Heat Loss Calculations! Where To Start please?

[milgo123]

Having a ground floor extension built to create an open plan kitchen dinner. In passing conversation with the builder he said that his plumber would want to replace my current 7 year old Glowworm 15r heat only boiler! Have not had any conversation yet as to why he feels this would be necessary.

During the build, 2 radiators will be removed and replaced with wet UFH in the rooms.

I'd like to hope that the plumber could provide good reason for his suggested boiler change but just so that I am in a position to challenge him could anyone recommend a resource where I could do my own calculations for the boiler size required?

Thanks

 

[muggles]

www.heat-engineer.com
Go for the £12 full survey. It'll take you a couple of hours but well worth it. I see no reason to replace a 7 year old boiler though

 

[milgo123]

Thanks muggles, I will take a look. I recall seeing that link mentioned before in an earlier post but couldn't recall it.

 

[dilalio]

Is the boiler to be moved during the works?

 

[milgo123]

@dilalio yes the boiler will have to be moved to a different location during the works

 

[ScottishGasMan]

With modern building regs, a well built extension added onto an old external wall can actually reduce the overall heatloss from a property. And unless your house is already very big then that boiler would likely be fine. Worst case if they don't have supporting calculations, which they wont as they never do, Then Id move the boiler to where it needs to go, run it as normal, and if in the very depths of winter it doesnt keep the place as hot as you want, look to swap it for a slightly bigger model.

Its a difficult one to put figures on due to the wide variaton in uk house types, but its thought that the average UK home needs between 6-8kw, just for perspective you have a 15kw.

 

[dilalio]

Boiler will need a new flue if being moved. There's also a risk current boiler will not like being moved... It happens.

 

[milgo123]

@ScottishGasMan this was actually my thinking also, so glad to hear that that it's not a stupid idea from someone with your experience ... Stick with the same boiler which could always be upgrade if it fails to provide enough heat. Thus far it has been more than adequate at heating the house (Victorian mid-terrace)and as you rightly state the new part of the house will be better insulated than the existing

The new position will be be on external wall as it now. Is it a guarantee that a new flue will be required?! Apologies if that is a silly question.

 

[ScottishGasMan]

New flue would be highly recommended, if the old ones sealed in well then it could easily be damaged on removing, and new wall may be thicker than old with the additional insulation.

Can't think of anything in black and white that says it MUST be, but I would certainly be looking to replace it if moving the boiler. Terminal sections probably <£100 so overall not worth any chances IMO