Tuesday, March 13, 2012

THE GREENEST INSULATION : A huge opportunity to reduce atmospheric carbon may be about to be lost

wood fibre board internal and external insulation with lime render
This is the most eco wall insulation: wood fibre board internal and external insulation with lime render. But it's the fossil fuel based polystyrene insulation that is getting the contracts.

A once-in-a-lifetime opportunity may about to be lost under the Green Deal to lock up a huge amount of atmospheric carbon in Britain's buildings to help combat climate change.

Later this year, the implementation of the Green Deal will kickstart the rollout of insulation of the nation's 29,000 homes.

Last Thursday's news, that the energy efficiency skills gap is being tackled with new funding to train installers and contractors in properly insulating properties throughout Britain up to the right standard, is to be welcomed.

But a huge question mark hangs over the choice of materials to be used for this job.

Not all insulation materials are equal; some are more environmentally sound than others.

There is a wide variety, ranging from the conventional; polystyrene and mineral wool; to the traditional and novel, such as sheep’s wool and hemp.

There is also a wave of new materials, derived from organic sources, by which I mean, ultimately, trees.

Principally these are woodfibre boards and batts, manufactured and sold in their most user-friendly form by companies such as Steico; and recycled cellulose, predominantly made and marketed by Excel Industries.

Any construction material derived from trees or other plants locks up in a building the carbon that it has absorbed from the atmosphere while growing, thereby helping to combat global warming.

It's a fantastic and cheap form of carbon sequestration.

By contrast, the current most commonly used insulation materials, such as phenolic foam board, expanded polystyrene boards and beads, and extruded polystyrene boards, are products of the petrochemical industry.

During their manufacture they emit carbon into the atmosphere, thereby increasing global warming.

Environmental impacts of insulation materials

The relative environmental impacts of insulation materials is a topic I examined thoroughly in chapter two of my standard textbook on the subject: Sustainable Home Refurbishment: the Earthscan Expert Guide to Retrofitting Homes for Efficiency.

Some people will tell you that recycled cellulose or wood fibre boards are more expensive. This is not necessarily so.

Last year I designed and built my own timber frame studio, which is super-insulated, and compared the cost of different insulation materials, from different suppliers. There is a huge variation, but I have to tell you that recycled cellulose made from old newsprint and treated against pests and fire is by far the cheapest.

It comes out at £12.49 per cubic metre when bought in 8 kg bags. Some “eco-" insulants are up to 25 times more expensive!

According to the most accurate figures available from the Carbon Trust, BSRIA and the University of Bath, in the Inventory of Carbon & Energy (ICE), expanded polystyrene has an embodied energy cost of at least 2.5kgCO2/kg.

Woodfibre board stores carbon at a quantity of 0.2 tonnes per cubic metre.

Doing a rough calculation, if one dwelling uses 20 cubic metres of this insulation, this represents a potential storage of 100 million tonnes of carbon throughout the country.

Is this significant? Yes. According to ICE's author, Craig Jones, the embodied carbon in buildings, taking account the projected future UK energy generation mix to 2050, is responsible for one third of their overall lifetime carbon cost.

Using organic insulation

Recycled newsprint works best when used in horizontal surfaces, like lofts; like most soft insulation it cannot be compressed, and must be covered up after installation if the space is to be used, because of the dust. Besides my loft I also used it underneath my floor.

It's the most environmentally sound insulation material you can possibly imagine. Apart from anything else, it is making use of a waste material.

The batts and boards made from wood fibre which I used are designed by the manufacturers for many different applications: between studs in walls, supporting concrete floors, or as tongue and groove cladding for the exterior insulation of a building.

The fibres for the latter are treated with wax to repel water, and when covered with a render (I used a very cheap proprietary lime render; all of this is part of the same complementary system) not only are weatherproof, but also allow the building structure to breathe.

This means that there is no condensation inside wet rooms and the building has an enhanced ability to withstand fluctuations in internal humidity.

By contrast, fossil fuel derived materials are not hygroscopic and do not allow the building to 'breathe'. Hence, when used for wall insulation, they can increase the risk of interior condensation.

There is one advantage which fossil fuel derived insulation has, and that is to achieve the same level of insulation using less depth of material. Typically you might need half the depth of phenolic or polystyrene foam than you would of wood fibreboard to achieve the same level of insulation.

This means that where space is a consideration, say to protect the internal dimensions of a room in internal wall insulation, or on the outside wall where the space beneath the eaves is limited for external wall insulation, then you would probably want to use, externally, mineral (rock & slag) wool batts and rolls such as Rockwool, which is relatively environmentally sound, certainly not as bad as foam. (Fibreglass mineral wool batts and rolls have a higher embodied energy than woodfibre.)


Recently, Greg Barker said that his department had been inundated by lobbyists from insulation manufacturers wanting to get their products on the approved list for the Green Deal, which the Department is currently compiling.

My concern is that accredited installers are only going to be trained to install insulation containing fossil fuel derived insulation such as extruded polystyrene as manufactured by the likes of Kingspan and Knaupf, and a huge opportunity is going to be lost to save carbon.

I know these manufacturers have been lobbying furiously to make their products standard for the Green Deal, because if they are, it will be worth millions to them.

It's very important to bear in mind that each material has its own method of installation, and therefore a different skill needs to be learnt by installers.

Whatever has been learnt by the army of installers that, after this autumn, is likely to descend on the country's homes, will determine which insulation materials are used. Once installed, they will be there for decades.

Talking of long timescales, these foams also do not decompose at the end of their life, but instead will stay around for hundreds of years.

By contrast, surplus or used wood fibre board and cellulose composts to beautiful fertile soil within a year. So easy to dispose of! So environmentally sound. So easy to work with during construction.


In my experience there is almost complete ignorance of the organic materials I am talking about amongst your average builders, contractors and installers. Only the members of the Association of Environment Conscious Builders and their friends seem to be aware of them.

This is because they have only recently become available in this country in any quantity. Previously, they were quite hard to source.

I don't mind praising Burdens, under the brand EcoMerchant for being the only mass market supplier to stock thee fantastic materials, as far as I know.

So there is a massive skills and awareness gap to fill.

Preferentially specifying the use of these materials on a large scale will stimulate the supply chain, create demand and bring the price down even more.

The use of these materials is also recommended by the Centre for Alternative Technology and the related campaign Zero Carbon Britain, which last year consulted the industry on which materials to advocate.

CITB-ConstructionSkills, which is delivering the training, says it will do so "to evidence competence against the Minimum Technical Competence as specified by PAS 2030 and the Competent Persons Scheme Operators for the specific annexes covered by this initiative".

When I asked them about this, they said “CITB-ConstructionSkills has no remit or authority to prescribe what materials are accredited for the Green Deal.

"It is the organisations that are applying to be certification bodies of products acceptable to the Green Deal who will make the choice. At present we are not aware of which organisations or standards will be used."

Of course, it is up to the suppliers and manufacturers of these materials to lobby for their products and standards.

I sincerely hope they have the budget and the lobbyists available to compete with the insulation giants who currently dominate the building energy efficiency sector.

I've asked them, but so far received no reply.

No comments: