Sisalwool 100 now live in WUFI®

Sisalwool 100 now live in WUFI®: natural fibre insulation ready for hygrothermal modelling

Sisalwool has expanded its presence in the WUFI® material database with the addition of Sisalwool 100, alongside the existing 50mm product entry.

This means specifiers can now model our 100mm natural fibre slabs directly in WUFI®, assessing thermal and moisture behaviour in real-world build-ups with verified material.

Why this matters for designers

With Sisalwool 100 now available in WUFI®, architects, energy consultants and building physicists can simulate vapour-open, moisture-regulating assemblies that use natural fibre insulation instead of conventional petrochemical products.

This supports the design of breathable constructions that balance heat flow and moisture movement, helping to reduce the risk of interstitial condensation while improving comfort and resilience over time 

Because WUFI® is widely used across the UK and Europe for hygrothermal analysis, inclusion of Sisalwool 100 makes it easier to evidence performance, test different build-ups and demonstrate compliance on projects where moisture safety and fabric-first design are critical.

About Sisalwool 100

Sisalwool 100 is a semi-rigid natural fibre insulation slab designed to friction-fit between timber studs, rafters and joists in walls, roofs and floors. It combines low embodied carbon with strong thermal performance, vapour permeability and acoustic benefits, making it ideal for both new build and retrofit in breathable construction.

As a vapour-open material, Sisalwool 100 allows moisture to move through the fabric when used as part of a well-designed assembly, supporting healthier internal environments and helping protect timber elements. Its rigidity and friction-fit installation also help minimise gaps, improving real-world performance.

Building on the 50mm WUFI listing

The 50mm Sisalwool product was already present in the WUFI® database, giving early adopters a way to begin modelling natural fibre options in their hygrothermal simulations.

Adding Sisalwool 100 extends that capability to the thicker slab format most commonly used in stud walls, roofs and suspended floors, unlocking more realistic design scenarios and detailing options.

Together, the Sisalwool entries in WUFI® make it simpler to compare natural fibre build-ups with conventional systems, quantify moisture safety, and back up specification decisions with robust modelling rather than assumptions

What this unlocks for projects

Having Sisalwool 100 in WUFI® means project teams can:

• Model full breathable wall, roof and floor build-ups using natural fibre insulation.

• Test different membranes, finishes and thicknesses to optimise moisture safety and thermal comfort.

• Evidence hygrothermal performance for clients, funders and approval bodies who expect data-led design.

This is particularly valuable for retrofits to solid-wall and heritage buildings, timber frame projects and low-carbon new builds where vapour-open design is a priority.

Using WUFI

If you are using WUFI® on current or upcoming projects, you can now select Sisalwool 100 directly from the material database when modelling your assemblies.

For designers who want to explore breathable, natural fibre options, this is the perfect moment to bring Sisalwool into your hygrothermal workflow and test how it performs in your specific build-ups.

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