MODERN METHODS 44 OF CONSTRUCTION
A Concrete Approach
to Part L Compliance
THE ‘ZERO CARBON’ HOUSING AGENDA SETS A NEW STANDARD FOR SUSTAINABILITY IN CONSTRUCTION. ONE OF THE WORST CURRENT OFFENDERS AS FAR AS BUILDING PRODUCTS ARE CONCERNED IS CONCRETE, WHICH PRODUCES COMPARATIVELY SUBSTANTIAL CO2
EMISSIONS DURING ITS MANUFACTURE.
Although the concrete industry has significantly improved its sustainable credentials in recent times, developers are still targeted to reduce the volume of concrete used in projects and reduce the impact of the concrete that is used – at the same time as increasingly stringent thermal performance is being dictated by Part L. Mark Gray, technical manager, Insulslab SFRC, explains how innovative new foundation systems are helping developers succeed in meeting these objectives as well as driving down overall development costs.
T
raditional foundation methods include suspended slabs, beam and block, raft foundation and piled foundations.
Concrete forms a critical part of these systems and in some cases, such as raft foundations, has to be used in conjunction with additional reinforcement. In addition, these standard foundation techniques can demand intensive ground preparation and excavation, leaving the developer with the challenge of either re-using the spoil on-site, or incurring the cost of removal.
With regard to Part L compliance, traditional foundation methods rely on a layer of insulation either above or below the ground floor slab. Dependent on additional compressive performance, even the best performing thermal resistant products would generally have to be 75mm in thickness to comply with current Part L Building Regulations.
However, recent innovations in foundation technology have led to the development of a new breed of integrated and super-insulated system, which reduces the overall volume of concrete required and at the same time exceeds Part L requirements – without increasing the floor depth with additional insulation.
A Concrete Choice These new super-insulated integrated systems reduce the volume of concrete required by using a special ‘waffle’ type foundation structure, which is constructed of interlocking expanded polystyrene (EPS) pods. Steel fibre reinforced concrete (SFRC) is then cast on top to deliver the foundation up to ground floor slab level.
The pods require minimal site preparation as the ground normally only needs to be excavated to a depth of approximately 600mm below finished floor level, before hardcore is laid and without the need to dig any trenches. While this means there is less of a void to fill with concrete, it also delivers
time and cost saving. This is because the installation process is much less labour intensive than traditional systems and there is less spoil to manage on-site.
Importantly, in spite of being new to market, there are BBA recognised systems available. There is currently one super-insulated integrated system with a BBA certificate, which covers the design principles of the system – offering developers and specifiers peace of mind when adopting this new technique.
By delivering the floor up to ground slab level, these systems also negate the need for an additional screed layer, which again is contributing to a reduction in concrete.
Exceeding Part L As super-insulated integrated systems take the foundation up to ground floor slab, thermal performance and sustainability are key specification considerations. With some systems shown to comply with Part L, when correctly specified and constructed, developers can expect to achieve typical U- values of approximately 0.10 – 0.12 W/m2K.
For traditional floor build-ups to achieve the same thermal performance as modern super-insulated integrated foundation systems, the insulation layer would typically need to be increased to an approximate thickness of 160mm to 180mm. As this would significantly increase the overall floor depth, additional excavation would be required to retain the original finished floor level. The time and resource necessary to undertake these works mean such an increase in insulation layer thickness is not viable.
Although these are challenging times for developers, with changes in legislation and the sustainability agenda sometimes conflicting with the need to keep build costs and time to a minimum, innovations in construction methods appear to offer the solution. For those willing to break new ground and adopt the latest techniques, there are tangible commercial benefits to be realised.
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