If you build to Passivhaus standard, there’s no point in putting in a wet heating system. In fact, the key to the economics of Passivhaus design is that a conventional heating system is rendered redundant: you’re supposed to use the resulting savings to help fund the efficiency measures. Instead of a boiler and radiators you might only need a small electric heating coil in your mechanical ventilation system.
Level 6 of the Code for Sustainable Homes is modelled on the Passivhaus standard. As a result, until the Code changes, you’re likely to see more and more developers trying to move towards electric heating systems. You might argue that given the quantities of electricity we’re talking about (15 kWh/m2.yr), even if you source the electricity from the grid, it’s no carbon catastrophe. Unless you consider the bigger picture.
Making new buildings zero carbon is an excellent requirement, but by focusing our efforts (and a hell of a lot of money) on ratcheting down the heat demand from new buildings, we throw away the huge opportunity of using new developments to slash emissions from existing stock.
As I think most informed folks would agree, new buildings are only a small part of the emissions problem (I’ve posted on this topic here and here). The argument goes that we must address existing stock in order to get anywhere near our carbon reduction targets for 2050 and do our part in avoiding the worst effects of climate change.
The overwhelming majority of emissions from existing buildings is attributable to space heating and any strategy to significantly reduce emissions must address this heat demand. Efficiency measures are a must: insulate cavities and roofs, switch to low energy lighting, improve controls, and so on. But these steps only get us so far. The only way you’ll ever turn a Victorian semi into a Passivhaus is to knock it down and start over.
By using new developments as energy hubs and extending heat networks into built up areas we can drastically reduce emissions from heat guzzling stock. Now we can take advantage of the economies available at the block or district scale and bring to bear a whole arsenal of low carbon energy sources: gas CHP, biomass boilers, biomass CHP, waste-to-energy, and heat from existing power stations. New schemes can provide the platform and existing buildings will share in the benefit.
At this point, I wanted to include some numbers about the cost effectiveness of reducing emissions with low carbon district heating versus micro renewables. As I started to put some numbers together, it became clear that it’s more of a graduate thesis than a blog entry (though please get in touch if you know any good studies on this). And then I realised that I was missing the point. The important thing here is not whether district heating is a better option for reducing carbon from existing stock but that regulations are pushing strongly against us finding out.
Despite the fact that heat makes up half of all the energy consumed in the UK, almost all regulatory attention has been focused on green electricity. Sure the Renewables Obligation might be a pitiful impetus to the industry but at least it’s something. Heat, on the other hand, has been completely ignored.
Professionals in the built environment need to be free to find the most cost effective route to reducing carbon, not just from new schemes but from existing buildings as well. There are a few essential changes that government needs to make to allow this to happen:
- Relax the efficiency requirements of the higher levels of the Code. Keep the zero carbon target and allow greater flexibility in how this is achieved.
- Recognise the carbon benefit of “greener heat” such as that from gas and biomass CHP, biomass heat only boilers, and waste to energy, especially when applied to existing stock. Recognise that carbon isn’t simply an issue for planning authorities and building control.
- Use new developments to decarbonise existing stock. Consider whether a portion (30 percent?) of carbon saved in adjacent existing stock via efficiency measures and low carbon district heating can count towards the emissions reduction requirements for a new schem
- Introduce a low carbon heat obligation (or feed in tariff) similar to that already implemented for electricity suppliers to encourage the spread of low carbon heat networks.
Only by recognising the importance of heat and giving professionals greater freedom in achieving zero carbon will we have a chance of meeting our long term carbon targets.
carbon limited 
Absolutely on the nose, as ever, Casey.
I see the logical step being a buy-out fund for developers similar to Section 106 payments. We should be identifying for UK PLC the most cost effective route. So rather than ratching up a 10% to 20% plus onsite renewables commitment, a developer should be given a choice to invest that money elsewhere, like on community scale low carbon heat networks.
Without doing the Phd to assess it and so totally finger in the air, I would bet that the accumulate cost of delivering 20% RE on site for a lot of schemes (or even zero carbon) could achieve at least double the carbon reductions if spent differently.
As much as the Government likes to let industry find the cheapest way forward, this area needs some serious strategic framework to allow it to happen.
Interesting, as ever.
Whatever happened to HOC’s, of which I was hearing so much last year?
They’re still around. The heat call for evidence brings them up again. The folks at BERR say they’re working hard on the UK strategy for complying with the EU renewable energy directive (15% by 2020). The say they expect the “lion’s share” of the UK target to be met with renewable electricity but that heat will also play a role.
I think one problem was that the call for evidence kept referring to “renewable heat” when really they needed to be focusing on low and zero carbon heat. They say this will be addressed in a second heat consultation this autumn.
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