Insulation over Beam & Block

[Mulberry View]

We have a Nudura build with Beam & Block floor. The B&B is now installed and grouted, we did all the work and the resulting floor is pretty level/flat. I think the finish is good enough that we can examine/rectify any imperfections. Sand blind or not? I intend to see what the floor is like once we've had a day or tidying it up, but I'm certain its better than usual building site standard.

 

Our internal walls are built from medium-dense concrete blocks on 100mm thick Marmox blocks

 

Our design showed 150mm of PIR, but we can now better this due to some changes in build. We have approx. 290mm from the top of the floor finish down to the top of the B&B. We plan on Microcement throughout, which totals 4mm, so 286mm for Insulation and screed. We intend on having UFH (yet to be designed).

 

What's the best split of Insulation and Screed for optimal performance? Drying time isn't a huge priority, although my head is fried all our other nonsense, I'd like to make some blummin' decisions and get this all underway before the weather cools down. I expect our Glazing to be going in late October or early November, all being well.

 

Any and all help is greatly appreciated.

 

 

[Russell griffiths]

200mm eps then screed, save a fortune over pir. 

[JohnMo]

22 minutes ago, Russell griffiths said:

200mm eps then screed, save a fortune over pir. 

No where near the same insulation value, though. I would do (did) 200mm PIR, the rest either concrete or screed.

[Mulberry View]

4 minutes ago, JohnMo said:

No where near the same insulation value, though. I would do (did) 200mm PIR, the rest either concrete or screed.

 

That's my thought. The money saving would be lovely, but I'd like to try to offset the poor performance of the Beam & Block floor as much as possible.

[Nickfromwales]

2 hours ago, Mulberry View said:

 

That's my thought. The money saving would be lovely, but I'd like to try to offset the poor performance of the Beam & Block floor as much as possible.

Ok, so what you need to do is grout and grout again, and then check it over to ensure there are zero gaps for cold air to even attempt to rise through. Then with cold air infiltration dealt with you don't have major issues to deal with.

 

If your ok with the cost go for 2x PIR, but you can go for 100mm EPS and then 100mm PIR over, as the cost benefit vs your lifetime will be negligible tbh. Then the ~86mm on screed. But.............

 

If you want long term cost savings, not short term ones, then have ~100mm concrete slab on top, and go all PIR for the residual build up; so 111mm of concrete and 175mm of PIR. It'll swing the maths around to long term lower running costs, comfort, and open the option of batch heating up.

 

UFH design can be tweaked to sympathise with this option to squeeze every last drop of juice out.

[Nickfromwales]

PS, if airtightness is dealt with meticulously, then a lot of these 'problems' evaporate. Ventilation heat loss is the biggest wallet/occupant comfort killer, fabric one can be almost set aside if you get AT + MVHR with a good spec.

[nod]

As above 200 + 75 

 

A self builder thing is getting hung up on bumps and hollows on the BB 

The insulation that you put dow won’t lay flat Till you dump 20 tones of sand and cement on it 😂

[Russell griffiths]

10 hours ago, JohnMo said:

No where near the same insulation value, though. I would do (did) 200mm PIR, the rest either concrete or screed.

We all know that, but do you need 200mm of pir in an nudura icf house, zero cold bridges, probably an air test of below 1   

dpm sealed up against the walls, insulation fitted tightly. 
 

ufh will probably only flick on for an hour a day. 
 

I just don’t see the need for such a high level of insulation when the ufh pipes are in the 80mm screed sat on top of the insulation. 
 

 

[JohnMo]

2 hours ago, Russell griffiths said:

We all know that, but do you need 200mm of pir in an nudura icf house, zero cold bridges, probably an air test of below 1   

dpm sealed up against the walls, insulation fitted tightly. 
 

ufh will probably only flick on for an hour a day. 
 

I just don’t see the need for such a high level of insulation when the ufh pipes are in the 80mm screed sat on top of the insulation. 
 

 

It's the only part of the house that once done, isn't easy to undo and improve, so why faff about for a few hundred pounds in savings. Do it once do it well. Unlike a ground bearing slab you are exposed to air temperature under block and beam so downwards losses are higher 

[Nick Laslett]

Jablite High Performance Plus + Insulation EPS70 vs Recticel Eurothane® General Purpose PIR Insulation

0.030W/mK vs 0.022 W/mk

Jablite

3x200mm sheets @ £148.29 Ex-Vat = £49.43 per board

Recticel

1x100mm sheet = £27.48 Ex-Vat 

1x 75mm sheet = £22.57 Ex-Vat

Total 175mm = £50.05

https://screedsdirect.co.uk/collections/recticel/products/recticel-eurothane-r-general-purpose-pir-board?variant=40556563300531

 

https://screedsdirect.co.uk/products/jablite-high-performance-plus-insulation-eps70?srsltid=AfmBOord9lW6rrH3pBXBluMjLWsRabq32G_jbK5bzgxaccxMfvfZJLZB

 

I buy most of my materials from these guys, free delivery on purchases over £500. 
 

