Cavity wall insulation in a 30 year old house

[MickR]

Hi,

We live in a house which was built in the early 1990's, and I've always assumed that as it would have been built with some form of insulation between the outer brick wall and the inner breeze block wall. However, when removing the vent from the drying machine at the weekend, you could see there's just a gap between the two walls, and the breeze blocks just appear to be totally normal with no insulating foam or layer either side, so

Is anyone aware of building regs at that time? I assume the breeze block would be a specific thermal block, sufficient for the regs in the early 90's

Also, would there be an advantage in retrospectively adding cavity wall insulation? Has anyone else been through a similar process?

Thanks

Mick

[Arborbridge]

Hi,

We live in a house which was built in the early 1990's, and I've always assumed that as it would have been built with some form of insulation between the outer brick wall and the inner breeze block wall. However, when removing the vent from the drying machine at the weekend, you could see there's just a gap between the two walls, and the breeze blocks just appear to be totally normal with no insulating foam or layer either side, so

Is anyone aware of building regs at that time? I assume the breeze block would be a specific thermal block, sufficient for the regs in the early 90's

Also, would there be an advantage in retrospectively adding cavity wall insulation? Has anyone else been through a similar process?

Thanks

Mick

Oh - a cavity in cavity walls? Well, I never. The cavity is there for a purpose, and anyone who decides to pour in insulation and bridge that gap does so at some risk to the health of their house, in my view. I have neighbours who have had to resort to removing insulation at great expense due to damp - no wet - problems.

Don't believe the snake oil salesmen. I wouldn't bridge that gap with anything unless and until I am compelled to do so.

Arb.

[MickR]

Thanks, that's exactly why I'm posting on LF, rather than getting in some "expert" with an ulterior motive

Mick

[BullDog]

Thanks, that's exactly why I'm posting on LF, rather than getting in some "expert" with an ulterior motive

Mick

I don't believe there's a universal truth here. Like many things in life, it depends on the details.

Our 1993 built house definitely has rock wool slab between the leaves of the wall. The rock wool slab leaves maybe a 1" or thereabouts cavity. It was built that way and we certainly don't have a damp issue.

My parent's house was built in the early 1970's. Not sure exactly the year. Sometime in the mid 70's (oil price shock etc) the house had rock wool blown into the cavity. When my parents bought the house, around 1978-ish there was a damp patch in one downstairs dining room corner. It turned out that rubble had been pushed into a corner and was bridging the damp proof course. It was cleared and 30+ years later it's still fine.

What would definitely put me off is if the property was in a location where there was frequent driving rain. There is information that can be found from Google searches where the country is divided up and classified into regions depending on the severity of the weather and driving rain in particular. There's information available, not from traders, about what to look for when considering retrofit cavity insulation. Worth a Google search.

In a nutshell, if the cavities are clear and the weather moderate in terms of driving rain. Then I believe there's a good chance it will be fine if installed correctly. That's probably one of the more difficult decisions.

How do I know this? I was asked by an elderly relative to look into this for them last year when energy prices were sky high. I said that given the significant west facing open aspect of the house where most of the rain comes from, I wouldn't do it. Hope that helps.

[kempiejon]

One of my chums used to enjoy winding up door to door cavity wall insulations salesmen - remember them? With an earnest look he would say that if the Lord had intended people to have their cavity walls full he would have made them that way.

Another mate has declined to have his insulated as the aspect of his property with, as another writer said, west facing prevailing rain.

[scrumpyjack]

I discussed this with our surveyor who we have used for all our building works over the last 40 years. He went carefully through all the things that could go wrong. I decided it really was not worth the risk. Anyway, heat rises so most loss will be through the roof rather than the walls. All our windows are double glazed. Not worth the risk, IMO, and the cost benefit is marginal at best.

[88V8]

....would there be an advantage in retrospectively adding cavity wall insulation? Has anyone else been through a similar process?

Our C17 is mostly not cavity, but we have a 60s extension which I had filled with blown fibre about 8 years ago.
It faces east.
So far no internal damp, but when I have had cause to look into the cavity, the fibre seems to be rather sparse and patchy so I am not convinced it's doing much good although equally may not have been able to do much harm.

There is another potential downside, other than through-damp, and that is corrosion of the wall ties. I don't know when stainless ties because the norm, not in 1960, and we have tie corrosion and consequent cracking of the outer skin, which I may have exacerbated with the insulation.

I would agree that the potential downside and the difficulty of removing any cavity fill would put me off doing it again.

V8

[Arborbridge]

Removing cavity insulation must have become a "thing" now - I'm getting speculative leaflets through the door from companies specialising in it, and I have seen vans around advertising this ability of the side.

I'm aware that some modern fillings could be better, but nevertherless, that cavity is there for a purpose, and water has a way of finding a route through any construction which shows it any weakness.

Arb.

