External vs internal insulation?

[KatyMac]

DD is looking at a flat/maisonette that might need additional insulation

There is little interior decoration to worry about and the windows also need replacing

So inside or outside?
Which is more cost effective for the amount of insulation?
Are any more sustainable than the others?
Thanks

Can't help but I would be interested in the answer

@mumwon I understand there are issues with both

Externally you have to consider the look of the building will 'render' improve it or make it worse? Never mind listed buildings or conservation areas (not in DD's case)

Internally it makes the rooms smaller and then needs decorating

But for a flat that needs windows and a new bathroom anyway adding it Internally is relatively easy

I'm thinking thin high insulation boards or foils

I got a surveyor to assess my house for insulation and due to the timber frame, I can only get internal. I was hoping for external for the superior performance and easier installation. With a flat there could be extra complications in doing external work so I would check any covenants over with a solicitor.

It's a maisonettes and frankly it's basically and extension on the back of a large victorian house

Possible 1960 brick built or maybe 70s no later

The door is in the back garden and the outside cantvreally be seen from the rod so rendering it - is unlikely to need planning permission I'd have thought

It's completely self contained with a flat roof (which concerns me) with only one connecting wall - I do wonder if it's converted or replaced outbuildings

I would avoid external insulation as I had this in my last rental and it caused mold in the house when previously there was none,had to have vents put in the roof to try and stop the spread.

The road is on the left and the maisonette is the flat roof

Damp does worry me but there isn't any signs or smell - no new decoration or furniture to hide it & obviously we'd have a structural engineer look at it and make a decision what sort we have

I'm just seeing if/what's possible

I had internal insulation put in (stone house) and it's made a massive difference. We removed the blown lathe and plaster so didn't really lose much room space.

external is more expensive and will alter the appearance of the building. Particularly odd if it is just one part of a large buiulding. It is unobtrusive if the building will be rendered or painted.

external cladding at ground floor level has to be stronger so it will not crack if someone bumps into it, e.g. with a wheelbarrow or bicycle.

Internal insulation doesn't take all that much space off a room, because it is only on the external wall(s). You can strip off the plaster but it doesn't usually make much difference. Rigid foam board has about twice the insulating power of fibreglass quilt so only needs to be half the thickness. I'd still go for 50mm though. Foamglas is seldom seen in UK but is fireproof and damp-proof.

Thin film and reflective bubble wrap is not as good as it's made out to be.

external cladding at ground floor level has to be stronger so it will not crack if someone bumps into it, e.g. with a wheelbarrow or bicycle

Or a car as its alongside the drive!!

Rigid foam board is what I was thinking, I guess

I thought there was superspecial stuff recently

@PigletJohn

Will doing the windows and the insulation in a planned/designed way minimise possibilities of damp

Insulation and windows do not generate water.

if the home is damp, there is a source of water in it; or insufficient ventilation to blow away normal moisture.

Most commonly and severely, wet washing draped around or on radiators. Sometimes a bathroom with no effective extractor fan.

Minor condensation, often in a bedoom, can result from excessive breathing, and can be managed by ventilation. Trickle vents or open windows are enough. Boiling pans in a kitchen release steam, so a cooker extractor will deal with that.

Building defects such as leaks from roofs, drains or plumbing need to be repaired. Sometimes water gets in around door or window frames, which must be repaired. Often paving has been installed above the level of the DPC, which allows water to bridge it. Chimneys can be damp which is usually a fairly easy repair.

Uncommonly, cracks in walls let rain in, or damaged render collects it in the gap.

A water pipe leaking under the floor can be particularly tiresome, so can a broken drain next to the house.

All these causes keep cropping up, it's just a matter of working out where the water is coming from.

As a rule of thumb, never allow anybody who sells silicone injections into your house.

@PigletJohn so basically its about 2 inches (sorry I don't think in metric in my mind!) that's interesting - would this work on a small Victorian Cottage?
& the council have tarmac or asphalt the pavement right up to the wall - technically (there is a tiny mini wall sticking away from the front of the house to show boundary) about 6 inches in on our land - so I thought about asking council to ask permission to dig a mini trench & put grit in against the wall because we have damp - Would this work?

if it's Victorian, it may well have lime plaster, which can be quite thick, so you would save a bit of room by hacking it off.

drill a few holes and see how deep you go before hitting brick.

As for the wall, some Victorian homes, especially after 1875, have a slate DPC, about two bricks above where ground level was when the house was built. It may be visible under or beside the front doorstep, or on the inside if you take out a couple of floorboards or look behind the skirting. It does not wear out and lasts at least 400 million years.

if there is no dpc, then I think the more brick that is exposed (so water can evaporate off it) inside and out, above ground level, the better. You may need to remove rubble or earth under the floor, and open airbricks. There is a thing called a "periscope vent" that is open above ground level outside, and channels airflow below the floor inside. Remove any plaster behind the skirting and space it off the bricks on battens to leave an air gap. On the outside there might be a cement plinth as an attempt to hide damp (it does not cure it)

On the outside, a trench filled with cobbles or pebbles (not gravel or grit) allows water to drain away, and large clean stones do not permit water to rise by capillarity.

Look for rainwater gullies and drains, which are often always cracked and leaking.

With luck the council will have a historic buildings preservation officer. If keen and well informed, s/he may know what methods have been successful in your area, and how to go about it. The may also be a local coven of the Victorian Society or other group.

This is an example of an insulated plasterboard. There is also a 27mm thick version. Some (not all) plasterers are skilled in its use. Electrical wiring should be run on the wall before fixing.

this is quite a good (rather long) explanatory vid.

PIR is the insulating board commonly use.

Knauf and other makers have their own instructional docs and vids.

I've been back and looked but I think it must be 9 inch walls

I'd still consider insulating it anyway as I imagine more insulation is better and while it's empty and undecorated seems like the time to do it....maybe help with sound insulation too

9inch is solid brick, no cavity (can also be concrete blocks)

it looks like the drains are leaking (green patches) and there is a dark (damp?) patch half way along the long wall, possibly from the gutter.

bathrooms especially benefit from insulation that can be tiled over to reduce condensation and warm up quickly.

Yep we have moved it to the no pile

Too much work for non capable people