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WWHR: What is Waste Water Heat Recovery?

11 Sep 2019 at 3:02 PM

Waste Water Heat Recovery (WWHR) units can help to lower CO² emissions in new homes.

They can provide a relatively low cost and low maintenance solution to lowering emissions within a Part L SAP Calculations, and unlike solar panels or other renewable technologies, many designers are unaware of what this relatively simple device is or how it works. So what is WWHR?

A WWHR unit is a system designed to retrieve thermal energy from hot water used in a shower before it disappears down the drain. This happens through a heat exchanger, in which cold mains water is passed around a copper waste pipe to gain a temperature rise, before continuing to the boiler ‘pre heated’. This in turn relieves the workload of the boiler.


How a WWHR system works (click to expand)

In carbon terms, the benefits of this system can be significant, and can often improve a SAP score by around 6%. As a system with no moving parts or maintenance routine, a WWHR unit can be considered a ‘fit and forget’ solution.

Most models resemble a length of copper piping and so can be fitted behind the scenes with little additional considerations by the builder or occupant.

So what about cost? As an example. the most popular vertical models from Showersave such as the Recoh-vert RV-3,  or Pipe+ HE cost around £400 to install.

Compared to much larger potential outlays for solar panels this makes WWHR an attractive prospect for those looking to save carbon.

Some estimates suggest that there is already a WWHR unit in 20% of new homes – see Housebuilders now fitting WWHR as standard.

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