Energy efficient housing

How Energy Efficient is Your House, Really?

Craig Dalzell – February 24th 2022

Building Homes With Real Data

It’s probably a question that more of us should be asking both as we move towards a zero carbon future but also as energy bills are shooting up dramatically around us (the energy bill for my household has just doubled and many folk are reporting even larger spikes than that).

Energy Performance Certificates, or EPCs, are the main measure we use in Scotland and in the UK to compare the energy efficiency of buildings with each other. However, as we laid out in our paper calling for EPCs to be replaced, these certificates don’t really measure the energy efficiency of your house – not directly anyway. They rely on a survey of the types of materials in your home, where they are installed and how many of them there are but this information largely feeds into a checklist that is scored against standardised results. They have little provision for “non-standard” materials. I’ve spoken to folk who had trouble with their EPCs because they self-built a wood-frame house but the checklist expected to see brick and our Energy Working Group has engaged with folk who have found their EPC rating vary wildly depending on how closely the inspector actually looked at their house. Often the inspections are short to the point of being cursory despite the importance that these ratings can have on everything from sale value to the improvements and retrofits that we may soon be required to do to our homes (barring adopting of our call that such retrofits should be done as a matter of public infrastructure rather than dumping responsibility on individuals).

Critically, the EPC rating doesn’t factor how a building is used. One that remains empty for most of the day while everyone is at work may require a completely different pattern of heating to remain a comfortable dwelling than one in which the occupants are working from home or if they are older, frail and sensitive to cold.

It seems like the EPC scheme is completely divorced from the function of the building (for a house, its primary function is to be a comfortable home for humans despite some who believe that its function is to be an accumulator of rent or capital value). Even radical buzzwords like “Fabric First” can be guilty of missing this. Adding that human element back to our metrics in doesn’t change the overall principle about making homes as efficient as they can be but it does lend things more towards a principle of “Folk First”. Fuel poverty is an extremely complex problem but policy-makers do not always treat it as such.

            However, there’s an even deeper problem with EPCs, the checklist makes little provision for the competence of the construction of a building or its state of repair. You could well have the fanciest, cutting-edge, more-panes-than-your-razor-has-blades windows, but if the person who installed them messed up and you have a draft coming through the frames, their contribution to your overall energy efficiency is going to be somewhat limited. And that’s not even a worst-case scenario when it comes to windows. I vividly recall giving a talk about a Scottish Green New Deal recently and mentioned this point. An audience member told me their story of discovering that the draft and water ingress around their window wasn’t due to gaps in the sealant, but due to the complete absence of sealant. A mild nudge against the window – or someone tripping and falling into it – could have sent the entire pane tumbling out of the building and onto the street four floors below. Almost anyone who has experienced the Scottish private rented sector will be able to share stories in the comments about landlords who have ignored urgent repairs, water ingress, mould or other health-harming issues in their properties.

            The issue of compliance in building standards is going to become even more critical as we raise those standards and smaller errors or flaws (such as a leaking window seal) become more significant as a proportion of avoidable energy losses from the building. In short, better building standards demands a better trained, more highly skilled, more vigilant workforce – along with the wages and conditions commensurate to the value of those skills.

            I used to claim that the main reason we needed actual legislation to improve building standards was that companies would only ever construct buildings at “minimum standards plus one”. But we’ve seen countless stories of homes signed off with everything from relatively minor snagging issues up to a disturbing percentage of new homes where owners report one or more major problems with the build – 51% in the YouGov survey mentioned in this report. Without robust inspection, compliance measures and a binding commitment to correct mistakes or shortfalls at the developer’s cost, no amount of regulation will ever succeed. Rather than “minimum spec plus one”, the tendency will be towards building to the “least compliance, avoiding litigation”.

            As it stands, the Scottish Government remains committed to its programme of improving building energy efficiency based on EPCs this may be inappropriate if we start building the kind of zero-carbon, Circular Economy, passive efficiency buildings that we know that Scotland is more than capable of constructing (one was demonstrated outside COP26) and these buildings end up being misbanded by inappropriate EPC surveys. The current plan is all Scottish homes should be at least EPC C by 2040 (with fuel poor homes being EPC C by 2030 and EPC B by 2040). This is evidently far short of a push for, say, passive efficiency grade housing but if we consider the Scottish Government increasing its commitment to ensure that all homes are EPC B or EPC A then how would this work if the EPC system itself fails? If your house is built to passive principles but somehow scores a low EPC rating because of a bad inspection or “non-standard” materials, what “improvements” could be made that would make a meaningful difference to the building? Would making the EPC rating threshold literally become a checkbox exercise to meet a legislative target? Would this lead you to installing retrofits that you don’t need or could possibly even compromise the efficiency of your house? What about the converse? How much money will be wasted by an occupier of an “EPC B” home that is still too cold for comfort because of draughty windows and gaps in the roof insulation? Could you end up buying a new house on the basis that it shouldn’t need any retrofits before 2045 only to discover to your personal cost that it does?

            In our paper on replacing EPCs, we’ve suggested something radical in its simplicity:– how about instead of idealised models and checkboxes, we measure how much energy a building actually uses and score it based on real data? The idea would be that a building’s energy use is actively measured for, say, twelve months after it is constructed and first occupied, after it is sold or changes tenancy, or whenever the occupant commissions a re-survey (perhaps after they’ve renovated or repaired the building in a substantial way). From this, we could simply calculate the energy usage in KWh/m2 and factor in recordings of the internal temperatures of the building throughout the year to capture data on fuel-poor households who self-ration or self-disconnect their energy use. A deeper survey of the building and its materials would still be useful – especially at identifying the repairs or replacements that would improve energy efficiency further in the most cost effective manner. This could then be built into a coherent strategy for any retrofits that are required and a costed plan for either doing them all at once or phasing the installation in the cheapest way, without having to waste resources by installing equipment that later needs to be replaced.

            Folk who know me know that I have a bit of an obsession about using real data like this to make public policy. When we don’t have it, or when we don’t look at it, Governments can end up setting inappropriate targets or find themselves making legislative demands that make no sense in certain edge cases. When it comes to planning future buildings this is absolutely vital. The results of our failures will be visible for decades. The results of our successes, perhaps for centuries.

1 thought on “How Energy Efficient is Your House, Really?”

  1. Case in point: We have just had an air source heat pump installed which has had the effect of our EPC Environmental Impact (CO2) Rating DROPPING from 94 to 74 because an ASHP uses electricity even though we are on a 100% renewable electricity tariff! Our previous heating was from a woodburner which is considered renewable!

Leave a Comment

Your email address will not be published. Required fields are marked *

Shopping Cart
Scroll to Top