Frankly Bee (2014)

EPC ‘A’, SAP Rating 118, Building Av. U-Value 0.17Wm2/K, APT 2.00m3/(hrs.m2) @ 50Pa.

A two bedroom, 78m2 two storey detached house, located in the south Lincolnshire fen village, Sutton Bridge. Formerly residents of Unity Gardens (HCA Sustainable Social Housing Scheme 2010) for three years, the family design brief was clear, to implement the same environmental design solution as their former home.

Frankly Bee was conceived utilising a passive solar design strategy, incorporating a high thermal mass superstructure which includes single thick dense external concrete block walls, insitu concrete ground and first floor slab.

The building is super-insulated with 200mm thick PIR insulation externally cladding the walls, 300mm thick extruded polystyrene insulation under the floor slab and 20mm PIR under the roof. As built elemental U-Values achieved are 0.10 wall, 0.06 floor, 0.10 roof, 0.83 triple glazing producing a building average U-Value of 0.17W/m2K.  

Designed in is a natural ventilation regime  (no mechanical ventilation) with passive stack vents installed to the kitchen, utility and shower room. Passive cross ventilation is achieved from the rear to the front of the property both at first and ground floors using the ‘Venturi Effect’ aided by the thermal gradient across the superstructure.

The as-built SAP Rating of 118 produced an ‘A’ EPC and a measured Air Pressure Test of 2.00m3/(hr.m2) @ 50 Pa.

After nine months of occupation the owners have recorded a stable internal air temperature of 230C with little diurnal variations.

The thermostat for the back-up electric under-floor heating system is set at seventeen degrees, there has been no energy used for charging the floors. Intermittent use of a 5KW wood-burner  during the winter provided additional heat as well as a ‘virtual hearth’.

During the first nine months of occupation the average daily recorded energy usage is 9.5kWhrs while average daily energy generation is 13.8kWhrs. The household at Frankly Bee are presently generating thirty two percent more energy than they consume. The highest solar energy generation months of July and August will see the gap between generation and use increase.