The issue of heat loss at the perimeter floor/wall junction, as well as other cold bridges around the building envelope can be successfully addressed through the use of Thermoblock, manufactured by Marmox (UK) Ltd. The loadbearing composite product has been developed to be incorporated into various wall constructions as a horizontal layer, equivalent to a course of bricks, in order to address a critical area of heat loss; thereby reducing energy bills and making a significant contribution to SAP (Standard Assessment Procedure) calculations. Each length of Thermoblock is comprised of ultra-high performance XPS insulation, encapsulating miniature columns of concrete; while the top and bottom are covered by alkali resistant glass-fibre mesh, retaining a surface of fibre reinforced polymer concrete to facilitate bonding. Individual units are 65 mm deep and feature a 15 mm overlap at either end, giving them an installed length of 600 mm; they are available in widths of 100 and 140 mm and are installed at the base of the inner leaf to an exterior masonry wall, normally level with the insulation beneath the floor screed. They can, however, be employed within a timber frame construction and at other positions such as beneath window openings or at first floor level, the roof-wall junction and under party walls.
Although a conventional DPC should still be incorporated into any wall construction, the impervious nature of Thermoblock means it forms a further horizontal barrier to moisture ingress. Wherever they are installed, the XPS with its ultra-low thermal transmittance increases the path for heat loss, making it a highly effective solution to dealing with the increasingly important effects of cold bridging. To achieve Level 4 of the Code for Sustainable Homes requires a 44 per cent improvement on energy performance set out in the 2006 edition of Part L to the Building Regulations.
In the very important area of the wall/floor junction, Enhanced Construction Details can cut heat loss by between 35 and 55 per cent; but utilizing Thermoblocks can reduce CO2 emissions still further to between 60 and 90 per cent, offering an important contribution to the points required in achieving CSH Level 4 or above. With the concrete columns having a y-value of 0.225 W/mK but occupying only 10 per cent of the overall area, compared to the XPS insulation with its thermal conductivity of 0.033 W/mK, the combined y-value is 0.052 W/mK. Crucially, being able to employ a defined, very low thermal transmittance – derived by thermal modelling or measurement – offers a far more advantageous result than adopting the ‘default’ figure offered in SAP. Using standard ACDs will add a heat loss of 0.08 Watts to the U-values for a property, while Enhanced Construction Details can cut this to 0.04 Watts; but incorporating Thermoblock can bring this right down to 0.01 Watts or less. The same principle applies to the European PassivHaus standard or the recently launched Fabric Energy Efficiency Standard (FEES), which the Government is now promoting as the route to achieving Zero Carbon construction. Overall Marmox Thermoblock presents a fully compliant solution to addressing the issue of cold bridging which is also CFC and HCFC free with a zero Ozone Depletion Potential, offering ease of installation. Furthermore the reduced energy consumption can also guarantee a pay back in as little as two to three years, depending on building configuration. Marmox (UK) Ltd. has published a fully illustrated, 16 page technical brochure on the benefits and application of Thermoblock, as well as offering a comprehensive specification advisory service.