This case study is conducted in order to assess the current and proposed situation for one office, the canteen and the drying room of the contractor’s accommodation as well as one subcontractor’s cabin in the construction village at Laing O’Rourke’s Xscape site. The proposed situation is based on implementing previously identified energy efficiency measures in each of these areas. This case study is based on the actual room sizes occurring in the Xscape construction village and also takes into account the surrounding area of the various rooms as well as the working behaviour of all employees. Working hours are assumed to be 11 hours per day during 5 days a week and 52 weeks in a year.

 

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The objectives of this case study are to determine the following qualities for each area for our proposed situation in comparison to the current situation on the Xscape construction site: 

1.       Annual energy demand

2.       Annual energy costs

3.       Annual carbon emissions

4.       Thermal percentage dissatisfied on a typical winter day

5.       Thermal comfort on a typical winter day

Further outcomes from the case study will be:

 

1.       Investment costs

2.       Payback periods

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Detailed dynamic thermal modelling simulations have been conducted with the following models: 

•          Office: 3m x 4m office room (improved insulation)

•          Canteen: 9.5m x 3m cabin (improved insulation)

•          Drying Room: 9.5m x 3m cabin (improved insulation)

•          Subcontractor’s Cabin: 9.5m x 3m cabin

•   Conventional cabin model (poor insulated)
•   Improved cabin model (well insulated)

 

 

 

 

 

 

 

                       

 

 

                         Office Model                                        Cabin Model

 

For all simulation a climate file for Oban (1994) has been used. The heating season has been defined for 01 October to 31 March (26 weeks).

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The office is a 3m x 4m room with 1m² glazing area and has the following characteristics:

Current situation: The following assumptions have been made.

Heating behaviour of occupants:

• 7:00 – 8:00 heater on maximum power (1 x 2000W)

• 8:00 – 18:00 heater on low power (1 x 750W)

Lighting behaviour of occupants:

• 7:00 – 18:00 lights on

The results shown in the tables below have been arrived from a combination of ESP-r simulations and calculations.

 

	Annual energy demand
Lighting	226.5 kWh
Heating	1235 kWh

 

	For a typical winter day (7:00 – 18:00)
Thermal percentage dissatisfied	40.53 % (16.51% standard variation)
Thermal comfort 1	1 h (mainly overheated)

¹ Hours per day where the dry resultant temperature lies between 20°C and 22°C

 

 

Proposed Situation:  Following energy efficiency measures have been applied

• High frequency ballasts
• Day light control system

• 1.5kW heater with automatic temperature control (starting time: 6:00)

 

The following assumptions have been made:

Heating:

• Heating control to maintain a dry bulb temperature of 20°C

Lighting:

• 25 % less lamp rating (HF control)

• 65 % annual savings through day light control (hardly surrounding buildings; clean windows, little use of blinds)

The results shown in the tables below have been arrived from a combination of ESP-r simulations and calculations.

 

	Annual energy demand
Lighting	59.5 kWh
Heating	471 kWh

 

	For a typical winter day (7:00 – 18:00)
Thermal percentage dissatisfied	8.25 % (10.05% standard variation)
Thermal comfort 1	10 h (mainly overheated)

¹ Hours per day where the dry resultant temperature lies between 20°C and 22°C

 

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The canteen consists of 5 cabins and has the following characteristics:

• Occupied by workers from 10:00 to 11:00 and 13:00 to 15:00
• Occupied by cleaner from 11:00 to 12:00
• 4 x 2kW heaters and 25 x 36W lights
• Infiltration: 2ac/h during tea and lunch time, otherwise 1ac/h

 

Current situation: The following assumptions have been made.

·        

      Heating behaviour of occupants:

• 7:00 – 9:00 heaters on maximum power (4 x 2000W)

• 9:00 – 13:00 heaters on medium power (4 x 1250W)

Lighting behaviour of occupants:

• 7:00 – 18:00 lights on

The results shown in the tables below have been arrived from a combination of ESP-r simulations and calculations.

