The loft 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. Therefore the first thing to do is to examine the need for additional insulation in the loft.

The cost of additional insulation in the loft often consists of the thermal insulation cost only. An efficient insulation thickness in lofts is minimum double the thickness in walls, for instance.  For additional insulation in lofts PAROC flexible slabs can be used.

If the wind protection in the wall does not come high up enough in the loft edge area it needs to be elevated using an appropriate building slab up to minimum 100 mm over the designed insulation upper surface. Leave a ventilation space of 30 – 50 mm between the upper edge of the wind protection and the roof. If there is not space enough for additional insulation in the roof edge areas, this can be compensated by adding insulation correspondingly in other areas of the loft.

> Installation guidelines

Existing structure PAROC Flexible slabs, e.g. PAROC UNS 37, 150 - 300 mm Renovation structure sawdust filling Lining paper Boarding It is important to leave a free space above the wool - minimum 100 mm – with ventilation to outdoor air.

Impact of additional insulation on structural moisture
Example: A 150 mm stone wool layer is added on top of an old 200 mm sawdust insulation in a loft. With an outdoor temperature of -10ºC the temperature of the old insulation below the additional insulation rises up to +8ºC and at the same time its relative humidity decreases from 85% to 30%. This means that the sawdust dries and at the same time it gives a fire-safe coating on top of the combustible insulations.