Lifetime costs |
| Capital cost £/m2 | Energy cost £/m2 | Maintenance cost £/m2 | Net present value £/m2 (60-year life) | Service life (years) |
Centralised air system |
Ventilation and heating (no air-conditioning) | 100 | 1.9 | 1.5 | 190 | 20 |
Constant volume (single zone) | 160 | 3 | 1.5 | 286 | 25 |
Variable air volume | 180 | 2.4 | 2.5 | 320 | 20 |
Dual duct | 210 | 3.4 | 1.5 | 361 | 20 |
Partially centralised air/water system |
Centralised air with re-heat | 200 | 3.1 | 2.5 | 336 | 25 |
Unitary heat pumps | 130 | 3.2 | 2.5 | 314 | 12 |
Fan coil units | 170 | 3.2 | 3 | 360 | 15 |
Local systems |
Heat and local ventilation (no air-conditioning) | 90 | 1.1 | 0.8 | 141 | 25 |
Split package units | 85 | 3.5 | 2.5 | 225 | 15 |
Variable refrigerant flow rate | 130 | 2.8 | 2.5 | 284 | 15 |
Costs are based on £/m2 of treated floor area (gross areas less plant rooms and other non-heated areas). |
Capital costs include supply and installation and the removal and replacement at the end of its service life. |
Replacement costs are 80% of original supply and installation cost. |
Maintenance and component replacement include: ductwork inspection and cleaning; filter replacement; cleaning fan coil units; maintenance of heating and cooling plant and controls to Heating and Ventilation Contractors’ Association standard maintenance specification. |
Costs are discounted to net present values at a discount rate of 6%. |
Energy and maintenance costs are annual figures. |