Heating Systems

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.

Here we consider Heating Systems and Heating Controls. We also cover the count of 'Habitable' rooms and the count of 'Heated Habitable' Rooms in the property. These can make a very significant difference to the EPC rating for a property.

As an option for improving your EPC rating, heating systems are more costly to replace or modify, but there is still even the potential to make a small increase in your EPC rating by making a smaller change to the heating controls for example.

The largest gains may be experienced when moving from a system using an expensive fuel to one using a lower cost fuel. (eg from electric storage heaters to gas boiler or Air Source Heat Pump).

There are also a couple of situations to mind out for which will cost you a few EPC points. We'll describe these in more detail in a few moments, but to encourage you to read the whole of this page, they are:

• Perhaps you have a decent Main Heating system (gas boiler and radiators for example) that heats all habitable rooms in your property, but you also have a fixed electric feature fireplace in the lounge or a fixed electric towel rail radiator in the bathroom or kitchen, or a fixed electric panel/fan heater somewhere. This disparity with the fuel used by the Secondary Heating device will bring the EPC rating down significantly, even if you don't use those heaters.
• Perhaps you have a decent Main Heating System (gas boiler and radiators for example), but you also have one or more habitable rooms that are not heated (by fixed heating), and you have no secondary heating present. The RDSAP methodology will assume you will use portable peak rate electric heaters to fulfil the heating shortfall in the unheated habitable room, and again your EPC rating will be affected significiantly.

Let's work through Heating Systems and maybe you can spot something you can change to improve your EPC Rating.

The EPC assessment allows for the recording of:

• The presence of up to two 'Main Heating' Systems
• The presence of one form of 'Secondary Heating'
• Any Heating Controls for the Main and Secondary heating systems.
• The count of 'Habitable' rooms in the property
• The count of 'Heated Habitable' rooms in the property
• How Domestic Hot Water (DHW) is heated - ie hot water to taps

We'll start with the number of 'Habitable' rooms in the property.

'Habitable' rooms include any Living Room, Sitting Room, Dining Room, Bedrooms, Studies and similar, and also Kitchen/Diner (defined as being able to accomodate a table and four chairs) - Open plan rooms are counted as one room, including when only separated by an open archway, and if a door has been removed and the hinge holes filled in - for example the classic example of between a lounge and dining room.

Not included are: Any room used soley as a Kitchen (and is unable to accomadate a table and four chairs), Hallways, Stairs, Utility rooms, Landings, Bathrooms, Clakrooms, Ensuites and any room without access to natural light.

A conservatory separated by an internal quality door from a dwelling is also regarded as a habitable room, but a conservatory separated by external quality doors from the dwelling is not a habitable room as the conservatory is disregarded from the assessment. A conservatory separated by an open plan archway is regarded as part of the habitable room to which it is attached and is not counted as an addditional habitable room in it's own right.

We then count the number of those 'Habitable' rooms which are heated in one way or another. This could be by either a 'Main Heating' system, or by a fixed 'Secondary Heating' source. We'll describe these next. Note though that bedrooms with only open fire-places are disregarded from the heated habitable room count when identifying the heating systems (main and secondary).

So, we'll come back to these two numbers in a bit - the count of habitable and heated-habitable rooms. We're interested in whether there's a difference between the two numbers, ie whether all the 'Habitable' rooms are heated or not.

Next, we work out what 'Main Heating' systems and 'Secondary Heating' sources are present in the property.

A main heating system is often:

• Gas Boiler (with radiators or under-floor heating)
• Oil Boiler (with radiators or under-floor heating)
• Electric Storage Heaters (when they are the main source of heat)
• Electric Panel Heaters (when they are the main source of heat)

Secondray Heating can include:

• Fixed Electric Panel heaters
• Electric towel rail radiator in the bathroom or ensuite
• Electric plinth heater in the kitchen
• Electric feature fireplace
• Electric ceiling heaters
• Electric under-floor heating mats

• Open Fireplace (with grate present)

• Closed Log Burner
• etc.

Usually, a property has one main central heating system, and possibly a source of Secondary Heating. Several details are recorded for up to two Main Heating systems, and just a single heating code can be entered to describe one form of Secondary Heating, if present.

Devices need to be fixed in place in order to be recorded. Portable electric fan heaters would not be recorded as a form of Secondary Heating because they are not fixed in place. A fixed electric feature fireplace in a lounge however would be recorded.

