Changes to zero carbon homes announced in Budget

The Budget, announced by the Chancellor last week, could change the definition of zero carbon homes significantly.


Just over two weeks ago, the Government’s Carbon Plan reasserted their commitment to making sure all new-build homes are zero carbon from 2016. However, the Budget set out last Wednesday has generated questions around this commitment. The Budget said that:

1) From 2016, new homes will no longer have to make a net addition of zero to the carbon footprint of the UK’s overall housing stock. This will surely have an impact on UK carbon emissions, 27% of which come from UK housing stock.

2) Building regulations no longer cover carbon emissions created as result of cooking or plug-in electrical appliances, such as computers or TVs. Appliances are responsible for a large proportion of domestic carbon emissions. If consumers do not manage their use of household appliances, in the absence of regulatory control, appliances are likely to negatively impact on the carbon footprint of UK housing stock.



Building regulations will not cover carbon emissions from cooking appliances

There have been both positive and negative reactions to the Budget amongst the house-building industry. According to the UK Green Building Council, these policy changes mean emissions caused by a typical house will only be reduced by two thirds over a year, not eliminated. Neil Jefferson, Chief Executive of the Zero Carbon Hub, said these policy changes require careful consideration; however the Hub is please that their Task Group’s work on Carbon Compliance will form the basis of changes to the Building Regulations.

Airtightness: are modern building methods compromising the air quality inside new homes?

The last revision to Approved Document L in 2006 introduced a new mandatory requirement for air permeability and pressure testing as a way of controlling heat loss through unwanted ventilation. It had been assumed that house builders who had not previously been required to focus on airtightness would be on a long learning curve and progress would be slow. But, contrary to expectations, test results demonstrate that the industry has risen to the challenge well with design airtightness targets routinely being met or exceeded.

A proportion of homes are hitting very high levels of airtightness – 5m3/(hm2), half the maximum deign limit set in Approved Document L 2006 – and for these homes there is a question as to whether the trickle ventilation installed is sufficient to maintain good indoor air quality and control moisture/mould growth. It has always been assumed that homes become leakier as they age, as the result of minor shrinkage and cracking as the normal drying out and settlement take place.

The NHBC Foundation recently published research to establish how airtightness is affected as homes age. Our study examined 23 homes that were reasonably air tight when first built. Between one and three years later, the air permeability of these homes was re-tested and we also took the opportunity to search for signs of condensation and mould growth. Occupiers of the homes were also questioned about how they ventilate the building.

Findings of the study

Though the sample size was small (and so the results should be treated with caution), there were some interesting findings. The study found that, while 15 homes became leakier, surprisingly eight actually became more airtight. The type of dwelling, the materials used to build and the type of heating system and ventilation used in the homes all affected variable changes in air permeability.

The study also found that occupants’ approaches to using ventilation differed widely between dwellings. During testing, many trickle vents, regular use of which is considered necessary to ensure good ventilation, were set to the closed position.

Of the eight houses where air tightness had increased, three were found to have a manifestation of mould. Significantly, ventilation systems available in these houses were set to the closed position. Despite this, there was only minor evidence of mould, suggesting that under-ventilation was not leading to unmanageable problems in practice.

This study forms part of work currently underway by the NHBC Foundation and the Zero Carbon Hub to consider the whole issue of indoor air quality in homes as we make progress towards the zero carbon homes of the post-2016 future.

Government to announce changes to Feed-in Tariffs

Solar panel initiatives have beneffited from Feed-in Tariffs

An article published yesterday in The Guardian revealed that the Government is poised to limit the size of solar panel installations that will benefit from Feed-in Tariffs (FITs).

Business Green also reported that the Government will later this week detail its plans to restrict subsidies paid to solar power plants through the FITs initiative. It is likely that only plants of less than 50kW capacity will qualify for FITs, which rules out many larger developments located around the UK.

The solar sector has warned that this latest move by the government will jeopardise many jobs that have been created by larger renewable energy developments.

FITs were introduced through legislation in 2010 with the aim of providing significant financial encouragement to the uptake of renewable technologies at a domestic or community scale. This initiative is one key method of improving the energy performance of homes and buildings, a requirement of the 2008 Climate Change Act.

Despite the increase in initiatives around the UK that harness the benefits of FITs, such as solar panel installations, the FITs scheme is still not widely understood. To help social landlords, householders and anyone else looking to find out more about FITs and develop their own projects, the NHBC Foundation has produced a report entitled Introduction to Feed-in Tariffs, which offers a guide to the FITs scheme and its implications. The report contains helpful details on:

• Eligible technologies
• How the FITs scheme works
• The financial returns of a FITs scheme
• The carbon dioxide emission savings that can be made
• Key issues and opportunities associated with FITs schemes.