Heating Controls

At the time writing, the EPC assessment methodology for existing dwellings is RDSAP 10. The example ratings indicated on this page however were calculated using RDSAP 9.94. Note that a significant methodology overhaul from RDSAP to the Home Energy Model (HEM) is proposed for 2027. In addition, government consultations indicate future changes to the format of EPCs and minimum rating levels required for private rental properties. Methods for improving EPC ratings will therefore change in the future.

In this article you’ll learn:

• What heating controls are and how they affect an EPC assessment.
• Which standard heating controls are normally expected on a wet central-heating system.
• How TRVs, thermostats and programmers are treated in an EPC assessment.
• What Time & Temperature Zone Control (TTZC) is and how it can improve an EPC rating.
• How load and weather compensation work and when they can be recognised in an EPC assessment.
• How smart thermostats are now treated under the latest RdSAP methodology.
• Why checking the PCDB is important before buying advanced heating controls.
• Why you should model any proposed change before spending money.

Heating controls are an important part of an EPC assessment. They influence how efficiently a heating system operates and how much fuel it consumes.

Controls such as programmers, room thermostats, thermostatic radiator valves (TRVs), weather compensators and load compensators can help reduce energy consumption by improving the way the heating system responds to the needs of the property.

The EPC calculation assigns different performance factors to different combinations of heating controls.

In some cases, upgrading or adding heating controls can increase a property's EPC rating.

For the most common 'wet' central heating systems such as oil and gas fired boilers, there are four categories of 'Heating Controls' that can be entered for an EPC assessment of an existing dwelling. These are:

• Standard Controls
• Time & Temperature Zone Controls
• PCDB Compensators
• 'Smart' Thermostats

For electric Storage Heaters, the heating controls on the older types consist of:

• Manual Charge Control, or
• Automatic Charge Control

For a central heating system powered by a boiler, standard controls include:

• Room Thermostat
• Programmer
• Thermostatic Radiator Valves (TRVs)

For the best rating you need to have all three of these registered as being present in your property.

If any are missing, or what you have in the property doesn't qualify, consider changing the controls so that you can legitimately register all of these as being present.

A room thermostat is a device often fixed to the wall in a hallway or living rom, on which you can set the target room temperature.

A programmer is a device on which you can set the days and times during which you'd like the heating system to operate.

Thermostatic Radiator Valves (TRVs) are devices fitted to one end of each radiator in your property, and they sense the temperature of the surrounding air in the room. They can be adjusted, usually with an indicator dial from 1 to 6 to set the desired room temperature. When the room reaches that temperature they automatically shut off the flow of water through that radiator to prevent the room being heated more than required.

Here are some example pictures of these type of devices:

A thermostat and a programmer can often be designed together within a single device, so if the device on which you set the target temperature is also the device on which you set the on/off times for your boiler then that is providing both functions.

For TRVs to be registered as being present, they need to be fitted on at least 50% of your radiators. This requirement is described in Convention 4.13. This includes all radiators, including those in non-habitable rooms.

Often it's the TRVs that properties lack. Consider adding TRVs onto radiators where they are not already present so that you qualify via the 50% rule.

Standard Controls - An Example Property

Fixed combinations of standard heating controls can be recorded in an EPC assessment.

The following results are from my own property and are provided to demonstrate the relative effect of these configurations.

Check out our Case Study 2 for more information of this property:

For my property, changing from no controls at all to Programmer Thermostat & TRVs gives me an increase of 4 SAP points.

If I already had the Programmer and Thermostat but was missing the TRVs and had those added (which is a much more common scenario), then I would only have a 1 SAP point increase. That single point though could combine with other points to take you over a banding threshold.

Always consult a domestic energy assessor to confirm what difference you would achieve in your own property.

What is TTZC?

Time & Temperature Zone Controls are Heating Controls that enable the independent programming of heating times and target room temperature of two or more separate areas (zones) within a property.

This is described in RDSAP Convention 4.17 as follows: "TTZC: A system of controls that allows heating times of at least two zones to be programmed independently as well as having independent temperature control. It includes wired or wireless remote or mobile control systems".

With TTZC you could have for example, one zone for upstairs and one zone for downstairs.

How Can TTZC Be Achieved?

TTZC can be achieved by using either:

1. Separate plumbing circuits, either with individual programmers for each circuit or a single programmer that has two channels, or
2. Programmable or Communicating TRVs

Standard TRVs provide independent temperature control, but they don't independently programme the heating times for each zone. This is why ordinary TRVs alone do not provide TTZC.

If you controls fitted which are sufficient to qualify via one of the above criteria, then 'Time and temperature Zone Controls' can be selected in the EPC assessment.

TTZC - An Example Property

The EPC rating is likely to improve with a property that has TTZC, compared to one that only has Standard Controls.

With my property, a 1950s mid terrace house, my rating would change as follows:

So, I would get an increase of 2 SAP points on my EPC rating if I could declare Time & Temperature Zone Controls as being present.

Your property is likely to differ, so contact a local Energy Assessor to review your property before making any changes.

Recording TTZC In An EPC Assessment

Time & Temperature Zone Control can be selected from a simple drop down option in the assessment to indicate it is present.

Alternatively a qualifying device can be selected from the Products Characteristics Database if it has been formally registered by the BRE as providing Time & Temperature Zone Control.

This list is available here:

https://www.ncm-pcdb.org.uk/sap/searchpod.jsp?id=17

Click on the option for 'Compensating Boiler Controls & TTZC', then leave all the drop down options as they are and click the 'Search' button.

On the results list, click the 'Category' heading twice to order the devices in reverse alphabetical order by 'Category' name.

All the TTZC devices will be displayed at the top of the list.

If your TTZC Heating Controls are in this list, with a category name that includes the letters 'TTZC', then it's likely they can be specifically selected within the EPC assessment.

