How to retrofit a home for energy efficiency

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How to retrofit a home for energy efficiency – such an important question in these days of high energy bills and changeable weather patterns. It all hangs on which elements of an energy efficient home are missing from your place.

You don’t have to do it all at once. You’ll get some benefit from everything you do.  When you can finally put it altogether, then you get the real payoff.

Wrapping up the house for a cold winter

Think of it like getting ready to go out for a walk on a really cold January day:

  • You put on your thick jumper to keep you warm. This is the insulation that goes on the inside or outside your walls and under the floors. It provides a thick barrier between the cold air outside and the warm air inside, so never the twain shall meet.
  • You put on your wind proof jacket – this stops the cold air blowing through the spaces in the knitting of your jumper. This is airtightness – where you close up every space where uncontrolled air can seep into your home. It means closing up every possible gap – between layers of insulation, where walls meet floors, even where lights go into the ceilings.
  • You undo the zip of your jacket when you start to get hot and sweaty to get in a bit of fresh air. This is controlling air through heat recovery ventilation. You want the place to be airtight, but you still need to breath and to get rid of the 14 litres of moisture that a family of four produce in one day (or 3.4 litres if you live on your own).
  • As you walk you begin to warm up. This is your renewable energy – probably an air source heat pump (ASHP).
  • If you’re lucky the sun shines down and keeps you feeling comfortably warm. This is your solar energy that provides you with ‘free’ electricity to run your ASHP and your home, maybe even your electric car.


There is one additional task that applies to older homes and that is to ensure the system is breathable. If your home was built before 1930 then this is something to check with your architect.  When the walls are breathable they allow excess vapour to move freely – vapour that can otherwise sit within the walls and cause damage.

Going cold turkey

Going cold turkey and taking on the job at one go is a great way to retrofit – from the point of view of the house. For home owners, it is expensive and means either moving out or living in a shambles for quite a few months.

We did it this way. We’d already started building an extension when we realised the opportunity for retrofit was upon us. It just made sense to carry on. We also just continued living in the space – never occurred to us to move out. This worked for us because we were project managing alongside the builder and wanted to stay in close touch with the process. Our builders were not retrofit experts so we would check each evening to make sure the work was done as we needed it to be. It meant we lived in a major mess for many months, but it allowed us to feel on top of the work.

I’ve since seen my daughter do it the more comfortable way by moving out. It made much more sense with two kids and the builders had regular weekly meetings to show progress and resolve any issues. The downside was that some of the budget had to go on rent, but it meant the builders didn’t need to clear up each day and they could get in numerous trades at one go

So it’s swings and roundabouts.

Retrofitting step by step

There is also the option to take the work step at a time. This is much easier on the bank balance and less upheaval. If you want to do it this way, it can be really helpful to have a whole house plan done by your architect. This covers all the work that needs to be done in order to achieve the energy efficiency you’re looking for and also outlines what order to take the work in.

It’s really important not to create more problems as you go along. Too much insulation and airtightness without ventilation can leave you with condensation and mould. So having a process worked out ahead of time enables you to take the work at your own speed safely.

We did this recently when we finally retrofitted the bedroom. We had excluded this from the thermal envelope during the major work just so we had a retreat. Once we had some money again, we took on the bedroom. It took me a while to realise this wasn’t going to drag on for months – I’d been so used to living in a building site – it was so good to have work start with an end in just a few weeks!

Beginner’s Guide to Eco Renovation

Once I got into it, I found the retrofit process quite fascinating. And having some knowledge was a real help when managing the builders. They were great people – reliable, good at their trade, easy to have around – but not experts in retrofit. So we had some challenging conversations at times. And we often have to persuade them to our way of thinking.

Since so few builders know the retrofit world yet, it falls to consumers to become part of the team and influence how the work goes. With that in mind, once I was warm and comfortable again, I wrote Beginner’s Guide to Eco Renovation to help you get to grips with the process. I want you to be able to have a sensible conversation with the builder without feeling out of your depth. That way you gain the warm home you want and save on energy.

To hear more about my rationale, listen to my TEDx talk – How you and your builder can help save the planet.





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