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Panel Construction

Your building’s timber frame will be made from a series of panels, which we manufacture in our workshop in Appleby, Cumbria.


Each panel is made from five main components, individually chosen for their quality and performance.


All the materials we use are either made in the UK, reducing the environmental impact of transportation, or sourced from UK suppliers, supporting local businesses.


How your panels are made:

  • We connect I-beams to create the core of the frame, typically spaced at 600mm centres.

  • The interior vapour-barrier board is then affixed to one face of the frame.

  • The panel is turned over and we affix the exterior Gutex board

  • We seal the joints and membrane edges with airtightness tapes and adhesive

  • Holes are cored into the side of the panel, allowing us to blow in the insulation material. These holes are then resealed.

  • We fit the exterior membrane to the exterior board

  • Battens are attached to the interior vapour-barrier board, creating the service cavity for your plumbing pipes and electrics. Later on, your plasterer will affix plasterboard to these.


Panel Components

Working from the exterior of your building inwards, the layers in each panel are:

  1. Exterior membrane – weatherproof and breathable

  2. Exterior board – insulating and breathable

  3. I-beam frame – rigid panel core

  4. Insulation filling

  5. Vapour-barrier board – airtight moisture management


Two other important components are special airtightness tapes and adhesive. You’ll find more details about each of the components below.

Exterior Membrane -
Fronta Humida


 On the outside of your timber panels, we put on a weatherproof shell. Picture it as your building’s Gore-tex jacket. It’s a breathable membrane that offers weather protection during construction, while also acting as part of the frame’s ongoing moisture control system.

The membrane we typically use is called Solitex Fronta Humida. It’s manufactured by Pro Clima, a German company whose materials are at the forefront of Passivhaus construction.


Why we chose Fronta Humida

Backed by Pro Clima’s excellent reputation for quality products that perform to the highest standards, Fronta Humida protects your frame from moisture coming in from outside, while also allowing any moisture introduced during the building phase to dry out.

Our supplier is Ecological Buildings Systems, the sole UK importer for Pro Clima products. They’re based near us in Cumbria. Visit their website for full details about their range of products for energy-efficient building.


  • Breathable
  • Weatherproof
  • Dustproof
  • Locally sourced from Cumbria-based UK supplier

Exterior Board -


 Beneath the Fronta Humida exterior shell comes a layer of Gutex wood fibreboard. This is an insulated board, which is permeable by water vapour to allow moisture to pass out from your building. It’s part of the system that regulates humidity in your energy-efficient home.


Why we chose Gutex


Gutex is a German company, based in the Black Forest. With an 80-year history, the firm is a leader in innovative, environment-friendly manufacturing. Gutex is well respected in the world of energy-efficient construction, due to the quality and performance of its products. All Gutex products undergo stringent quality control tests by the company and are subject to approval by an independent, authorised test and certification agency (FMPA, Stuttgart).

Gutex insulation boards are manufactured from raw material obtained from forests in the Black Forest, where only sustained forestry practices are employed.

The company’s quality and environmental protection management system is certified according to DIN EN ISO 9001, ISO 14001 AND EMAS 11 (EU Eco Audit Ordinance).


  • Biologically harmless
  • Environmentally-friendly manufacturing
  • Superb regulation of humidity
  • Locally-sourced from a Cumbria-based UK supplier
  • Strong board with tightly jointed insulation

I-beam - Finnjoist


 At the heart of our panel system is a frame made from engineered I-beams. We currently use the Finnjoist I-beam, made by Metsä Wood at their King’s Lynn plant in the UK. These I-beams are manufactured from high-quality, oriented-strand board (OSB3) web, and flanges made from the company’s own Kerto laminated veneer lumber.


Why we chose Finnjoist I-beams

 The Finnjoist engineered timber i-beam joists deliver strength and rigidity. The Kerto used for the flanges is incredibly strong and stable, and it does not distort or shrink. The end product is an I-beam that’s lightweight yet incredibly strong and reliable.

Fully engineered and factory produced to give uniform strength, rigidity, size and weight, it outperforms traditional solid wood construction.


  • I-beam manufactured in the UK
  • Strong environmental credentials
  • Engineered for strength & rigidity
  • Certified to PEFC Chain of Custody standard

Insulation - Gutex Thermofibre


 Once the interior and exterior boards are in place and sealed, we fill the panel with insulation. The product we typically use is Gutex Thermofibre. Made entirely from sustainably managed Spruce and Fir trees in the Black Forest, Thermofibre is a high-performance wood-fibre insulation offering very high U-values.

We inject Thermofibre into our panels to a specific high density, so that no settling occurs when the panels are erected upright. For the life of your building, your panels offer a complete, reliable insulation layer.


Why we chose Thermofibre

 In every way, Thermofibre is an eco-friendly and highly effective insulation. It contains trapped carbon, it mitigates atmospheric carbon. But it also is fully recyclable, for example, in the manufacture of new wood fibre products. It has an incredible degree of fire resistance and offers effective acoustic insulation, too.


  • High U-value
  • Extremely environmentally friendly
  • Fire resistant & sound insulation
  • Minimal waste & is fully recycleable

Interior Board - Smartply Propassiv


On the inside of your building, your timber panels will have an interior vapour-barrier board. We generally use Smartply Propassiv, made by Medite Smartply. This board is a structural OSB panel with integrated vapour control and air barrier properties for use as structural sheathing in timber frame structures. Airtightness is engineered into the OSB panel substrate, whilst SMARTPLY's in-house speciality surfacing technology provides an integrated vapour barrier with consistently high vapour resistance over the entire surface.


Why we chose Propassiv


This structural board is the main component that makes your building airtight, which is the key to reducing the amount of energy you’ll use for heating. Research by the Building Physics Laboratory at the K.U. Leuven and on-site experience showed that traditional OSB boards are not always airtight.

To combat this, Medite Smartply developed the Propassiv board, providing a consistent airtight layer to the highest industrial standards. The board is 'Passive House Institute (PHI)' Certified, and is CE marked and manufactured to the highest quality standards to comply with ISO 9001.


  • Highly airtight board
  • Factory-fitted vapour control layer
  • Sourced from UK-based supplier
  • Passive House Institute certified

Tapes & Adhesives - Tescon and Orcon F

Various tapes and foam

We use only the best tapes and adhesive available on the market to ensure our panels are fully sealed. We pay the highest attention to detail when sealing our panels, because it’s absolutely critical to our airtightness and vapour-control system.

The products we use are from Pro Clima, the German company that manufactures some of the other airtightness and vapour-control products we use.


To seal the exteriors and interiors of our builds we use Tescon Invis. We also use Orcon F adhesive sealant (the stickiest, strongest stuff we’ve ever come across!). We source these from Ecological Building Systems in Cumbria.


  • Tescon Vana tested for 100 years’ adhesion
  • Airtight bonds
  • Orcon F permanently flexible for reliable adhesion
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