Heating Controls

At the time of writing, the methodology for EPC assessments of existing dwellings is RDSAP 9.94. This updates to RDSAP 10 on 15th June 2025 and a significant methodology overhaul from RDSAP to the Home Energy Model (HEM) is proposed for 2026. In addition, government consulations indicate future changes to the format of EPCs and minimum rating levels required for priate rental properties. Methods for improving EPC ratings may therefore change in the future.

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

• Standard Controls
• Time & Temperature Zone Controls
• PCDF Compensators

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:

• Thermostat
• Programmer
• Thermostatic Radiator Valves (TRVs)

With standard heating controls, ideally you want to have all three of these registered on your EPC assessment 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 thermostat is a device often fixed to the wall in a hallway on which you can adjust the target temperature you'd like the room to be heated to.

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, ususally with an indicator dial from 1 to 6 to set the desired room temperature. When the room reaches that temperature they automaticlaly 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:

In the examples shown above, the thermostat would be located in a hallway or maybe the lounge. The programmer would be fitted in the boiler itself, and the TRVs would be fitted to one end of each radiator.

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 not in habitable rooms.

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

Here is a list of standard heating controls that can be chosen in the system. The EPC rating displayed is that which my house achieves with each option chosen. Check out our Case Study 2 for more information of this property.

How the rating changes for your property will differ from this, so always check with an energy assessor to see what rating you will achieve before making any changes:

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.

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 EPC 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".

Additional direction is provided by Convention 4.19 that "Heating control from a mobile app can only be included where a fixed receiver is present and there is evidence of the type of controls (time, temperature, zone)"

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

TTZC is likely to involve 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 (in contrast, standard TRVs only offer independent temperature control).

If you have such controls fitted then this enables the selection of 'Time and temperature Zone Controls' in the EPC assessment.

The EPC rating is then likely to improve, compared to Standard Controls alone.

With my property, a 1950s mid terrace house, my rating would be 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 do contact a local Energy Assessor to review your property before making any changes.

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

Additionally, there is a separate list of specific devices which have been registered with the Building Research Establishment (BRE) as being recognised 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 devies 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.

At the time of writing the devices in the list on the PCDB include:

• Genius Hub, PH-HUB-D , ErP Class VIII
• Navien, Smart Plus , ErP Class VIII
• Bosch, EasyControl eTRV , ErP Class VIII
• ESi Controls, 2ZPCBOT , ErP Class VIII
• EPH Controls, CP4 , ErP Class VIII
• Honeywell Home, Evohome , ErP Class VIII
• Myson, Unisenza Plus Electronic Thermostatic Head , ErP Class IV
• Myson, Unisenza Plus Programmable Thermostat RF , ErP Class V
• Navien, Smart Plus , ErP Class VIII
• Drayton, Wiser TTZC , ErP Class VIII
• Radbot 1, SCV100 , ErP Class VIII
• Radbot, 2R , ErP Class VIII
• Ideal, Halo Air Wi-Fi 2-Zone , ErP Class VI
• Ideal, Halo Air RF 2-Zone , ErP Class VI
• Baxi, Baxi uSense 2 , ErP Class VI

Some of these 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 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 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 new 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, I am still trying to get Alpha to iron out this issue.

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.

For heating controls on storage heaters, we'll cover this in 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.

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