U Values 2014 Leaving Cert Construction

**Questions and Solutions from SEC**

Using the following data, calculate the U-value of the insulated concrete ground floor:

Concrete floor slab thickness 125 mm

Extruded polystyrene insulation thickness 200 mm

Damp proof membrane (DPM) thickness 0.30 mm

Sand blinding thickness 30 mm

Hardcore thickness 225 mm

Thermal data of floor:

Resistance of top surface of floor (R) 0.104 m2 °C/W

Conductivity of concrete (k) 0.160 W/m °C

Conductivity of polystyrene insulation (k) 0.031 W/m °C

Conductivity of damp proof membrane (DPM) (k) 0.450 W/m °C

Conductivity of sand blinding (k) 0.160 W/m °C

Conductivity of hardcore (k) 1.260 W/m °C

Using the U-value of the concrete ground floor obtained at 5(a) above and the following data, calculate the cost of heat lost annually through the concrete ground floor:

Dimensions of floor 13.0 metres × 7.0 metres

Average internal temperature 21°C

Average external temperature 7°C

Heating period 12 hours per day for 39 weeks per annum

Cost of oil 95 cent per litre

Calorific value of oil 37350 kJ per litre

1000 Watts 1 kJ per second