Alternatively, if you are looking for devices which could fulfill the requirement of TTZC, then look down the list and research each device (with a category of 'TTZC') on the Internet to see if they are of interest to you and compatible with your boiler.

Contact a local energy assessor to ensure that any devices you are interested in can be included, and what difference they could make to your EPC rating before making any changes or spending any money.

Some of the devices could be easy to fit in order to increase your EPC rating with little effort. You'll need to review the list in consideration of your heating system as some are manufacturer specific and some might not be appropriate for you.

Here are a couple of the simpler ones in more detail plus one that's not on the list. I'm not sponsored and I haven't used any of these devices myself, although I'm interested in them due to my EPC rating being on the threshold of becoming a C rating:

Radbot 1 TRVs

Drayton Wiser

This appears to come in the form of a smart thermostat kit which replaces your existing thermostat and programmer. Additional smart TRVs can be added. It supports OpenTherm. The initial kit is available at around the 200 GBP mark.

TP-Link Kasa

This comes as a starter Kit plus additional smart TRVs available from Toolstation and Screwfix for example. These aren't on the PCDB but should qualify for TTZC at a low cost if you replace a few of your existing TRVs with them. The kit doesn't replace your existing boiler programmer or thermostat. The starter kit seems to be around the 45 GBP mark and additional TRVs at 33 GBP. A smart app can be used to configure temperatures and heating times.

With standard heating controls, the flow temperature of the water pumped around the system is fixed. Often this might be set as high as 70 degrees Celcius.

Control is 'traditionally' effected by turning the boiler on and off as the room temperature falls below and then rises above the target temperature set on the thermostat.

This usually leads to the room temperature rising beyond the target temperature after the boiler has been switched off, and then falling below the target temperature before the boiler fires up and the radiators eventually get hot again.The boiler ends up cycling on and off repeatedly.

There are some advanced heating controls however which adjust (i.e. 'modulate') the flow temperature of the water being pumped through the radiators and make the boiler slightly more efficient. There are two main ways in which this is possible:

Load Compensation - by taking into consideration the difference between the current room temperature and the target temperature set on the thermostat.

Weather Compensation - by taking into consideration the temperature outside the property, compared to the temperature inside.

With load compensation, the flow temperature of the water is generally lower than would 'traditionally' be set with standard controls. Additionally, it is further reduced as the room temperature approaches the target temperature on the thermostat. This behaviour reduces the load on the boiler, avoids overshoot of the target temperature in the room, makes the boiler operate in condensing mode more (if applicable), and prevents the boiler cycling on and off so much. You'll notice the radiators are cooler to the touch and the boiler runs for longer periods of time.

Weather compensation considers the temperature outside the property. The idea is to keep the flow temperature generally low, but to increase it as the heating demand for the property increases when the weather outside is cold. In the winter, with lower outside temperatures, more heat needs to be generated inside the house to maintain the required room temperature. This balances the increased heat being lost through the walls and roof etc. Adjustment is available of a 'Weather Compensation Curve' which controls how the flow temperature varies dependant on the outside temperature.

In both cases, balancing of the radiators in your property becomes more important.

It is possible to connect Compensator Controls to your boiler and have these recognised in the EPC assessment, and get a slightly improved rating. The difference is fairly small, and it relies on the specific heating controls being present in the Product Characteristics Database (PCDB). Additionally, your boiler needs to be on the 'Compatible Boilers' list within the PCDB for that device.

Again however, adding this small gain to points from other areas of improvement could take you over a threshold from one EPC band to another.

In my house, I have an Alpha Intec2 28X boiler. I purchased an un-used Alpha Weather Compensation Sensor on eBay for £30 and a second hand Alpha Climatic Controller on Gumtree for £65. Both were available in the PCDB, and I had these fitted by a plumber.

It would appear that selecting either of these in the assessment (for a similar Alpha boiler) would only increase the EPC rating for my property by 1 SAP point.

In my case however, I came across a problem (which I knew about before fitting these devices) and I have not been able to include them in the EPC assessment of my property. This is because the devices are not actually listed in the PCDB as being compatible with my specific boiler.

In reality they are actually compatible, it's just that a mistake has been made in the PCDB listing, either by Alpha or possibly the BRE. After many months, Alpha have still not sorted this issue out.

More information on my particular boiler and controls are available here: Case Study 2 and also here: Resolve PCDB Issues.

More information about choosing a suitable compensator controller is available on our Case Study 1 page where we look to improve the EPC rating on a property with a Worcester Bosch 30i ErP boiler.

Again, always obtain advice from a local Energy Assessor about what improvement in rating could be achieved by changing the heating controls in your property before spending any money. Their advice will enable you to make an informed decision.

Occasionally EPC methodology is updated to make assessments more accurate, and one such update occurred on the 7th June 2026 to RDSAP 10.0.01.

This has enablbed 'smart' thermostats to be recorded in new EPC assessments of existing dwellings.

More to come on this subject soon....

For heating controls on storage heaters, we'll cover this subject more on our page about High Heat Retention Storage Heaters.

Essentially, older models use Manual Charge Control, more modern models use Automatic Charge Control and the most recent High heat Retention Storage Heaters have additional efficiency measures built into them.

Before purchasing any heating controls, check with a qualified Domestic Energy Assessor what impact they are likely to have on your property's EPC rating.

The improvement achieved varies between properties and some controls must be recognised within the PCDB to receive full credit.

• Heating controls can improve a property's SAP score and EPC rating.
• The benefit achieved varies between properties
• Some advanced controls may require PCDB recognition to receive full credit
• Always seek advice before purchasing controls solely to improve an EPC rating

Click here to return to our 'Improve Your EPC' main page, and see if there is another way you could improve your EPC rating.