Separate heating system in extension - acceptable?

[smp50]

I'm considering an extension on the side of my two-bedroom end-of-terrace house. The current heating system is a Baxi Bermuda backboiler serving five radiators (two upstairs, three down).

I had an opportunity to replace it with a modern boiler but my best quote of £2400 meant that it made no financial sense when I considered how little I paid for gas already, and what % saving I might achieve with a new boiler.

The extension would add three or four rooms and I'm not sure plugging them in to the existing heating system would be sensible, as it may not be able to serve it very well. Also, there's no obvious way to plumb through to where the extension would be, as all the radiators and other stuff are on the opposite side of the house, if that makes sense. There'd be a fair bit of new pipework involved and I'm not sure where the best place would be to hook it up.

The extension will include a utility room which will then house the gas meter (currently on the outside side wall of the house, so there is certainly gas available. No water nearby, but this could be brought through somehow.

My idea is that it may be better to have a new and separate heating system in the extension, with its own boiler, installed as the extension goes up. What do you think of this - does it make any sense?

The alternative is to indeed put a new boiler in the extension area, but then hook that up to the rest of the house as well.


1) Try to run the extension on existing boiler.
2) Have a separate boiler system, keep old one in old part of house.
3) Install a new boiler system for both.


Any thoughts?

Thanks,

 

[stem]

Your old boiler will be inefficient compared to newer condensing models. As you will probably need a new boiler for the extension anyway, a larger one to cover the total duty won't be that much more expensive and therefore you will recoup the cost of the difference more quickly. In addition you can feel happy that you will be helping the environment, and you will also only need to pay for one boiler serviced every year. So personally I would go for option 3.

 

[muggles]

You need a heating engineer to advise you of how much spare capacity you have with your existing boiler before you can make an informed decision on this

 

[Agile]

Almost certainly your existing boiler has adequate output to cover a new extension.

That quote is way too high for a heat only boiler to replace the back boiler. Should be about £1600.

I suspect that it is for a conversion to a combi which you don't need or would be advised unless its a small flat with two or less living there.

Tony.

 

[Elkato531]

Hang on Tony, without seeing the job you can't say the price is too high. It will certainly need re-siting so there's new pipework to be run and could involve conversion from semi gravity to fully pumped. Could easily get to 2.4K if not more.

 

[muggles]

Tony likes to make sweeping statements without seeing the job, it's one of his things, you learn to ignore it eventually....

 

[smp50]

Thanks for the replies, guys. Should I get the plans for the shell of the extension sorted out yet or devise them in conjunction with a plumber, so that I can sure it all fits together properly? I guess he'd have to go in and do stuff before the floors went down, anyway.

Your old boiler will be inefficient compared to newer condensing models. As you will probably need a new boiler for the extension anyway, a larger one to cover the total duty won't be that much more expensive and therefore you will recoup the cost of the difference more quickly.

I'd have to do some sums, I suppose. My gas bills are very low already (£2/month when I'm living alone!) and I would essentially never recoup savings made with a more efficient boiler.

In addition you can feel happy that you will be helping the environment, and you will also only need to pay for one boiler serviced every year. So personally I would go for option 3.

As an aside, I suspect the environmental cost of retiring and removing a working boiler, then manufacturing a brand new one and installing it, hugely outweighs the cost of continuing to run the old one at lower gas efficiency. It's like knocking down an old house to build a new one with better insulation - kind of defeats the object.

Hang on Tony, without seeing the job you can't say the price is too high. It will certainly need re-siting so there's new pipework to be run and could involve conversion from semi gravity to fully pumped. Could easily get to 2.4K if not more.

That was with me doing all the water and electric up to where he needed it, too. Pricey job, but I did have two quotes around the same mark :/

Almost certainly your existing boiler has adequate output to cover a new extension.

You need a heating engineer to advise you of how much spare capacity you have with your existing boiler before you can make an informed decision on this

Fair, I'll have to get someone in. I doubt they have much vested interest in saying I should keep the old one, though, right?

