Bricks, earth/clay blocks that have been fired at high temperatures to form a kind of ceramic, were probably originally used in Europe by the Romans in the Mediterranean, who may have got the idea from the Middle East. The use of bricks in Northern Europe became popular in the early middle ages and remained gently so until the industrial revolution, when large-scale production and use really took off in England.
Bricks are durable, versatile, weatherproof, have a high thermal mass, and add to the local vernacular if the raw material is sourced locally.
On the down side, bricks have a high embodied energy and therefore a high CO2 footprint. The extraction of the clay has a long-term impact on the landscape, and the firing process produces many gaseous pollutants – on which strict limits are placed in the UK.
Bricks can be reused as long as Portland cement mortar or render has not been used, as it is very difficult and costly to remove; otherwise they can be downgraded for use as aggregates or hardcore.
Concrete blocks have been around for as long as bricks – they were even used in some of the pyramids, although their use wasn’t popular until production was standardised in the mid 19th century. By the early 20th century their manufacture had become a recognised industry, and now they are ubiquitous worldwide.
The earliest blocks made in the UK mixed cement with local aggregate, which was often waste from neighbouring industry. For example breeze (from the French ‘braise’, meaning hot coals) was produced by gasworks and coke ovens – hence breezeblocks.
The blocks were lightweight, cheap, and easy to use, and became popular for use as internal partition walls. It was the advent of cavity wall construction that dramatically expanded the industry.
Concrete blocks come in a myriad of shapes and forms nowadays, but generally divide into three – Dense, Lightweight, and Aerated. The denser the block the more structural and the higher the thermal mass; the lighter it is, the better its insulative properties. Different aggregates will be used in different weight blocks.
Concrete blocks have a high embodied energy, largely because they use cement, but also because of the extraction of aggregates. Blocks are now being produced that substitute the cement and virgin aggregate with more sustainable alternatives.
One of the best alternatives to concrete blocks are clay blocks, of which Ziegel are the best known. The clay is extruded to give a honeycombed block that is lightweight, insulative, hygroscopic, inexpensive, and of very low impact, whilst retaining the structural and thermal mass properties of concrete blocks.
Insulated concrete form blocks (ICF) are made from recycled wood chip and cement, which create a formwork which is filled with concrete on site. Their chief advantage is that they enable rapid construction, but they are also a good insulator and contain recycled material. However, due to cement use their embodied energy remains high, and they don’t make the best use of their potential thermal mass.
The use of straw in building dates back to Palaeolithic Africa, but in the modern construction sense straw has been used in thatched roofs in Europe for the last 1000 years or more. However, it wasn’t until the advent of the bailer in the 1850s that straw bales were used for walls, particularly in the Nebraskan Sandhills, which as pioneers found, were devoid of much building material.
Straw bale buildings are cheap, simple and fast to construct, although it is imperative that the straw does not get wet as this will cause it to rot. The rendered finish is generally as ‘organic’ looking as you might expect a straw bale building to be, although this doesn’t need to be the case.
Straw bale walls sequester carbon, are highly insulating, hygroscopic, and have an inherent thermal mass – they do however take up a lot of space on plan!
Structural Wood Panels or Solid Wood Panels (SWPs) are literally just that – solid timber panels formed to create load-bearing wall, floor, and roof panels, with doors and windows incorporated. Insulation and cladding is added to the external face to achieve high standards of thermal performance.
There are different panel/system types, depending largely on the methodology of layering, stacking and fastening the softwood boards. The more common cross-laminated panels are formed by gluing boards across each other in layers; an alternative technique is to assemble a solid panel through gluing or dowelling together a series of timber 'posts'.
The maximum panel size is about 15m x 4m due to road transport restrictions. The panels can be assembled to create most types of building including housing - Murray Grove in London reaches a record nine storeys.
The advantages of prefabricated components are speed, efficiency and precise tolerances. SWPs have all these features combined with environmental and energy-efficient attributes such as use of a renewable resource, carbon sequestration, low waste, relatively low embodied energy and inherently high standards of airtightness and thermal efficiency.