The Larch House & The Lime House

Two social homes built and certified as Passivhaus, using Welsh timber throughout – for structure, cladding and joinery.

About this project

One 3-bedroom and one 2-bedroom Passivhaus built for the United Welsh Housing Association. The designs were winners of the BRE’s Welsh Passivhaus competition for show homes for the 2010 Eisteddfodd.

Construction Method

In order to use Welsh timber, the depth of the studsin this closed panel softwood frame system was limited to 225mm, which is the largest available section of Welsh C16 softwood. Although more than double the normal thickness for closed panels, further insulation was added inside and outside thus achieving the very low u-values required by the Passivhaus standard. The insulated envelope forms a simple box, with a conventional timber roof above.

The timber story

A key part of the competition brief was to use local materials and products where possible, to minimise embodied energy from transport and to encourage the development of the Welsh sustainable construction sector. 

  • Structure/internal joinery: Welsh Sitka spruce

  • Cladding/external joinery: Welsh larch

  • Passivhaus certified windows and door of Lime House: Welsh larch, thermally modified in Anglesey

Further information

Home Grown Timber in UK Construction, Vol.1*

Images: Jefferson Smith and G Pargeter

*Case study kindly provided by Woodknowledge Wales.

Key contacts


United Welsh Housing Association




Pendragon Design and Build Ltd

Timber Supplier

Holbrook Timber Frame; Pembrokeshire Timber Store (Cladding)

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