Cavity block Insulation

Radiant Cool Crazy Nightmare

Apologies if this has been posted before, I had a look and couldn't find any threads relevant to my question. I recently purchased a property that was built using 9" cavity blocks. During the cold spell just gone I noticed that the external walls were very cold to the touch and the bedrooms were very hard to heat.
I am getting new windows installed as the old ones are of zero use, but I would also like to see what options are available to me regarding insulation. From looking online there appears to be mixed reviews about pumping cavity blocks with an expanding foam type insulation, but again all I could find were posts/forums from several years ago. I had a look at external insulation, but being honest the cost is prohibitive. Dry lining the interior is a bit of a non runner as there are young kids in the house and another one due in the next few months.
It is a 3 bedroom semi with a converted attic, built circa 1978 if that matters. Any advice or recommendations would be much appreciated.

goz83

I live in a 3 bed semi with converted attic which was built around the same time. I have lived here since the mid 80s.

Inthink th main issue with pumping the walls is there is still a lot of cold transferring through the walls and the insulation won’t stop most of that. The obvious options are what you have listed and I faced the very same issue. The house was always cold and always had the gas boiler running. The walls were always cold. The bathroom was the coldest room in the house and some days you wouldn’t want to sit on the loo for fear of shrinkage

Anyway, when we bought the house from my Dad, the first room we renovated was the bathroom, as we wanted a bath for the kids. We decided to install warm board insulation on the 2 external/cavity walls because we were retiling the room anyway. The bathroom became the warmest room in the house. Over a few months, we got all the external walls insulated from the inside. The biggest difference was when the hallway was done. The walls were often so cold that they were like cold radiators....emmitting a draught.

So while it might seem like big hassle, it isn’t really. If your house is like mine, the smallest bedroom will need 2 walls insulated and the larger bedrooms will only need one wall done. It’s a quick job and well worth it.


The attic is just stuffed with fibreglass behind the plasterboard. Does the job.

decky1

wouldn't have much faith in getting cavity walls pumped if any of the cavities were full of cement the beeds will not get through, best bet is the Warm Boards think the smallest is around 25mm + largest around 50 mm go for the large one ,you need only do the external walls.

Calahonda52

Go EWI at same time as windows: hand windows on outside of wall before the EWI gets installed and it minimises thermal bridging.
Bring insulation up through soffit board to meet with attic insulation c/w properly installed ventilation baffles.

IIRC a lad wit user name SAS did this in 2007 and documented it here

decky1 wrote: »

.....you need only do the external walls.

Not if you want to address the thermal bridges with interior walls meeting external walls.

Radiant Cool Crazy Nightmare

Thanks everyone for the replies and suggestions.

Just to add, I have already replaced the rear three and the only side window on the house as they were never changed by the previous owner, they were the old aluminum single pane windows and I noticed a difference almost immediately. The front three windows will be installed in the next week or two, they are double glazed but old and inefficient, when the blinds are down over them you can see the blinds waving back and forth with the draught. The front door and porch doors are also replaced from the previous owners wooden and aluminum ones which were also cold and draughty.

goz83 my home is very similar to yours, the bathroom was baltic. I noticed it warm considerably after the new window went in, I also changed the vent from the open style one which was there when we moved in, some days you could feel a strong breeze howl through it, I just put in the ones that have a slide on them and that has really allowed it to warm. I may have to go down the road of doing it room by room if the new windows don't suffice. The small cold front room and the bathroom are both on the exposed gable side of the house.

Is the warm board you lads mentioned the slab with insulation on the back? I did carpentry for a few years a good while ago, never served my time though. I dry lined a good few older homes with lats, dpc and insulation inbetween the lats with a slab over and then a skim finish. Do the warm boards go straight onto the wall and then require a skim aswell? I have never heard of them as an option and it's something I will definitely have a look.

Water John

Some would just tape and skim the joints, esp in commercial buildings. Can't see any reason why not in domestic situations also. They would be ready for painting in 24/48hours. The normal two are 38 and 50mm total width.

Lumen

Water John wrote: »

Some would just tape and skim the joints, esp in commercial buildings. Can't see any reason why not in domestic situations also. They would be ready for painting in 24/48hours. The normal two are 38 and 50mm total width.

