Thermal Design

Sustainable design begins with place, and our place is Wales. In Wales, we especially need homes that can be kept affordably warm and dry during a typical cold, damp winter. A newbuild is not properly sustainable and affordable if built with cheap imports and inferior thermal design. For a better house, we went back to the drawing board:


The hollow structural building HSH panels are built from FSC Welsh spruce and galvanized steel webs and clad with tongue and groove spruce boards. Once on site, they can be erected on to a ready prepared base in just a few days.

As soon as the external panels and internal walls and floor are in place and the roof trusses fixed, the whole house is wrapped in a breathable waterproof membrane. Fitting this is very important and if properly done will give a draft free, warm, comfortable, breathable house. The membrane has all the joints sealed with tape, battened with 50 x 25 mm timber to form a service void on the inside and then dry lined with plaster board and painted with VSO free breathable paint.


There are several different options for the roof covering. Our preferred material is Colorcoat Urban® another Welsh product by Tata.  It is a raised seam coated steel system that is really very clever. Not only is it affordable, it has excellent eco-credentials and well detailed looks very similar to an old lead or zinc raised seam roof.


The external wall can be clad in locally grown timber - Larch, Douglas Fir or Western Red Cedar or wood wool board, then a two coat render of Glaster™ from Ty Mawr is applied.  This is an alternative to traditional lime mortars, plasters and renders using various colours and grades of crushed, recycled glass instead of sand.


The wall panels are specially designed to use Warmcell recycled cellulose insulation, made by the Welsh company Excell. Warmcell 500 is made from recycled paper with non-toxic additives. It was developed to combine high levels of insulation with excellent breathability.

With a thermal conductivity value (k) of only 0.040 W/mK, this is “super-insulation” and goes a long way to allow us to achieve an external wall U value of 0.12. The same insulation is applied to the hollow floor cavity and the roof has Warmcell 300 blown in over the upper ceilings with ventilated space above, achieving a U value of 0.09.


We are currently seeking a company that can compete in an extremely competitive market for highly efficient windows, doors and other internal joinery made from Welsh Timber in a local factory.


We are proud to announce that our building system has achieved the LABC accreditation and registration.  This creates a clear path for people building with the system to apply for an LABC warranty to gain insurance and raise finance through mortgages.

The HSH panel design has passed British Standard and Euro 5 Standard for racking and engineering and we have already built to Sustainable Building Code 4. We are now aiming for Code 5, having made improvements to air tightness and cold bridging at first and ground floor levels.

And also...

Our new building system is very flexible. Of course you can use our tried and tested designs, but there is also plenty of scope to build with the components to your own specifications. Whatever your building or community requirements, we can work with you or your architect to help meet them in a sustainable way.