Internal Wall Insulation Systems

There is more to installing insulation internally than just achieving low U-Values. Interstitial condensation, airtightness, thermal bypasses and potential cold spots will affect the effectiveness of the insulation system. For internal insulation very often more is not the best approach. 

Unity Lime IWI Systems

The modernisation of old and historic buildings where changes to the external façade are not permitted can present a real challenge to specifiers and builders. Insulation of the exterior walls can only be carried out internally, but unsuitable insulation can lead to interstitial condensation causing critical problems for the building shell. Moisture damage and biological degradation are common symptoms where the use of conventional internal insulation systems with vapour barriers and non breathing systems are used.

By insulating an existing exterior wall with standard insulation on the inside the dew point is on the cold side of the insulation, in the existing wall. Moisture damage and degradation of the envelope are common symptoms. Often vapour barriers are used to prevent moisture passing into the existing structure. However these membrane solutions often do not work properly in refurbishment because the sealing fails and/or is not feasible on integrated elements such as partition walls or timber beams that commonly have cracks. This then results in significant amount of moisture penetrating these areas leading to condensation and decay.

Unity Woodfibre IWI systems work with the physics of moisture transfer rather than attempting to work against it with the inclusion of vapour barriers. Condensation accumulation is prevented by a combination of:

    • Vapour openness – allowing vapour diffusion through the wall
    • Hygroscopicity, high absorption of vapour as it diffuses through the woodfibre prevents moisture build up at the interface of existing wall and insulation.
    • Moisture storage – Hygroscopicity combined with a relatively high density gives the material the capacity for moisture storage that prevents accumulation of liquid condensation
    • Moisture redistribution through highly capillary active woodfibre ensures there is no localised excess moisture

Lime Plastered Finish

Lime plaster directly onto the insulation board for a beautiful vapour open build up that achieves excellent airtightness and further improved climate regulation internally. 

The best option for historic vapour open monolithic constructions where it is not possible to insulate externally and not appropriate to use vapour closed insulation systems. 

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Dry Lined Finish

An excellent option for building that want to continue with a plasterboard and skim option for consistancy throughout the building. 

This option is the best option for building where services may need to be acess more often over the years as it is simple to install a service batten onto the hard surface of the insulation prior to palsterboarding

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Bathroom & Basement Options

In some situation woodfibre isn’t the best option, this is true for rooms below DPC, and in wet rooms where the walls need to be fully tiled reducing the breathability of the wall. 

In these situations the best sustainable product to use is Cork. Still highly insulting and vapour open, cork is highly resistant to rot and is far more suited for applications where XPS or similar products would have been used. 

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Additional systems are available and the systems can be combined to create an extremely high performance. For more information please contact our technical department.