Case Study 2 - 1950s Terrace House - 43E to a C (without CWI)

At the time of writing the methodology for EPC assessments of existing dwellings is RDSAP 9.94. The much anticipated RDSAP 10 update has not happened yet and a significant methodology overhaul from RDSAP to the Hone Energy Model (HEM) is proposed for 2025.

This is the house I live in, and it's of the same design as the properties in Case Studies 1 and 3.

We bought this propery at auction in 2014, and the EPC rating was 43E. That EPC is about to expire this year because it's now 10 years old. We renovated the property during 2015 and 2016, and we want to improve the EPC rating further if we can, into the C band, by spending as little further money as possible.

Let's see what we can do.

Looking at our existing EPC issued in 2014, here is the Features table:

This information is a bit out of date now. Let's review where we are currently:

Wall - This is still a cavity wall without any insulation. We don't currently intend to fill the cavity due to cost. We have concrete Finlock guttering on the house and because this is prone to leaking and letting water pass down the cavity, we need to have the guttering cut off and replaced with UPVC before we have the cavity filled. It's possible I might tackle this myself with help from a builder neighbour at some point but for now we'll leave it as it is. The gutterring has had a glass fibre liner previously fitted which reduces the risk of water leakage for the time being.

Roof - The energy assessor states there is 50mm loft insulation. They got this completely wrong. In fact, 250mm loft insulation was present at the time this EPC was issued and an installation certificate is present in the loft, detailing this, although we have fitted loft legs and boards, compressing the insulation and can only declare 200mm now. It's still an improvement on the 50mm declared previously though, and being a bove 150mm will not trigger a related recomendation in any new EPC.

Window - We still have these same double glazed windows, as before, with aluminium thermal spacer bars and they are classed as 2002+ in age. We plan to leave these as they are as there isn't really any benefit to replacing them with anything newer from an EPC rating perspective. From RDSAP10 it will be possible to declare double glazing fitted from 2023 onwards but at the moment it is not and the cost of replacing them in the near future would overweigh any benefit.

Main Heating - This is where we have made a big difference. The property had a limited number of storage heaters as the main source of heating. The heaters were not present in all habitable rooms, resulting in the Secondary Heating entry in this table (see below). We replaced the storage heaters in 2016 with a full gas central heating system, and this single change has made the greatest difference to the EPC rating. The boiler we have is a pretty modern gas condensing combi boiler - it's an Alpha Intec2 28X. We'll come back to this boiler in a moment...

Main Heating Control - Now that we have a modern gas combi boiler running radiators in all habitable rooms in the property, in terms of heating controls we have the best set of 'standard controls', consisting of: TRVs (required on at least 50% of the rads), Programmer and a standard Thermostat. We'll come back to Heating Controls in a moment....

Hot Water - Previously provided by an electric immersion heater, this now comes from the gas combi boiler instead - this is a far cheaper way of heating water compared to the electric immersion heater we had before.

Lighting - We now have LEDs in all light fittings. This only makes a small difference, likely just 1 SAP point improvement to the EPC rating.

Floor - This is still a solid floor. We do not intend digging it out and putting solid floor insulation in place due to the cost, effort and low return in terms of EPC rating increase.

Secondary Heating - Here it lists: "Portable electric heaters (assumed)". This is an importat signal to recognise if you have this on your EPC. This was created by the RDSAP system automatically, most likely due to one or more habitable rooms in the property not having a source of space heating present. RDSAP assumes that portable (peak rate) electric heaters will be used to fill the heating shortfall of the property. That is a costly fuel, and for electric heaters it assumes they will be used for 20% of the floor area of the property. If you have this listed, but you also have a central heating system using a cheaper fuel such as mains gas, it will ordinarily reduce the EPC rating of your property signififcantly. For us, that wasn't quite the case at the time of this old EPC, and we now have the gas combi boiler, all habitable rooms are heated, and we have no forms of secondary heating, so when we have the EPC conducted again there will be no form of secondary heating listed and our rating will not be cut down.

So, we want to improve our EPC rating to a C if possible as that's a bit of a Holy Grail for older properties, and we'd like to see if that's possible without Cavity Wall Insulation, and by spending as litle money as possible.

The new Labour government of 2024 has indicated the MEES requirements for rental properties will be raised to a C rating by 2030, although we don't intend to rent this proerty out.

Next we run a Home Energy Report, which is just like an EPC, but without the formal lodgement proces at the end. We do this to find the current rating of our house, and think about what we can do to improve it further. It also means that without a newer EPC being lodged, we still keep our old D band EPC in case we might be able to claim under a scheme for some insulation in the future (often a D or lower rating is required to qualify for such schemes).

During this assessment, I had to make a change to our electric feature log burner that we have in the lounge. This is never used, and sits as a focal point in the old fireplace. We had to fit a trailing socket and in-line plug in the cable to make absolutely sure it became classed as a portable heater, rather than a fixed heater (and therefore a form of Secondary Heating). Being portable, it is discounted during the EPC assessment.

See our page about Heating Systems to see what effect this electric heater could have had on the EPC rating.

So the rating has come out at a 68D. That's just one point short of being in the C band. We need to get at least one more point from somewhere. How can we do that, and can we do it cheaply?

After some checking in the RDSAP software here are some options:

If I had the money, I'd probably choose to re-batton and re-felt the roof, have the Finlock guttering cut off and replaced with UPVC and have CWI installed and Solar PV.

