Granab Ventilated subfloor

Avoid moisture, mold and bad indoor air with the Granab system and underfloor ventilation

A large number of villas and houses are affected annually by moisture damage in the basement or by elevated moisture levels in the base plate. To get healthy houses, it is important that moisture from concrete floors in basements or from the base plate is ventilated away and not built into the floor construction.
In addition to control and possibly. measures with new drainage and filling material around the house foundation, floor joists made of wood or plastic carpets that are mounted or laid directly on the basement floor must be removed and a drying of the concrete floors must be carried out. The Granab system with galvanized steel floor joists is consistently made of inorganic material and is adjusted upwards from the concrete floors to the desired height. The air in the space between the subfloor and the upper floor is then continuously ventilated away and you get a dry and nice environment.

In case of uncertainty and risk of significant moisture content or emissions from the base plate or floor construction, the air gap under the finished floor should be ventilated by mechanical ventilation in combination with a moisture barrier being mounted on the floor joists. The Granab system is height-adjusted as standard from 30 – 420 mm and leaves a free air flow under the studs. The space under the floor forms a separate “room unit” (tight box), which is ventilated independently or in special cases combined with other ventilation.

System 3000N with moisture barrier on top of the bars.

System 7000N with moisture barrier on top of the bars.

Principle ventilated subfloors

Separate mechanical ventilation in the “room unit” under the floor through an exhaust fan that sucks the air via perforated air ducts of, for example, standard spiral pipes. The supply air to the ducts takes place via an air diffuser with a filter that takes the supply air from resp. room unit. Supplementation of supply air can be done through, for example, an extra outdoor air valve.

Installation of ventilated subfloor

1. The old floor is removed.
2. The concrete slab is cleaned of all organic material.
Granab Floor control system with subfloor ventilation and insulation is installed.
4. New floor is laid. Done!

Our systems

Granab subfloor system 3000N

For adjustable height 30 – 140 mm, excl. Floor covering.

Granab subfloor system 7000N

For adjustable height 70 – 140 mm, excl. Floor covering.

Granab subfloor system 9000N

For adjustable height 70 – 140 mm, excl. Floor covering.