[Arborbridge]

....would there be an advantage in retrospectively adding cavity wall insulation? Has anyone else been through a similar process?

Our C17 is mostly not cavity, but we have a 60s extension which I had filled with blown fibre about 8 years ago.
It faces east.
So far no internal damp, but when I have had cause to look into the cavity, the fibre seems to be rather sparse and patchy so I am not convinced it's doing much good although equally may not have been able to do much harm.

There is another potential downside, other than through-damp, and that is corrosion of the wall ties. I don't know when stainless ties because the norm, not in 1960, and we have tie corrosion and consequent cracking of the outer skin, which I may have exacerbated with the insulation.

I would agree that the potential downside and the difficulty of removing any cavity fill would put me off doing it again.

V8

And wall ties offer a perfect route for water to travel across.

[tjh290633]

Our cavity wall insulation has been in place for about 45 years now, with no problems whatsoever.

There was a considerable reduction in heating costs after installation and it paid for itself in a very short time. Our next door neighbours had an extension which was built in polystyrene blocks and concrete was poured into the cavity. The exterior was then rendered.

If the insulation is installed initially, board can be used, which is a better solution.

TJH

[Dicky99]

Thanks, that's exactly why I'm posting on LF, rather than getting in some "expert" with an ulterior motive

Mick

I don't believe there's a universal truth here. Like many things in life, it depends on the details.

Our 1993 built house definitely has rock wool slab between the leaves of the wall. The rock wool slab leaves maybe a 1" or thereabouts cavity. It was built that way and we certainly don't have a damp issue.

My parent's house was built in the early 1970's. Not sure exactly the year. Sometime in the mid 70's (oil price shock etc) the house had rock wool blown into the cavity. When my parents bought the house, around 1978-ish there was a damp patch in one downstairs dining room corner. It turned out that rubble had been pushed into a corner and was bridging the damp proof course. It was cleared and 30+ years later it's still fine.

What would definitely put me off is if the property was in a location where there was frequent driving rain. There is information that can be found from Google searches where the country is divided up and classified into regions depending on the severity of the weather and driving rain in particular. There's information available, not from traders, about what to look for when considering retrofit cavity insulation. Worth a Google search.

In a nutshell, if the cavities are clear and the weather moderate in terms of driving rain. Then I believe there's a good chance it will be fine if installed correctly. That's probably one of the more difficult decisions.

How do I know this? I was asked by an elderly relative to look into this for them last year when energy prices were sky high. I said that given the significant west facing open aspect of the house where most of the rain comes from, I wouldn't do it. Hope that helps.

There's some man down the pub wisdom in this thread but Bulldog's wisdom is a bit more balanced.

1990 was a transitional year for the new Building Regs when features like cavity insulation would become standard, but because it was passed in 1990 there would have been a period before it was widely adopted, which may explain why yours has open cavities. Though are you sure there's no insulation? It may have been locally disturbed / removed when core drilling the hole for the vent. You'd have to stick your hand into the void and explore.

The benefit isn't marginal it has a very short payback period which is why the majority of open cavities have been filled now under various grant schemes over the last few decades.

Most are problem free but there have certainly been publicised instances of serious problems in some properties, in particular dwellings in very exposed geographical locations with blown fibre type fill. In some cases this had to be removed at great expense. I believe that polystyrene bead fill is much less problematic.

As with all grant related feeding frenzies there were also instances of rogue traders drilling holes in brickwork and pumping in hardly any insulation at best, and none at worst.

If yours really hasn't got cavity fill you could explore whether you'd qualify for a grant under the Great British Insulation Scheme.

[funduffer]

We have a 1960’s bungalow, that had blown fibre cavity wall insulation in the main part of the house, but nothing in the 1980’s extensions.

We have had the blown fibre removed and the whole house insulated with polystyrene beads.

We have done other improvements as well, but gas usage is 40% lower than it was 3 years ago.

About £3k to remove and replace the insulation.

Should pay back reasonably quickly.

I think you will find modern materials don’t have any real issues with damp etc.

FD

[BullDog]

We have a 1960’s bungalow, that had blown fibre cavity wall insulation in the main part of the house, but nothing in the 1980’s extensions.

We have had the blown fibre removed and the whole house insulated with polystyrene beads.

We have done other improvements as well, but gas usage is 40% lower than it was 3 years ago.

About £3k to remove and replace the insulation.

Should pay back reasonably quickly.

I think you will find modern materials don’t have any real issues with damp etc.

FD

Seems to me that polystyrene beads is a much better option than rockwool fibre. I can't imagine the polystyrene beads having anything like the possible issues where wind blown penetrating rain happens on occasion.

[todthedog]

If you look on the interweb there are maps which show the regions unsuitable for cavity wall
https://www.labc.co.uk/sites/default/fi ... 0Map_0.jpg
I phoned the Building Research Establishment and asked, we live in Wales and was told I would be a fool to install it. Really helpful chap.
Hope this helps