catlad said:
Put your vcl under your joists and insulate behind fascia's.
Click to expand...
That is an interesting point, I am wondering why in all the diagrams the VCL is never under the joists though?

catlad said:
Have a look at the Celotex site they have some good diagrams.
Click to expand...
Had a look but their drawings don't seem to answer my doubts

bobasd said:
tofu, why not put up photos of above and below whats existin at your eaves.
joists typic run through and pick up the fascia.
having a soffit can change how the insulation is done at the eaves and at the verges.
Click to expand...
The roof has been re-done from scratch and changed from pitched to flat and actually my original question can be regarded as more academic than practical as I am afraid I have little room to have builders change design now and we have had some little frictions here and there in the past already re:insulation.
Anyway, here is a picture, is not a great one sorry, I am not on site at the moment.

image.png


The inside is obviously to the right of the pictures and over the room there are joists running parallel to the cavity wall.
From what I gathered the fascia will be installed on those overhangs.
Essentially if you are laying a warm blanket on top of these joists, how do you prevent cold from coming in through the fascia and for that cold to actually trickle down into the cavity? Rock wool I suppose? But then all that rock wool will be below the VCL? Unless the fact that it is sitting on a cavity wall means it is going to be aerated enough?
 
thers a few odd lookin things in your photo. why not get competent person on site to give you some advice?
 
bobasd, do you mind quickly commenting on a couple only of odd things?
I don't see the option of calling someone competent over mainly because of three or four annoying reasons:
. the work has progressed
. the work has already been delayed quite much more than expected so wouldn't like to hold it back even more
. how do I find a person which is competent, really?
. even If I had this contact, this person wouldn't probably be able to come round in the next day or two
 
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