When we  built our new assembly shop in 2012, we were given an opportunity to fulfill a long held ambition to build a low-energy building. For those of you who are interested, there are lots of facts and figures about how we aimed to achieve a carbon negative building.  This is basically a big steel shed but this simplicity lends itself to some careful thought about environmental issues.



Rather than the regulation 80mm thick composite roof panels, we chose the best available at 120mm thick.  The walls are the same (rather than the regulation 60mm) but they will ultimately be over clad with black painted feather edged board which fits in with local architecture.  There is 100mm thick insulation under the floor.


Air permeability

If you want to keep the air in a building warm then you have to keep the air in the building!  Most materials are porous; plasterboard, breeze block, timber, brick.  But not steel - that's why we opted to use steel composite panels for the roof and walls. The problem is then to ensure that the joints are well thought out and well sealed!  There are also 4 roller shutter doors and these have also had to be made draught proof.



The more daylight we can get into the building, the less electricity we use on artificial lighting.  It was recommended that we had 20% rooflights, any more than this and the building may overheat.  For the welfare of the staff we hope to soon install windows at eye-level so that they can see our lovely surroundings.



Unfortunately LEDs haven't yet been developed for use in tall industrial buildings so we opted for the best currently available.  When I say best, I mean luminaires that provide the most lux per watt.  These consist of four 5' fluorescent T5 strip lights in a highly reflective housing.  The secret to saving energy is to have intelligent control and we have motion sensors so that if the building is unoccupied the lights will first fade down to 30% for safety then fade off.  The clever bit though is to maximise the gain of the roof lights and this is done with light level sensors so the lighting fades up and down to compensate for daylight keeping a constant light level at all times. Perfect for scenic artists!



When we first moved to this site, we bought a big wood burner to dispose of our scrap wood off-cuts and provide heat for the existing building.   We used to burn about 12 tons of wood a year heating one workshop thus preventing about 10 tons of CO2 from entering the atmosphere. We invested time and money insulating the existing workshop and we are now heating all three spaces (assembly shop, workshop and dutch barn) with the same 12 tons of wood.  The new building has underfloor heating fed from the new biomass boiler, which also feeds hot water to the office/green room radiators doing away with the old electric boiler.  Now we are carbon neutral for heating.



As the roof of the new building faces due south it seemed to make sense to cover it with solar PV panels.  We have been limited to a 44kWp (kilowatt power) system as this is all that the local grid can cope with.  However this ties in nicely with 20% roof lights and 80% panels.  It is estimated that we generate 42mWh (megawatt hours) per annum.  Last year we used 38Mwh so with the reduction in consumption used for heating, we generate more than we use, and this excess is then exported to the grid for others to use.  A house uses about 10Mwh.



Our main consumption of water is for toilets and washing paint brushes.  We currently leave all the rainwater to flow into the river Cam, which passes about 100m away from our door. There are plans afoot to harvest some rainwater for both of these uses but we are also looking into recycling the paint water by separating out the paint from the water.  More on this later (when we know more)!