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Lessons in Zero Carbon Construction

Lessons in Zero Carbon Construction

A school building project in Exeter has come to the attention of your blogger this week, not because Plastic Surgeon has been called in to undertake some repair, but because it is set to be the first in the UK constructed to the German PassivHaus standard – or effectively .

We would therefore like to congratulate BAM Construction – a long term client of Plastic Surgeon – on being awarded the contract to build the Montgomery Primary School on behalf of Devon County Council. And such is the significance of the scheme that it bears some further examination.

As with many projects, the highly sustainable new structure is being erected in the grounds of the existing establishment to avoid the expense and upheaval of using decant accommodation.  It is on programme for completion by the start of the next academic year in September, when the 1920s building will then be demolished.

The new Montgomery Primary has been designed by the Exeter based multi-disciplinary practice, NPS: crucially undertaking the role of services engineer as well as architect. With the planning process having shifted emphasis early in the conceptual stages – as the project team switched from the premise of relying on green energy to power a conventional building, to creating classrooms which will require only the very minimum of energy input.

So instead of installing a biomass boiler and buying electricity on a green tariff, NPS opted to go down the PassivHaus approach where a super-insulated shell needs only 15 KW hours of energy per square metre of space, every year, for heating. This is roughly a tenth of a typical new school’s consumption.

To achieve this NPS has chosen to employ a modular, precast concrete system to offer thermal mass as well as bringing the air leakage rate down to below one cubic metre per square metre of wall space an hour. The PassivHaus standard also dictates that the U-values will also be below 0.15 W/m2K.

Large arrays of solar PV panels will ensure that all of the school’s electricity needs are covered by power generated on site, while mechanical ventilation with heat recovery will recycle the warmth produced by the occupants, to ensure the back up electric heaters will only be required in extreme weather conditions.

The Building Research Establishment, or BRE, has been monitoring a number of domestic scale PassivHaus projects around the country, and it can be hoped that the Montgomery Primary School in Exeter will be the first of many such zero carbon education establishments to accommodate pupils and their teachers.

While the project team predicts that the new school will be able to meet future climate challenges up to 2080, it should also be remembered that embodied energy and power consumption are not the only factors in the sustainability equation: and that the way a property’s on-going maintenance is handled is also of real importance. Furthermore, any school remains a physically challenging environment, with ‘robust’ patterns of occupation leading to damaged fixtures and fittings.

We will hope then that when the inevitable chipped sinks and worksurfaces happen, and doors get gouged by a trolley, or a section of flooring is scratched, that the estates department remembers there is an eco-friendly alternative to replacement.

Plastic Surgeon’s south-west team is based close by and will be pleased to help, either this autumn or over the next seven decades.