Zero carbon schools

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Zero carbon schools – are they possible? Not with the current targets that expect every school to become a miniature power station, argues Richard Brailsford. But the targets are achievable if we take a holistic approach, Richard says – and encourage whole towns to work together to meet their energy needs with renewables.

The EU has committed to a carbon emissions reductions target of 80% by 2060.  Our government is committed to reaching that target by 2050. There is also a commitment to 20% reduction in both energy use and emissions by 2020 - and 20% of our energy must be provided by renewables.

In the UK, buildings are responsible for around 45% of total C02 emissions. It is arguable that it would be most economical to improve existing stock. But the government is only setting targets for new buildings. These are, presently, that new schools should be ‘carbon neutral’ by 2016, other new government buildings by 2018 and other new buildings by 2019.

The biggest single area of government spend on buildings is the “Building Schools for the Future” programme, which will replace, refurbish or remodel every secondary school in England. The ”Primary Capital programme” for the refurbishment/remodelling or occasionally the replacement of the country’s 23,000 primary schools is also coming “on stream”. Energy use is only one part of sustainability - but the energy targets for primary schools are predicted to be even tighter than for secondary schools.

What will be achieved by 2016? This question is still out for consultation. The most ambitious target would be for energy targets to apply to schools which open on January 1st 2016. The least would be for schools which start design on or after December 31st

2016. The agreed target will lie between the two. But whatever the final detail - as projects generally take between three and five years from inception to handover, the final date is only two or three project cycles away.

This is a major change and challenge for an industry whose products may be asked to last 100 years and where a major refurbishment would not normally be expected for 15 to 20 years. If energy savings are to occur in reality, this will also mean changes in the way that teachers operate their spaces. It is tragic that none the early waves of BSF schools included formal post-project reviews and monitoring to show us which energy saving measures were the most efficient.

In this drive for ever more efficient and ‘cleaner’ schools, there are a number of factors making this drive for reduced emissions even harder to achieve for designers and operators. Three of these are:

  •  IT use in education is increasing. While the power requirements of individual devices is decreasing, the overall effect is a year-on-year overall increase in electricity use.
  • Anecdotally, classrooms have always been under-ventilated and stuffy. But Building Bulletin 101 (Ventilation of School Buildings) now asks for C02 level indication in classrooms so that teachers can see when the ventilation rate needs increasing – by opening the windows or other air inlet devices. This is bound to lead to better ventilated classrooms – but, unfortunately, more energy consumption.
  • Extended use of schools means use in the late afternoon and evening. The standard methodology for judging the acceptability of temperatures in schools, in summertime, assumes that occupancy ceases at 16.00hrs - just as the school is beginning to warm up from the delayed effect of the noonday sun. As schools are used through this period, it is likely that cooling may be introduced into some rooms, especially where serving “paying customers”.

What does ‘zero carbon’ mean? At it’s most effective, it would mean the total effect of the school, whatever the hours of operation. Under this definition, extended and community use of the school may reduce the emissions from the UK overall. But this would be an even harder target to achieve for any one school. At it’s least onerous, ‘zero carbon’ would only mean the core hours of operation and would be based on similar loads to those used for building regulations compliance.

Again, the definition is out for consultation. It is possible that the result of the consultation exercise will be different definitions for ‘Carbon neutral’ and ‘Zero Carbon’ - one including just the loads of the unoccupied building and one including the effect of pupils and staff !

The present target for new secondary schools purchased under BSF is a target between these extremes - on the road to zero. It is based on the emissions from the building (and those loads which form the Building Regulations check) being less than 40% of the Building Regulations requirement in 2002, and relates to the core hours of use of the school.

The BSF target relates to the total emissions in use. At this point it is worth pointing out that there is (intentionally) often a large difference between the emissions which a design team models for Building Regulations compliance and the actual total emissions. In order to be workable, the Building Regulations methodology compares the proposed building with an identical building created at the time, by the software, which would meet the Building Regulations. In order to provide comparability, this check does not take into account factors outside the control of the construction team.

