Cavity wall insulation? Worhwhile?

twopenny

I had the beads in a 1920s semi.

The insulation worked when the heating was on and it kept the warm in. I could have the thermostat on lower by a bit.

But it was south facing open on 3 sides and the sun no longer warmed it in the shoulder seasons so I had to have the heating on longer.

John_the_Boy

I had the grey carbon beads as an upgrade to the tradition white ones as they were supposed to give better insulation. Couldn't say if they were better or not but they made a real difference in terms of retained heat the next morning. Make sure the company inspect your cavities to ensure there isn't any rubbish that can cause bridging and thus damp. When I had my survey the surveyor asked me to accompany him around and showed me the cavities using his endoscope (if that is the right term) camera.

TUVOK

twopenny said:

I had the beads in a 1920s semi.

The insulation worked when the heating was on and it kept the warm in. I could have the thermostat on lower by a bit.

But it was south facing open on 3 sides and the sun no longer warmed it in the shoulder seasons so I had to have the heating on longer.

That's very interesting thanks, the back of my house faces south and thus obtains a lot of heat that way, will bear your info in mind.

John_the_Boy

If you have windows facing south (as we do) then the cavity wall insulation will help keep the thermal gain from the sun through the windows. If just brick wall that it will do as twopenny says. 

ComicGeek

TUVOK said:

I had a door step visit this week from a 'Smart Energy' rep.
Their  product is Thermalite 'B' carbon bead cavity insulation.
Any one had experience of this product and firm, also is cavity wall insulation safe long term.

My property is a semi detached house , built in 1995 with internal wall thermal block and conventional outside brick, no flat roofs.
My house has double glazed windows and insulated loft.

In order to save money on heating bills is this the way to go using cavity wall insulation or what other ways?

All opinions, views would be appreciated. 

If it was built in 1995, then 99.9999% it will already have cavity wall insulation. Might only be 25-50mm insulation, but you definitely don't want to install anything extra that bridges the existing cavity insulation.

My house was built in 1989, and fairly typical of that age with 25mm insulation batts in a 75mm cavity. That residue 50mm cavity needs to be kept completely clear, otherwise moisture could track through. 

The rep is an idiot. Recycle their company details and move on.

John_the_Boy

Mine was built in 1998 with no Cavity Insulation. I asked the builders why and they said they used thermal breeze block to achieve the same effect (supposedly anyway). The builders were Bryant if that helps.

stuart45

Thermal 4 inch blocks were used in the 70's to achieve a U value of 1.0.
I've used 5 and 6 inch blocks in the 80's, but by the late 90's these thicknesses of thermal block alone wouldn't achieve the required U value. I remember @ComicGeek being surprised that even in the 80's I'd built a house with a clear cavity, as he said the calculations didn't make the U value of 0.6.

TUVOK

John_the_Boy said:

Mine was built in 1998 with no Cavity Insulation. I asked the builders why and they said they used thermal breeze block to achieve the same effect (supposedly anyway). The builders were Bryant if that helps.

My house built in 1995 and I was also told that due to being built inside wall with thermal block, no cavity insulation required. 

knightstyle

When we looked at this some years ago the general thought was that it would save about 3% of our heating bill when we had the heating on.  After doing the figures we realised it would not pay back in our lifetimes!

jj_home_80

Cavity wall insulation can help with heating costs, but it’s crucial to get the right type for your walls. If your house was built in 1995, it may already have some insulation—worth checking first. Thermalite ‘B’ beads are supposed to resist moisture better than older methods, but I'd be cautious about doorstep sales. Get independent quotes from reputable installers (e.g., BBA-approved) and check if your walls are suitable before committing.