To support the insulation in the suspended timber floor, a breathable membrane should be installed. The membrane can be draped over the joists and stapled into place to create a 'tray' in which the insulation can be unrolled. The depth of the tray should be approximately equal to the depth of the insulation being installed.

If the floor is not being removed and there is enough access, the insulation can be installed from underneath. Again a membrane to hold the insulation in place would be required. This method of insulation is very popular in existing buildings as suspended ground floor joists are common and are uninsulated a great number of homes.

Premium or Comfort insulation rolls are suitable for this application, with Premium giving a superior performance and Comfort being the lower priced. For the purpose of these calculations, Comfort has been used.