 

	Annual energy demand
Lighting	2831.4 kWh
Heating	4680 kWh

 

	For a typical winter day (8:00 – 16:00)
Thermal percentage dissatisfied	52.63 % (19.77% standard variation)
Thermal comfort 1	0.5 h (mainly overheated)

¹ Hours per day where the dry resultant temperature lies between 20°C and 22°C

 

The picture below demonstrates the dry resultant temperature inside the canteen on a typical winter day. The upper line shows the dry resultant temperature, the lower line shows the ambient temperature.

 

 

 

 

 

 

 

 

 

 

 

 

 

                                               

 

 

 

                                                        Ambient and canteen’s dry resultant temperature

 

 

There is a discomfort inside the canteen due to overheating and poor air quality.

 

Proposed Situation: Following energy efficiency measures have been applied.

• High frequency ballasts
• Occupancy sensor for lights
• 1.5kW heater with automatic temperature control (set from 8:00 to 15:00)
• 5 ventilators with 550m³/hr with heat recovery and CO² sensor (rated 150W)

The following assumptions have been made:

Heating:

• Heating control to maintain a dry bulb temperature of 20°C

Lighting:

• 25 % less lamp rating (HF control)

• 64% annual energy savings (lights are on from 10:00 to 12:00 and 13:00 to 15:00)

Ventilation:

• Switched on 4h per day

• 7.7 ac/h per cabin with 70% heat recovery

The results shown in the tables below have been arrived from a combination of ESP-r simulations and calculations.

 

	Annual energy demand
Lighting	764.5 kWh
Heating	3550 kWh
Ventilation	780 kWh

 

	For a typical winter day (8:00 – 16:00)
Thermal percentage dissatisfied	13.78 % (17.95% standard variation)
Thermal comfort 1	4 h (mainly overheated)

¹ Hours per day where the dry resultant temperature lies between 20°C and 22°C

 

As stated in the table, the dry resultant temperature cannot be maintained over the whole day. However, a comfort temperature of 20°C dry resultant temperature is maintained during tea and lunchtime as shown in the graph below. The upper line shows the dry resultant temperature, the lower line shows the ambient temperature. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

                                           Ambient and canteen’s dry resultant temperature 

 

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The drying room consists of 2 and a half cabins and has the following characteristics:

•          Intermittent occupied (mainly at tea and lunchtime and before work end)

•          2 x 2kW and 8 x 150W heaters

•          9 x 36W lamps

•          Infiltration: 1.5 ac/hr during working hours

Current situation: The following assumptions have been made

·           Heating behaviour of occupants:

• 0:00 –24:00: 2kW heaters on medium power (2 x 1200W)
• 0:00 –24:00: 150W heaters on full power (8 x 150W)

        

Lighting behaviour of occupants:

• 7:00 – 18:00 lights on

 

The results shown in the tables below have been arrived from a combination of ESP-r simulations and calculations.

 

	Annual energy demand
Lighting	1019.3 kWh
Heating	22464 kWh

 

	For a typical winter day (7:00 – 18:00)
Thermal percentage dissatisfied	88.37%  (24.3% standard variation)
Thermal comfort 1	0 h (always overheated)

¹ Hours per day where the dry resultant temperature lies between 20°C and 22°C

 

The picture below demonstrates the dry resultant temperature and ambient temperature inside the drying room for a typical winter working day. The upper line shows the dry resultant temperature, the lower line shows the ambient temperature

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

                                                         Ambient and cabin’s dry resultant temperature

 

It is shown that a dry resultant temperature about 40°C is maintained 24 hours during working days without ventilation. It is obvious that there is wastage of energy in addition to the problem that the clothes do not dry overnight.

 

Proposed Situation: Following energy efficiency measures have been applied.

·        

• High frequency ballasts
• Occupancy sensor for lights
• 5 x 1.5 kW heater with automatic control to replace all existing heaters
• 3 Ventilators with 220m³/hr with heat recovery and humidity sensor (rated 130W)

The following assumptions have been made:

·         Heating:

• Heating control to maintain 20°C dry bulb temperature (24h per day)

·         Lighting:

•  25 % less rating (HF ballast)
•  Lights switched on for 20% of working hours

·         Ventilation:

• Switched on 24h per working day
• 3 AC/hr per cabin with 75% heat recovery

 

The results shown in the tables below have been arrived from a combination of ESP-r simulations and calculations.

