25 Storey Residential Tower, 10-20 years old

Building Overview:

  • 25 storey high rise residential tower
  • The building is heated with electric baseboards
  • The building has a high and low zone each served from the domestic hot water heaters mounted in a roof top mechanical room.  There are 8 risers in each of the zones (high and low) and there is a 150 mm diameter line supplying hot water from the mechanical room to the lower zone (approximately 36 meters below the mechanical room).
  • Heat source: direct fired gas water heaters with a nameplate efficiency of 80%
  • Indoor design temperature: 20ºC
  • Gas cost: $9.846/GJ
  • Service life: 20 years for the domestic water piping
  • Domestic water piping within the mechanical rooms is insulated, but the pipe chases are not
  • There is a re-circulation pump on the system, which is controlled by an aquastat, so that the supply and return temperatures remain relatively constant (leaving water temp = 60ºC, entering water temp = 50ºC)

Modeled Scenarios:

  1. No insulation on hot water pipes
  2. Insulation on hot water pipes (25mm thick for pipes 25-50mm in diameter; and 40mm thick for pipes 65-150mm in diameter)

Results

With insulation, the power savings would be over 30 kW.

Over the course of one year the following savings would result from the use of insulation.

Table  – Annual Energy and Greenhouse Gas Savings

Resource Annual Reduction
Energy Saved (kWh) 320,085
GHG Emissions CO2e (tonnes) 58.8
Total energy consumption 2,249,000 kWh
Energy savings due to pipe insulation 320,085 kWh, or 14.2% of total consumption

The estimated payback for the investment in insulation during construction would be less than 2.7 years based purely on the energy costs.