We're looking to keep the costs as low as possivble though, and after some extended thought, there are two avenues we are persuing, and they are likely to provide an improvement of one SAP point each.

The first approach is to upgrade the heating controls on the boiler to some form of Compensating controller rather than the existing ON/OFF controller. The other is that if we can record evidence of the age of the heating pump, and if this pump complies with the newer ErP energy efficiency legislation we can declare it's age as  '2013 or later'.

Our boiler is a gas combi and the heating pump is located within the casing, out of view from any passing Domestic Energy Assessor. In the absence of any documentary evidence, an energy assessor would declare the age of that heating pump as 'Unknown'.

If we can confirm the pump qualifies, and we also gather documentary evidence which would ideally be digital photographs with geo-location tagging in the meta-data, then I think most energy assessors and any EPC auditor would be happy to declare the pump age as 2013 or later.

Any modern smartphone should be sufficient. The geo-location data is likely to satisfy the curiosity of any EPC auditer - EPCs are occasionally audited for quality control.

We will take a close up photo and a couple of mid-field photos showing the location context of the boiler.

I forgot to take these photos when we had the boiler serviced in March so I'll have to wait until the next service to do that cost effectively. I'm not GasSafe registered so I'm not supposed to be taking boiler covers off myself.

We're pretty convinced the heating pump will be dated '2013 or later' because the boiler was fitted brand new in 2015/2016 and we'd expect the components to be similarly dated.

We have a page dedicated to this subject here.

When we had the Alpha boiler fitted in 2015, I remember the heating engineer Mark offering us a choice of controller to supply with it. There was a range from a very simple timer, all the way up to the Alpha Climatic Controller which had lots of dials and buttons. We went with the Alpha Digistat, partly to make things straightforward but largely because it was towards the lower end of the cost range.

Having now become much more interested in energy assessment, and boiler efficiency, and EPC ratings, I found myself revisiting this choice of controls, and recalling that day when Mark showed me the brochure.

Researchig online, I discovered that our boiler is not OpenTherm compliant, and has a proprietry Alpha BUS interface for connecting heating controls. We could therefore fit a Nest Learning Thermostat, but it would still only operate in ON/OFF mode with our boiler, or I could purchase an Alpha branded control instead.

After more research, we bought a second hand Alpha Weather Compensation Sensor on eBay for £28 and a second hand Alpha Climatic Controller on Gumtree for £65.

These provide modulation of the water flow temperature of the boiler based on two things:

• Load Compensation – considering the difference between the actual room temperature and the target temperature
• Weather compensation – similarly considering the temperature outside the house compared to inside the house.

The main noticeable effect is that the boiler runs with lower temperature water running through the radiators. Also, as the room approaches the target temperature, the boiler reduces the flow temperature so that the room does not overshoot the target temperature. The boiler operates for longer but at a lower load and should not fire on an off so much as it would have done with the previous controls. These things make the boiler operate slightly more efficiently than before.

Similarly, due to the weather compensation sensor, in the winter when the temperature outside is cold, the boiler will raise the temperature of the water to compensate for the additional heat being lost through the walls of the house. Otherwise it keeps the temperature lower when not required. There is a control to adjust the 'Weather Compensation Curve' to match the energy loss of our house.

We had these devices fitted at the last boiler service in March and I'm really happy with them.

Then it came to getting them recognised in the RDSAP software however, and that's where we hit a major problem.

I use the RDSAP GO app from Elmhurst to conduct assessments for EPCs and Home Energy Reports. It's quickly evident you can only assign one or other of these products to the boiler, not both of them at the same time.

Additionally, if I try and assign either of them to the boiler, the software raises an error. A quick call to Elmhurst technical support didn't give me any further information other than confirming it was an issue within the Product Characteristics Database (PCDB / PCDF), which is the external database that holds information about boilers and compensation controllers. The EPC assessment draws information in from this database about your boiler etc for use in the overall rating calculation.

I was able to identify the cause of the problem in the end.

Our boiler, the Alpha Intec2 28X is listed in the PCDB. Also, the Alpha weather compensation sensor, and the Alpha Climatic Controller are also both listed in the PCDB.

The problem is that the Intec2 28X is not present in the list of 'Compatible Boilers' held against either the weather sensor or the climatic controller. Other Alpha boilers are present in those compatibility lists, and if I select one of those boilers and assign the climatic controller, it succeeds, and we get one additional SAP point on the EPC rating for our property.

For our boiler, the Intec2 28X though, we are currently stuck.

I emailed Alpha to make them aware of this technical issue, and those initial emails were not acted on by the frontline staff. I then wrote to Alpha and they did then engage and assign a product engineer to help. They contacted the Building Research Establishment (BRE) who host the PCDB, cc'ing me in on the emails, and the BRE have been absolutely rubbish - they have not responded at all. Unfortunatley, my contact at Alpha has now left the company amd I have written to Alpha again to see if they would be willing to assign another product engineer to chase the BRE. It's been 4 months already and I am not holding my breath. I expect the 1 SAP point from the heating pump age will become available to me faster than this SAP point.

So at the moment we are stuck with our current path of thinking. We are not able to claim the additional 1 SAP point towards the EPC rating from the climatic controller, and I'm waiting until the next boiler service for the one from the heating pump age.

I'll post an update when we make some progress.