TeploTie used in zero carbon retrofit
Ancon TeploTie, the innovative low thermal conductivity wall tie, has been used in the UK's first retrofit to achieve zero-carbon Level 6 of the Code for Sustainable Homes.
Although not one of the largest construction projects in the UK, it could be one of the most significant. Improvements must be made to the energy efficiency of existing housing stock, if the UK is to make serious carbon emission reductions. Architect John Christophers is confident the principles employed here in this single dwelling could be replicated on a larger scale.
The project involved the upgrade and extension of the architect’s own 2-bed semi-detached family home in Birmingham which was built in the 1840s with solid brick walls. By using the vacant parking lot at the side and adding a rooftop studio, floor space in the house has doubled. Most importantly, the existing house has reached the same demanding energy efficiency standards as the new extension. There were three key elements to the success of the project; these were creating a super-insulated envelope, achieving high airtightness levels and installing renewable energy systems.
The front elevation is internally insulated to preserve the original brickwork. The rear of the property was dismantled, extended and re-built using some of the original bricks. The U-value of the walls is now 0.11W/m2K, which is 16 times better than before. Almost every thermal bridge was designed out. This included all metal fixings which it was feared would compromise the thermal performance.
Exclusive to Ancon, TeploTie wall ties are manufactured from extruded basalt fibres. They have a thermal conductivity of just 0.7Wmk and so are excluded from U-value calculations. They are ideal for retrofit projects as they can be post-fixed into existing walls, as well as be built into the bed joints of new masonry.
TeploTies were fixed with resin into the existing Victorian brickwork and built into the new internal structure. They were used extensively throughout the project wherever a fixing was required to cross the insulation; also being used to fix into timber. TeploTie wall ties are available for cavities from 50mm to 300mm. This project uses a 250mm insulated cavity, filled with material reclaimed entirely from recycled waste newspaper.
John suggests other benefits of a super-insulated envelope: "The greater wall thickness is put to good use by forming window seats. Windows and other openings are carved through the walls and roof using splayed angles to frame views and modulate daylight."
The structure is made from clay blockwork, rammed earth floors and solid Victorian brickwork. John explains why the use of these heavyweight materials helps the performance of the building: "This high thermal mass made with low carbon building materials seemed the simplest, most sustainable and least expensive way of ensuring the building would not overheat in the predicted hot summers, which can happen with lightweight construction."
The UK is committed to reducing carbon emissions to 80% of its 1990 level by 2050. The built environment is expected to account for about half of this reduction. Whilst programmes are in place to drive energy efficiency in the new-build market, the real challenge is in enhancing those buildings that already exist, the vast majority of which will still be in use in 2050. It is estimated that this will involve the refurbishment of 26 million homes and two million non-domestic buildings.
Grant Shapps, Minister for Housing and Local Government, says, "Improving energy efficiency in homes, particularly older homes, will have a key part to play in reducing overall emissions. Nearly a quarter of the housing stock consists of solid-wall homes, many of which are period properties. Retrofitting these properties will be crucial if we are to meet our target".
This project qualified under the Code for Sustainable Homes as more than half was new-build. The design has been audited by the BRE and verified to Level 6, Zero Carbon status (i.e. the net carbon emissions of the building are zero).
Over 90% of the heating and hot water requirements are provided by solar panels installed on the new roof, built at just the right pitch and orientation for maximum efficiency. A top up woodstove meets the remaining needs with enough timber on site from some essential tree surgery to last approximately seven years.