Breathable Insulation System - Baumit OpenSystem EWI Guide

Baumit OpenSystem:
Breathable Insulation

Whether you are building a new home or refurbishing an old one, Baumit OpenSystem is the best option for breathable wall insulation. All components contain vapour permeable insulation and thus allow the walls to breathe. This creates optimal living conditions whether in summer or winter. 

The Baumit OpenSystem uses EPS wall insulation boards containing numerous holes of 2 to 3mm diameter. These ensure high vapour permeability and enable water vapour to be released externally. The OpenSystem consists of 99% air and only a small proportion of EPS render, which in turn requires very little energy to produce, therefore resulting in low environmental impact.

  • Unique OpenAir technology
  • Breathable insulation 
  • Cosy healthy climate

Comfort at all times

In addition to the temperature, an important factor in enabling a comfortable living climate is relative humidity. With typical indoor temperatures of between 19 and 22 ° C, humidity should be between 40 to 60%. Therefore approximately 10 litres of water vapour per household per day needs to be diffused to the outside. Baumit OpenSystem with its vapour permeable insulation and high breathability ensures a comfortable indoor climate. 

A façade that lasts

The Baumit OpenSystem has some notable features that help buildings to not only perform well but also to look good for many years to come. 

The Baumit OpenSystem combines the best fixing technology, breathable insulation board, and high-performance insulation to help create a building that will last for decades to come.


  • Complete wall build-up
  • Highly breathable insulation boards
  • Prevents condensation from water vapour
  • Ensures a comfortable indoor living climate

The System

Every element in the OpenSystem has been specially developed, tested and improved upon over time to be as efficient as possible when working together as a system. The heart of the system is the insulation boards. The polystyrene-based board feature a patented system of holes to ensure rapid drainage of water vapour, however even with ‘holes’ provides the same level of insulation as regular insulating boards.

System components

Open System

Base- new masonry or original base
1. Final Topcoat - Baumit StarTop  is a highly weatherproof topcoat render, complete with silicon binder and a new functional filler, providing the building with a quick-drying finished façade surface in damp weather conditions.  
2. Primer - Baumit PremiumPrimer is a ready-to-use primer for synthetic and mineral decorative finishes. It has high covering power and regulates absorption.  
3. Basecoat - Baumit StarContact White is a vapour-permeable, adhesive and basecoat reinforcing render. 
4. Reinforcement - Baumit StarTex is warp-resistant and alkali-resistant glass fibre mesh that is used to produce a reinforced mortar layer on torn old rendered facades.  
5. Insulation - Baumit OpenTherm is a highly breathable, thermal insulation made from expanded polystyrene. The insulation is specially designed for brickwork and similarly breathable masonry.  
6. Adhesive - Baumit StarContact White is a vapour-permeable, adhesive and basecoat reinforcing render. 
7. Fixing - Baumit StarTrack adhesive anchors bring many advantages. No thermal bridges and allows good adhesion without additional fixing.