For the building structure we decided on a wooden frame with glulam beams. I considered :
- block work with cavity and on the flat with external insulation (I was advised that this was going to be difficult with the number and size of window openings on the south facing walls).
- standard wooden frame with panels
- Thermal Block -http://www.thermibloc.fr
- Poroton Blocks.
- ICF (Insulated Concrete Formwork)
- Another block that was certified by the passive house institute (but the certificate appears to not have been renewed on the passive house institute web site)
The reason for selecting wood was that I feel that this is going to suit our lifestyle and offer flexibility with the internal layout if changes are required in the way the building is used in the future (room layout or open plan).
The advantages I feel for us will be that when heat is needed it would easily be supplied and if heat was not needed it could be switched off if we are not in the house. The temperate climate in the UK and Ireland is unique (one day 5 degrees next day 13 degrees) and I feel that this will allow us to lower or raise the temperature quickly thus possibly reducing our heating bill.
The external wall system will be cement board with an acrylic finish, a ventilated space, and a vapour membrane (Solitex WA) stapled with stainless steel staples with the membrane sealed on the perimeter (to keep wind and small insects out) using a proclima adhesive called Orcon F. The OSB board will not be installed directly behind the vapour membrane but situated 220 mm deep into the wall structure.
(My understanding for doing this is that there is a higher risk of extra moisture being trapped in the OSB board if it was on the outside . By increasing the insulation less heat would escape to dry the board over varying Irish weather cycles. This could then decrease the structural strenght of the board if moisture was not released quickly enough.)
A few drawings will hopefully explain the above.
The walls will be filled with Isover Metac situated behind the air tight membrane. (I am thinking of it as a zoo strategy i.e keeping the fibres behind the glass in this case the air tight membrane). I am considering Cellulose or Hemp on the internal partitions ( I am looking for something that is cost efficient and provides thermal capacity.)