If you want a 100% "green" renovation with excellent thermal performance but a tight budget, the answer literally lies in the recycling bin.
Cellulose Insulation is a material manufactured from 80-85% recycled paper, mainly old newspapers and cardboard boxes. It is arguably the smartest, most affordable and most environmentally friendly insulation solution, and it is applied in a way that is completely different from conventional boards. Let us see why.
Most people's first reaction when they hear "paper in the wall" is fear: fire, mould, rodents. The "magic" that minimises these risks lies in the composition: 15-20% of the material consists of boric acid salts (borate), which completely change the paper's behaviour regarding fire and pests.
Cellulose does not ignite the way you might imagine. The boric salts melt under heat, forming a glassy crust on the surface. The material carbonises only superficially, preventing the flame from spreading. Fire classification: Class B-C (Euroclass).
Boron does not only protect against fire. It is lethal to termites and ants, prevents mould growth and acts as a repellent for rodents, which cannot tolerate these borate salts.
Cellulose is not sold in boards or rolls, but in bags as loose grey fluff. A specialist blowing machine mixes this fluff with air and blows it through a flexible hose into wall cavities, ceiling voids or attic spaces.
The result is remarkable: the cellulose literally reaches every corner, wrapping around pipes, cables, sockets and every irregularity in the structure. It creates a completely monolithic insulation layer with zero joints or gaps. This means it eliminates the thermal bridges and air currents that escape between conventional boards.
Among so many insulation alternatives, three critical advantages set cellulose apart.
Cellulose is the ultimate solution for horizontal surfaces: the technician sprays 20-30 cm "like snow" above a plasterboard ceiling or onto an attic floor, covering everything uniformly in minimal time.
As a wood derivative, cellulose inherits significant thermal mass. It stores solar heat and delays its entry into the interior by up to 10 hours. This translates to coolness even in August, without air-conditioning!
Of all biological and natural insulation materials (cork, wood fibre, hemp, wool), cellulose is consistently the cheapest. The ideal choice for an eco-friendly renovation on a limited budget.
⚠️ Watch for "Settling": In vertical walls, if cellulose is not blown at sufficient density, gravity gradually pulls it downward, leaving uninsulated gaps at the top of the wall cavity. This work is not a DIY job - it requires specialist equipment and an experienced operator.
We want to insulate an old timber roof crammed with electrical cables, water pipes and uneven gaps between the wooden joists. We test two approaches.
The installer painstakingly cuts the boards to exact sizes, struggling to fit them around the pipes. Despite their best efforts, small gaps remain around the cables - cold air leaks through.
In under 3 hours the specialist operator has sprayed the entire roof. The cellulose hugs every cable, fills every millimetre like a foam. Result: 100% airtight seal - using a material made from old newspapers!
💡 Conclusion: If you are renovating an old house or dealing with a cold roof full of pipework, cellulose delivers rock-wool-level performance with the massive bonus of total seamless sealing, a 100% recycled ecological profile - and the lowest price in its category.
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