Solid wall insulation

Rosa_Damascena

Bendy_House said:

Rosa_Damascena said:

1920s house here, I had the external render stripped back to brick before adding 75mm insulation and new render. The total thickness to the brickwork is 100mm and it is so much warmer than the icebox that it was.

Is this a solid wall, Rosa, or cavity?

Solid as it gets.

Bendy_House

Rosa_Damascena said:

Bendy_House said:

Rosa_Damascena said:

1920s house here, I had the external render stripped back to brick before adding 75mm insulation and new render. The total thickness to the brickwork is 100mm and it is so much warmer than the icebox that it was.

Is this a solid wall, Rosa, or cavity?

Solid as it gets.

I can totally understand external insulation working just as well as internal when it's a solid wall. I still cannot get my head around the effectiveness of external insulation on an open cavity wall, regardless of whether it's capped off along the top. I'd much rather go 'internal' in that case.

takay9

Rosa_Damascena said:

1920s house here, I had the external render stripped back to brick before adding 75mm insulation and new render. The total thickness to the brickwork is 100mm and it is so much warmer than the icebox that it was.

Externally insulating would definitely be my preference, just our budget won’t stretch that far. I guess it would be £15k+ for a 3/4 bed detached house? Interesting to know that you can transform a cold house to bring nice and warm, it sounds great.

FreeBear

External wall insulation has advantages & disadvantages (as does internal). With external, you may (will) need to move down pipes and soil vent pipes. Detailing around window reveals and roof line is critical so that you avoid ingress of rain. On the plus side, done right, most cold spots/bridges are avoided. You can get a crisp modern finish if you so desire. The walls on the inside will act as a thermal store and keep the house warmer once the heating switches off. On the downside of that, the walls will take longer to warm up.

Insulating internally - It can be done room by room, so spreading the cost if the budget is tight. You loose a bit of floor space, and any radiators under the windows along with sockets etc have to be moved. If you must have radiators hung off the wall under  window, thought needs to be given to fixings up to the task of taking the weight. Wall units in the kitchen also need extra work.. Some parts of the house will be difficult or impossible to insulate (stairwell being one). Attention to detail in the void between ground floor ceiling and the floor above is needed, or you'll end up with a cold spot in that area. As the insulation is on the inside, the walls will no longer be an effective thermal store, so the rooms will cool down a bit quicker once the heating is off. But on the plus side, they will warm up quicker. If you have fancy brickwork on the outside that you want to save (for architectural value perhaps), internal insulation will not interfere with it. Another advantage is that you get nice flat & smooth walls to paint or paper over.

Insulating solid brick walls internally, I favour fixing vertical battens to the wall with a strip of DPC material between brick & timber. A layer of Celotex/Kingspan boards stuck to the battens, sealing the joints with expanding foam and then taped with aluminium foil tape. Horizontal battens are then fixed over the top and screwed to the vertical battens. The space between these battens are then filled with another layer of Celotex and joints again filled & taped. Final layer is then plasterboard fixed with screws, not nails. For the kitchen area, if wall units are to be hung, good quality plywood should be used in place of plasterboard. It would also be prudent to increase the number of vertical & horizontal battens & fixing screws so that loads are transferred tot the brick wall more effectively.

When it comes to selecting insulation, don't go wasting money on stuff like YBS SuperQuilt - Despite their claims, multifoil insulation is a pretty poor performer.

WustyRex

Wycamol Isotherm 4mm damp and insulation felt . A simple but 100% effective alternative to thick internal insulation. Can be plastered over with a base coat then skim making is a lot cheaper too. 

Bendy_House

WustyRex said:

Wycamol Isotherm 4mm damp and insulation felt . A simple but 100% effective alternative to thick internal insulation. Can be plastered over with a base coat then skim making is a lot cheaper too. 

Interesting stuff, Wusty. Do you have actual experience of it?

By the time it's been adhered to the wall and over-skimmed, the layer is 10mm thick. All for 4mm actual insulation? Are you sure it's effective?

How does it compare with Wallrock?

Grenage

4mm is going to do !!!!!! all.

Bendy_House

That could be true, Grenage, but I recall - many many moons ago, on a cold wee Skottish island, a relative covering their walls with a polystyrene sheet which couldn't have been more than 1/8th-inch thick. Totally impractical, of course - one careless rub and it was scoured.

BUT, I also recall - as a child - touching it and thinking, "How the 'ell is this 'warm'?!"

My issue with the Wycamol is the loss of 10mm thickness, to gain only 4mm's worth of insulation. A hell of a lot of work, too. There is surely as better way?!

DiamondLil

Rosa_Damascena said:

1920s house here, I had the external render stripped back to brick before adding 75mm insulation and new render. The total thickness to the brickwork is 100mm and it is so much warmer than the icebox that it was.

Ditto here too - 1920s solid walls. We added 50mm (couldn't go thicker because of the roof shape) and it's made a huge difference not only to the warmth of the house, but also to the length of time the warmth is retained.