Typically, the use of IT in most schools is higher than the base Building Regulations case. The building is rarely operated exactly as modelled, with, say, windows left open more than modelled and “special” loads such as laboratories, pools, kilns, hairdryers, the use of any lifts and over-door heaters. There is presently a project to looking at amending the Building Regulations check to reduce these variations.

The present BSF target of 27 kgC02/m2yr covers the total emissions from the school during defined “core” hours. Should the facility emit more C02 during these core hours (and if within several other definitions within the payment mechanism), the providing consortia are financially penalised by being required to pay the frst 10% increase in fuel costs, and 50% of the increase thereafter. Should
the building be more efficient in operation, a similar mechanism applies to reward the consortia.

It can be argued that to reduce emissions further from the present level of carbon reduction (the so called “Carbon 60” target and the PFS target) - solely at source (i.e. at the school) - would be poor value for money to the UK in terms of the emissions reduction per pound spent by government.

Low energy schools currently incorporate high levels of insulation, high amounts of heat reclaim and a low carbon heating source such as biomass boilers and/or solar hot water heating. By far the majority of the remaining emissions are due to electrical loads.

To reduce the C02 effect of these electrical loads requires the electrical supply to be decarbonised, either on-site or off-site. As many readers will verify, on-site generation of electricity is expensive, and it introduces increased maintenance requirements.

‘Small’ wind generation, although fun for kids, rarely saves more emissions than were necessary to manufacture the windmill. ‘Large’ wind is usually problematic in an urban environment. Their cost is dropping, but photovoltaic cells are still expensive, need careful planning and need to be cleaned regularly.

Introducing combined heat and power generation into schools would be feasible. But to be efficient, it has to be limited to a size where the heat output can be utilised, with the only summer load being the daily domestic hot water demand. Very large storage tanks are required to fatten out peaky loads. I believe that improving the C02 content of the electricity supplied to the site is a more cost effective solution.

The government seems to accept that it will be difficult to drop the present target level. So what else can they do?

To look at reductions at a national level is clearly a massive undertaking. We are progressing only slowly. To date, we have been most successful in building individual supply points, such as wind farms. We have been far less successful in joining users together to optimise economies of scale and variations of load patterns. City or area CHP (Combined Heat and Power) systems with their associated energy supply networks (generally supply cables and buried pipework) deliver carbon reductions in energy supply at a local level far more quickly than is likely to be achieved by attempting to make the same emission savings at a national level. Schemes in Leicester, Southampton and London have proven operating records, and demonstrate fundamental engineering practicalities where there has been a will to solve the legal and commercial issues. The Government’s strategy for CHP (2004) aimed for 10GWe (i.e. 10,000 KW of electrical generation and accompanying heat generation) by 2010!

City-wide schemes can still be beneficial. One way of achieving a “Carbon neutral school” would be to build schools which are “lowest practical carbon” - at the present target levels or slightly better. Practitioners could then improve the carbon footprints of buildings in the vicinity of the schools by an amount equal to or greater than the remaining emissions from the school. The net effect of the schools would then be Carbon neutral - using what I believe would be the most cost effective methodology.

If nationally the maximum impact is to be achieved, emission savings through more efficient generation should be made. To not improve the energy supply would be a lost opportunity. I believe it would be a major waste of resources to attempt to make all the savings on-site.

There are several mechanisms by which this near-site generation could be achieved within the present schools building programmes. The building consortia providing the facilities on a BSF ‘whole area basis’ could also provide the energy network and energy generation. Or they could be provided as a separate funding stream. They need not be operated by either the BSF consortia or the council and could, if it were preferred, be operated by a specific energy supply company (‘Esco’) who can advise on its design and may be willing to provide partial funding, to be repaid over the life of the project.

Richard Brailsford is a project director at the architecture firm AECOM (formerly Faber Maunsell).


Taken from 21st Century Schools

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