How would you insulated if building block and block ?

[Big Jimbo]

I think i am going to end up building from block and block. The outside will be rendered on the bottom half, and cement clad planks on the top half (ventilated). I would like to achieve better than regs insulation levels if poss, and not to expensive. I am not sure im keen on the rigid type cavity insulation. No offence to any bricklayers on here, but it's hard enough to get the cavity batts fitted well, let alone tounge and groove ridged panels. I could live with perhaps battens on the inside leaf, with insulation in between, if that could also provide me with a cavity for electrics.

Any ideas from the smart, and helpful people on here ? Thanks in advance.

[joe90]

It’s what I did using rockwall batts (200mm) as long as your brickie is good at keeping it clean (mine were) or consider blown beads.

[Carrerahill]

24 minutes ago, Big Jimbo said:

I think i am going to end up building from block and block. The outside will be rendered on the bottom half, and cement clad planks on the top half (ventilated). I would like to achieve better than regs insulation levels if poss, and not to expensive. I am not sure im keen on the rigid type cavity insulation. No offence to any bricklayers on here, but it's hard enough to get the cavity batts fitted well, let alone tounge and groove ridged panels. I could live with perhaps battens on the inside leaf, with insulation in between, if that could also provide me with a cavity for electrics.

Any ideas from the smart, and helpful people on here ? Thanks in advance.

We used PIR, fully sheets with foamed and taped joints. Bricklayer put the internal walls up to a level first, then left all the wall ties sticking out, I worked out I could just push a full 4x8 sheet of 50mm PIR over the ties and they just poked through, I added the retention discs and could install about 8 sheets in 30-40minutes, it was comical how fast it went on, we got a really tight fit, jointed and taped it all and it looked like a perfect foil box. 

 

If I was doing it again, I would probably use 75mm PIR, I would even look into stretching it to 100mm PIR, but it makes the walls thick at 350mm, but then, not really that much worse than a TF and block build using block 100mm, cavity 50mm, and 150/175mm TF. So only 25/50mm in it.

 

 

[Carrerahill]

This was during tape-up:

 

 

[Big Jimbo]

@Carrerahill That is a seriously neat job.

[Carrerahill]

5 minutes ago, Big Jimbo said:

@Carrerahill That is a seriously neat job.

Thanks, our bricklayer has been building things for us for about 6 years now, he is very accommodating, and does it all as weekend shifts so it creates timeframes for me to get my bits done without it impacting him. I know this will not suit all but it suit me perfectly. This was done last summer and I was doing 6-7 sheets a night after work before dinner - it was an easy shift. If you ask your guys to build like this and fit the insulation as full sheets you will get a nice neat job like this. I think the key here was installing full sheets to minimise joints and just generally make it look much neater. 

 

 

[LSB]

I'm surprised at how thin you are allowed to put insulation at 75 or 100 , we must include 150 in our block / block cavity wall.

Will be the same as you are doing, just thicker.

This came from BC with the latest regs.

 

[JackofAll]

Going with 300mm full fill knauf dritherm 37. Got 130 packs for 17euro a pop from BnQ when on offer normally 53 euro a pack.

[Big Jimbo]

39 minutes ago, JackofAll said:

Going with 300mm full fill knauf dritherm 37. Got 130 packs for 17euro a pop from BnQ when on offer normally 53 euro a pack.

Well B n Q won't have been selling it for a loss, so shows how at full price it is overpriced.

[LSB]

1 hour ago, JackofAll said:

Going with 300mm full fill knauf dritherm 37. Got 130 packs for 17euro a pop from BnQ when on offer normally 53 euro a pack.

that's a brilliant price, when was that
we went for dritherm 32 @ 150mm thick and the lowest price we were quoted was much higher @ £30 excl VAT
 

Edited May 5, 2023 by LSB

[JackofAll]

47 minutes ago, LSB said:

that's a brilliant price, when was that
we went for dritherm 32 @ 150mm thick and the lowest price we were quoted was much higher @ £30 excl VAT
 

Started buying last October and would buy all they had, when it came back in would do the same. Bought last lot in January before it went back up. Think it was old stock as there are 8 batts to a pack think the newer packs may have 12. Was going to go the 32 route with 250mm cavity but Iceverge here put the 37 idea in my head bigger cavity but same performance at cheaper price.

