I've lived in my brand new house for just over a year now. It is semi detached with 3 bedrooms (master with en-suite, 2nd similar size to master, 3rd small box room) and I am finding that my small bedroom and the en-suite to my main bedroom won't hold their temperature... I'm wondering if there is any advice I've not considered.

Having spoken to the developer about this back in the early part of this year, they suggested it was due to both rooms having 2 walls each exposed to the outside and sent a plumber round to "balance the radiators", which helped somewhat in the other rooms, but I'm still facing these 2 rooms being colder.

The small bedroom has a single, small radiator the width of the window - I believe that this should be enough given the size of the room, whereas the ensuite only has a half-height towel heater to provide the heating. Again the en-suite isn't a gigantic room so should be sufficient to keep it warm, however this room has an extractor that I'm unsure how well it is sealed while off.

Could there be something more at play here? Perhaps a lack of cavity wall insulation? Perhaps poorly sealed windows/sills?

I've had a bluetooth thermometer/hygrometer in each of the rooms for the last week to try and highlight the issue. I began with the doors to these rooms open to try and acclimatise them to the rest of the upstairs, and then closed the doors to show how the temperature drops off. For info, the monitors were places in the middle of the rooms.

FYI - The thermostat here was set to 18.5C

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Upstairs floor plan:

  • Green: Thermostat
  • Blue: Radiators
  • Red: Rooms in question

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  • 1
    If there is a thermostat on this level, it would be helpful to show where it is on the floor plan. You might also edit your original post to add info about radiators in the other rooms on this floor.
    – MTA
    Dec 10, 2022 at 21:09
  • Windows are usually the biggest heat lost areas, both cold rooms seem to have the smallest windows. New houses today should have very good insulation in the walls.
    – crip659
    Dec 10, 2022 at 21:29
  • get the $200 flir iphone/andorid attachment and take a look at the thermal pictures. narrow down the coldest areas. You'll be able to see the problem. well worth the money for the attachment. Dec 10, 2022 at 21:59
  • @MTA I have updated the image to show the upstairs thermostat and the radiators
    – physicsboy
    Dec 11, 2022 at 11:49
  • Bedrooms 1 & 2 are probably the warmest because they only have 1 wall exposed to the outside. Also, it's not unusual for a builder & his architect to design the house such that the master bedroom is the most comfortable as if this wasn't the case they would receive a lot more complaints.
    – SteveSh
    Dec 11, 2022 at 13:23

1 Answer 1


In a home with only one zone (thermostat) it's unfortunately common for parts of the house to differ in temps, mostly related to windows and outside walls.

Since you mentioned "radiators" I'm assuming hydronic heating. To keep the other rooms warmer, you'll have to reduce flow to the radiator(s) where the thermostat is located.

Hard to provide more advice w/o knowing more. Just keep working at it until you get the system balanced.

The only other thing I can think of is to create a multi zone system with thermostats in each zone, if even practical given your heating system layout. Even if possible, it would be a VERY EXPENSIVE fix. It would involve plumbing changes, wiring, new thermostats, installation. ...Again a very expensive fix. I would think you could work thru what you have now and by regulating flow, get at least close to balancing your current system.

  • 1
    Not an uncommon approach to use thermostatic valves that effectively make each radiator a zone with no huge system-wide changes.
    – Ecnerwal
    Dec 10, 2022 at 23:00
  • @Ecnerwal Agreed, but a retrofit can be very expensive. A multi zone heating system should have been installed in the first place. Maybe individual thermostatic valves could be installed less expensively , but again,not knowing more about the plumbing/piping makes it hard for us to give thorough advice. Dec 11, 2022 at 2:33
  • @GeorgeAnderson I have updated the diagram with radiators and showing the thermostat. I do have the standard thermostatic valves on all except for the main bedroom. I was advised by the plumber to keep the valves fully open and regulate the flow via the outlet valve instead...
    – physicsboy
    Dec 11, 2022 at 11:54

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