The Environmentally Responsible Construction and Renovation Handbook
Implementing Water Conservation
Water consumption in a green office building should be significantly less than a similar building typical of current renovation practices. The goal of 30% reduction in water use in renovated and fit-up buildings relative to a conventional office building with similar features and systems is considered achievable in many cases. Life cycle cost analysis was used to ensure that the systems prescribed are cost effective. The methodology used to assess the economic viability of retrofitting water conservation measure for any particular technology is given in RPSB 5 Phase Water Audit Protocol Workbook. The same methodology can be used by the designer to assess technologies that have not undergone economic analysis elsewhere, or it can be used to verify the economic viability of previously assessed measures if it is believed that the given analysis is not representative of a particular situation.
Requirements for extension, alteration, renewal or repair of plumbing systems are set out in the National Building Code of Canada. The NBC requires that every plumbing system shall be designed and installed in accordance with appropriate municipal, territorial, or provincial regulations or, in the absence of such regulations, in conformance with the National Plumbing Code of Canada. Specific requirements for meeting the GOP are incremental to the National Plumbing Code, and are generally cost effective.
Water conserving measures are divided into three categories; domestic water, HVAC, and landscaping, and are discussed in the following sections.
Heating, Ventilation, and Air Conditioning (HVAC) equipment can, by design, use a considerable amount of water. There are often opportunities for water conservation with HVAC equipment. The Project Manager should tour the building with the maintenance supervisor to ascertain the viability of each of the measures described below. Where viable, within the constraints of the existing building and the renovation project, the viability of the following measures should be assessed:
- No open loop equipment of any kind is to be installed. Any existing cooling equipment that releases water directly to drain should be replaced.
- Use a demand control to manage blow-down frequency in cooling towers. Water evaporating from cooling towers leaves behind the minerals and other particles commonly found in fresh water. As make-up water is introduced, the concentrations of these materials rise. Eventually, the cooling water must be purged in a blow-down cycle to avoid excessive accumulation of mineral and biological matter. These blow-down cycles are usually on timers that drain the entire system on a fixed frequency. Water quality sampling is to be done on a regular basis after system commissioning to ensure blow-down cycles are tuned to the local water and weather conditions.
- Use counter-flow evaporative cooling tower system with low drift loss specification – In larger commercial buildings, evaporative cooling towers use significant amounts of water. Water use reductions are achieved through good design. Counter-flow cooling towers are generally more water efficient than cross-flow types. Drift loss should be specified at no more than .002% of the total water flow.
- Check and calibrate humidifier controls annually to ensure humidifier operation is maintained at the minimum possible.
- Consider the use of catalytic chemical treatments that maintain minerals in suspension to minimise the need for cooling tower blow-down (however, the environmental impacts of these chemicals must also be taken into consideration).
- Consider the use of rain water for cooling tower make-up.