Interior roof insulation

Depending on the desired insulation thickness, the rafters are doubled on the inside of the attic. Two variations are shown here for the construction (see detail drawings).



General advantages

The big advantage of the ISOCELL cellulose is not only its good insulation value and rapid processing, but also its outstanding protection against heat. 
The high storage capacity of the ISOCELL cellulose insulation provides for a noticeably delayed passage of irradiated solar heat
Attics in particular thus remain cool into the night.

Injection process

The injection specialist comes with his truck to the building site and bring along everything he needs: the injection machine and the material. Only the injection hose needs to be brought into the attic, not enormous amounts of material. By means of radio control the injection specialist controls the injection machine on the truck, which an assistant fills with cellulose. The hollow spaces are insulated without joints and settlement-free in short time.

Installation procedure

  1. 01

    Doubling on

    Depending on the desired insulation thickness, the rafters are doubled on the inside of the attic. Two variations are shown here for the construction (see detail drawings).

  2. 02

    Vapour retarder

    The vapour retarder is laid overlapping and is mecha-nically fixed by means of tacker staples.

  3. 03


    Now the laths are attached at a centre-centre distance of approx. 30 cm. The laths are positioned directly on the sealing of the overlaps in order to additionally relieve the adhesive joints.

  4. 04


    The airtight taping and sealing of overlaps, connec-tions and penetrations is very important. See the brochure ‘Air-tightness in detail’ regarding this.

  5. 05



Solution in detail

Component section

1) Concrete or clay roofing tile
2) Timber lathing, spruce (e = 30 cm)
3) Counter lathing (min. 5 cm)
4) Roof underlay (e.g. OMEGA Roof underlays)
5) Sheating (spruce)
6) Rafters / doubled (e = 75 cm)
7) ISOCELL cellulose insulation
8) Vapour Retarder (e.g. AIRSTOP DIVA)
9) Transverse lathing, spruce
10) Gypsum fibreboard


lateral doubling

direct doubling

Technical data

Building material Layer thickness (mm) λ W/mK Fire class (EN)
Concrete or clay roofing tile 50 0,7 A1
Timber lathing (e= 30 cm) 30 0,13 D
Counter lathing (min. 5 cm) 50 0,13 D
Roof underlay (e.g. OMEGA Roof underlays) 1 0,5 E
Sheating (spruce) 24 0,13 D
Rafters / doubled 200 0,13 D
ISOCELL cellulose insulation 200 0,039 B-s2,d0
Vapour retarder 1 0,2 E
Transverse lathing (spruce) 24 0,13 D
Gypsum fibreboard 12,5 0,27 A2
Insulation material thickness (mm) Insulation material density (kg/m³) *GWP (kg CO2 äqv./m²) or total structure PHI (phase shift in hours) **U-Value (W/m²K)
200 48 -35,25 10,4 0,208
220 48 -37,79 11,2 0,188
240 50 -40,66 12,1 0,171
280 50 -45,80 13,6 0,146
300 52 -48,78 14,6 0,136
340 52 -53,97 16,1 0,12
360 54 -57,07 17,2 0,113
400 54 -62,32 18,7 0,101

* GWP Total (Global Warming Potential)
** U-Value (W/m²K) for ISOCELL Cellulose was calculated with λ = 0,039 W/mK 


ISOCELL offices

A requirement for more space prompted the ISOCELL company to convert the attic. 
So-called shed dormers made a generous room layout possible. The bright office space is not only a workplace, but also offers space for discussions, creative meetings and discussions with employees.

Attic in new buildings

ISOCELL cellulose is also very popular in the const-ruction of new buildings. Above all in the case of roof areas with complex symmetry and dormers, the injection system offers the optimal solution for a jointless and waste-free insulation. 
In summer the ISOCELL cellulose impresses with outstanding protection against heat.