Retrofit, very well. These four areas are actually established practices in the industry. We rank them in terms of the percentage of buildings, or the number of buildings, that need to pursue these practices. In the next slide, you'll see where these buildings are located.
It is really important that it's not just a discussion about energy, but that it's also a discussion about carbon.
The recommissioning is something that industry is already doing, but it needs to be expanded. It just means that the system in the buildings work well and they work as they're intended. There's an instant savings for anybody who pursues that.
What we're really looking for, which needs to be incentivized and drawn forward, is retrofit. We say deep retrofit because these are savings of 20% to 40%. It's not just what we call a shallow retrofit, where you just replace the lighting and make a little bit of an improvement. It needs to be a deeper retrofit that looks at the building's systems, not just the lighting but all the building's systems, which, eventually, looks at the building envelope and looks at the energy source.
You could improve a building by simply switching to improve energy efficiency, but also, as the gentleman Mr. Luymes has said, switching from fossil fuel to a heat pump, for example, that uses electricity. They're highly efficient now. You can achieve a lower carbon building that way.
What I'm trying to say is that it really depends.