Sustainability: On-site renewables | Features

Renewable technology	Candidate buildings	Prerequisites	Potential barriers	Annual saving per £100,000 of capital cost
				kWh	kg CO2
Tower-mounted mwind generators	Industrial, distribution centres	Average site wind speed minimum 7 m/s	Environmental impact. Site space for large turbines	100,000	43,000*
Building-mounted “micro wind”	Most types of building	Average site wind speed minimum 3.5 m/s	Environmental impact. Roof space for small turbines.	40,000	17,200*
Photovoltaic roof or panels	Most types of building	Roughly south-facing, unshaded	Available roof space	12,500	5,375*
Photovoltaic rain screen or glass	Prestige offices or retail	Roughly south-facing, unshaded	None	9,000	3,870*
Passive solar water heating	Residential and commercial, hotels and leisure	Roughly south-facing, unshaded. Requirement for hot water	None	50,000	9,500†
Ground-source heat pump	Most types of building	Feasible ground conditions	Site space for pipes	40,000	7,600†
Borehole cooling	Offices, hotel, leisure	Feasible ground conditions	Site space for pipes	12,000	5,160*
Biomass boilers	Most types of building	Space and convenient source of fuel. Requirement for heat in summer	Environmental impact and maintenance	100,000	19,000†
Biomass CHP	Industrial, hotel, leisure, hospital	Space and convenient source of fuel. Requirement for heat in summer	Environmental impact and maintenance	(P) 28,000 (H) 63,000	(P) 12,000* (H) 12,000†

* compared with electricity; † compared with gas