Energy efficient new build

[apmh64]

Hi, we have recently received planning permission for a new build and are in the process of deciding on the best approach for the build. We are looking for an energy efficient house (wall u-values of around 0.14) with a concrete first floor and have two options in mind:

1) Insulated concrete formwork (ICF) with SIPs roof.
2) Brick and block with CavityTherm wall insulation and a SIPS roof.

I wondered if anyone else had built using either of these approaches and if they would share their reasoning on why they went the way they did?

Thanks.

 

[freddiemercurystwin]

Why not just do the lot in SIPs? If you don't mind timber walls that is.

 

[apmh64]

We did look into SIPs and actually visited a build but are not too keen on the wooden walls and ICF or brick and block are more suitable for the concrete first floor I understand.

 

[^woody^]

Do you actually know what design the house will take? It's not good deciding on a certain construction unless you know that it is suitable for the design

 

[apmh64]

I think we are ok with the design, we have had both conventional and ICF builders review the designs and both are happy their techniques are suitable. The house itself is not of an unusual design, a two story L shape build with the end of the L single story and a loft conversion.

 

[Norcon]

Rendered dense block/ Dense block, plaster and 200mm cavity filled with Kingspan Ecobead will give you 0.15.

A lightweight block construction might lower it a bit further but would need checking with an SE on the load bearing.

 

[apmh64]

Thanks for the idea of using lightweight blocks, if that will help u-values I will mention it to our SE. We are looking at using cavitytherm rather than kingspan as I understand we are able to have a 125mm cavity and get a u-value of 0.15 and so save a little of the interior space.