Wandering round the sustainability maze


A look at the concept of sustainability and what it actually means for construction materials, followed by thoughts on how individuals can respond to the challenges it presents.

Joe Shlabotnik on Flickr

Joe Shlabotnik on Flickr

1. Trying to understand sustainability

Think Brick, from the Brick Development Association, is, unsurprisingly, a firm advocate of bricks. On their website they make prominent reference to the sustainability of brick.

Brick is an environmentally sustainable material for buildings of the future.

They have a document – Sustainable Strategy for the Brick Industry – which reports progress on key performance indicators relating to the industry’s sustainability strategy that was initiated in 2002.

This is a comprehensive, data-driven review covering, amongst others things, health and safety, carbon dioxide emissions, energy consumption and capital investment.

To my mind the report demonstrates that the brick industry has become more sustainable over the past decade, although this is moderated, as the report acknowledges, by recent ‘adverse trading conditions.’

So, brick has become a more sustainable construction material, but it’s not clear how it compares to other construction materials.

2. Quantifying claims of relative sustainability

Elsewhere on the Think Brick site, I pick up two pieces of information that may help me understand the relative sustainability of brick.

(a) Embodied energy is the amount of energy it takes to manufacture and supply bricks to their point of use. Bricks have been labelled as having high embodied energy due to their process of manufacture. However, in measuring sustainability it is necessary to take into account a material’s life cycle performance, as well as the amount of energy consumed in the manufacturing process.

The current figure for total embodied energy CO2 for clay bricks (excluding flettons) is 202 kg CO2/tonne. This equates to 28kgs of CO2 per m2 of bricks in a square metre of 102mm wide brickwork (60 bricks).

(b) The BRE’s latest Green Guide to Specification assigned the highest possible accreditation A+ to every external wall it rated that contained brickwork.

Will these help me?

3. Concrete states its case

I’ve always pigeon-holed concrete as being a poor performer on the sustainability front because of the energy and water consumed during production, and the problems with recycling the material at the end of a structure’s life.

Maybe this is why SustainableConcrete.org.uk exists?

It’s upfront, straightaway.

Sustainability is a key issue for the UK concrete industry.

And it outlines the concrete industry’s strategy to resolve this issue.

The documentation, as with Think Brick, is detailed and data-driven.

Our vision is that, by 2012, the UK concrete industry will be recognised as the leader in sustainable construction, by taking a dynamic role in delivering a sustainable built environment in a manner that is profitable, socially responsible and functions within environmental limits.

I pick out that the carbon dioxide emissions involved in the production of concrete are 88.1kg CO2/t, a figure which has fallen from 103.1kg CO2/t in 1990.

I’m presuming that this figure is comparable to the figure of 202kg CO2/t for bricks, although I know that the brick figure included transport to site, whilst the concrete figure doesn’t.

The report notes that ‘the local supply network for concrete means that delivery distances are short and the fuel used during haulage (and the associated CO2 emissions) is minimised’ and that they hope to develop a methodology for capturing this data in 2010.

I appreciate sustainability is more than carbon dioxide emissions, but I now have numbers to compare.

SustainableConcrete.org.uk provides a table detailing the embodied carbon dioxide of different construction materials.

Rather confusingly at first, the neat figure of 88.1 kg CO2/t evaporates because different concretes have different values. It’s 75 for dense concrete aggregate block, 153 for in situ structural concrete and 240 for aerated concrete block.

Brick isn’t mentioned, UK produced steel structural sections is 1932, UK sawn hardwood is 470 and UK sawn softwood is 430. The last two surprise me somewhat.

4. Timber fights back

This data is generally confirmed by the University of Bath which has been working on a ‘database to determine the embodied energy and carbon of a large number of building materials’.

