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Bosig at window head
Bosig at window head
Bosig board at door threshold
Bosig board at door threshold
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Bosig Phonotherm 200 (RG550)

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  • Product Overview
  • Technical Details
  • Downloads
  • Installation guide

Product Overview

Main purpose

An insulated rigid plank/board used to minimise thermal bridging through structural supports around windows, doors and foundation junctions. Being rigid, it provides the needed structural support and takes secure fixings easily.  

Use it on

Window, door and foundation junctions where a structural support is required that would typically interrupt the building’s insulation.  Also steel or timber beams at load bearing points.


Phonotherm 200 (RG550) is an insulation board ideally suited for door thresholds and window installations, where it is important to minimise thermal bridging. Because of its physical stability coupled with the optimal thermal performance, this adaptable product very effectively minimizes the risk of thermal bridging at critical building junctions.

Where to use it

Bosig can be used around windows, doors and foundation junctions. Especially where highly insulated walls meet other high-performance elements like windows and doors. The structural support needed in these locations, when made from traditional materials like aluminium, steel or timber, can cause significant thermal bridges and heat loss from the building.

Bosig is often used at load-bearing points on structural beams (e.g. steel or timber beams where they rest on foundations or penetrate external walls etc). With a compression strength of 7000 kPa, Bosig is extremely strong so can effectively minimise thermal bridging in these areas.

What it does

Bosig Phonotherm can be, cut, drilled, screwed, nailed or machined just like timber. It functions as an excellent insulator and will minimise thermal bridges. It has high strength and greater stability than timber, plywood or MDF; it won’t expand or contract when subjected to changes in temperatures, moisture or humidity. It is available with grooves on the surface for plastering or rendering on to and is also supplied smooth for all other applications.

How it works

The presence of a thermal bridge allows heat to bypass the thermal envelope despite the ever increasing demands for improved u-values on walls, doors, windows etc. Bosig Phonotherm optimises junctions where thermal bridges occur and reduces heat loss.

Why we love it

The effect of thermal bridges is amplified in highly insulated buildings and can be a significant cause of heat loss. Thermal bridges can lead to surfaces being cool enough for condensation to form. Condensation and the risk of mould and structural damage can be avoided by carefully controlling thermal bridges. Bosig is a highly versatile and simple insulated replacement for many structural materials making it easier to solve thermal bridging in numerous situations.

Bosig Phonotherm 200 (RG550) insulation board is made entirely from upcycled polyurethane, a material that would typically be disposed of in landfill and does not contain any formaldehyde.


  • Inert and stable board
  • Simple to cut and shape
  • Green building product
  • Super-strong board


  • The boards are very stable.They won’t dry out or shrink and are thermally stable between -50 and 100°C.
  • 100% water resistant, will not absorb and store moisture, so no risk of swelling or decay.
  • Like timber, can be cut to any shape or size and machined on site.
  • Highly resistant to chemicals
  • Available with grooves to provide an excellent surface for plaster
  • Utilise raw materials otherwise destined for landfill 
  • Manufacturing complies with environmental standard ISO 14001
  • Free of formaldehydes
  • Versatile, robust and resilient performance even in damp climates
  • High resistance to deformation under load


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Technical Details

Key Technical Data

Technical Datasheet

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  • Download

Material Safety Datasheet (MSDS)

  • Download


  • Download

Environmental Product Declaration (EPD)

  • Download
  • Download

Declaration of Performance (DOP)

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System Brochure

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Installation Guide

How to Install

Bosig Phonotherm 200 can be sawn, drilled or machined like it was timber. Carbide tipped power tools or well maintained (sharp) hand tools can be used for installation.

Bosig Phonotherm used on a window sill
Bosig Phonotherm used on a window sill
Bosig Phonotherm used on a window head
Bosig Phonotherm used on a window head
Bosig Phonotherm used on a door threshold
Bosig Phonotherm used on a door threshold
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