How do they make a Part L door?

I've tried to JFGI but have had no success so thought I'd ask here.
Probably just a hypothetical question but, looking for a replacement timber door, I see that some are 'Part L', as in they have a low enough U-value to satisfy some arbitrary rule that most of us ignore. (And quite within the rules if the frame stays in place.)
Most of them pretty unattractive and none of them what I need, but I got to wondering how they're built to achieve that status. There's not much room to fill a door with PIR or something, but maybe that makes enough of a difference. Would have thought that would make them a bit light-weight though for an exterior door.
Any ideas folks?
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GMM wrote:

Is this link of any use?
http://www.igdoors.co.uk/assets/docs/IGDoorsBrochureV25.pdf
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On 04/12/2013 20:51, Cash wrote:

Interesting selection, but they all seem to be composite or steel. I can imagine ways of insulating those materials effectively, but it's timber I'm particularly interested in as if I (or anyone here really) wanted to build one from scratch, timber is the likely material of choice.
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On Wednesday, December 4, 2013 10:00:16 PM UTC, GMM wrote: ...

I got CB approval by calculating the insulation of the door I proposed to make and submitting it. The proposal was a sandwich containing Celotex but was made to match the doors elsewhere in the house.
email me on laws at bcs dot org uk if you'd like me to send you what I sent them.
Robert
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On 05/12/2013 08:59, RobertL wrote:

Thanks Robert, that would be very interesting. Will send a mail now.
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"GMM" <GlMiMa-AT-yahoo.co.uk> wrote in message

This is one I made. http://www.flickr.com/photos/ara-chloroptera/6174139073/in/set-72157627608971673
Essentially a timber frame filled with rigid foam. The face could be any material/thickness you want for security.
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On 05/12/2013 06:36, harryagain wrote:

Indeed it could be but it has to fit with the rest of the house so, like most people I suspect, I'm constrained to a 'normal'overall thickness.
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On Wednesday, December 4, 2013 7:42:28 PM UTC, GMM wrote:

Will it have DG and be subject to horizontal rain, particularly wind driven ?
If so, get / make a door which has proper drain holes at the bead base (5-6 mm as I recall), a correct drain profile (5 degrees as I recall) and uses a glazing spacer to lift the DG panel out of the wet area?
There is a BS standard covering this, and countries such as NZ and others h ave detailed design documents from their own testing.
Otherwise you may find water coming through the internal bead and your nice engineered door swelling and leaking all over the place. I know :-)
Making your own is not that difficult - I plan on doing the same, going fro m 44mm to something deep enough to get a bit of celotex or XPS in the lower panel. Shockingly the lower panel on some is so thin it just runs in water when the humidity is actually quite low, really really thin stuff.
I guess the most waterproof door would be a very thick one (60mm?) with a S G outer (set in whatever putty substitute) and a DG inner which is removeab le should the need arise. It would eliminate all the nonsense and achieve T ripple Glazed (TG).
For some reason the TG I have seen, even in timber, always use a DG outer a nd SG inner. Considering the inevitable issues with sealing/draining timber DG I would have thought SG outer was better. Perhaps it is for security or coatings.
You can change the door-only under Part L, and there is a <50% glazed area rule too. I am not sure you can change the frame-only when that frame compr ises a glazed portion (eg, replace all the timber components with deeper to permit celotex in large timber areas without either getting ugly inside or outside re surface locks and hinge positioning.
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On 06/12/2013 21:47, snipped-for-privacy@ntlworld.com wrote:

The one I have in mind (if I tackle it) is actually well out of the weather as it's between the back of the hallway and the conservatory, so it wouldn't see any rain. The conservatory, which is ultimately on the list for improvement, gets down to outside temperature pretty swiftly as it's very well ventilated, and it's clear that we lose significant amounts of heat by that route. Of course, a good part of the problem would be cured by any half-decent new door, as the existing one is slightly warped so has proved difficult to draught proof. Naturally, nobody sells a door that's a good match for it in the size, which is what got me thinking about the possibility of building one. In that case, it would make sense to make it as close to well insulated as possible. I'm not really concerned about the rules, as nobody would ever know I had changed it in a position like that, but they do provide some useful targets to aspire to.
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I'd be interested to see how you get on, please post back if you go ahead. I have similar plans in mind but for a laminated security door rather than an insulated one. My biggest concern is the long term stability of the build, I don't want to go to all that bother and then have it warp by even a couple of mm.
If you were to use 10mm WBP ply outer skins then you would have room for an inch of celotex within a 46-48mm standard beefy door. As well as a solid border and beefy fills for locks and hinges I'd suggest an internal cross or similar made from edge on battens, bonded and fixed through to join the skins to enhance rigidity and hopefully stability.
If you've had trouble with draughts then the laminated construction would lend itself to making it a rebated fit with double seals, one against the main door face and one against the rebated one.
--
fred
it's a ba-na-na . . . .
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On Saturday, 7 December 2013 12:35:25 UTC, fred wrote:

Airogel insulation would allow the thickness to be reduced.
John
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snipped-for-privacy@gmail.com writes

Not something I have come across before, interesting thank you.
http://en.wikipedia.org/wiki/Aerogel
In summary, about 55% more effective per unit thickness than PIR foam.
Expensive which is not surprising considering how it is made but it will limit its use to specialist areas. Let's hope it becomes cheaper as it becomes more mainstream.
For the door app, a single layer of 10mm Aerogel would be about 60% as effective as 1" celotex and cost about 40quid, with two layers being 25% more effective but costing 80quid.
My external doors here are 48mm so I'd prob stick with a celotex core but 20mm Aerogel would either allow a thinner door or the use of beefier 12mm ply skins to make 44mm overall.
--
fred
it's a ba-na-na . . . .
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On Friday, December 6, 2013 9:47:07 PM UTC, snipped-for-privacy@ntlworld.com wrote:

How does rain get to be horizontal, *without* being wind driven?
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I recently made something like this; I needed a door for the garage I'm (slowly) converting into a workshop and it was not a standard size. Because the workshop is not ready yet I only had limited facilities -and skill! :( I made the outline from standard size timber 38mm thick with 3 horizontal members and 'Z' bracing from narrow strips of wood. I put a triangular gusset where the lock would be fitted. I used dowel joints - (limited skill and facilities)' I faced both sides with 5.5 WBP ply and fixed this with drywall screws at 3" spacing all round the outer edge and into the horizontal and diagonal members. I drilled a number of 20mm hole in the inside skin and used them to inject expanding foam into the voids. It has been up for 6months now and, touch wood, seems to be satisfactory. If I was doing it again, I would probably use thinner ply for the skins and would try to find some marine ply at a reasonable price.
--
Chris Holford

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