How much is saved turning off rads?

TheDocker

We have a mid terrace house 120 years old with GCH using a combi boiler. There are 10 rads and presently, I’m home during the day (with the dog). 

One of us (not me) has a preference for keeping internal doors open so all rooms are aired and heated regardless of the fact I can only be in one of 2/3 rooms during the day. 

I want to know if it’s possible to quantify how much it costs to heat each radiator, or what difference it could make to running costs if radiators are turned off (and doors closed, obvs).  I’ve read several posts suggesting the main room thermostat should she set on high and use the rad valves to control temperature of each room. I can’t see how that works, as the boiler is still ‘on’ regardless of how many rads are off. 

Is there any literature about this? 

Cheers.

Verdigris

The problem with not heating some rooms is that there will be a condensation risk in the cold rooms, unless the building is very well insulated.

A better strategy would be to have the TRVs in the little used rooms set low and to adjust the flow temperature on the boiler to a level that gives a return temperature of 54 degrees, or lower, to fully utilise the condensing effect of the boiler, and get the most heat out of your gas.

There will probably be one "always open" radiator in the system, quite often in a hallway, or where the main thermostat is located, that you should not fiddle with.

Ultrasonic

The only way to really get a good handle on the real difference for you is to experiment.

I generally keep internal doors closed in winter and use TRVs to heat the rooms I really care about warm but other areas are cooler.

markin

Someone else who tried it said they use 17kw per hr with just 2 rads and pipe work losses, i think most rads are around 2kw, But unless the doors are all insulated and sealed you will be letting in wet warm air that will then condense on cold walls and windows.

Petriix

You will definitely save some money, but it's very hard to quantify as it will vary massively depending on how much heat leaks into the rest of the house. For the past couple of winters I've often heated the living room with a wood burner and closed off the reset of the house, turning the main thermostat down to keep the heating off. Burning scavenged wood is definitely cheaper than gas. 

BUFF

TheDocker said:

 I’ve read several posts suggesting the main room thermostat should she set on high and use the rad valves to control temperature of each room. I can’t see how that works, as the boiler is still ‘on’ regardless of how many rads are off. 

.

This is wrong. Your roomstat (assuming in your mainly used room) should be set to the room temp. required. If you have a TRV in the same room as your roomstat that should be set to max to avoid the roomstat & TRV fighting for control. The roomstat can completely switch off the boiler when it reaches required temp. thereby saving energy, a  conventional TRV can't. (just closing rads down with the roomstat set to max would save some energy but not as much as totally shutting the system down when not required but you may overheat your main room unless you also have a TRV in there)

It gets a bit trickier if your roomstat isn't in the mainly used room as your spaces may not heat equally & the roomstat needs to be set at a temp in it's space that allows for the system to run long enough to bring your main room up to the required temp. there but not  too long. You will get to know how your house/system reacts though & learn what temp you need to set to get the required temp elsewhere.

On an old house though I would suggest turning TRVs in unused rooms down to.e.g. 1-2 (generally 10C-15C) rather than off or frost as this is less likely to potentially cause issues with interstitial condensation.