In building a new assembly shop we have been 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 aim 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.
Insulation
Rather than the regulation 80mm thick composite roof panels, we have chosen the best available at 120mm thick. The walls will be the same (rather than the regulation 60mm) but they will be over clad with black painted feather edged board which fits in with local architecture. There will be 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 have chosen 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 will be 4 roller shutter doors and these will also need to be draught proof.
Windows
The more daylight we can get into the building, the less electricity we will use on artificial lighting. It has been recommended that we have 20% rooflights, any more than this and the building may overheat. Then for the welfare of the staff there will be will be windows at eye-level so that they can see our lovely surroundings.
Lighting
Unfortunately LEDs haven't yet been developed for use in tall industrial buildings so we are opting for the best currently available. When I say best, I mean luminaries that provide the most lux per watt. These will be four 5' fluorescent T5 strip lights in a highly reflective housing. The secret to saving energy is to have intelligent control and we will 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 will fade up and down to compensate for daylight keeping a constant light level at all times. Perfect for scenic artists!
Heating
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 building. As the current workshop is un-insulated the heater is a very important part of the company. We currently burn about 12 tons of wood a year thus preventing about 10 tons of CO2 from entering the atmosphere. We will be insulating the existing workshop and the aim is to heat both spaces with the same 12 tons of wood. The new building will have underfloor heating fed from the new biomass boiler, which will also feed hot water to the office/green room radiators doing away with the current electric boiler. So we should be carbon neutral for heating.
Electricity
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 (kilo watt 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 will generate 42mWh (mega watt hours) per annum. Last year we used 38Mwh so with the reduction in consumption used for heating, we will generate more than we use. This will be exported to the grid for others to use. A house uses about 10Mwh.
Water
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)!
