When building new there is a very strong case for why you would want to build to a low energy standard such as Passivhaus. Applying the methodology is relatively simple, it doesn't cost that much more, the buildings will then be easier to maintain and they’ll be more comfortable. If you’re already doing an extensive retrofit of a building, it also makes very good sense to aim for the Passivhaus or EnerPHit standard. This is because the additional work and the additional cost involved is quite limited. As new build and extensive retrofits of buildings don’t account for a huge amount of the work that’s done on UK housing stock what tends to happen is most people do a little bit of work here and there, and maybe when they can stand the disruption and afford it they will do a bigger piece of work. If you find yourself in this position you may be wondering whether to wait until you can afford a whole-house retrofit or to take a few energy saving measures. The crux of this is that with a piecemeal approach it’s very difficult to achieve Passivhaus performance, even if it is practical to produce very substantial improvements in the energy performance of the building. So where does that leave you? Is the money going to arrive any time soon?!
Cost is still the greatest challenge we face if we hope to bring our housing stock to a low energy standard. Dr Brenda Boardman in her book ‘Achieving Zero Delivering Future-Friendly Buildings‘ proposes that every building and every house in the UK should reach the Passivhaus standard by 2050. It would be a mighty task. [Dr Boardman will be a guest in a future House Planning Help Podcast episode.] For now at least, unless you personally have the money to carry this out, there are no other funding sources available. In the future this may change for regulatory reasons but if you want to be pragmatic in what kind of interventions are practical and good value now (assuming you have made as many lifestyle energy saving choices as you can) you may find yourself back at the piecemeal approach.
If you go down this route the most important thing is to make sure each of those pieces of work add up to a cohesive whole over time. Set up a trajectory for your building to get it from where it is now to this enhanced performance. Get professional advice, which may be an approach like this:
- Look at your energy bills. How many kwh per m2 per year are you using? The figure might be 300kwh per m2 per year.
- How long do you intend to live in the property? Typically that could be another decade or two.
- What budget do you have available? Energy prices over that time might go up by a factor of 2 to 4, taking a rough guess based on past historical energy prices. If we know your available income based on your pension, in order to be spending about the same amount of money on energy as you are now when you’re a pensioner you need to achieve a certain energy target. Typically this might end up in the range of 50-80kwh per m2 per year.
- With an energy target, an energy strategy can then be worked out which calculates what choices need to be made given the constraints. By doing this work piece by piece over a long period of time, you know you will eventually achieve the target.
It's worth bearing in mind that certain work, such as changing the windows, is quite low impact and can be achieved in a very short space of time. Conversely internal wall insulation will typically make a lot of mess and involve redecorating the room.
As we start to look at the challenges of retrofitting on the House Planning Help Podcast we will be hearing from Tom Pakenham from Green Tomato Energy about how he retrofitted his Victorian home to the Passivhaus standard. He will also share his advice on how to improve the energy performance of your home.