Brambles, Hertfordshire

Passive House Plus home that generates all its own electricity and powers an electric car

A certified 'Passive House Plus' that is also a 'Lifetime Home' perfect for people of all ages and physical abilities; a resilient building running on 100% renewable energy with no operational energy costs.

The house incorporates a well-matched battery for greater utilisation of on-site renewable energy and to provide resilience in the event of power outages.

The house feels immensely solid and sound-proofed, with a UK-manufactured frame made from Swedish engineered timber beams filled with cellulose insulation; free from toxic chemicals. Fire safety is even stronger than statutory requirements, with dense, fire-proof wall linings and a sprinkler system throughout – as in all our houses.

Energy usage and energy flow has been recorded at 5 minute intervals for more than a year. The result is a monitoring report that is already complete and will be published early 2022 (see preliminary link below). The report will show that this house generated 62kWh/m2/yr, which because of its extraordinary energy-efficiency, means that it generates ~3x more energy than it imports from the grid each year (21kWh/m2/yr). Also it exports ~1.5x more energy (34kWh/m2/yr) to the grid in a year than it imports. It uses sophisticated algorithms to run on renewable energy throughout summer and winter, canceling the cost of energy imports by exports with a modest annual profit from energy sales.

This all-electric house is comfortable, healthy, secure and resilient. The extremely low energy demand (even in winter) is mostly met by its own rooftop solar panels. In the depths of winter, when on-site energy generation might be scarce, a home battery stores spare renewable energy from the grid – via a unique energy tariff that takes cheap wind energy from the grid when the grid has excess to requirements and because of its superb energy-efficiency, unused energy is sold back when it's most valuable and needed to help stabilise the grid. 

A reversible electric heat pump is used mainly to heat water for bathing and kitchen use. The 100% fresh air ventilation system is integral to the heat pump, discretely and efficiently delivering any supplementary heating or cooling that might be required through the fresh air, while constantly cleansing the indoor air of viruses and any other contaminants. Space heating and cooling use so little energy that they are only a secondary requirement. Automatic solar/security blinds are concealed above every window to control solar gains. When active cooling is occasionally needed, this is powered directly by its own solar panels.

The house stores its own rainwater for re-use, and treats effluent ecologically, returning it to the land locally (where it arguably belongs) rather than effectively sending it out to sea.

This house demonstrates how we can build today to meet the ecological imperatives of our time. It will protect against a changing climate and will last several times longer than a power station. As such it will be a gift to future generations, not a liability.

Photography: Tim Crocker (delayed due to the pandemic, with more to follow).

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