“Net Zero”, the idea that a community makes a zero contribution to global warming, is an elusive concept. It usually involves some sort of cheating – or, to use more diplomatic language, it involves leaving out various sources of emissions from the calculations. For instance, the UK government’s definition of “net zero” ignores the emissions incurred in producing stuff that we import, as well as international aviation and shipping. Companies that claim to be “net zero” usually just mean that they have switched their energy supplier – switching by itself doesn’t do anything useful, it is only helpful if it leads to the construction of new renewable generators that would not otherwise be developed. And institutions like schools need to consider the carbon embedded in their buildings, materials and supplies, as well as things like heating and lighting.
Still, if working towards Net Zero leads to a reduction in greenhouse gas emissions, it is a good thing, even if the absolute level doesn’t stand up to much scrutiny.
In the case of a school, the first thing to sort out is the heating. Now most people alive in Britain today will remember being told by their parents to turn the lights off when they leave a room. This raises an interesting fact: given the improvement in lighting (LEDs rather than incandescent bulbs) and the reduction in the carbon intensity of electricity over the last few decades, it is now likely that turning the heating off when you leave a classroom – assuming you can – is several times as significant, in terms of carbon savings, as turning the lights off. This statement makes a number of assumptions, such as it being sufficiently cold outside for the heating to be on in the first place, and the lighting to be reasonably up-to-date, but the broad conclusion is pretty safe. So make sure each room has its own independent thermostat! You don’t want to be cold, of course, but maybe wear an extra layer before turning the heating up? Oh, and by all means switch the lights off as well when you leave …
Next, look at your transport. How do pupils and staff get to school? This goes back to my first point – it’s no use have a “net zero” school if everyone gets there each day in separate cars! So the school needs to look at alternatives: pressurizing the local council to provide a bus service, if not already available; providing cycle facilities; encouraging car pooling; raising money by charging for parking …
Does the school provide food? If so, how often is meat is on the menu, and what type? Sorry to be direct about this, but diet is one of the biggest contributors to climate change; and is generally under-recognised in statistics because land opportunity costs (i.e. the foregone possibility to use land in both Britain and abroad in a way that captures carbon if it’s already tied up for animal grazing) are not usually considered. There’s lots of research going into this area: the difficulty is knowing how exactly to measure land opportunity costs, which is why they are usually ignored completely.
Anyway, back to buildings. If the school buildings already exist, start with insulation (roof, floor, cavity wall) and windows (double glazed?). One thing to be aware of is damp: unscrupulous suppliers have been known to fit insulation that makes damp problems worse. Another important issue is ventilation: sometimes people think that a property needs to be sealed – no fresh air – but that is not the case. Heat exchangers allow air to go in and out of a building whilst trapping most of the heat from the air that is being exchanged. Fresh air is essential and the net heat loss is minor if heat exchangers are properly installed.
Heat pumps (ground source, if you have the space, are more efficient) might work – but they tend to require good insulation as a prerequisite, and might not be appropriate if your school was built, say, in the 1960s. So for an existing building, you might be stuck with a boiler. In this case, a hydrogen-ready efficient gas boiler is probably the best you can do (switching to hydrogen when it becomes available). Don’t be fooled by biomass, which is largely a con. Burning biomass emits more carbon dioxide than burning natural gas for the same amount of heat output. Most of our biomass comes from abroad (the Americas mainly) and – just by convention, not physical reality - isn’t counted as part of our “carbon footprint”. If land is available to grow biomass, that should happen anyway, without all of the emissions associated with transporting it thousands of miles, processing it into pellets, and then burning it!
If you’re lucky enough to be able to erect new buildings, then definitely install heat pumps at the same time: the resultant emissions will be much lower than even the most efficient gas boilers would release. You might also consider putting electric PV solar panels on the rooftops – though this is less important than sorting out the heat source as discussed above.
It’s good to tap into the experience of other schools, as you don’t want to ‘re-invent the wheel’. Before you begin, it’s worth researching which schools have already invested in energy-saving buildings and contacting them. One in my area is Leighton Park: it’s private, which might bother some people, but worth taking advantage of their experience in spite of that.
Energy Consultant on the behalf of SOS-UK