I’m sure you can find cheaper versions of the EPS, but I try to stick with established brands where I can. 
 

My vote would be for highest ceiling height possible with a U value 0.11, with 100mm of concrete for best decrement delay and heat capacity. Over the long term ceiling height trumps everything for me. No idea if concrete actually performs better than screed, I’m sure someone will correct me if necessary. 

Edited August 9 by Nick Laslett

[Mulberry View]

18 minutes ago, Nick Laslett said:

Jablite High Performance Plus + Insulation EPS70 vs Recticel Eurothane® General Purpose PIR Insulation

0.030W/mK vs 0.022 W/mk

Jablite

3x200mm sheets @ £148.29 Ex-Vat = £49.43 per board

Recticel

1x100mm sheet = £27.48 Ex-Vat 

1x 75mm sheet = £22.57 Ex-Vat

Total 175mm = £50.05

https://screedsdirect.co.uk/collections/recticel/products/recticel-eurothane-r-general-purpose-pir-board?variant=40556563300531

 

https://screedsdirect.co.uk/products/jablite-high-performance-plus-insulation-eps70?srsltid=AfmBOord9lW6rrH3pBXBluMjLWsRabq32G_jbK5bzgxaccxMfvfZJLZB

 

I buy most of my materials from these guys, free delivery on purchases over £500. 
 

I’m sure you can find cheaper versions of the EPS, but I try to stick with established brands where I can. 
 

My vote would be for highest ceiling height, with 100mm of concrete for best decrement delay and heat capacity. Over the long term ceiling height trumps everything for me. No idea if concrete actually performs better than screed, I’m sure someone will correct me if necessary. 

 

Thanks for the reply @Nick Laslett. Our ceilings are a minimum of 2.5m throughout, but the whole Kitchen/Dining/Living room is under a 5° sloped ceiling that rises from 2.5m to about 3.3m, they are already quite generous. My current levels are to provide a completely flush threshold to our Dining Room door.

 

But overall, you appear to be saying that the PIR route is minimally more expensive and so, in your opinion the better route?

[Russell griffiths]

4 hours ago, JohnMo said:

It's the only part of the house that once done, isn't easy to undo and improve, so why faff about for a few hundred pounds in savings. Do it once do it well. Unlike a ground bearing slab you are exposed to air temperature under block and beam so downwards losses are higher 

When I did the costs on mine it was £3000 extra for pir over eps. 
that’s a good chunk more than a few hundred pounds. 
 

[Nick Laslett]

4 hours ago, Mulberry View said:

But overall, you appear to be saying that the PIR route is minimally more expensive and so, in your opinion the better route?

I like @Nickfromwales two suggestions. I also think the EPS suggestion from @Russell griffiths is fine. 

[SteamyTea]

20 hours ago, Mulberry View said:

What's the best split of Insulation and Screed for optimal performance

That is an interesting question.

You can work out the thermal inertia for each element, from that you can calculate the power delta over time.

As long there is enough stored energy in the floor to last 18 hours (for a cold winters day), the difference then gets taken up by the insulation thickness.

 

s = J m⁻² K⁻¹ / (t i u) 

Where tiu is the thermal inertia calculated from J m^-2 K^-1 s^-½ for the materials chosen.

 

Easy.

 

 

[Mulberry View]

44 minutes ago, SteamyTea said:

That is an interesting question.

You can work out the thermal inertia for each element, from that you can calculate the power delta over time.

As long there is enough stored energy in the floor to last 18 hours (for a cold winters day), the difference then gets taken up by the insulation thickness.

 

s = J m⁻² K⁻¹ / (t i u) 

Where tiu is the thermal inertia calculated from J m^-2 K^-1 s^-½ for the materials chosen.

 

Easy.

 

 

 

I would love to have the intelligence to be able to turn that into something practical, but I don't know where to start. LOL.

[SteamyTea]

2 minutes ago, Mulberry View said:

 

I would love to have the intelligence to be able to turn that into something practical, but I don't know where to start. LOL.

Think it of it as how much fuel is in the car (thermal capacity) and what MPG it does (thermal resistance or U-Value)

As a general rule, the faster you go (bigger temperature differences) the more fuel you use (greater thermal losses).

Easy now isn't it.

[saveasteading]

Yes to levelling off sand, but I'd suggest add cement to the sand.

Otherwise you will have gaps for ever.

 

Then go 100mm eps, then 100mm pir with staggered joints, then 90 screed.

 

Insulation provides diminishing returns with thickness, so this is a pragmatic proposal. Ie the saving with eps is quite a lot, but the extra heat loss will be low.

[Nickfromwales]

If the levels not crazy out-of-whack there’s probably no need to do anything other than grout. 
 

With 2 layers vs one thick one, the sheets will sit down nicely and conform, even more so when you dump the concrete on top!! 
 

Doubt this needs time and money throwing at it tbh.