The green credentials for brick walls vary, with three main factors:
- the embodied energythe total amount of energy it takes to make a material (or a building). See more on embodied energy depends on what sort of bricks are used
- the environmental policy of the manufacturer
- the effect on the wall design
The embodied energy of bricks can vary from 0.7 MJ/Kg for Limestone bricks to 8.2 MJ/Kg for facing bricks. This compares with 0.99 MJ/Kg for normal concrete. It is however usually difficult to ascertain what any particular type of brick rates at. Flettons use the least energy in manufacture with soft mud/stocks using the most and ordinary clay bricks being intermediate
TRADATimber Research and Development Association A trade association with a strong reputation for research and publication on all things timber did some research which compared the embodied energy in timber frame walls with lightweight concrete block (at about 3.5 MJ/Kg)
Timber frame wall – 7,450kWh
Lightweight Concrete Block Wall – 12,816kWh
So since lightweight concrete blockwork has about half the embodied energy of the least energy intensive brickwork then a brick wall might contain between 3.5 and 40 times as much embodied energy. Very rough figures but it gives an idea. The Scottish company Errol Bricks and Ibstock both make unfired bricks which have very low embodied energy. Encos are just starting to do Encobricks and Encoslips which are carbon neutral.
The environmental policy of the manufacturer will determine the CO2Carbon dioxide is a gas which is given off when carbon based materials such as fossil fuels (coal, oil, and natural gas) are burned. It is called a greenhouse gas because it works like the glazing of a greenhouse and causes global warming production per tonne of bricks, how much pollution is caused in and around the brickworks (which are usually close to where the clay is mined) and how much wastage is created. The history of pollution from brickworks is lamentable and most of them have a long way to go in terms of improvement. For instance, check this recent environmental report from Ibstock who claim to be one of the leaders in cleaning up their act.
It’s hardly trailblazing stuff but at least fairly honest. Brickworks have traditionally been very inefficient in terms of energy, have been emitters of fluorides and other halogen gasses (which are now controlled) and have been responsible for leaving large areas of countryside in an ugly and degraded state. This latter is mainly a result of large rectangular lagoons where the clay has been mined. Unlike gravel pits which have often produced quite interesting and beautiful wetlands which are useful for recreation and wildlife, clay lagoons tend to be a bit of an eyesore and not very good at supporting a wide biodiversity. Before settling on a manufacturer, try to find out about their environmental track record. This goes for clay roof tile manufacturers as well.
The effect on wall design is to do with the total thickness of walls once they have a fair degree of insulation. Using a brick outer skin rules out using the more ecologically sound insulations such as Warmcel, cork or wool unless there is also a cavity between the brick and the insulation. This is because of the possibility of condensation on the inner surface of the brickwork damaging the insulation. The cavity adds another 25 – 50 mm. to the wall thickness. Achieving PassivhausSee more on the Passivhaus standard. The PassivHaus Institute has pioneered a standard for low energy buildings. It includes very low energy usage and ways of achieving this. The word is derived from the idea of buildings which are fundamentally low energy and passive solar heated rather than using extra gadgets to heat them. See Passivhaus for the UK branch of the organisation. standard by packing 300mm of insulation into a traditional brick and block wall produces a total thickness of about 550mm which is so thick that windows become less effective in terms of view and daylight and it actually takes up a great deal of footprint on the ground, which is expensive in terms of buildable space.
Compared with much of mainland Europe the UK has been fearful of modern design and this has led to a rejection of anything that is not brick or stone in appearance. Especially timber and composite boards, which are more ecologically sound and can provide a less space wasting rain screenthis is a (usually thin) outer cladding on a wall which prevents rain, snow, etc getting at the structure of the wall behind. see more on rain screen, have been slow to gain popularity. Of course brick manufacturers have been at the forefront of advertising the supposed benefits of their product. There is a slight wind of change at the moment and most architects designing houses are only too willing to get away from boring old brickwork.
The standard size for modern bricks is 215 x 65 mm. and a 10mm joint is used. This then coordinates with blockwork. The standard block size is 440 x 215 so if you include the joints then a block length is the same as two brick lengths and a block height is the height of three bricks. Also this means that a block set on its end is equal to 6 bricks in height and a brick on end is the same height as a block, This means less cutting of blocks and allows wall ties to coordinate properly. There are on line ready reckoners by companies such as Ibstock to work out brickwork dimensions and configurations.
The Building RegulationsThese are the mass of regulations that cover safety, health, welfare, convenience, energy efficiency etc. in the way buildings are constructed. Not to be confused with Planning consent (which is more to do with whether you can put up the building in the first place). See more on the regulations part AThe Approved documentsApproved documents (England) are detailed publications which come under the English Building Regulations. They are based on tried and tested methods of building and if you follow them you are assured of complying with the Regs. The equivalents for Scotland are the Technical HandbookUnder the Scottish Building Regulations, the Technical Handbook gives construction principles, which, if you follow them guarantee compliance with the Regulations, for Wales: the Approved documents (Wales), and for N.I. the Technical BookletsUnder the Northern Ireland Building Regulations, the Technical Booklets give construction principles, which, if you follow them guarantee compliance with the Regulations, (England) part A, deals with building structures covers the structure of a building. This Approved Document goes into a lot of detail for traditional masonry buildings but almost none for timber frame, steel frame, earth building SIPsStructural Insulated Panels - prefabricated (usually in a factory) timber panels often forming part of an integrated building system and aimed at fast site erection. see more on SIPs etc. For these you will need to consult a structural engineer (while SIPs structures are usually handled by the manufacturer)
With most forms of construction there will be implications concerning fire safety. These are covered in the Building Regulations and you can see examples of how to conform with these in Part BThe Approved documents, (England) part B, deals with fire (Fire Safety)
Site preparation and resistance to contaminants
This section, Part CThe Approved documents, (England) part C, deals with Site preparation and resistance to contaminants (C1) and Resistance to Moisture (C2), covers site remediationthe term applied to the method of dealing with pollutants and contaminants in the ground. The Building Regulations cover this in detail. See info about Approved Document C – Site preparation and resistance to contaminants and moisture along with protection from nasties which might affect the construction and occupants such as damp, rain, radon etc. There is an abridged version of the Approved Document specially for houses.
NHBCThe National House-Building Council describes itself as being "the leading warranty and insurance provider and standards setter for UK house-building for new and newly converted homes" Technical Guides free on line