The type of fuel used by the heating systems significantly affect the EPC rating. The worst case fuel in terms of cost is peak rate electric. This would be the case for fixed electric panel heaters, fixed convector heaters etc.

Storage heaters are better because they use cheaper rate electricity during the night to charge up. Oil boilers in comparison are better, and Gas boilers would be better again.

Heat Pumps are a little different as although they run on electricity, because of the way they work they can often operate with an efficiency of 300-400% compared to only 100% for electric panel heaters. As their efficiency can vary so much dependant on the system design and installation, their specific efficiency for the EPC assessment is taken from their entry in the PCDB.

There is a table of fuel costs located in Table 11 of SAP2012. If you are interested, take a look at that table to compare fuel costs.

Generally, if you change your heating system to a cheaper fuel you would expect your EPC rating to improve. Always check with a local Domestic Energy Assessor however before making significant changes as this will make sure you know what the effect will be, and you'll be making an informed decision.

Firstly, take a look at our Case Study 3, which is a property that has no Main Heating system at all, and no form of Secondary heating present either. This example demonstrates possibly the most extreme case of improving an EPC rating by upgrading a heating system. The EPC rating is currently very poor indeed - it's a 30F despite all other aspects of the property being quite good. Where heating is absent, the RDSAP methodology assumes the worst case in heating will be used to fulfill the shortfall - which is the use of peak rate electric heaters (possibly portable). In the Recomendations on the EPC for this property, it indicates that installing a central heating system based around a gas boiler would bring the EPC rating up to 74C (combined with solid floor insulation) - perhaps we could make a guess and interpolate that it would be 71C without the solid floor insulation. That would be a massive improvement of 41 SAP points. This is probably the most extreme example and it's this big because of the very large difference in the cost of heat provided by peak rate electricity compared to that of gas in an efficient condensing boiler.

A whole central heating system including pipes and radiators, where there wasn't one before could cost perhaps up to £10,000 though, so it would take a significiant investment to implement.

Also, if gas is not already present at a property, there may be additional costs in getting a gas supply connected, and in some cases that could be very expensive or just not feasibly possible at all, depending on location and building type. If you don't have gas, and you were interested in getting it connected, do find out from your energy supplier how to go about doing that and how much it would cost. It might cost less than you think. I had to get gas connected to our property, and it only cost £200-£300 back in 2015 because there was a gas main running directly in front of our house.

Rather than using gas however, the future direction is really that of Heat Pumps. this is partly due to their efficiency, but also due to the move away from carbon based fuels, in order to meet the Government's committment to reduce carbon emisions by 2050. In the future, gas boilers will be banned from new builds, gas boilers will be banned from being installed or replaced in existing dwellings. Oil boilers will be similarly affected.

Taking a look at the relative costs, Electric heating costs about 4 times the kW rate compared to gas - info here: https://www.uswitch.com/gas-electricity/guides/uswitch-guide-to-kwh/#what-is-the-gas-and-electricity-cost-per-kwh-in-the-uk

Electric heaters such as panel heaters, fan heaters etc. can only be a maximum of 100% efficient. That means that if we have an electric heater and it uses 1KW of electrical energy, it can produce a maximum of 1KW of heat. In comparison, although gas condensing boilers are often in the low 90s% efficiency, but because of the much cheaper price per kW they are still much cheaper to run.

Comparing with Heat Pumps, although these also run on electricity, they work by moving heat from one souce to another instead of actually generating that heat. Their efficiency (referred to as COP - Coefficient of Performance) is highly dependant on the design and installation of a system but would normally be between 300% to 450%. Because of this efficiency, they are an efficient form of heating that runs on electricity, and combined with the aspect of CO2 reduction are the future of heating in the UK.

When a form of Secondary Heating is identified and recorded on an EPC assessment, the RDSAP methodology assumes that a proportion of the floor area of the property is heated by it. This varies from 10% to 20% of the floor area, depending upon the type of fuel used. Peak rate electric is the worst at 20%, and wood burners for example are at 10%. These values are listed in a Table of SAP 2012, which can be viewed on the Building Research Establishment (BRE) website.

Note that the presence of a form of Secondary Heating is recorded, irrespective of whether that heating device is actually operated by the occupier of the property.

