Any recommendations for external insulation? As part of cladding or rendering?

[starpatch]

Hi, after this weeks news on climate I am looking ahead and thinking of saving up for external insulation. Any recommendations of good products? Or websites with good information on this? My house is currently quite poorly insulated (but does already have loft insulation and cavity wall insulation, but it is just quite cold) I am wondering if this could make a big difference.
Thanks

Don't have any specific recommendations, but our Victorian terrace was externally insulated a few years ago under the government green deal scheme (now defunct). It was essentially polystyrene bricks, slapped on the back of the house, which were then rendered over. It's made an appreciable difference in terms of warmth in the winter, what was an extremely cold house is now absolutely fine in winter.

we have external insulation on part of the house and its made a huge difference. Ours is also effectively polystyrene covered in modern render. However, we had solid walls - no cavity wall insulation at all - and we upgraded all our windows in that section to modern double glazed windows from old double glazed or single glazed windows. Doing EWI means you really have to consider upgrading windows at the same time as well installed EWI wraps around the windows to give a good thermal seal.

However, if you have got cavity wall insulation, I would query if it is effective, and also what type of floors and windows you have. If they are suspended wooden floors, are they carpeted or if sanded floorboards, are they insulated underneath the floorboards. Likewise, what state are the windows in? Is the house draughty?

Thanks both that is very helpful. The house is carpeted. It has double glazing which seems to be effective. Yes I don't think the cavity wall insulation is 100% effective, but some people seem to be a bit doubtful about topping it up. I think the real weak points are the modern extension (not sure if the extension roof is insulated no internal door it is open plan with living room), the radiators are badly put up, fitted too close to the walls including external walls and its an ex council house with LOADS of air vent bricks. I am not sure what to do about the air vent bricks, when I closed the ones upstairs I did found I got mould.

the air bricks should be open to allow sub floor ventilation - upstairs ones suggest it is for old chimney and likewise should be kept open.

I really rate EWI - it does deliver much improved heat retention in winter. However, it is expensive and doesn't deliver huge savings. We are saving money - bills have gone down, due in part to new boiler - and we no longer have problems with mould in the corner of bedrooms. We are overall considerably warmer and also better ventilated - we open windows in winter for a short time knowing that the house soon warms up again quickly - but from a financial calculation, the payback period is very long. We covered up old pebbledash with the EWI so improved the look of the house - we would consider the outlay of cost of EWI worthwhile on that basis as we will not need to repaint in the near future at a cost of £1k to £1.5k each time (labour and materials)

Thanks Sally. I would really like to be well enough insulated to get a heat pump, but it seems like that isn't possible on my budget.

It's expensive, but worth considering if you have solid walls and are going to have the house rendered anyway. Not often seen in UK but I have seen it done in continental countries, bolted to the walls and then a cement board over the top which is then thinwall rendered with something like K-rend or Decopierre.

With external cladding, the ground floor needs something that will withstand impact damage from wheebarrows, kids' bikes, people bumping or falling into it, leaning spades against it, incompetent car parkers. When I watched a rural house being done in Switzerland, they used the rendered cement boards, but regional stone on the ground floor like a cavity wall.

My own house has slate cladding on one side (coastal area, it sheds stormwater) but the ground floor is clad in shiplap which shrugs off impacts and it would be easy to replace a damaged board.

Knauf have a system and you can find videos and construction diagrams online. It shows weatherproofing, jointing and fixing. They might have an Approved Installer scheme.

Foamglas is also very good, and fireproof, but not often seen in UK.