Grass
insulation
Grass insulation is a flexible biobased batt, designed to be fitted between the members of a frame or a roof. Made from fibre recovered during the maintenance of public green spaces, it puts a local, renewable plant resource to use.
What is grass insulation?
Grass insulation is a flexible biobased batt, made of grass fibres from the maintenance of public green spaces, combined with recycled jute fibres and a binder. The grass does the insulating, while the jute and the binder hold the batt together. The fibre puts to use an abundant resource that is regularly available.
The batt is vapour-open and regulates moisture within the build-up. Its moderate density gives good thermal performance in winter and a useful phase shift in summer, as the fibre can store heat temporarily. Its flexible texture makes it easy to fit on site.
The insulation is fitted between rafters in roofs, between studs in timber frames, or between joists in floors. Light compression when fitted ensures continuous contact with the structure, with no gaps or thermal bridges.
It is made in Belgium, at Auvelais, from grass sourced locally, within a short regional radius. Used batts go back to the factory to be fed into the manufacture of new batts, in a closed loop.
Installation & uses
The batt is fitted between the frame members, lightly compressed. It is cut with a knife or a toothed-blade saw, then adjusted to fit the shape of the cavity.
It suits pitched roofs, timber-frame walls and floors, in new build as well as renovation. In roofs, an airtightness membrane is fitted on the inside to protect the hygrothermal behaviour of the batt.
The material must be kept out of the rain during transport, storage and installation. Once protected by the finished envelope, it keeps its performance over the service life of the building.
At end of life, the batts can go back to the factory to be fed into the production of new batts, and site offcuts can be composted locally.
About the producer
Gramitherm is a Belgian producer of biobased grass-fibre insulation, based at Auvelais in Wallonia. The company uses grass collected during the maintenance of public green spaces and local meadows, within a short regional radius.
Its flexible batts are intended for timber construction and internal insulation, with a closed recycling loop at the factory and a Walloon biobased label.
Technical performance
EN 13171 (mineral/plant wool) · ETA-21/0260 · EN 16785-2:2018 (biobased) · EN 15804+A2 (EPD)
FAQ
Is grass insulation loadbearing?
No. The batt is non-structural and fits between the members of a frame. Its tensile strength parallel to the faces exceeds 20 kPa to EN 1608, with dimensional stability of ±2% in length and class T2 for thickness.
What is its embodied carbon?
Its embodied carbon (A1-A3) is negative: one kilogram of Gramitherm stores around 1.5 kg of CO₂ equivalent. Reference: B-EPD Gramitherm 100, established for the 100 mm batt by the University of Liège, to EN 15804+A2. A supplement covering all thicknesses is available via TOTEM.
Which thickness should I choose?
Fourteen standard thicknesses, from 45 to 240 mm, plus a special 30 mm. Batts measure 1,200 × 600 mm, or 1,200 × 450 mm as a special format. Thermal conductivity 0.041 W/m·K to EN 12667.
What happens to it at end of life?
The batts go back to the factory and are fed into the manufacture of new batts. ETA-21/0260 assumes a service life of at least fifty years.
Alongside
Same layer, same use · three materials to compare.
