Wood fibre or cellulose – which blow-in insulation is right for your project?

Anyone wishing to build or renovate sustainably cannot do without eco-friendly blow-in insulation materials. They fill cavities completely, produce no off-cuts and boast an outstanding environmental footprint. With ISOCELL, you can choose from a wide range of high-performance blow-in insulation materials for every application – from cellulose and straw (Plantacell) to mineral-based variants (GRANUBLOW) and the classic wood-based options.

In this blog article, we focus on a direct comparison of two truly natural materials: the tried-and-tested ISOCELL cellulose insulation made from recycled newspaper and WoodyCell wood fibre insulation made from fresh wood fibres. But what are the differences here, and why is cellulose regarded as the technological pioneer in many areas? We’re carrying out an in-depth practical assessment using the latest data from our specialist department.

Before we look at the differences, it is worth considering the similarities. The base material for both insulation materials is the same: wood. This gives both systems unbeatable advantages over conventional insulation materials:

• Seamless perfection: Both insulation materials are blown into the cavities by machine. They adapt perfectly to any irregular shape, cable or pipe penetration – with absolutely no waste.
• Moisture regulation: As organic fibres, both products are vapour-permeable and have capillary conductivity. They can absorb moisture and release it again in a controlled manner, ensuring a healthy indoor climate and protecting structures.

Cellulose has been used successfully as thermal insulation since the 1920s. This means that today we have over 100 years of long-term experience in sustainable construction at our disposal – a time-tested success story that fits perfectly into the modern world of construction. 

The classic ISOCELL cellulose insulation is produced from clean, single-grade daily newspaper using an upcycling process that has been optimised over three decades. The latest building physics tests show that this all-rounder comes out on top in many areas:

• Better thermal conductivity & flow resistance: Cellulose offers even better thermal insulation than wood fibre. Higher airflow resistance minimises airflow through the insulation layer and effectively prevents rotational airflow. This means significantly lower heat loss with standard wind-tightness in buildings.
• Maximum protection against summer heat: Contrary to the common assumption that wood fibre is unbeatable in this respect, cellulose offers a phase shift that is up to 30% higher. This ensures noticeably better protection against the summer heat.
• Outstanding sound and fire protection: With over 100 different configurations offering verified fire protection, cellulose provides tested safety. In terms of airborne sound insulation, test results show that cellulose even outperforms standard solutions by up to 10 dB. Furthermore, it achieves the excellent fire class B-s2,d0 (flame-retardant) in accordance with European standards.
• Optimal fibre structure & faster installation: Thanks to an optimised fibre structure, cellulose has very high resilience, better loft and excellent flow properties. The fibres interlock perfectly within the compartment, preventing any ‘nesting’, and the settling behaviour ensures maximum safety. Installers on site also benefit: the blow-in process is completed up to twice as quickly.
• Greater safety through moisture protection: Cellulose has higher capillary activity and a greater moisture-retention capacity. This actively protects adjacent timber components from moisture spikes.
• A leader in environmental performance through a circular economy: during production, cellulose requires up to four times less primary energy (manufacturing energy) than wood fibre and has up to five times the CO₂ storage capacity. Certified by Nature Plus, ISOCELL cellulose is produced in regional facilities using exclusively green electricity. Furthermore, the material is fully recyclable: there are tried-and-tested methods for recycling (using extraction stations and material testing of aged cellulose) as well as for processing into charcoal fertiliser for long-term carbon sequestration.

And what about printing ink? A widespread myth concerns the printing ink used in old daily newspapers. However, there is clear reassurance on this point: for many decades now, printing inks have been subject to strict chemical regulations. Independent tests for toxic substances confirm this high standard: ISOCELL cellulose fibre has been awarded the prestigious natureplus certification. This sets the strictest limit values for constituents and monitors them regularly, thereby guaranteeing in black and white the high quality of our cellulose insulation in terms of building biology.

WoodyCell is a natural blow-in insulation made directly from wood fibre. It is used wherever contractors and building owners place particular value on the characteristics of wood.

Solid performance: As a natural product, wood fibre also offers good protection against summer heat and a stable, elastic fibre structure. However, to ensure a consistently sustainable overall impact, it is advisable to pay close attention to the exact origin of the product when building sustainably, as longer transport routes or the country-specific electricity mix at the manufacturing site can influence the carbon footprint.

Whilst the economic and practical conditions form an important foundation, it is ultimately the technical details that determine long-term living comfort. Let us therefore take a look at the building physics properties and values in a direct comparison:

A direct comparison shows that, whilst both systems offer excellent environmental performance, ISOCELL cellulose insulation proves to be the clear technological and economic frontrunner in practice.

• ISOCELL cellulose is your first choice if you do not want to compromise on your project. It offers an optimal all-round package comprising thermal conductivity, outstanding sound and fire insulation, and unbeatable protection against summer heat. If you also want to benefit from installation that’s twice as fast and maximum settlement stability with a minimal environmental footprint, this is the perfect choice.
• WoodyCell wood fibre remains a solid option for specialist projects where the focus is deliberately on the use of wood fibres.

Good to know: ISOCELL’s wide range of products offers the right solution for every requirement. In addition to the two wood-based insulation materials, GRANUBLOW offers mineral variants for specialised applications, whilst Plantacell (straw) provides further forward-looking, purely agricultural alternatives.

Whatever you decide – with the high-performance ISOBLOW blow-in machines, all the insulation materials mentioned can be installed quickly, cleanly and efficiently by a specialist.

Not sure which product is best suited to your specific project? Our ISOCELL experts will be happy to advise you personally.