Yes

The government’s Zero Carbon Hub has recently conceded that, when it comes to cutting CO2 emissions, paying attention to the building fabric should take precedence over investment in add on renewables.

Micro-renewables do not reduce energy consumption and there is growing evidence that micro-generation of energy is an inefficient and costly means of producing energy. Recent studies have shown conclusively that it is improvements to the energy efficiency of the building fabric and macro-renewables (eg large-scale wind farms) which offer the greatest CO2 savings per £ invested.

The Passivhaus approach and methodology has an important role to play in the retrofit and refurbishment of existing buildings. Clearly, though, we must be pragmatic. It would be unrealistic to expect to be able to retrofit to Passivhaus standard in all cases. However, the Passivhaus approach not only gives us a useful tool in refurbishing buildings to the optimum level, but also brings expertise and a clear understanding of effective measures for optimal refurbishment. Many of the teams implementing retrofits under Technology Strategy Board’s Retrofit for the Future scheme are adopting exactly this approach, using the Passivhaus methodology even where the actual standard cannot be achieved.

We need a strategic approach to refurbishment, prioritising improvements to the building fabric as far as possible, alongside district planning of the heat supply. Micro-renewables will have some part to play, but are not the key to achieving really significant reductions in carbon emissions from the existing building stock.

Chris Herring, Green Building Store Director and Technical Adviser, Denby Dale Passivhaus

No

The Passivhaus approach has a valuable role in the design of new dwellings, but it does not realistically translate into the retrofitting of existing homes. Some exemplar projects have achieved this standard in retrofit, but it begs the questions: at what cost, and is it necessary to go this far?

Passivhaus retrofits usually involve extensive work to dwellings that require tenants to be temporarily re-housed. Also, it requires tenants to take on a lifestyle that is not necessarily to their taste or ability to live with. For example, the very low levels of heating required in Passivhaus homes may be inadequate for the sick or elderly, or indeed many able bodied people who feel a need for active heating in their home – however well insulated it is. This human need for ‘dynamic’ heat input can significantly change the affordability index.

To retrofit the UK’s existing homes in a short space of time we need practical, robust methods that can be built quickly around a family in occupation. This can be achieved using high (but not extreme) levels of insulation and air tightness coupled with a modest amount of renewable heat input from a low carbon source such as a heat pump or a biomass system.

In my view these renewable technologies are the most convincing model for the ‘eco-upgrade’ envisaged in the new ‘warm homes, greener homes’ strategy. This approach, coupled with the inevitable decarbonisation of the electricity grid and demolition of the worst properties, can produce a national housing stock that is indeed fit for the future.

Denys Stephens, sustainability manager, Penwith Housing Association

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