# External Insulation around Doorway Canopy of Corpo House



## GORL (16 Sep 2011)

Hello Folks, 
Would be most grateful for advice / opinions.
Going to get external insulation done on two up two down 50s corpo house.
All fine and straightforward enough except for the front projecting canopy over the front door.  The advice we're getting is that we need to insulate that as with the rest of the house, otherwise we'll get a cold bridge.
I've seen many of these done, and in my opinion it ruins the look of the house.  The canopy ends up looking bulky and blocky and loses all its 50s style.
I don't want to be too precious about it, but I think the modernist look and proportions of the canopy projections of the corpo houses give them their character.
Anyway, if there's no alternative I'll go ahead and get it insulated but I'd prefer if there could be some solution whereby I don't have to end up with a doorway canopy that looks like a michelin man.
If anyone has had it done and come up with a design solution I'd appreciate any tips!
thanks


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## hastalavista (16 Sep 2011)

what material is the canopy?
How is it fixed to front of house?
How is it supported?
Could it be taken down and refitted?


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## GORL (17 Sep 2011)

Answers to Questions:
1. The canopy is made of concrete with, I'm assuming, steel reinforcements inside.
2. I'm guessing that the steel reinforcements that are connected to the wall of the house in some way but this is hidden by the concrete.
3. There is no bracket or other external support so it can only be supported by the horizontal attachment to the house wall.
4. Assuming that we could remove the canopy intact can anyone suggest how we would re-attach it to the outside of the external insulation?
There are thousands of these types of houses with this canopy partuicularly around Dublin so perhaps someone has experience in removing the canopy or that would know how the canopy is attached to the house wall?


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## hastalavista (17 Sep 2011)

Thanks for the reply: its a cantilevered  steel reinforced concrete slab which you are stuck with, hence why people have gone with the Michelin man look


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## GORL (17 Sep 2011)

Thanks hastalavista - yup, that's about the size of it.  But there must be solutions?  Anybody? Or if we just leave it uninsulated, is the cold-bridge from a small canopy over the front door gonna be a big problem?


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## hastalavista (17 Sep 2011)

GORL said:


> Thanks hastalavista - yup, that's about the size of it.  But there must be solutions?  Anybody? Or if we just leave it uninsulated, is the cold-bridge from a small canopy over the front door gonna be a big problem?



It depends how the house is built but it is  a problem as the cold will travel  in behind the insulation on the wall.

If it were my house I would cut it off with a con saw


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## onq (17 Sep 2011)

I know the detail well and I agree with you about keeping the look being important.
Although hastalavista's suggestion appears brutal at first reading it may hold the solution.

One possibility is to remove the concrete canopy and get an insulated one fabricated to match in metal.
This would be similar to the insulated replacement window cills some external insulation companies are offering.


ONQ

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## GORL (18 Sep 2011)

Thanks onq
That's exacty the kind of thing we were thinking of.  Haven't a clue where to start regarding geting a matching one fabricated in metal.  Could you suggest what kind of tradesperson / supplier would we need to be contacting?  Many thanks again


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## onq (18 Sep 2011)

You're very welcome.

I think there may be a bit of design work in this.
At some point in this process, you may need to take some professional advice.

- The support for the new canopy and its mechanical fixing.
- The wind resistance required for this now, lightweight canopy.
- The weathering detail where the the canopy meets the wall upstand.
- The finish of the canopy and the means of fabrication and material selection.

As I stated, some of the insulation suppliers use local metal fabricators to supply insulated cills.
There is a degree of research required in terms of what materials such a highly exposed element should be made from.

Metal, plastic and fibreglass carcasses will require to be painted, lightweight construction has no mass to resist wind loading so needs secure fixing, etc.
Metals need particular care when being formed into shapes, expscially if welds are used because these can corroded in exposed conditions.
Even metals like aluminium are high conductors of heat, so there is a question mark over this solution.

Poltruded fibreglass has been gaining some traction as a material recently
Here is an article on protruded fibreglass, which may be useful.
I have no direct experience of it, but its good to research.


ONQ

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All advice on AAM is remote from the situation and cannot be relied upon                              as a defence or support - in and of itself -         should       legal        action    be      taken.
Competent legal and building professionals should be asked to advise in                              Real Life with rights to inspect and issue       reports    on     the         matters    at      hand.


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## hastalavista (18 Sep 2011)

Just to add, now that the goggles [ not googles! ] are on and I hear the con-saw ticking over; bearing in mind  all that onq has penned on the issues around light weight structures, have you considered a porch?

I have seen this solution used where the porch is built as a stand alone structure outside, and touching but not fixed to the external insulation and it is just weather flashed to the insulation.

In fact the porch was built  out from the house by the thickness of the insulation first and plastered etc.

If I recall correctly its a Passiv Haus detail


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## onq (18 Sep 2011)

Well, just to consider this a little...

