Cold Extension - Insulation Issues?

[EinTopaz]

3 hours ago, marshian said:

OK just a suggestion from previous pictures I can see that removing a row or two of tiles means you can look down the cavities - can you not add suitable 2.4 m length of wood vertically down the cavity with a taper at the end to straighten/push the PIR back to being in contact with the internal wall face - then as they blow in beads pull out each length of wood knowing that the beads already in the cavity will keep the PIR in contact with the internal wall face.

 

Insulation company would then be happy with the consistent gap from an infill perspective?

 

Obviously if you can't push it back with 2.4m length from above  then it's a bust from that perspective so a bit of wood 

 

It's not a bad suggestion but no i dont think so. As we've got cavity closers over the windows etc. It's going to be hard to consistently get the stuff pushed back to the wall. 

I don't think I have the energy or the heart to have all the bricks removed and have this all re-seated properly.  So i'm guessing my only option now is external wall insulation. Anyone know a company in the North West that they'd recommend? 

[Redbeard]

Most on here would suggest filling the residual cavity if there is any suggestion whatsoever that the cavity may be less than 100 per cent free from air ingress. That could be a significant issue. You don't want to have a bunch of expensive insulation hanging on the outside looking pretty (only). NB I have not read all the thread, juts the 1st page or so, so I may have missed relevant stuff. 

 

Edit. Tried to send you a message, but 'EinTopaz cannot receive messages'. Do you or the moderators know why?

Edited April 9 by Redbeard

[marshian]

1 hour ago, EinTopaz said:

 

It's not a bad suggestion but no i dont think so. As we've got cavity closers over the windows etc. It's going to be hard to consistently get the stuff pushed back to the wall. 

I don't think I have the energy or the heart to have all the bricks removed and have this all re-seated properly.  So i'm guessing my only option now is external wall insulation. Anyone know a company in the North West that they'd recommend? 

 

 

What about a "mouse trap" arrangement - drill holes in mortar and insert dowels to push insulation back under windows

[Mr Punter]

Before you go much further, have you had an airtightness test to discover where any leaks might be coming from?  Seal up the opening to the house so you just test the extension.

[EinTopaz]

4 hours ago, Redbeard said:

Most on here would suggest filling the residual cavity if there is any suggestion whatsoever that the cavity may be less than 100 per cent free from air ingress. That could be a significant issue. You don't want to have a bunch of expensive insulation hanging on the outside looking pretty (only). NB I have not read all the thread, juts the 1st page or so, so I may have missed relevant stuff. 

 

Edit. Tried to send you a message, but 'EinTopaz cannot receive messages'. Do you or the moderators know why?

 

Thanks for the heads up, i've just messaged you directly.

I wasn't fully following the bit you meant by the air ingress. But can carry that on in the message. 

[EinTopaz]

3 hours ago, Mr Punter said:

Before you go much further, have you had an airtightness test to discover where any leaks might be coming from?  Seal up the opening to the house so you just test the extension.

I did yeah, pretty early on, we noticed air coming through wall light fittings etc. Those are all fixed now. I know what the problem is, it's poorly installed wall / ceiling PIR board, which im trying to resolve.

 

[EinTopaz]

4 hours ago, marshian said:

 

 

What about a "mouse trap" arrangement - drill holes in mortar and insert dowels to push insulation back under windows

 

Was starting to consider that myself yeah. Not a bad shout. Will see if it's possible. 

[Redbeard]

26 minutes ago, EinTopaz said:

I wasn't fully following the bit you meant by the air ingress. But can carry that on in the message. 

 

It's about thermal by-pass.

 

If you do EWI and somehow cold air gets into the 'sandwich' inside of the EWI you just have a very expensive fat layer of render.

[Iceverge]

Has my suggestion of closed cell foam to expand and put the boards tight to the inner leaf been lost in the ether? 

 

 

[Mike]

On 08/04/2025 at 12:33, EinTopaz said:

Just wondering if anyone on here has come across this and know what options i still have open to me?

I've not seen it, but I do recall reading that it's possible to break up the insulation within a cavity wall and extract it. Maybe using a robot rodent + vacuum cleaner, or something. You'd need to track down a specialist company.

 

[Nickfromwales]

13 hours ago, EinTopaz said:

 

Thanks for the heads up, i've just messaged you directly.

I wasn't fully following the bit you meant by the air ingress. But can carry that on in the message. 

Please do try to keep relevant content on here wherever possible, or summarise if you have an “Eureka!” moment, as solutions gained off air do not benefit the masses  🙏.

 

Gratsi!

[Nickfromwales]

14 hours ago, EinTopaz said:

 

Was starting to consider that myself yeah. Not a bad shout. Will see if it's possible. 

If you know where the sand and cement were bought / type / manufacturer etc then raking out and removing a whole brick(s) is not terribly difficult or compromising. 
 

The only issue with a 12-15mm dowel is that it may just stab the PIR if it requires a little ‘grunt’. 
 

You could rake out T section, eg where courses of mortar meet the perps, and then mitre-bond 2 bits of door stop together to mate a T piece to slide in, to get a bit more footprint to apply the pressure (only required anywhere where the dowel doesn’t work of course).

 

The only bump in the road here will be, if there’s big snots of mortar preventing the full sections of PIR being pushed back uniformly.

 

Good luck.

 

LINK

 

This can be bought to go into an angle grinder to make light work of raking out. You can get a shorter one to start off with, then the longer one to finish off 👍

[MikeGrahamT21]

Did you ever get in touch with cavity removal experts like i mentioned earlier in the thread? Some certainly noted that they removed foam cavity, though not PIR specifically, it may well be do-able.

