Hot Water Cylinders for Passivhaus Project

McDonald Engineers has secured a major project to design and manufacture its POWERflow unvented cylinders for a housing association which is building homes to meet the Passivhaus standards.

The nature of the Passivhaus approach and its use of renewable energy sources means that the hot water system can often use more energy than the heating of the building.

It is therefore essential to design a highly efficient hot water solution which maximises the use of renewable energy and minimises heat losses of both the cylinder and the pipework.

McDonald Engineers designed, manufactured and supplied 210 litre and 300 litre POWERflow unvented cylinders with high performance solar thermal finned copper coils to extract the maximum out of the sun’s input.   The cylinders were insulated with a market leading 100mm of high density foam insulation.  This maximised efficiency and provided the lowest heat loss figures from any Unvented cylinder.

Minimising the heat loss of the pipework requires careful positioning of the hot water cylinder to minimise the potential for dead legs, which is when excess hot water is left in the pipework when the hot water tap is switched off. The ideal position of the hot water cylinder in a Passivhaus project is therefore generally as close to the centre of the property as possible.

McDonald Engineers’ Sales Director, Jamie Stewart, explained “We worked closely with the client on the project to ensure the hot water solution not only provides them an excellent supply of mains pressure hot water, but most importantly the heat losses were absolutely minimal.  This is something we can achieve with our bespoke manufacturing service.”

He continued, “Our technical sales team specialise in designing and developing hot water systems which meet the exact requirements of the project, whether it’s incorporating multiple fuel sources, delivering mains pressure, maximising efficiency or to fit within a tight space.”

To find out more about our bespoke hot water cylinders to suit Passivhaus projects contact us now on 01592 611123 or email