Staying with the canopy for a minute - 

You could use metal angles supporting a concrete canopy set out the depth of the insulation off the wall.
The heat transfer would be limited to the total cross section area of the supports.
The insulation would pass behind the rear edge of the canopy.
The supports would be surrounded by insulation.
Lot of weight to cantilever though.

Going with the porch detail -

You could design the porch roof and/or side wall so that it looks like the original canopy was incorporated into it.
If you're semi-detached, and your neighbour agreed to match it, you could have a nice "set piece" entrance.
If not you could just return the horizontal down the side and some council houses have this detail already.

ONQ

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All advice on AAM is remote from the situation and cannot be relied upon                               as a defence or support - in and of itself  -         should       legal        action    be      taken.
Competent legal and building professionals should be asked to advise in                               Real Life with rights to inspect and issue        reports    on     the         matters    at      hand.


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## onq (18 Sep 2011)

And not to put too fine a point on it, since hastalavista mentioned goggles, do not do this yourself and pay particular attention to health and safety even if you're only watching the work.

ONQ

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All advice on AAM is remote from the situation and cannot be relied upon                               as a defence or support - in and of itself  -         should       legal        action    be      taken.
Competent legal and building professionals should be asked to advise in                               Real Life with rights to inspect and issue        reports    on     the         matters    at      hand.


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## Superman (18 Sep 2011)

Another option worth considering (and depending on the location of the canopy) is to put insulated plasterslab on the inside at the locations where the canopy touches the wall - e.g. on the inside wall of the entrance hall.
It would probably be significantly cheaper.


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## hastalavista (18 Sep 2011)

Superman said:


> Another option worth considering (and depending on the location of the canopy) is to put insulated plasterslab on the inside at the locations where the canopy touches the wall - e.g. on the inside wall of the entrance hall.
> It would probably be significantly cheaper.



This does not address the cold bridging problem/detail as once the cold gets into the wall it travels so the internal insulation would need to be fitted to address this


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## Superman (19 Sep 2011)

hastalavista said:


> This does not address the cold bridging problem/detail as once the cold gets into the wall it travels so the internal insulation would need to be fitted to address this


It does if the internal insulation covers a sufficient amount of the internal wall. A cold bridge is a short section of a reasonably good conductor. A long section of a reasonably good conductor is like a short bit of a reasonably good insulator.
If you are forcing the cold bridge to be 2m or so long of a block wall, then the cold bridge isn't all that great anymore.  If the cost of this detail is a fraction of the cost of removing and reinstating a concrete canopy then the cost of the amount of energy lost through the cold bridge over the lifetime of the building may be less than the additional cost of the canopy.


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## GORL (19 Sep 2011)

Thanks for all the very considered responses hastavista, onq and superman! Lots of food for thought there. 
We're definitely set on keeping this canopy if at all possible, rather than turning it into a porch as hastalavista suggests, although this does seem to be a common thing for people to do.
We thought about the internal insulation also, as superman suggests, but the point at where the canopy meets the house is about the same point as the first floor meets the wall internally so internal insulation at this point sounds a bit tricky - lifting floorboards, insulating around joist supports etc. Would otherwise have been a handy option!
I think ONQ has come closest to providing the solution so We are thinking of doing the following:
1. Remove the existing canopy
2. Have a piece of strong metal manufactured in the shape of a 'T'. Solidly secure the top of the 'T' to the wall with the long piece of the T extended out over doorway to form the canopy.
3. Have 100mm external insulation fitted on the wall.
4. Have a weathering detail manufactured similar to those for insulated cills for the point of where the canopy meets the wall.
5. Have 25mm external insulation fitted around the metal canopy piece (giving a total canopy height of c.50mm which is roughly the same as the existing canopy).
6. Have the wall and canopy finished in the same render to simulate the existing finish.
Can you see any pitfalls in the above?
Really appreciate all the help so far.


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## onq (19 Sep 2011)

There are pitfalls with anything where you are working from a verbal description - I prefer to see drawn details and specifications. 

Don't discount Superman's solution, but you need to go minimum 900mm past the cold bridge and you may as well insulate that entire outer elevation of that room.


ONQ

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All advice on AAM is remote from the situation and cannot be relied upon                                as a defence or support - in and of  itself  -         should       legal        action    be      taken.
Competent legal and building professionals should be asked to advise in                                Real Life with rights to inspect and issue         reports    on     the         matters    at      hand.


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## onq (19 Sep 2011)

hastalavista said:


> This does not address the cold bridging problem/detail as once the cold gets into the wall it travels so the internal insulation would need to be fitted to address this



Its not so much that is it looks like a dog's dinner unless you slab the whole of that wall.


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## hastalavista (20 Sep 2011)

onq/Superman:

we are all on same track re the internal insulation, how far, where do you stop, rest of wall, sockets, switches, skirting boards, architraves,window reveals/head, windowsill, radiators, ceiling, floor etc etc.

You both took more time to explain.
Keep well


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