carbon limited

Phil Clark at Zero Champion sent a request under the Freedom of Information Act for figures on CO2 emissions for Portcullis House, the office building for Members of Parliament across the road from Big Ben. When he received a response he wasn’t sure if performance was good or bad. It’s bad:

Ignoring the figures for 2006-7 given in Phil’s blog entry because of uncertainty about the source of electricity (discussed below), I looked at 2005-6. For that year, Portcullis House used 7,230,601kWh of energy and emitted 630.2 tonnes of carbon. They don’t specify a breakdown for fossil fuels and electricity.

So doing a bit of maths, the figures look like this (see end of entry for details on the calculations):

I added in two sets of figures for comparison:

• Econ19: this has been the standard reference for energy consumption in offices in the UK for the last 18 years. It’s badly out of date and the figures are too high (worse luck for Portcullis House), but it’s all we have. It’s based on measured figures from the 1990’s and the targets I used were for “good practice” in a standard air-conditioned office.
• Original Arups target at design stage – this comes from the BSJ article quoted by Phil, but the numbers look really low so I may have misinterpreted the article.

So the building uses 50% more electricity and 60% more gas than a crappy 1990’s air conditioned office block. And 500% more electricity and 300% more gas than the Arups predictions.

But this isn’t a standard air-conditioned building! Wavy precast concrete ceilings and high admittance surfaces allow cooling using thermal mass; borehole cooling; displacement ventilation; heat recovery via thermal wheels; light shelves; lighting that dims according to available daylight, and so on. This is state of the art green and it’s gone wrong somehow. Is it the IT power loads? Is it the select committee rooms that double as television studios? I don’t know.

According to the Parliamentary Answer:

All electricity consumed on the parliamentary estate has come from renewable sources since 1 February 2007, therefore there will be no carbon emissions resulting from electricity consumption in future. This has contributed to the reduction in carbon emissions for the year 2006-07.

The comment in the P.A. about electricity being carbon neutral because it comes from renewables is a slippery one. If they mean they’re using a green tariff, it’s definitely not carbon neutral electricity. Even on those tariffs that buy one unit of renewable energy for every unit they sell, typically less than 10% of the ROCs are retired. While the end user might consume a unit of renewable electricity, the corresponding ROCs are sold to other electricity suppliers who might use them to prove the credentials of their own green tariffs. It’s double counting. So at best that might be 50% carbon neutral. But anyway, the GLA won’t let developers claim green tariffs as carbon savings so why should Portcullis House get away with it?

Whichever way you cut these figures, it’s not good. We need to figure out what went wrong.

Here’s how I got to the above figures. First, convert the carbon to CO2 (multiply by 44 and divide by 12) to get 2310.7 tonnes. So now we know how many kWh they used in total and what their total CO2 emissions were. Using carbon intensities for mains gas (0.19kgCO2/kWh) and mains electricity (0.422kgCO2/kWh) and a little excel magic, we get a solution for annual electricity and gas consumption. The total floor area you get by working backwards from the figures in the P.A. (7,230,601kWh divided by 332 kWh/m2 gets 20,712m2).