Design decisions

On this page, we describe some of the decisions that were taken in response to the QB2/QB3 design criteria. We will also outline the key technologies that make the Cube Project buildings so energy efficient and, hence, environmentally friendly.

Energy generation

The Cube Project buildings are designed to generate all the energy they need, averaged over the year. For example, in its “home” configuration, QB2 was equipped with two Mitsubishi PVP 148 solar modules, each around 11m2 in area and each with a peak power output of 1.48kW. These were installed by Peter Morgan from Morgans Electrical, as was the remainder of the electrical system. Peak power is only produced from the PV panels in strong sunlight, but data show that we could expect around 280W in electrical power averaged over the year. This gives us 6.8 KWh a day or 2,480 kWh per year.

Energy Use for Heating and Electrics

QB2/QB3 are well insulated buildings, constructed from a bespoke post-and-beam system developed by us with our partner Bolton Buildings. Our prototype QB2 was clad on the outside by FSC-certified English Sweet Chestnut from Vincent Timber and, on the inside, by FSC-certified birch plywood. There is 120mm of PIR insulation in the walls, 120mm in the floor and the ceiling, and with Nordan’s NTech triple-glazed Passivhaus windows and door. Heat loss (including 2 air changes per hour) is around 30W per degree C of temperature difference between the outside and inside temperatures. Given an estimated 2020 degree-days of heating requirement per year, this would give 1450 kWh of heat loss over the year, or an average of 4 kWh/day. The space-heating and water-heating demands of QB2 were met by an Ecodan Air-Source Heat Pump (ASHP) from Mitsubishi Electric, linked to a DeLonghi Climaveneta MHD30 fan coil supplied by ICS Heat Pumps, and to a hot-water tank. For QB3, we used a through-wall air conditioning unit manufactured by Windy, coupled with an Ariston Nuos 200FS hot-water tank with integrated air-source heat pump.

Water use is minimized by the use of low-flow, high-performance showers and taps, so we assume a demand for 100 litres of hot water per day, at a temperature of 40 degrees above mains water temperature. Heating the water will, therefore, require an additional 4.6kWh of heat per day, giving a total heat demand for water and space-heating of 8.6kWh. Assuming that the coefficient of performance of the heat pump is equal to 3 (this is the number of units of heat that can be generated in the building for each unit of electricity supplied), we will use 2.9kWh of electrical energy per day to meet this total heat demand, or 130W on average.

Electrical demand is estimated at around 150W on average, including energy for high efficiency LED lighting, a low-energy LED TV, an induction hob, a combination microwave oven, an A++ rated fridge, a Ventair or Vent Axia heat recovery ventilator, a Berbel Firstline recirculating cooker hood, an A+++ washing machine, and a laptop computer.

Other environmentally friendly features

QB2 was designed to sit on Swift Miniplinth foundations that use much less concrete than would a traditional slab, are both reusable and recyclable, and leave no lasting imprint once removed. Similarly, the building was anchored to the ground using Spirafix Ground Anchors that each resist over a tonne of pull-out force, but that are removable by simple unscrewing. Both options, and others, are available for new QB2s and QB3s.

The composting toilet used in QB2 was jointly developed with Andy Warren from Natsol Ltd, adapting their standard pedestal to the particular space demands of the Cube. The system separated urine from solid waste, the former mixing with the Cube’s grey water and flowing to a soak-away (probably via a reed-bed), and the latter being composted.

QB2 had bespoke furniture, including two armchairs designed by Mike Page and Linden Davies and constructed from sustainably sourced wood by Ben Whistler Ltd. The upholstery usesd a special fabric developed by Camira Fabrics, comprising 75% wool and 25% fibres derived from nettles. The mattress was made from natural latex with an organic cotton cover. For seating, QB3 used two Moon chaises longues manufactured by LINA.

Finally, the roof is covered with an EPDM membrane, though options exist for “green” roofing and for attaching solar PV panels.

The website for Dr Mike Page's Cube Project at the University of Hertfordshire