Concrete Compass: Low energy buildings
Navigating to useful resources and guidance
A fabric-first approach for improving the energy efficiency of buildings is an undeniably good idea. Concrete and masonry can be used very effectively to provide cost effective building enclosures with high thermal performance and is an opportunity to append the long life low maintenance benefits associated with these materials.
The Concrete Centre has a wealth of guidance that can inform the design of low energy buildings:
Read 'Keep it Tight' article in Concrete Quarterly 251: Focusing on how concrete techniques are helping to build Passivhaus developments, including Rick Mather’s 53-home Chester Balmore scheme in north London.
Read 'In Search of New Lows' article in Concrete Quarterly spring 2020, looking at airtightness, passive cooling, passive solar design, demand-side response and post-occupancy evaluation. Incudes a case study on Agar Grove, London.
Specifically for the design of housing there is also:
Also explore the links in this section for more information on embodied and operational CO2 for housing and structural frames.
Design of building fabric to improve energy efficiency
The entire building envelope of any building, its walls, roof, floor, and openings have a role to play in minimising heat loss through improved insulation, reduction or avoidance of thermal bridges and improved airtightness. Thermal mass also has a positive role to play but this can also be provided by internal structure such as wall and floors.
Below are links to useful further guidance on each area.
Thermal Performance Part L1A includes a large selection of performance data for walls and floors for a variety of concrete and masonry construction solutions and different types of insulation. Each are illustrated with their construction dimensions and corresponding insulation (U values) and thermal mass value (k-value.)
Reducing thermal bridges
A comprehensive range of high-performance masonry construction details are available to download with pre-calculated PSI- values (ψ-values) for use with SAP to meet thermal bridging performance criteria using different block types and insulation options. These details provide an effective means of showing the reduction of a dwelling’s overall heat loss from thermal bridging, and offer a far less punitive alternative to the default ψ-value included in Part L1a 2013.
The Modern Masonry website provides further explanation and all necessary links.
A range of innovative new products are also available from specialist suppliers to reduce thermal bridging using concrete and masonry construction. These include cavity wall ties and insulated precast sandwich panel connectors with very low levels of thermal conductivity, plus high performance lintels and insulation for cavity walls, as well as thermally insulated balcony connectors.
Construction using concrete and masonry has been shown to provide excellent levels of airtightness. Cast insitu and large format precast panels are inherently simple to detail providing a robust, durable structure with few joints. A plasterboard lining and well pointed joints can improve the performance of blockwork. For higher performance levels a parge coat or plastered finish have has been shown to be very effective. More details on airtightness.
The thermal mass of concrete can be harnessed effectively to reduce the energy consumption of building in various ways. It can be optimised to suit the energy profile of the building in question. A summary of different approaches include:
- Thermal mass for cooling – to avoid or reduce use of air- conditioning in buildings with large internal heat gains. E.g offices, schools, libraries, data centres.
- Thermal mass for heating – to reduce energy use in the heating season by utilising stored internal heat gains.
- Thermal mass and passive solar design – optimising use of solar energy to reduce energy consumption of heating.
- Thermal mass for passive cooling in housing – reducing the risk of overheating and potential eneegy consumption for mechanical cooling.
- Thermal mass with active cooling and heating – using embedded pipes to optimise the thermal mass effect and/or speed up thermal response.
- Thermal mass with demand side response – utilising thermal mass to optimise peaks and troughs in energy grid supply.
Further guidance on the use of thermal mass.