I had a quote for exactly this on my own home from a contractor who mostly did commercial stuff, but I hesitated because of (what I think are) the usual concerns about dew points and thermal looping behind the boards. Plus I didn't want to lose internal space.

goz83

Radiant Cool Crazy Nightmare wrote: »

Is the warm board you lads mentioned the slab with insulation on the back?

SNIP

Do the warm boards go straight onto the wall and then require a skim aswell? I have never heard of them as an option and it's something I will definitely have a look.

So it sounds like we have the same lay-out as I suspected.

Yes, they are plasterboard with foam insulation on the back. I went with 50mm (or more) and it really made a huge difference. In the bathroom, the boards were installed using plastic plugs (see below) which are better than the steel ones, which can cause cold patches.


We tiled right over the boards in the bathroom, but a skim coat was needed in the other rooms and a lick of paint. I decided to tile the window sills, rather than get new boards.

It's a relatively inexpensive job and to me it made the most sense.

Calahonda52

goz83 wrote: »

...I went with 50mm (or more) and it really made a huge difference. In the bathroom, the boards were installed using plastic plugs (see below) which are better than the steel ones, which can cause cold patches.


.

But are required to meet fire regs, at least two per board IIRC

Water John

Also there is stuff to be put on the metal ones after, just to keep them from rusting and showing through the plaster.

Radiant Cool Crazy Nightmare

Really appreciate all the replies. I will be going with the warm boards as suggested by goz83. The main priority is the small front bedroom so will put the boards up on that myself in the coming months to have it done by summers end, I'm lucky enough to have a friend who is a decent plasterer so he will skim it no hassle. If that makes all the difference that I hope it will then we can get cracking on all the exterior walls. I never thought of these insulated slabs as an option as I was thinking of the old style dry lining which would be a right pain. Thanks again for taking the time to reply.

Calahonda52

What the plan for any pipework and sockets on the walls you are doing

malinheader

Water John wrote: »

Also there is stuff to be put on the metal ones after, just to keep them from rusting and showing through the plaster.

I coated the metal heads twice with paint suggested by painters. Rusting still came through and ended up papering the wall. I would only use the plastic one's if doing it again.

Radiant Cool Crazy Nightmare

I am only going to do the small front bedroom first to see how I get on and I will be doing the two external walls in said room. There are no sockets on any of the external walls upstairs. Rads under every window that will need moving. In my group of friends from home we have most trades covered. He has to come back to fit a negative head pump for the attic en suite so I am going to try time that with doing the front room.

goz83

I was lucky that the only radiator needing to be meddled with was the one in bathroom, which we were replacing anyway. All the other rads are on internal walls. We kept it on the same wall and just had the pipes moved a couple of inches away from the wall before putting up the insulation.

Radiant Cool Crazy Nightmare

Only a thought I am having now, but what would anyone in the know think of placing a radiator cover over the existing rad that's in the room at the minute and then running the warm boards into the cover. The covers I looked up online are about 8" deep, would that leave the part of the wall behind the rad as too much of a weak point? If the cover would suffice I could start this job in the next while and then I am only relying on a plasterer to do his thing. I am not at home at the minute but the rad is small, definitely no longer than 30". Appreciate all the comments and questions as I can do a small bit but always stay away from the likes of plumbing and sparks.

Water John

The rad needs as free air circulation as possible. You could put the reflective sheeting behind the rad.
Don't know if there is a light slab with 12 mm insulation?

goz83

Radiant Cool Crazy Nightmare wrote: »

Only a thought I am having now, but what would anyone in the know think of placing a radiator cover over the existing rad that's in the room at the minute and then running the warm boards into the cover. The covers I looked up online are about 8" deep, would that leave the part of the wall behind the rad as too much of a weak point? If the cover would suffice I could start this job in the next while and then I am only relying on a plasterer to do his thing. I am not at home at the minute but the rad is small, definitely no longer than 30". Appreciate all the comments and questions as I can do a small bit but always stay away from the likes of plumbing and sparks.

I wouldn't recommend doing that. When the radiators are off (which is most of the time, you will have a gaping hole in the insulation. There is not much work involved in moving the radiator out a couple of inches.