 

 

	Annual energy demand
Lighting	152.9 kWh
Heating	7,567.6 kWh
Ventilation	2,433.6 kWh

 

	For a typical winter day (7:00 – 18:00)
Thermal percentage dissatisfied	6.03%  (0.43% standard variation)
Thermal comfort 1	10.5 h (always overheated)

¹ Hours per day where the dry resultant temperature lies between 20°C and 22°C

 

The picture below demonstrates the dry resultant temperature and ambient temperature inside the drying room for a typical winter working day. The upper line shows the dry resultant temperature, the lower line shows the ambient temperature

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

                                                 Ambient and cabin’s dry resultant temperature

 

It is shown that a dry resultant temperature about 20°C is maintained 24 hours during working days. Thus, the drying room of improved standard provides an effective environment for clothes drying.

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The subcontractor’s cabin is a 9.5m x 3m cabin with the following characteristics:

• 3 occupants for 5 hours per day
• 1 computer (7:00 –18:00)
• 2 x 2kW heater and 5 x 58W lamps
• Infiltration: 4ac/h (doors open)

 

Current situation: The following assumptions have been made.

·       Heating behaviour of occupants:

• 7:00 - 9:00 both heaters on maximum power (2 x 2000W)
• 9:00 - 18:00 both heaters on middle power (2 x 1250W)

Lighting behaviour of occupants:

• 7:00 – 18:00 lights on

 

The results shown in the tables below have been arrived from a combination of ESP-r simulations and calculations.

 

	Annual energy demand
Lighting	912 kWh
Heating	3965 kWh

 

	For a typical winter day (7:00 – 18:00)
Thermal percentage dissatisfied	24.34%  (30.58% standard variation)
Thermal comfort 1	2 h

¹ Hours per day where the dry resultant temperature lies between 20°C and 22°C

 

 

Pictures below demonstrate the dry resultant temperature inside the subcontractor’s cabin for a typical winter day. The upper line shows the dry resultant temperature, the lower line shows the ambient temperature

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

                                                      Ambient and cabin’s dry resultant temperature

 

It is demonstrated that the required dry resultant temperature of 20°C cannot be maintained. During a typical winter day the dry resultant temperature inside the subcontractor’s cabin will typically be below the required comfort level. Thus, discomfort will be experienced.

 

Proposed Situation: Following energy efficiency measures have been applied.

·         Improve insulation

• 36W T5 tubular fluorescent lights
• Occupancy sensor for lights
• 1.5 kW heater with automatic temperature control (start time: 6:00)

 

The following assumptions have been made:

• Doors mostly closed (1.5 ac/h)

Heating:

• Heating control to maintain a dry bulb temperature of 20°C

Lighting:

• 25 % less rating (HF control)

• Lights 55% switched off (5h per day switched on)

The results shown in the tables below have been arrived from a combination of ESP-r simulations and calculations.

 

	Annual energy demand
Lighting	191 kWh
Heating	1567 kWh

 

	For a typical winter day (7:00 – 18:00)
Thermal percentage dissatisfied	10.69%  (18.12% standard variation)
Thermal comfort 1	10 h

¹ Hours per day where the dry resultant temperature lies between 20°C and 22°C

 

 

Pictures below demonstrate the dry resultant temperature inside the subcontractor’s cabin for a typical winter day. The upper line shows the dry resultant temperature, the lower line shows the ambient temperature

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

                                                           Ambient and cabin’s dry resultant temperature

 

It is shown that a dry resultant temperature above 20°C is maintained between 8:00 and 18:00. Thus, the cabin of improved standard provides a comfortable working environment for subcontractors.

 

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The following two tables summarise all results gained from the case study for:

•          One contractor’s office

•          The contractor’s canteen

•          The contractor’s drying room

•          One subcontractor’s cabin

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