 

I think your options realistically are going to be removal and reinstatement if possible, or take down the outer skin, sort the issue and rebuild.

[crispy_wafer]

9 hours ago, Iceverge said:

Has my suggestion of closed cell foam to expand and put the boards tight to the inner leaf been lost in the ether? 

 

 

 

Got me curious, so had a search, would you be thinking a product like this?  HoneyFoam 600 Insulation Spray Foam Kit | AB Building Products

[Nickfromwales]

30 minutes ago, crispy_wafer said:

 

Got me curious, so had a search, would you be thinking a product like this?  HoneyFoam 600 Insulation Spray Foam Kit | AB Building Products

Does that require holes to inject being made at very high frequency? It's a spray rather than an 'injectable' product?

 

I'm not sure if the 'right' product is a slower curing foam, eg so it travels much further before the curing process begins, as otherwise you'll have a lot of circles vs a continuous sheet of new material.

 

58 minutes ago, MikeGrahamT21 said:

Did you ever get in touch with cavity removal experts like i mentioned earlier in the thread? Some certainly noted that they removed foam cavity, though not PIR specifically, it may well be do-able.

This would be an excellent option. Any update @EinTopaz?

[Iceverge]

Walltite and Technitherm are brands that have/had a BBA cert from memory. 

 

Not cheap but a vastly superior idea to dismantling your house. 

[Iceverge]

@SteamyTea has been sniffing foam for many years. Perhaps he can chip in. 

[Redbeard]

3 hours ago, Nickfromwales said:

17 hours ago, EinTopaz said:

Thanks for the heads up, i've just messaged you directly.

I wasn't fully following the bit you meant by the air ingress. But can carry that on in the message. 

Please do try to keep relevant content on here wherever possible, or summarise if you have an “Eureka!” moment, as solutions gained off air do not benefit the masses  🙏.

 

Gratsi!

 

Yep, did that for just that reason - replied on the open forum. Thanks for the reminder anyway.

[EinTopaz]

13 hours ago, Iceverge said:

Has my suggestion of closed cell foam to expand and put the boards tight to the inner leaf been lost in the ether? 

 

 

Im still not sure how to apply the foam, looking for a company to do this. Don't fancy ballsing it up myself. 

[EinTopaz]

13 hours ago, Mike said:

I've not seen it, but I do recall reading that it's possible to break up the insulation within a cavity wall and extract it. Maybe using a robot rodent + vacuum cleaner, or something. You'd need to track down a specialist company.

 

With it being PIR interlocking stuff, I imagine that's going to be a complete nightmare. May as well remove the bricks at that point

[EinTopaz]

5 hours ago, Nickfromwales said:

Please do try to keep relevant content on here wherever possible, or summarise if you have an “Eureka!” moment, as solutions gained off air do not benefit the masses  🙏.

 

Gratsi!

Will do, to be honest it was simply a recommendation of some local businesses for me to enlist the help of,

[EinTopaz]

5 hours ago, Nickfromwales said:

If you know where the sand and cement were bought / type / manufacturer etc then raking out and removing a whole brick(s) is not terribly difficult or compromising. 
 

The only issue with a 12-15mm dowel is that it may just stab the PIR if it requires a little ‘grunt’. 
 

You could rake out T section, eg where courses of mortar meet the perps, and then mitre-bond 2 bits of door stop together to mate a T piece to slide in, to get a bit more footprint to apply the pressure (only required anywhere where the dowel doesn’t work of course).

 

The only bump in the road here will be, if there’s big snots of mortar preventing the full sections of PIR being pushed back uniformly.

 

Good luck.

 

LINK

 

This can be bought to go into an angle grinder to make light work of raking out. You can get a shorter one to start off with, then the longer one to finish off 👍

From the building WIP photos everything looks really flush to that inner block so i'm actually not sure how it could've broke away like this. Its got me questionning whether my cavity really is 150mm total. That is what the builders told me, but then i'm wondering why they've only used a 90mm interlocking PIR, as I can see the receipt for that material specifically. Why not have a smaller cavity and save on the footings if its not going to be filled? Or why not go thicker PIR. I'm going to dig on this a little. 

[EinTopaz]

5 hours ago, MikeGrahamT21 said:

Did you ever get in touch with cavity removal experts like i mentioned earlier in the thread? Some certainly noted that they removed foam cavity, though not PIR specifically, it may well be do-able.

 

I think your options realistically are going to be removal and reinstatement if possible, or take down the outer skin, sort the issue and rebuild.

I did, couldn't find anyone who could reasonably remove PIR. Can remove beads or even Wool roll  but not PIR, so far.

My issue with removal is, I dont even know if the replacement would be as good a U-value. If its beads for example. So id rather repair what's there and add more stuff over the top, ideally. Simply for the fact that its more insulation after all the cost and time. 

 

 

[EinTopaz]

3 hours ago, Iceverge said:

Walltite and Technitherm are brands that have/had a BBA cert from memory. 

 

Not cheap but a vastly superior idea to dismantling your house. 

Is there a minimum cavity size needed though? This was the issue I ran into with EPS beads, the company insisted on minimum cavity 40mm consistently to avoid issues with damp. 

[SteamyTea]

6 hours ago, Iceverge said:

@SteamyTea has been sniffing foam for many years. Perhaps he can chip in. 

Not kept up much this week, it is school holidays, so I am silly busy.

 

But yes, have sniffed most foams in the past, so what was the question?