There are two cases where Secondary Heating can work against your EPC rating. These are:

• Where Secondary Heating uses a fuel that is more expensive that that used by your Main Heating System
• Where you have unheated habitable rooms, the use of portable peak rate electric heaters is assumed if there is no other Secondary Heating declared

You won't see any EPC recomendations telling you about either of these two things.

If you have a good central heating system, and that is the source of heating in all of your habitable rooms, but you also have a source of secondary heating recorded that uses a more expensive fuel (such as peak rate electric) then this will adversely affect the EPC rating.

See my example below where this would reduces the rating on my property by 6 SAP points. This is regardless of whether you actually use that item of secondary heating or not. The EPC assessment does not consider how you actually use the heating systems.

If you have a difference between the number of habitable rooms, and the number of heated habitable rooms in your property, and you have no other form of Secondary Heating declared, then the RDSAP methodology will assume that portable electric heaters will be used to fulfill the heating shortfall.

Again it will reduce the EPC rating, and in the example of my house it reduces it by 6 SAP points.

If you have electric storage heaters and you are wanting to improve your EPC rating, as you research your options online you might come across an enticing advert for electric panel heaters, with a description such as:

"Electric Radiators offer a modern, energy efficient heating solution for any space. Unlike traditional radiators, electric radiators provide 100% conversion of energy to heat, precise temperature control for each room and the latest energy saving technology, ensuring optimal comfort and reducing energy wastage."

At the end of the day, these are just electric panel heaters and like any other electric panel heater will use peak rate electricity during the day to heat your home. If you fit them as a replacement for your storage heaters your EPC rating will go down because you are now using peak rate electricity to heat your home rather than overnight cheaper rate electricity which storage heaters use to charge up.

There are many examples in online forums where property owners express their disappointment that their EPC rating has gone down in this situation. These people have been duped into making this change and didn't understand the consequences of their actions. The advice therefore is to avoid fitting peak rate electric panel heaters.

In the example of my own 1950s terraced property, which we cover in Case Study 2, I recently re-assessed it to see what the EPC rating would be, and it calculated as a 68D.

I have a condensing gas combi boiler fitted in 2015, and no secondary heating recorded because I have made the decorative electric log burner in my fireplace detachable.

I have 5 Habitable Rooms and 5 Heated Habitable Rooms. If however I redcue the number of Heated Habitable Rooms by a count of 1 - effectively recording that I have one Habitable room in my house that is not heated by the main heating system, the following happens:

In the absence of any recorded form of Secondary Heating in the property, the RdSAP system will decide that additional heating will be required to heat that room and it will assume, and declare on the EPC, that portable electric heaters will be used.

The EPC rating on my property, due to that one change, reduces by 6 SAP points down to 62D, which is a really significant drop.

Similarly, from the baseline of 68D, if I had not changed the wiring for my decorative electric log burner, and it was therefore still considered a fixed device and had to be recorded as Secondary Heating, then the EPC rating would also have reduces by 6 SAP points to 62D.

One approach to avoiding this situaton therefore is to ensure all your rooms that are classified as 'Habitable' rooms are heated by the Main Heating system in the house, and remove any forms of secondary heating (particularly electric) if your main heating system runs on a cheaper fuel.

You won't see either of these things listed in the recomendations on an EPC.

Note that other combinatons of heating fuel type may not be of such a concern. In an example of a large detatched property I assessed which had an oil based boiler as it's Main Heating, and a log burner in the lounge as Secondry Heating, the presence of that log burner did not detract from the EPC rating, so it depends on the individual property and combination of heating/fuel type.

As mentioned elsewhere, check with a local energy assessor to see what difference would be made with your particular property before proceeding with any works.

Perhaps the property has a gas boiler. Details are taken of the boiler - Make, Model, GC Number, and a note of whether it is a combi or system boiler.

Usually we can identify the exact model of boiler within a product database called the PCDF, which we access within the EPC assessment system. If we cannot locate the boiler, or cannot locate an identifying label on the boiler at the property then we can instead enter generic codes for the type of boiler, but they won't use as accurate figures for the efficiency and performance of the boiler when calculating the EPC rating.

Here we take my property (covered in Case Study 2) and model it with different forms of heating system. In each case we note the EPC rating as follows:

In the above table, all references simply for 'gas' means 'mains gas' rather than LPG.

Information to follow regarding the ratings....

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