defining a zero carbon standard

zero carbon house is being extensively monitored by Lubo Jankovic, Professor of Zero Carbon Design at Birmingham School of Architecture, Birmingham City University to assess its technical performance. Prof Jankovic has found the house is not just zero carbon but carbon negative, meaning that, over the course of a year, the house actually absorbs carbon dioxide from the atmosphere.

Defining a technical standard for sustainability is not easy. Although a variety of standards exist, they measure different parameters and are not readily comparable.

The Passivhaus standard

The leading Passivhaus design standard, developed in Germany in the 1990s, was considered for zero carbon house. While respecting the rigorous work of Dr Wolfgang Feist on energy usage and thermal bridging, full Passivhaus accreditation of zero carbon house seemed too prescriptive an option at a time when no Passihaus retrofit standard existed. In practice and in use, zero carbon house actually meets or exceeds many of the Passivhaus measures. (See Insulation and Airtightness (technical) for a full comparison of Passivhaus standards with zero carbon house standards achieved.)

Crucially, however, Passivhaus measures only energy use and does not look at other issues in the larger sustainability picture, such as where that energy is generated, its fossil fuel carbon profile, water usage, etc.

The UK Code for Sustainable Homes

Another standard was published in October 2007 just as detailed design work on the zero carbon house was beginning: the Code for Sustainable Homes. The Code certainly has flaws. Parts of the methodology, such as the rainwater calculations and materials ratings, can seem counter-productive. On site renewable energy is not a panacea. But the attempt at a holistic approach is surely very welcome when the joined-up nature of sustainability is still little understood in UK. The original Code covered nine areas:

Carbon dioxide emissions, and energy use, including requirements for heat loss, low energy lighting, clothes drying, A(+/+) rated white goods & cycle storage.
Reduced water use, including the use of rainwater.
Materials with low embodied energy and responsibly sourced.
Minimizing surface water run-off to reduce flooding.
Waste, including facilities for recycling, composting and management of construction site waste.
Reduced pollution, especially from insulating materials.
Health and well-being through good use of day-lighting and sound insulation.
Management, including the process of construction, site CO₂, water, air and pollution, and police security standards.
Ecology, preserving wildlife and improving biodiversity.

Levels were rated 1-6, driven by the carbon reduction targets in the first section. Level 5 required a 100 per cent reduction in carbon as historically measured by the Building Regulations – principally heat loss. Level 6 went further, including hot water, lighting and electrical loads. For level 6, net carbon emissions needed to be zero, meaning no fossil fuels are used, only renewable energy.

The Code has now been scrapped by the British Government but it did help to make a significant step change in UK housing and building practice. The original version remains a rare example of the finest type of conviction politics, a precursor to the 2008 UK Climate Change Act, and the zero carbon house is designed to the original stringent standard.

The concept of “zero carbon” is now beginning to be understood more widely and it transforms our thinking: a building can actually produce at least as much energy as it consumes, and if its energy use is reduced sufficiently, it becomes feasible that it is entirely run from renewable energy.

Monitoring by Professor Lubo Jankovic

zero carbon house is being monitored using the pioneering methods devised by Professor Jankovic. The instrumental monitoring of the house was carried out to study the real life performance, collecting data of energy production and consumption as well as indoor thermal conditions.

Professor Jankovic and his team found the total annual heating energy has reduced from 59 MWh (based on the original two-bedroom 1840 house) to 1.78 MWh, and annual carbon emissions have reduced from 21,000 kgCO₂ to -660 kgCO₂.

More information on the way Professor Jankovik is developing the studies in zero carbon retrofit can be found at Designing Zero Carbon Buildings.