Retro EcoFloor^™

With all suspended floor systems, it is essential that the space underneath the floor is adequately ventilated.  This is normally achieved via air bricks installed on two opposing external walls. 

Building Regulations set out the requirements for ventilation and NHBC provides further guidance. In summary, the requirements are:

• There must be at least 150mm of ventilated space between the underside of the floor and the ground. This is measured from the top of any ground coverings to the lowest point of the floor (or insulation under the joists if fitted).
• The underside of any wall plates must be at least 75mm above the ground covering.
• Air vents in external walls should be positioned so ventilating air can freely move between opposite sides of the building and can ventilate all parts of the space. 
• On each external wall, air vents must be no more than 2m apart. 
• Air vents should be at least 450mm away from a corner
• The vent openings should be either 1500mm² per linear metre of external wall, or 500mm² per square metre of floor area. Whichever area is the greatest will be the minimum amount of ventilation required.
  • The vent opening is the total area of the holes in air bricks through which air can pass.
  • An external wall is a wall on the perimeter of the building with the outside world on the other side. This does not include walls between neighbouring properties.
  • The walls between individual rooms in the building and dwarf walls supporting the floor joists can be ignored; these typically have ventilation gaps to allow air to flow through.
  • The floor area is the total area of ground floor with adjoining suspended floor; it would exclude any solid floors. Any suspended floors not connected to each other are treated as different floors and each would have its own specific ventilation requirements.
• Vents should incorporate suitable grilles to prevent vermin entering the sub-floor, and the grills must not resist the air flow.

If these requirements cannot be achieved by adding new vents or reconfiguring existing vents, mechanical ventilation will be required.

• A push-pull ventilation system with at least two fans is needed, one fan to pull air in and one to push air out.
• If vent openings can only be installed on one wall, the mechanical ventilation must use ducting to place vent openings at the opposite side and create airflow across the entire space.
• Any ducting or ventilation pipes used must be at least 100mm diameter

If the exterior ground level is high enough to prevent vents being installed straight through the wall, an offset (periscope) ventilator can be used. This allows the interior and exterior openings of the vent to be at different heights to account for the different ground levels.