Energy Performance Certificates

What’s wrong with our existing houses? Spoiler alert: they are not using too much energy for heating. The opposite is true: far, far, far more energy needs to be expended to keep them adequately warm and avoid adverse health impacts on occupants as well as a slow deterioration of the building fabric. Mould, while being a sign of a poorly performing building fabric, can also be caused by infrequent, intermittent, and only partial heating. If houses are not ventilated appropriately in addition, and who wants the little heat that was generated to escape again, a perfect storm is created.

Now, it’s not that houses are improperly heated because people don’t like it warm. Many, many, many simply can’t afford to heat their homes. Energy poverty is real and amplified by the very energy-hungry homes that we have allowed to be built.

This is where we are at, and the immediate intervention has to be to give people the means to heat more. A lot more. And not 10 years in the future. Now.

In the long run, deep retrofit programmes can help with reducing the difference between the heating requirements of a home and what people can afford for heating. This may also help with reducing carbon emissions, but probably not by much, because: if I currently don’t heat at all, as I can’t afford to, being able to heat a little and be warm will not reduce my overall energy use. It will make all the difference for my quality of life, though, and save billions in health costs and loss of productivity.

What is the role of Energy Performance Certificates, that some people advocate for our housing stock?

Overseas, they come in two flavours: one is rating the energy performance of houses based on utility bills, adjusted by annual climate files for the location. This will obviously not work for us, for many reasons: for starters, when you are heating with electricity, you would need a separate meter for your heating device to get the data. And when you are heating with wood, you typically don’t keep a perfect record of how much wood you used. And even if we were able to get the data: we would seemingly perform splendidly – but not because our houses are so energy efficient, but because we are not spending nearly enough energy on heating them.

The other type of EPC looks at the building instead and rates it based on certain factors. This analysis is typically fairly limited, as the money available for the analysis is scant, about the hourly rate of an expert consultant. So, if I am sufficiently qualified to know what I am doing, I can spend an hour on analysing the building and writing a report. For a proper analysis, I would need to know: to begin with, the exact geometry of the house, and all areas of the thermal envelope. For existing houses, there are often no plans available, and even if they are, the house as is may look very different from the one that was consented. Next, I need to know the exact composition of the elements of the thermal envelope, and let’s say, I know that 90 mm insulation was put into the wall cavity 30 years ago: what was the thermal conductivity, have they been put there properly, and are they still performing as intended? Does this double-glazing have an Argon fill, and if so: how much Argon has leaked out since it was installed? What’s the situation with thermal bridges? Moving on to ventilation heat loss: what’s the air change rate of the house? How much of this is infiltration? Onwards to gains: what factor am I assuming for internal gains, and on what basis? Do I know the shading situation on each window? To do all this with a modicum of accuracy, and put into a conclusive report will take days.

So, for this second type of EPCs, we either get results with such a high margin of error to lose all credibility, or we need to spend thousands on each and every assessment for millions of houses.

What should we do instead? This depends on the WHY. What are we trying to achieve? If we are trying to identify houses that need immediate intervention: giving nurses and doctors the ability to refer patients whose conditions can clearly be attributed to their housing to a team of retrofit experts would be my choice. Obviously, the team of retrofit experts would have to be resourced to properly and swiftly remedy the situation.

If we are trying to get an overview of the condition of our housing stock for policy purposes, I would give university researchers some money to collate all the existing research on this topic and make estimates based on this. This will not be perfectly accurate, but I propose that for this purpose, ballpark figures that we arrive at with little expense are good enough.

If we are trying to force building owners into retrofitting their houses based on the rating, I suggest that we have miles of litigation ahead of us, as I for one would challenge any EPC received with good cause. There are simple measures that can indisputably highlight the failings of a building, such as temperature measurements in rental accommodation - the result of an EPC on the other hand is easily refuted.

If we want to improve the housing stock over time – I outlined a programme of work here: https://www.dhirubhai.net/pulse/getting-houses-we-deserve-kara-rosemeier/?trackingId=ydDCogkZS96p7NLkRDRBDA%3D%3D

If we are trying to reduce climate impacts, I suggest we pick a different battle, such as increasing requirements for new houses – or, far more impactful – reducing pollution in other sectors. Many, many homeowners would love to upgrade their homes but do not have the means to do this, so if we are serious about it, we need a big stash of cash. And, as there are only so many retrofit experts available, this will take decades. I am not saying it’s not worth doing, it surely is. What I am saying is: I do not see a place for EPCs in this journey other than diverting money away from where it is needed.

To everyone advocating for introducing EPCs for houses in Aotearoa: please tell us the problem that EPCs are supposed to address, and why EPCs are the best tool to get results!