New boiler sizing advice

Londonjoe

It's an old 1930's semi detached.

It was extensively extended in 2008, with the equivalent of another house being put on the side (double strorey, side and rear extension).

The old part of the house hasn't got cavity wall insulation as I believe it is solid wall, where as I would assume the next extension probably has.

The old front of the house has old single glazing, which probably doesn't help matters and there seems to be some crawl space between the bottom of the original house (hallway) and the floor (feel's draughty in the hallway, from the floor).

I do use the heating on the weekend for a few more hours and you're right that the boiler seems to be working at full tilt as it never slows down or switches itself off.

C_Mababejive

I think in your situation, construction and insulation issues are definitely the points to address. Until you can look into that and afford it, i think you need to create winter warm spaces and effectively abandon the rest of the house so make sure living room is comfortable and put an electric blanket on bed . Turn heating off or down to save money as you seem to be effectively spending money to keep the pigeons warm.

saveallmymoney

Draughty suspended floor, solid walls, single glazing - definitely sounding like an insulation problem to me.

Put TRV's on every rad not in the room with the thermostat, and get a decent thermostat as that will help a bit.

topicalcat

Certainly looks like you can save money by insulating. Start of by insulating underneath that suspended timber floor. The best pay and quickest payback probably.

But do make sure there are adequate air bricks to maintain ventilation otherwise you will end up with rotten joists and damp. If they are covered with soil or blocked then clear them. This is very important, particularly with houses of this age which depend on that underfloor ventilation to prevent damp. This could be a DIY job and quite cheap to do. You can staple or wedge insulation between the joists from underneath. From the room side You can add an insulation foil backed layer under the carpet underlay as well, this will act as a vapour barrier and reflect heat back into the room. Commonly sold to be used with wood strip flooring systems.

All a lot cheaper than double glazing which would be nice to do for the future but has a much longer pay back period and of course causes more disruption with redecorating etc.