Inventory of Carbon and Energy
[nb/ note the change in units]

Virgin steel section: 2.78 kg CO2/kg
Sawn hardwood: 0.47 kg CO2/kg
Sawn softwood: 0.45 kg CO2/kg
Recycled (42.7%) steel section: 0.44 kg CO2/kg
General (Common Brick): 0.22 kg CO2/kg
Concrete, general: 0.13 kg CO2/kg

This may be so, but The UK Timber Frame Association leads the reply and compares the embodied energy – note that this is different from embodied carbon – of common building materials.

Timber frame wall – 7,450kWh
Lightweight concrete block wall – 12,816kWh
(i.e. 1.72x more embodied energy in concrete)

Timber ground floor – 2,669kWh
Concrete slab on ground – 6,992kWh
(i.e. 2.61x more embodied energy in concrete)

Different units, different data ….

5. Lies, damned lies and statistics

Trying to make sense of this evidence I find two sources that place my quest for meaningful quantification in perspective.

First, Ireland’s Department of the Environment, Heritage and Local Government tells me that:

Embodied energy or CO2 values should not be used directly to compare one material against another. The comparison has to be made between components that perform the same task.

Whilst a piece from the Simons Group on embodied carbon concludes:

So how can you compare the carbon footprint calculated to one set of boundaries for one product, to the footprint of another calculated to a different set of boundaries? Quite simply, other than the very basic cradle to site and cradle to grave assumptions you cannot.

Until there is a standardised way of calculating the statistics are difficult to use, which leaves us with claims and counterclaims, although the adoption of PAS 2050Assessing the life cycle greenhouse gas emissions of goods and services – may help.

6. BRE’s Green Guide

Before I give up there’s brick’s A+ Green Guide rating for external walls.

If I go and check the ratings for Building type (Commercial), Category (External wall construction) I find that most types are graded A+ and that steel, timber, concrete and brick all feature prominently in these designs.

In fact it appears to my eyes that it’s not the materials that count, but the design and construction method.

So blockwork cavity walls are good. They are all graded A+ whether they use new or reclaimed bricks, and aircrete, lightweight solid blockwork or dense solid blockwork.

Brickwork on a framed construction is always A+ whether it’s a timber-framed or a light steel-framed construction.

Whilst curtain walling is never graded above a B whether it’s an aluminium or timber system.

7. Conclusion

I’ve probably made mistakes and misunderstood key concepts or data in my short journey into the sustainability maze, but it’s not difficult to become dazed and confused. Which is my point.

Perhaps these will suffice as conclusions. Please tell me if I’m wrong.

A. Sustainability is an increasingly important issue for product manufacturers. This is good. Sector leaders – often represented by trade associations – are working to improve their performance.

B. But don’t accept greenwash. There’s a good post on this on our sister blog.

C. It’s very difficult to compare the sustainability of different materials. Your time is better spent sourcing bricks from a manufacturer committed to the industry’s sustainability standards if it’s bricks that you want, rather than trying to compare the sustainability of brick, concrete, steel or timber as materials.

D. The design of the building is generally much more important than the materials. You can source FSC timber but if you use it to construct a timber curtain wall system it’s still not going to be graded higher than a B.

E. The use of the building is as important as the design. The success of a green project will always be limited by its weakest points (an inefficient boiler, lack of insulation or an occupier who runs it inefficiently).



3 Responses to “Wandering round the sustainability maze”

  1. Wandering round the sustainability maze « Building Says:

    […] original here: Wandering round the sustainability maze « Building Posted in Building | Tags: and-check, are-graded, brick-all, Building, category, […]

  2. Tweets that mention Wandering round the sustainability maze « Building -- Topsy.com Says:

    […] This post was mentioned on Twitter by Robin Brittain, Benedikte Ranum, Christian+Cija , Nemesis Republic, Stephen Bird and others. Stephen Bird said: A thorough look at how/how not to define sustainable construction products via @ESIBuilding http://bit.ly/a0yz44 […]

  3. OwenP Says:

    Here’s an interesting yet frivolous footnote: the carbon footprint of crisps is over three times greater than that of concrete: http://is.gd/blw2b

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: