At the end of June, Parliament formally committed the UK to achieving net zero greenhouse gas emissions[1] by 2050. This change, contained in an amendment to the 2008 Climate Change Act, is a hugely significant moment for the refurbishment industry. It is estimated that around 80% of the buildings built pre-2010 will still be in use by the middle of the century and the energy performance of many of these buildings will have to be significantly improved if we’re to achieve the ambitious net zero target.
Insulation retrofits can be expected to form a key part of this effort particularly for the UK’s stock of 8 million solid walled homes. Most of these homes do not feature any wall insulation, leading to high levels of heat loss.
The simplest method of retrofitting insulation in these buildings is via an external wall insulation approach where insulation is fitted outside the walls behind render or brick slips. This isn’t always possible, however, either due to planning restrictions placed on period properties or simply because the owner doesn’t wish to change the outer appearance of the property. The alternative is an Internal Wall Insulation (IWI) approach where insulation is fitted on the inner face of the walls behind drylining.
Before you begin this or any other major refurbishment work aimed at improving the energy efficiency of a property, it is important to take a step back to consider all of the factors at play.
Whole House Approach
At the planning stage for any improvements, the project team should carefully consider how the property is used, as well as looking at the type of construction, heritage of the property and the layout of internal spaces. By adopting this so called ‘Whole House Approach’ and developing a clear strategy which adequately allows for future interventions, it should be possible to maximise the cost efficiency of any measures and avoid any unintended consequences.
If you are considering installing IWI measures, a detailed survey should be carried out before you begin the work. The surveyor should cover a variety of points such as:
- internal and external investigation around all areas on the walls (particularly around the damp proof course) and surrounding floors, ceilings and roofs to identify any cracks, issues with pointing quality or areas of damp, mould growth or rot;
- ensuring adequate ventilation provision via controlled routes (such as air bricks or extractor fans);
- assessing external walls which may be subject to driving rain and considering measures to address them. These can include extending overhangs, repointing or applying an external render;
- look for potential thermal bridges (penetrations through the wall and insulation layer which can allow heat loss and cause condensation to form). These include cable, pipe or duct penetrations and areas around windows and doors; and
- consider where areas such as floors might be upgraded in the future and plan for how these might interact with the measures taking place on the walls.
With a thermal conductivity of just 0.018 W/m·K across all thicknesses, Kingspan Kooltherm K118 Insulated Plasterboard can provide a slim option for IWI applications.
If defects are identified, then a programme of works should be drawn up to address them. It is essential that walls are in a dry, stable and good state before you begin this work.
The most suitable insulation solution will depend on the construction of the property walls. In some cases a moisture-open approach is the best one, for many others, a moisture-closed approach is needed. An experienced contractor should be able to assess your walls and advise on this.
Of course, as the insulation is being installed internally, it is preferable to keep the build-up as slim as possible to retain room space. Insulation products with a lower thermal conductivity (lambda value) are more effective at preventing heat escaping, meaning a slimmer thickness can be fitted to achieve the desired level of insulating performance. The latest phenolic insulation boards have the lowest thermal conductivity of any commonly used insulation board (as low as 0.018 W/m·K) making them particularly suitable for IWI applications.
It is also worth considering insulated drylining products. These combine insulation, plasterboard and a vapour control layer in a single board helping to speed up the installation process.
During the installation you should check that all joints between the insulation materials are tightly butted, as any gaps can create cold spots in the wall, allowing heat to escape and potentially allowing condensation and damp to form. Similarly, care should be taken to ensure areas such as window jambs are properly insulated.
Further information is available in the BRE book ‘Reducing thermal bridging at junctions when designing and installing solid wall insulation’ (FB 61).
The Right Solution
Each refurbishment project presents different challenges, but by adopting a whole house approach, it should be possible to identify the most suitable solutions. IWI installations can provide a highly beneficial option for some hard to treat properties, and by adopting best-practice during design and installation and utilising the latest premium performance boards, it should be possible to maximise internal space whilst effectively limiting heat loss.
For further information and technical support, please contact:
Tel: +44 (0) 1544 387 384
Fax: +44 (0) 1544 387 484
e.mail: info@kingspaninsulation.co.uk
website: www.kingspaninsulation.co.uk
