Energy myth-busting: Is it cheaper to have heating on all day?

Northern_Wanderer

richardc1983 said:

You have zones already, each room that has a TRV has a zone.

Think of your house as one big room but you have a number of rads to heat that big room. You shut off rooms you don't use but they are still part of the same house, even with doors closed heat will leach into them from the thin door, walls and floors which means the remaining rads are heating a larger space. 

Having less rads to heat means your boiler when modulating low is unlikely to be able to ramp down low enough to satisfy the few rads left on which means it cycles. When a boiler cycles you don't want this because you end up with unburnt gas in the chamber that is purged at the start and end of each cycle.

What do you run your boiler flow temp at? The idea is to get that down as low as possible but while being able to have all the other zones open so that the house is comfortable. My boiler uses opentherm which can mean the rads have water as low as 30c flowing through. 

I have it set on the eco setting, an Ideal Logic Combi. Not sure what temp that equates to but have been happy with that since I got the GCH as I cut my bills by more than half (back then) compared to THTC storage heaters and I am WARM now. Loft is well insulated to current standard at least, cavity wall insulation.

I do feel that the hall rad is a little small and the kitchen is a cool room due to large window, exterior door, old flue and two air bricks. Kitchen rad always on full so probably not powerful enough, don't really need it warmer but I think it drains the hallway heat.

I am about to install thick/ warm exterior door curtains. Not much I can do about heat loss in kitchen. Except, there is no door between it and hall. So I wondered if installing a door there would help reduce gas?

I only had one rad on frost protection, all other rooms comfortable upstairs. But are you saying that by turning some of the rads up that the house would be heated quicker and save gas as thermostat turns off boiler?

Ultrasonic

richardc1983 said:

I’ve mentioned above if you have a large room such as a lounge with two rads, would you turn off one half of the room as you only use half of it or would you have both turned on? The rest of your house is the same...

No, it's not the same, because it takes time for heat to move from one room to another. 

richardc1983

Northern_Wanderer said:

richardc1983 said:

You have zones already, each room that has a TRV has a zone.

Think of your house as one big room but you have a number of rads to heat that big room. You shut off rooms you don't use but they are still part of the same house, even with doors closed heat will leach into them from the thin door, walls and floors which means the remaining rads are heating a larger space. 

Having less rads to heat means your boiler when modulating low is unlikely to be able to ramp down low enough to satisfy the few rads left on which means it cycles. When a boiler cycles you don't want this because you end up with unburnt gas in the chamber that is purged at the start and end of each cycle.

What do you run your boiler flow temp at? The idea is to get that down as low as possible but while being able to have all the other zones open so that the house is comfortable. My boiler uses opentherm which can mean the rads have water as low as 30c flowing through. 

I have it set on the eco setting, an Ideal Logic Combi. Not sure what temp that equates to but have been happy with that since I got the GCH as I cut my bills by more than half (back then) compared to THTC storage heaters and I am WARM now. Loft is well insulated to current standard at least, cavity wall insulation.

I do feel that the hall rad is a little small and the kitchen is a cool room due to large window, exterior door, old flue and two air bricks. Kitchen rad always on full so probably not powerful enough, don't really need it warmer but I think it drains the hallway heat.

I am about to install thick/ warm exterior door curtains. Not much I can do about heat loss in kitchen. Except, there is no door between it and hall. So I wondered if installing a door there would help reduce gas?

I only had one rad on frost protection, all other rooms comfortable upstairs. But are you saying that by turning some of the rads up that the house would be heated quicker and save gas as thermostat turns off boiler?

Your house would probably warm quicker and would stay warmer as the other rads are not trying to heat the larger thermal mass that is unheated. Your other rads that are too small could you replace them for Type 22 double convector rads?

richardc1983

Not if internal doors are left open, e.g some people turn spare bedrooms down but leave internal doors open, this is the point he is making.

Ultrasonic

richardc1983 said:

Not if internal doors are left open, e.g some people turn spare bedrooms down but leave internal doors open, this is the point he is making.

Well yes, but there might just be a solution to that if you think about it... 🙄

richardc1983

Ultrasonic said:

richardc1983 said:

Not if internal doors are left open, e.g some people turn spare bedrooms down but leave internal doors open, this is the point he is making.

Well yes, but there might just be a solution to that if you think about it... 🙄

But that’s not how most people use their homes. If you use any of the rooms then heat them the same as the other rooms. I wouldn’t shut doors to rooms I don’t use due to risk of stale or damp build up. Keeping the air moving is key. 

Northern_Wanderer

I meant if I closed the kitchen door as it is poorly insulated. Not sure that I would install a door to leave it open.

The kitchen has a K2 double panel, it and hall could be upgraded I guess but have some other things to do in house for now. Maybe before next winter!

I could leave the living room door open and that may distribute heat more uniformly, unsure if that would save on gas. I'm glad I have two rads in living room and no storage heaters though. Can't imagine being able to pay for those now and still be cold.

kmcottrell

Interesting that all the toing and froing is only about radiators and not underfloor!

richardc1983

kmcottrell said:

Interesting that all the toing and froing is only about radiators and not underfloor!

Think it’s already accepted that underfloor heating is ran at a lower flow temp and for longer periods due to the response times. 

Ultrasonic

richardc1983 said:

Ultrasonic said:

richardc1983 said:

Not if internal doors are left open, e.g some people turn spare bedrooms down but leave internal doors open, this is the point he is making.

Well yes, but there might just be a solution to that if you think about it... 🙄

But that’s not how most people use their homes. If you use any of the rooms then heat them the same as the other rooms. I wouldn’t shut doors to rooms I don’t use due to risk of stale or damp build up. Keeping the air moving is key. 

People who choose to heat some rooms more than others to save money do though! You can't dismiss the logic because you'd apparently leave the doors open.

I'm in my lounge at the moment and the door is shut. I obviously open and close it many times per day to walk in and out so it's not like it's hermetically sealed and some sort of stale room as a result. Having the door shut does though help keep the room warmer for a lot longer than if I had it open the to cooler hallway beyond. 

Going back to my original point about time, there is a very important distinction to be made between simpler steady-state models that assume a fixed temperature in each room 24/7, and the real-world situation of just having rooms at higher temperatures at the times they need to be. For the latter, the time it takes heat to escape from a room matters. Even people who rarely leave their homes don't need rooms to be as warm at night.