 

[ScottishGasMan]

I would suggest that even if you do split the systems and only fit a boiler to cover the extension, that you make it a big enough boiler to deal with the full house. then when your back boiler does pack in you can tie it into the current system, even if it means keeping the main house open vented and still using the cylinder for hotwater, there are ways to achieve all this.

However personally, i would just make the new boiler do the lot from the word go. if you gas bill on a BBU is £2/month either you never use it for anything other than the little pilot light, or somethings not quite right with your setup/meter.

also, have you looked into moving the meter into the extension? or are you assuming you can build the extension around the current gas meter? as Im pretty sure you cant, and to move a gas meter can become quite pricey on its own.

 

[Razor900]

My gas bills are very low already (£2/month when I'm living alone!)

I'd expect the pilot to use more than that even if it never fired !!

 

[smp50]

I'd expect the pilot to use more than that even if it never fired !!

Naturally, I turn the pilot light off if I'm not going to use the boiler for weeks/months on end. Hell, I lived here from January '13 to November '14 with a completely drained system, haha.

I worked out that my pilot light costs around £90/year....

also, have you looked into moving the meter into the extension? or are you assuming you can build the extension around the current gas meter? as Im pretty sure you cant, and to move a gas meter can become quite pricey on its own.

Yea, I'm aware of this issue but haven't looked into it properly yet. The meter is on the outside of the side of the house and the extension would cover it up, indeed. I know lots of houses with gas meters on internal walls in the garage etc., though - I guess it was allowed at one time?

 

[ScottishGasMan]

At one time yes, but to go backwards and make it so an outside meter is now inside I don't think is allowed

If you really don't use the heating that much then it might be worth just hooking the extension onto the bbu, even the baxi 401 can supply 12kw, which in theory might be enough to cope with the extension given it will need to meet fairly tough insulation regs, you need to know what boiler you currently have and then work out what the new extension would require, getting pipes to it shouldn't be too much trouble considering the upheaval of a extension anyway.

 

[Agile]

It was and still is allowed.

But building around an existing external meter is NOT allowed. It will need to be relocated and that can cost up to £1000.

You can calculate the heat loss of your existing house using formulae available on the wen or in the FAQ on this site.

The new extension being built to current insulation standards will have very little additional heat requirements but for the sake of calculation you could add say 60W per square metre.

Tony

 

[smp50]

At one time yes, but to go backwards and make it so an outside meter is now inside I don't think is allowed

If you really don't use the heating that much then it might be worth just hooking the extension onto the bbu, even the baxi 401 can supply 12kw, which in theory might be enough to cope with the extension given it will need to meet fairly tough insulation regs, you need to know what boiler you currently have and then work out what the new extension would require, getting pipes to it shouldn't be too much trouble considering the upheaval of a extension anyway.

I plan to 1) let the new bedrooms, probably to normal modern humans who use hot water, and 2) sell the house one day, so I should probably just hold my nose and make it all 'horrible and modern.

Something just came to mind - say I had the gas meter moved so that it was on the outside of the new outside wall... could they even do that before the wall was built? By which time it will be too late to dig up the old pipes and move the meter, right? Or can they put the meter up attached to some temporary structure and then fix it to the wall once it's built? It will be right in the way of the builders, I would imagine.

 

[Agile]

They will probably want to move the meter to an existing outside wall and then move it again to the final position. That's to cost you more!

They are not very well organised or helpful either as I am discovering at home. ( No gas connection for three weeks? )

Tony

 

[smp50]

They will probably want to move the meter to an existing outside wall and then move it again to the final position. That's to cost you more!

They are not very well organised or helpful either as I am discovering at home. ( No gas connection for three weeks? )

Tony

Does the entire "live" pipe run need to be external, i.e. no part of it passing under walls or rooms? I could stick it round the back of the house next to the electricity meter, but then the pipes would be under the new extension still, even if the meter wasn't in it.