Howe Dell Primary School, Hatfield

Howe Dell Primary School in Hatfield, Hertfordshire has been awarded an ‘A’ rated Display Efficiency Certificate (DEC) – an award which only 0.5 per cent of buildings in the UK have achieved. 

In addition to features such as wind turbines, solar panels, water recycling and a sedum roof, the design incorporates a combination of the Tarmac TermoDeck high thermal mass ventilation system, and an innovative, underground, inter-seasonal heat store. During the summer this captures heat from a solar collector located under the school play ground, where pipes filled with a mixture of water and anti-freeze transfer the heat to a thermal store located beneath the school buildings. When heat is needed, the warm water is circulated via heat pumps to an underfloor heating system and pumped to an air handling unit supplying the hollowcore concrete floor slabs at the heart of the TermoDeck system.

With its high thermal mass, TermoDeck is ideally suited to low energy school design and has been used in many projects. Its ability to utilise low grade heat and to temper the fresh air coming into a building makes it a particularly effective year-round system. This is achieved by the excellent heat transfer that occurs as the air travels through the cores of hollowcore concrete floor slabs, allowing thermal mass to be exploited to a greater extent than would normally be possible. During the summer months, night ventilation cools the slabs so they can in turn cool the building the following day. During the winter months, internal gains absorbed by the slab and heat from the inter-seasonal store warm the incoming fresh air, helping ensure a comfortable and healthy internal environment is maintained.

Tarmac TermoDeck has a number of performance merits, and by combining the two systems within the Howe Dell primary school, an exemplary energy rating is delivered through a combination of daily and seasonal heat storage.

Debra Massey, headteacher at Howe Dell Primary School, said: “We have received many accolades over the past two years, but being awarded an 'A' rated DEC is a momentous achievement for the school. It recognises the school’s innovative design and is testament to the teamwork of all those involved in the project.”

Project team

Client: Hertfordshire County Council
Architect:Capita Architecture
Engineer: Fulcrum
Contractor: MACE