Blocks for inner skin

[Iceverge]

EPS beads here. They're fine although I am slightly suspicious of the claimed k value of 0.033. I think 0.035-0.037 world be closer in reality. 

 

Over all would recommend.

[Ben1984]

5 minutes ago, Iceverge said:

EPS beads here. They're fine although I am slightly suspicious of the claimed k value of 0.033. I think 0.035-0.037 world be closer in reality. 

 

Over all would recommend.

Thanks. I will do some research into this. It's likely that I will be doing my own blockwork so there would be no installation cost (just my time) associated with the mineral wool. I would, presumably, have to pay someone else to install the beads so this might be a deciding factor for me.

[Ben1984]

I've done some calculations. I'll share them here incase they are of use to someone else (or someone can pick me up on any mistakes).

 

I have about 420m2 of external cavity wall area which will sit on a total of 114m of foundations.

 

I have compared the two following options:

 

Option 1 - 20mm external render/100mm dense block/150mm 32 cavity slab/100mm dense block/20mm internal render+skim finish - which will give me a u-value of around 0.20 (not sure I trust the calculator I've used to reach this figure)

 

Option 2 - 20mm external render/100mm dense block/200mm 37 cavity slab/100mm dense block/20mm internal render+skim finish - which gives me a u-value of around 0.18

 

Costings 

 

Option 1 - £11,500

420m2 of 150mm 32 cavity slab ~ £7000 

37m2 of concrete in footings (based on 600mm wide and 550mm deep) ~£4000

1000 wall ties ~ £500

 

Option 2- £10,240

420m2 of 200mm 37 cavity slab ~ £4200

44m2 of concrete in footings (based on 700mm wide and 550mm deep) ~ £4840

1000 wall ties ~ £1200 (not sure about this figure, more research required)

 

I can use concrete lintels on almost all the openings so there are no additional costs there.

 

Unless I am missing something, it would appear that it is infact cheaper to go for the 200mm cavity option which also provides a better u-value.
 

 

 

Edited 9 hours ago by Ben1984

[Iceverge]

@tonyshouse

 

http://tonyshouse.readinguk.org/

 

Good blog here from tony. Don't know if he's still active or not. 

 

Similarly from Green building store there's a series of videos about denby dale passivhaus, great details for a cavity wall house. 

 

 

[LiamJones]

5 hours ago, Ben1984 said:

What software/calculator have you used to produce this? 

 

 

Ubakus.de

[Ben1984]

54 minutes ago, LiamJones said:

Ubakus.de

Thanks, that's seems much better than the calculator I had been using

[SBMS]

25 minutes ago, Ben1984 said:

Thanks, that's seems much better than the calculator I had been using

We are doing our second build and have opted for 200mm cavity with eps beads. Coming out around 0.15 u value. We are doing dot and dab however I am going to use aerobarrier for air tightness.  It negates the need for a parge cost on Inner block, performs sealing around windows etc. will be doing it pre plaster. Not commonly used on here so I will be reporting back how it goes when we get to that stage of the build.

[Iceverge]

4 minutes ago, SBMS said:

We are doing our second build and have opted for 200mm cavity with eps beads. Coming out around 0.15 u value. We are doing dot and dab however I am going to use aerobarrier for air tightness.  It negates the need for a parge cost on Inner block, performs sealing around windows etc. will be doing it pre plaster. Not commonly used on here so I will be reporting back how it goes when we get to that stage of the build.

 

Are you not worried about using excessive amounts of the aero barrier caulk? 

 

Keep us posted. 

[Ben1984]

52 minutes ago, SBMS said:

We are doing our second build and have opted for 200mm cavity with eps beads. Coming out around 0.15 u value. We are doing dot and dab however I am going to use aerobarrier for air tightness.  It negates the need for a parge cost on Inner block, performs sealing around windows etc. will be doing it pre plaster. Not commonly used on here so I will be reporting back how it goes when we get to that stage of the build.

I think I could hit the same 0.15 u-value by using a better quality mineral wool but it would pretty much double the cost of the insulation. I'm failry certain I would never get that £7000 back! I've re-done my calculations on ubakus.de calculator and they are coming out at 0.17 with 200mm of Knauf 37 - I'm more than happy with that.

 

I've had a quick look at the aerobarrier - seems like a good idea. Have you got a quote for your project yet? I don't think I will need it with a wet plaster finish but i'd be interested to have a rough idea of what it might cost.

[Iceverge]

 

Here's one of a few technical videos about denby dale. Well worth the view. 

 

I would alter the foundation, thresholds and window detail slightly but it's a great starting point.