Waste water heat recovery (WWHR) is a technology using a heat exchanger to recover heat from waste water, primarily from shower, in order to reduce energy consumption for water heating.

WWHR can be used in SAP as an effective measure to comply with Part L1A for new residential projects mainly because:

1. High efficiency WWHR can improve the dwelling emission rate (DER) by approx. half to one point, which in many cases is critical to achieve Part LlA compliance.
2. The cost of WWHR systems is low in comparison with many other types of energy saving products. A WWHR system (e.g. a vertical pipe) costs approx. £500. This is comparatively low compared with other energy saving products including high spec glazing and renewable technologies. For example, a 0.5kWp PV panel system will cost approx. between £1000 and £1500 to install.
3. WWHR systems are easy to install with no maintenance issues over the long term. High efficiency WWHR is traditionally in the form of vertical pipe system, which can be easily fitted during the construction stage. If additional points are needed for SAP purpose when project is complete, horizontal systems can be retrofitted under the shower tray or bath tub. The recent advancement in WWHR technology has seen emergence of relatively high-efficiency horizontal systems which normally had an efficiency of below 30%. For example, Recoup Easyfit+ claims to reach efficiency of 47%.

When selecting WWHR, architects or designers need to pay particular attention to:

1. Efficiency of the system: higher the efficiency, better the SAP rating will be. Designers should aim for minimum efficiency level of 50% to maximise the SAP points therefore the vertical system should be the first choice if viable.
2. Shower type: the shower will need to have a thermostatic mixer which can regulate the desired output temperature.
3. The number of WWHR systems required. If there are multiple shower rooms in the house, designers may need to consult the WWHR suppliers for the optimal solutions.

Innervision Design Ltd has undertaken SAP and SBEM for a wide range of residential and commercial projects. We take pride in the quality of our services. Please get in touch for a friendly discussion and some initial advice. For more information, please visit our website: http://www.innervision-design.co.uk/sap-calculations-and-epc.php