Case study: Compact service unit

Bryn Bragl is a vanguard development in South Wales where 14 homes were built to become one of the first energy-positive social housing schemes in Wales.

The development by Wales & West and Zenergy Design, includes four one-bedroom flats, eight two-bedroom semidetached homes and two four-bedroom homes all built to be energy-positive homes where more energy is put back into the National Grid than used.

The aim was to ensure low running costs for their residents and provide a comfortable, healthy environment. Dr Jo Patterson, director at Zenergy and research fellow at Cardiff University explained “the heating and ventilation system included in the whole house approach had to be at a reasonable cost whilst not taking-up too much space.”

The PKOM 4 compact service unit ventilates the homes whilst recycling heat, also providing efficient heating, cooling and hot water. Dr Patterson specified the PKOM 4 because “being able to choose a service unit that has separate heat pumps for heat and hot water means residents do not have to compromise on the warmth of their home, whilst water is being heated.” For two years it has performed extremely well in Cardiff University’s award-winning ‘SOLCER house’ heating and cooling it efficiently, whilst providing fresh air – even more important at the current time of COVID.

In January 2021 Wales & West Housing made contact with residents in a ‘What Matters?’ questionnaire and delighted at “… how happy residents are with their heating and hot water systems. This is really good news, particularly as it’s been one of the coldest snaps in January for quite a while.”

Obviously, the more heat we recover, the less we need to generate…

Nothing can deliver fresh filtered air and remove moisture together with pollutants like a whole house ventilation system.

Typically 80-95% of the heat of the extracted air is recovered, increasing comfort levels and undeniably reducing heating bills.

The PKOM 4 offers about 969L of hot water per day allowing ventilation with simultaneous heating in living areas of between 67-208m² .

The beauty of the system is that it has two heat pumps, one to provide either heating or cooling and the other to concentrate on domestic hot water – this makes the PKOM 4 one of a kind!


The touch screen display panel allows access to:

  • Temperature required
  • 24/7 programming
  • Holiday function
  • Air volumes
  • Anti-legionella cycles
  • Solar panel
  • Supplementary heating
  • CO2 levels
  • Humidity
  • Heating and
  • Cooling.

There is also a handy smartphone app to enable remote operation.