EXTERNAL WALL INSULATION /
PASSIVHOUS REFURBISHMENT
PermaRock’s EPS-Passiv external wall insulation (ewi) system was installed as part of a number of energy efficient measures retrofitted to a detached 1869 Victorian house in Hereford, helping contribute towards creating a low-energy, Passivhaus standard house.
This project, one of the first refurbishment projects in the UK to achieve such standards show how using PermaRock external wall insulation systems can help achieve Carbonlite and Passivhaus targets on existing hard to treat and solid wall dwellings. PermaRock can also be design and supply systems for incorporation into new buildings to Passivhous and Code for Sustainable Homes (CSH) levels 4-6 standards.
PermaRock (the external wall insulation manufacture and supplier) were involved during all aspects of the project, from design stage right through to installation, advising and assisting the Architect (who was also the Client) on issues related to the external wall insulation element of the project, as well as providing design details, which have been utilised by the AECB, the Sustainable Building Association, within its Guidance Documents.
Prior to the recently completed works, the solid brick cottage had difficulties in achieving and maintaining an even temperature in such a poorly insulated and draughty house and the expenditure of all this energy never resulted in a healthy or thermally comfortable environment. With this in mind the owners decided that the time had come for a radical improvement to the insulation and energy standards of the house. To meet their own expectations, a successful outcome for the project would result in whole house CO2 emissions for heat and power being reduced by approximately 80 - 85% compared to the average measured performance of a typical UK house of the same size.
Work began on a design that applied low-energy, low-carbon ‘design rules of thumb’ and used design skills which would result in performances to those reported by the Passivhaus Institut for continental Passivhaus refurbishments. It was hoped that a demand of no more than 22k Wh/m2.yr would be possible. This set extremely challenging targets for improving the thermal performance of the building fabric through high levels of insulation, ‘thermal bridge-free’ junctions between walls, floors and roofs etc and aimed for a very airtight building envelope (0.97 m3/m2hr @50 Pa were achieved – an excellent result).
An Infra-red Thermographic Survey was undertaken of the property by Thermal Inspections Ltd (www.thermal-inspections.com) to prove effectiveness of the building as a Passivhaus and to establish the buildings overall thermal condition. The report (available from PermaRock) concluded that the building showed no evidence of thermal bridging or unnecessary heat loss and the images show heat loss comparisons to other neighbouring solid wall properties on the street.
Arguably the biggest single contributor in achieving the required standards was the use of PermaRock’s EPS-Passiv external wall insulation system, which incorporated 250mm of high performance expanded polystyrene insulation, and helped bring the U-value of the external solid brick walls down to 0.11W/m²K. PermaRock first applied a porge coat to the existing wall surfaces to seal them and to provide a sound, homogenous airtight layer onto which the ewi system could be attached.
The adhesively bonded and mechanically fixed system had to overcome a number of issues during design stage to enable Carbonlite/Passivhaus targets to be made possible. As well having to be ‘air-tight’ the system was designed to produce thermal bridge-free junctions. In order to significantly reduce the thermal bridges that insulation fixings generate, PermaRock’s system employed special theromodowel fixings recessed into the insulation and capped with insulation disks. The fixing design was thermally modelled and found to assist in maintaining a low u-value which contributed to keeping the heating demand at the required level.
To create the desired aesthetics, PermaRock’s K-Finish (through-coloured render) with a 1.5mm aggregate was used. This silicone-based render incorporates advanced ‘clean concept’ nano-technology and photocatalytic pigmentation that provides a high degree of breathability and water repellency to the surface, and delivers superior resistance to dirt pickup, maintaining a cleaner, fresher appearance for much longer than traditional and acrylic renders.
The end result is an ‘exemplar’ project in terms of the energy and thermal performance which can be achieved through retrofitted measures, especially by the application of an external wall insulation system.
If you wish to achieve low energy Passivhaus/ Carbonlite standards on either an existing or new buildings please do not hesitate to contact PermaRock’s Technical Department for further information.