[LSB]

9 minutes ago, JackofAll said:

Started buying last October and would buy all they had, when it came back in would do the same. Bought last lot in January before it went back up. Think it was old stock as there are 8 batts to a pack think the newer packs may have 12. Was going to go the 32 route with 250mm cavity but Iceverge here put the 37 idea in my head bigger cavity but same performance at cheaper price.

pity I've just had my first batch delivered 🙂
although, this is only a 1/4 of what we finally need.

I looked at our local BnQ and they don't even sell this stuff so maybe Ireland is different, being in the EU (wish we still were)

 

[jayc89]

How wide are you cavities? I'd get up to wall plate, fit cavity closers and blow it full of EPS beads (drill holes from the inside, then fill and plaster). 150mm cavity should get you well within building regs. 200mm cavity should see you reaching PH numbers. 

[Big Jimbo]

Sounds like a good idea. I wonder what the extra cost of cavity beads would be ?

[jayc89]

Just now, Big Jimbo said:

Sounds like a good idea. I wonder what the extra cost of cavity beads would be ?

 

I plan on doing this for our extension, when I looked into pricing last year, there was very little difference between it and the cost of material + labour for the bricks to fit batts as they go. Plus with this method, you don't risk gaps etc (the companies I spoke with also do a few inspection holes to confirm a full fill). 

[Big Jimbo]

1 minute ago, jayc89 said:

 

I plan on doing this for our extension, when I looked into pricing last year, there was very little difference between it and the cost of material + labour for the bricks to fit batts as they go. Plus with this method, you don't risk gaps etc (the companies I spoke with also do a few inspection holes to confirm a full fill). 

@jayc89 i will have to look into it. sounds good though.

[Iceverge]

Mineral wool batts or blown beads. 250mm cavity here with blown beads. 

 

Have you seen the denby dale videos from green building store? Also @tonyshouse did a blog. 

 

 

[Andehh]

Mineral woolen bats, check every couple of days for snug fit! 

[Chanmenie]

18 hours ago, LSB said:

I'm surprised at how thin you are allowed to put insulation at 75 or 100 , we must include 150 in our block / block cavity wall.

Will be the same as you are doing, just thicker.

This came from BC with the latest regs.

 

You would not need 150mm PIR to meet building regs, 100mm should do it ?

[jayc89]

Our Architect said a 100mm cavity with 90mm Kooltherm is now the minimum, although we will be going for 150mm cavity will EPS beads blown in. Very similar in reported u-values, but I'd have more confidence that the beads have provided a better covering. 

[Iceverge]

4 hours ago, jayc89 said:

Our Architect said a 100mm cavity with 90mm Kooltherm

 

Kooltherm £££££

 

Another steak dinner for the Architect and a week in the Rivera for the Kingspan salesman. 

[cwr]

We went for 240mm cavity blown beads, gives a 440mm thick wall. Partially did this as the solid wall in the footings would be exactly 1 block length thick.

[Dave Jones]

recticell all day long.

[Big Jimbo]

25 minutes ago, Dave Jones said:

recticell all day long.

But getting brickies to fit that well is going to be hard work IMO.

[Iceverge]

1 minute ago, Big Jimbo said:

But getting brickies to fit that well is going to be hard work IMO.

 

Blown beads.

 

Leave the cavity run as low as you can. Right to the foundation if you can get your SE to agree. Don't cross the cavity with the DPM. Have a separate DPC on the outer leaf. 

 

This will give some allowance for mortar droppings not to bridge the cavity above DPM as they'll just fall to the abyss harmlessly. 

 

Then fill the cavity with blown beads. 

 

If you have a line of aerated blocks in line with the floor insulation you'll get performance matching an insulated raft foundation.