The cold attic often forms the biggest uniform surface in a building and the main part of all heat escaping through the building envelope tries to penetrate through the roof. To maximise energy efficiency, first check if the attic needs additional insulation.

The cost of additional insulation in the cold attic often consists of the thermal insulation cost only. For instance an efficient insulation thickness in cold attics is minimum double the thickness in the walls. For additional insulation, we recommend PAROC Blowing wool.

If the wind protection in the external wall does not come high enough in the loft edge area, install a wind diverter. Leave ventilation space (30–50 mm) between the upper edge of the wind protection and the roof. If there is no space for additional insulation in the roof edge areas, compensate by adding insulation correspondingly in other areas of the loft.

Alternatives:

a. Allow a blowing wool contractor to perform the insulation work.
b. If the need for additional insulation is small, spread granulated stone wool yourself using a rake


Renovation attic, BLT
  • PAROC blowing wool 
  • Sawdust filling
  • Lining paper
  • Inner surface
It is important to leave free space above the wool (min. 100 mm) with ventilation to the outdoor air.

Using flexible slabs is an effective method for updating roof insulation. The wind diverter ensures ventilation in the cold attic area, and makes the connection between the outer wall and the roof more airtight.

Renovation, attic, flexible 
  • PAROC eXtra 
  • Sawdust filling
  • Lining paper
  • Inner surface
It is important to leave free space above the wool (min. 100 mm) with ventilation to the outdoor air.


Impact of additional insulation on structural moisture

Example: A 150 mm stone wool layer added on top of 200 mm of old sawdust insulation in a loft. With an outdoor temperature of -10ºC, the temperature of the old insulation below the additional insulation increases to +8ºC, while its relative humidity decreases from 85 % to 30 %. This means that the old sawdust insulation dries and the new stone wool insulation gives a fire-safe coating on top of the combustible insulation.