Paroc Air is a simple and safe solution for making dry flat roofs. PAROC Air keeps the roof structure dry without any mechanical systems. The basis for this simple but effective solution is natural air pressure.

Effective roof insulation has three or four insulation layers. The lowest insulation layer forms a uniform base for the vapour barrier. The vapour barrier prevents moist air from leaking into the insulation layer. Due to the continuous stone wool base, the vapour barrier remains intact even during small structural movements. 

The top of the intermediate insulation layer has a series of grooves which forms a network of ventilation channels. Porous stone wool with high vapour permeability doesn’t absorb the moisture into the insulation but allows moisture to move to the ventilation grooves where it is led out from the construction through ventilation hoods. 

On the top of the grooved insulation layer there is a thin and rigid stone wool board. It covers the ventilation channels and carries the load from human traffic during installation and maintenance.

Below you can find some examples of effective roof solutions like Paroc Air, one-layer insulation system, two-layer insulation system and passive house solution.


Flat roof, steel 6
  • Roof membrane
  • Mechanical fasteners
  • PAROC ROB 80(t)
  • PAROC ROS 30g or ROS 40g
  • Vapour barrier
  • PAROC ROS 30
  • Supporting structure

 Insulation solution with U value
 PAROC ROB 80t 20 mm   20 mm
 PAROC ROS 30g 180 mm 190 mm
 PAROC ROS 30 140 mm
 PAROC ROS 50 50 mm 50 mm
 U value, W/m2K 0.09 0.14


Paroc also offers flat roof solutions without ventilation grooves: 

One-layer insulation system

Use one-layer insulation system for structures with an insulation thickness that is less than or equal to 180 mm. Install the roofing membrane directly on the insulation. Mount the insulation slabs with glue or mechanical fasteners through the membrane. Always install a vapour barrier under the insulation layer regardless of the supporting structure.

Flat roof, steel
  • Roof membrane
  • Mechanical fasteners
  • PAROC ROS 50 (minimum recommendation)
  • Vapour barrier
  • Supporting structure: corrugated steel or other 

Two-layer insulation system

A two-layer insulation system consists of a thicker insulation layer with a thin rigid roof board on the top. The thickness of the main insulation layer varies between 50 and 200 mm and the top board from 20 to 50 mm. The top layer distributes the load. The advantage of a two-layer insulation system over a one-layer system is improved energy efficiency. The two-layer insulation system has no slab joints going through the whole insulation layer.

Flat roof, steel 2
  • Roof membrane
  • Mechanical fasteners
  • PAROC ROB 80(t)
  • PAROC ROS 30 (minimum recommendation)
  • Vapour barrier
  • Supporting structure: for example corrugated steel 

Passive houses

Passive house insulation requires up to five layers of insulation. This solution is useful for Paroc ventilated roofs, where the upper intermediate layer has grooves in the surface. We recommend the ventilated solution as the number one solution, because it brings extra safety to the building.

Flat roof, steel, grooves, passive house
  • Roofing membrane
  • Mechanical fasteners
  • PAROC ROS 80t (d1)
  • PAROC ROS 30g (d2)
  • PAROC ROS 30 (d3 + d4)
  • Vapour barrier
  • ROS 50 (d5)
  • Load bearing steel

    Block of flats  
Recommended U-value   W/m2K  0.06 - 0.09
 d1  mm  20
 d2  mm  110
 d3 + d4  mm  180 + 180
 d5  mm  50
 Total insulation thickness  mm   540

According to the definition of a passive house provided by the Passive House Institute, the annual heating, cooling and primary energy demand should not exceed certain values. Although good thermal insulation plays a major role in achieving the Passive House standard, it alone cannot ensure compliance. The requirements for other building components and devices can be determined by various calculations tools, such as the Passive House Planning Package (PHPP), available at