We're considering various options to increase the thermal efficiency and comfort of our terrace and need some help from those in-the-know.

The house is a typical over the passage, two up two down, 1890's mid terrace. The bedrooms upstairs go over the passage and we have a flying freehold on the passage.

The downstairs rooms are significantly colder than upstairs and more so now that we've just added an additional 200mm of loft insulation to the existing 100mm.
The passage runs the length of the house and the external wall is regular brick non cavity and very, very cold in winter. The radiators can be going full blast and the room is still freezing.

I'd like to add a layer of external thermal cladding to the passage wall and ceiling (the area under our bedrooms) and wanted to know if anyone has done this and what they used.

I aloso want to lift the floor boards and insulate under them and either go for strippped wooden beams or carpeting again. What should I use for best results under the floorboards?

Thanks all!

Assuming you have no problems with damp in the wall then you have lots of options. However, if there's any damp then you need to solve that before reducing the teperature gradient across the wall.

Next question is how much space you can afford to lose? Some insulating materials are bulky. Do you want to use eco materials or not?

Wood is a pretty good insulator, ecological and cheap. 21mm pine (floorboards) with a 1cm air gap behind screwed to a wood or steel frame will get you an aesthetically pleasing result without losing too much space. You can put a thin multi-layer insulator behind it if you're not worried about damp. It's easy to work around windows and easily removed to get at electrics and so on. Think about which bits you might need to remove and end there.

Rockwool backed plaster board is a cheap solution but bulky and a pain if you have to move radiators, get around windows or have things you want to access.

They're the two I've used and am pleased with the results. Warmer rooms and no condensation. Over to other STWers for more ideas.

I would look at externally insulating both floor and wall.
Again, be aware of damp issues, water ingress etc and sort before you do insulation.
For both, look at breathable insulation that avoids trapping moisture in (think Goretex jacket vs plastic jacket time).
I would suggest looking at NBT Pavatex Woodfibre boards – put rockwool (usually v cheap) in between joists of floor over passage or Hemp/Wool if you feel flush, then an Woodfibre board. You can then render straight onto this.
For the walls, you will need to use a foam baotd (XPS usually) up to damp proof level and then a woodfibre over DPC to join the over passage area. Again, render straight onto with a breathable render (not sand /cement).
Under floorboards do be very aware of damp issues, make sure its vented. Again, look to put in Wool or Hemp as it is breathable and hygroscopic (helping avoid damp in the wood), then a breathable membrane for airtightness, then floorboards back down.
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Done the above many a time, including my own and mates houses.
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The Energy Saving Trust have an excellent manual on all this, and the NBT website has some great manuals and information.

The insulation will be in the passage, so no space lost inside the house (its small enough).
I was thinking of a wooden frame work of battens (screwed vertically to the wall) with giving me 20mm or so for insulation. Then protecting/covering/cladding this with a sheet of plywood or wooden boards, but nothing too thick that impacts significantly to the area of the passage.
Need ideas on insulating and cladding materials.

You could do that, but bear in mind that each batten is a 'cold bridge', so reducing your insulation value. It would work OK though. Nice solid ply that someone could not 'bump' and damage would be best, make sure it drains out bottom OK and use as much insulation as you can, 20mm is barely worth the expense and hassle. 50mm-100mm would be great, but everything is an improvement on a solid brick wall…

Also, consider a door at each end, properly installed to make the passage 'inside' space, and less/no draft through it.

I would go for the door each end as said above,stops the draught etc,and can be used for storage etc.

Matt_outandabout – thanks for the post. Everything I was after! The passage is totally dry except in VERY wet and windy conditions when a bit of water blows in and we don't have any damp on this external (passage) wall.

The DPC is about 2-4 bricks high (from the injection drill holes). Just to understand what you said, I should insulate with XPS upto the DPC then have Woodfibre boards above this level, to the ceiling of the passage and across the ceiling. Under the ceiling Woodfibre boards is rockwoool. Is there anything behind the Woodfibre boards on the wall? If so what do you recommend.

For the floor, what stops the insulating material falling right through? Is the wool in stiff board form or similar to the expanded glass loft insulation stuff? Also what breathable membrane for thd floor would you recommendd.

Though the material itself is a little questionable from an environment point of view, in used per unit of thickness the foil coated blown urethane insulation is the best you can get and in use is very efficient – useful if you want to minimise space lost – take a look at Kingspan products – they have a useful website. They also have cladding solutions that minimise cold bridging.

Woodfibre straight on walls, render on top to protect them (or a good ply board).
A good hemp/wool batt will stay up, but if you need support for them, then staple in some cheap gardeners netting and then fill joist depth with insulation.
Any builders paper will do – doesn't need to be weather proof, just to stop the draft. The stuff we sold and recomed was Pro Clima, but its not cheap. A 'cheap' but breathable roof membrane would be fine.

The passage is shared access for 5 properties and most have bikes and wheelie bins that get dragged through daily. So I can't afford to reduce the internal dimensions too much.
If battens create cold bridges how do you attach the Woodfibre boards to the wall?

I'm going to talk to the neighbours and see if they will go in on it with me and improve their property at the same time and sharing the cost.

edukator mentioned "multi-layer insulation", they're themost efficient in terms of insualtion per unit thickness. Something like actis tri iso super http://www.just-insulation.com/super10.html

tri-iso / multilayer is a pile of poop in my experience and opinion, and in many insulation experts opinion.
Avoid, avoid, avoid.
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Woodfibre is crewed to the wall with themally broken fixings from Fisher or similar.

Said it above but PIR PUR foams have the best insulation properties – we spec it on projects were space is tight, but also as it is efficient in use, but anything will be better than you have now……