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Speckel Floor System Calculation Methodology

  • Updated

The approach for the Speckel Floor System R-Value calculation has been derived from CIBSE Guide A Section 3.5 Ground Floors and Basements.

Following the guidelines of CIBSE Guide A, there are four modes of floor:

  • Ground Contact with edge insulation

  • Ground Contact without edge insulation

  • Suspended Floor (insulated)

  • Suspended Floor (uninsulated)

Procedure

  • The floor is initialised as if it were in contact with the ground.

  • Relevant components for each type of floor are collected.

  • Determine if the floor is edge insulated or suspended above the ground, and if so collect other necessary components.

  • Using the complete collected components, these are combined into the final calculation to produce an R-Value of that floor type.

Ground Contact Collection

All floor types require a number of inputs

  • floor area

  • floor perimeter

  • ground type (and its conductivity)

  • surrounding wall width

  • the thermal resistance of the floor itself.

NOTE: The thermal resistance of the floor is derived solely from ‘any all-over insulation layers above, below, or within the floor slab’, with some pre-described surface resistances added. In addition, the floor perimeter is solely the perimeter of the floor that is exposed to unconditioned space.

Edge Insulation Collection

There are two approaches for edge insulation - direct edge insulation applied to the floor and surrounding wall, or when the surrounding wall has a lower conductivity than that of the ground. The first option is currently unavailable on Speckel, however the check for the second option is always performed if the floor is not suspended.

If the floor is edge insulated, then components derived from the surrounding wall thermal resistance, thickness, and depth are collected.

 Suspended Floor Collection

A floor is deemed to be suspended simply when the user specifies a height above ground greater than zero metres. There are a few more inputs required when this condition is me;

  • wind speed at ten metres above ground level

  • the wind shielding factor

  • area of ventilation openings per unit perimeter of the surrounding wall.

There are two types of suspended floors, which then determines which calculation methodology is used: uninsulated and insulated, with the latter relying on the calculation of the former.

NOTE: The thermal resistance of the floor itself is treated differently here again. For uninsulated floors, it is treated as a regular centre pane R-value calculation, adding R 0.17 twice for internal and external surface resistances. For insulated floors, it is treated as a thermally-bridged (if the design is deemed so) thermal resistance, omitting the surface resistances. Here, we use AS/NZS 4859.2:2018 to calculate and then omit the surface resistances.

Calculation

As mentioned above, the calculation methodology is dependent on the inputs of the user. The base method is that of a simple ground contact floor, which is then used by all other methods (but is changed slightly when suspended).

  • If edge insulation is detected in the design, then the edge insulation factor is calculated which will alter the final result.

  • If the floor is found to be suspended, then the calculation performed is always for the uninsulated suspended floor.

  • If the floor is found to be insulated, the previous calculation (where the floor thermal resistance is considered without insulation) is then used in conjunction with its prescribed thermal resistance.