Eco Build

All Timber Frames is a dedicated timber frame construction company based in Cheriton Fitzpaine, eight miles from Exeter.

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It is now almost universally accepted that we are experiencing changes to our climate brought about in part by decades of over-reliance on fossil fuels, to power industrial growth, to heat our houses and run our motor vehicles.

The result has been an increase in greenhouse gas emissions which if unchecked will result in a rise in global temperatures of up to five degrees centigrade, enough to have a devastating impact on the world’s population.

In 2005 The Stern Review on the Economics of Climate Change was set up. The conclusions of this report pointed to the need for decisive measures on curbing the rise in carbon dioxide emissions in order to prevent the adverse affects on economic growth and population dispersement caused by rising temperatures and sea levels. The UK Government’s response was the Climate Change Act of 2008.

Under this Act the UK Government has committed itself to legally binding greenhouse gas emissions reduction targets of at least 34% by 2020 and at least 80% by 2050, relative to 1990 levels, with legally binding 5-year carbon budgets governing the trajectory to the 2050 target.

With around 45% of the UK’s CO2 emissions coming from buildings, 27% domestic, 18% non domestic, principally from space heating and cooling, water heating and lighting, it is not surprising that the main thrust of the Government’s efforts to reduce CO2 emissions has been directed at reducing these emissions from the UK’s housing stock. For existing housing this has led to various initiatives to encourage home owners to insulate their properties and change to more efficient condensing boilers. For new homes the Government has instigated changes to the Building Regulations that are designed to increase the thermal efficiency of buildings, and therefore reduce CO2 emissions, and to establish the Code for Sustainable Homes.

The Government’s aim is that all new houses will be zero carbon by 2016, with new non-domestic buildings reaching the same standard by 2019. These targets equate to Code 6 in the Code for Sustainable Homes. As we move towards these targets the Building Regulations have been the regulatory framework to force through the changes.

Within the Building Regulations there are two key measures relating to CO2 emissions from buildings, Target Emission Rates, TER, and Dwelling Emission Rates, DER. The TER is the level of emissions set down for each of the notional building types, for example detached homes, terraced homes and flats, whilst the DER is the actual emissions rate for each built property. The DER is established by the SAP calculations. To gain Building Regulations approval it is a mandatory requirement that the DER is better than the TER.

With successive Building Regulations the TER has been lowered, and this has forced buildings to be constructed in a way that results in less CO2 emissions. For example the TER in the 2010 Building Regulations was 25% lower than in the 2006 Regulations. The 2013 Building Regulations which come into effect in October of this year will see a further reduction.

To date the basic principle of the move to zero carbon standards has been a ‘fabric first’ approach, with energy efficient fabric and services being prioritised over renewable energy generation technologies. This is because it is easier, and cheaper, to reach the targets by improving the fabric of the building than by utilising renewable technologies to heat and light the buildings.

Before the move towards zero carbon housing, timber frame construction was the first choice for anyone who was serious about sustainable construction, now an eco build is even more imperative.

The production of building materials and the construction processes demand energy use and therefore result in CO2 emissions, this is known as embodied carbon and can account for about 20% of the whole life carbon cost of a building. The advantage of timber is that it has a negative embodied CO2 value, even allowing for transportation, the more timber that is used in a building the lower its’ carbon footprint will be. The forests from where the timber is sourced acts as a carbon sink, CO2 is absorbed from the atmosphere and stored. Old trees are less efficient than young trees in carbon capture, so the felling of trees for building materials and then replanting with young saplings actually helps in the removal of CO2. When trees are turned into building materials the CO2 is locked up and stored. By purchasing timber from responsibly managed forests under the FSC scheme means that timber is a naturally renewable resource. The area of Europe under forestation is growing annually. As the demand for timber increases this trend will continue.

With the move towards zero carbon, timber frame construction is the natural choice for everyone working towards Code compliance. The Code is divided into 9 categories:

1. Energy / CO2

2. Materials

3. Surface water run off

4. Waste

5. Pollution

6. Water

7. Health and Wellbeing

8. Management

9. Ecology

These categories are further sub-divided into 34 separate categories, with points being awarded for compliance with each of them, the total number of points determining the Code level achieved. Timber Frame has a natural advantage over masonry construction in 6 of the 9 different categories.

  • Energy

    It is widely recognised that it is cheaper to obtain a given U value by insulating the external wall panels of a timber frame than by insulating the cavity walls in a masonry construction. It is also far easier to achieve the very low U values required to achieve Code 6 using timber frame construction. The lower the U value the more thermally efficient the building, therefore less energy is needed to provide space heating with a consequent reduction in CO2 emissions. The lower the emissions the more points are scored.

  • Materials

    Timber earns more points because of its lower embodied CO2, as well as in the responsible sourcing credits category compared to masonry products.

  • Waste

    Timber frame manufactured off site produced very little waste, as little as 2%. With masonry construction as much as 15 – 20% of the materials delivered to site end up as waste. Timber products are also easier to recycle. Both these areas result in more points being awarded through using timber frame construction.

  • Pollution

    Timber frame lends itself to the use of natural, environmentally friendly insulation products which score better in the category relating to pollution generated by the production of the insulation products used in the build

  • Health and Wellbeing

    In all the published tests timber frame construction performs better in sound testing compared to masonry build. The better the sound test result the more points are awarded. Timber frame is also easily adapted to comply with the Lifetime Homes requirement.

  • Management

    Within this category points are awarded for the level of site impact on the neighbouring properties. Timber frame has a quicker construction timescale, it generates less noise, less dust, and has less deliveries. A timber frame construction site also uses less energy in the construction process. This means that timber frame scores better in this category compared to a masonry build.

If past experience is anything to go by there is likely to some fudging of the issues as we approach the 2016 deadline. There is an ongoing debate as to what constitutes zero carbon, and how it should be defined. There is also talk of Allowable Solutions, where developments that fail to achieve the zero carbon benchmark can opt to pay into a scheme that delivers verified carbon saving projects for community and national benefit.

What however is certain is that the Building Regulations pertaining to the thermal performance of houses is going to get more stringent. The self-builder who is planning their build today needs to be looking to the future with regard to the thermal performance of their house, what is considered well insulated today will soon appear average. This will have an impact on the future value of the home. If possible your home should be built to the standards that will become the norm in a few years from today. This will mean that the external wall thickness will be greater, and this needs to be addressed in the planning application drawings. As a matter of course architects draw their external walls as 300mm thick. This allows for a 140mm timber frame wall panel, a 50mm cavity and a 100mm external block cladding. It also works for a masonry construction of 100mm inner block work, 100mm cavity and 100mm external cladding. The problem then arises that if the client wishes to increase the timber frame thickness to allow for additional insulation this will either increase the overall dimensions of the building and therefore will not reflect the planning permission granted or alternatively the internal dimensions of the rooms will be compromised. If you know at the pre-planning stage that you intend to use a timber framed construction for your eco build instruct your architect to show 400mm, minimum, external walls. It is always easier for planning purposes to build a smaller house than to move in the opposite direction.



The snug luxury of natural insulation