The new floors have now been laid.  The floor slab is 150mm of dense concrete, which sits on top of a new layer of insulation which is 250mm thick.  Around the side of the floor slab is 50mm of edge insulation.

Floor insulation being installed, which will be below the new concrete floor

The new floor slab will act as a heat store to help keep the house warm through winter, with heat loss from the slab to outside of the house minimised by the insulation below and around it.  The heat then only has one way to go; back into the house as the air temperature drops below that of the floor.

The new concrete floor slab being poured over the insulation layer

In summer the floor slab will act in reverse as a cooling mechanism, because as the air temperature rises above that of the floor, the excess heat will be absorbed into the dense concrete.

The mass of the original solid walls will act as a heat sink in a similar way, helping to cool the house in summer and heat it in winter, once it is fully encased in insulation, which is the next major phase of the retrofit.

Although we believe we’ve come up with a very energy-efficient retrofit design, and combined with the energy offset provided by the investment in the community wind turbine will deliver a zero carbon solution, there is still one critical element over which we have limited control – the tenants.

In highly energy-efficient houses that combine high thermal mass and significant levels of insulation to remove the need for a space heating system, it is vital that the occupier appreciates the design concepts and how to live in the house; if you leave a window open in winter the house is going to get cold!

Therefore we will be working with the tenants moving into the retrofitted houses, to help them understand how the houses are designed, and more importantly how they need to occupy the house to ensure this design is effective.

This subject was covered during a seminar at the recent National Energy Management Exhibition (NEMEX), and included a name check for Hockerton Housing Project.