Sat, 18 Apr 2026 14:12:58 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=12958&Focus=216351#Comment_216351 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=12958&Focus=216351#Comment_216351 Mon, 05 Jan 2015 23:44:39 +0000 theloneboarder
I hope one of you smart chaps/ladies might be able to share an opinion.

I am currently building a 120sqm single story house. It's not going to be passive but it will be very well insulated.

We are having a UFH system throughout the whole house (stone floors except for bedrooms). We will be on mains gas and also have a woodburner stove in the living area.

Here is the question.... is it worth me having a thermal store and a stove with a back boiler ?

As we are on mains gas, I intend to have a combi boiler and as I see it, the options are either: combi & expansion vessel or combi, thermal store and back boiler.

Other points to consider are: the stove is to be a feature so I don't want to go down the industrial back boiler route, I cannot install solar panels, I have a free supply of logs.

Basically, I think that the combi/expansion would suffice but is it be worth the extra cost of getting the thermal store and back boiler so that I can make use of the free hot water created by the stove.

I don't like the idea of sitting in front of a fire and thinking "this could be heating my hot water for free" and I also don't want to pay £1-£2k extra on plumbing just to have a thermal store that will take me 10 years of burning logs to get it to pay for it's self. Assuming that I will be in the house for 5 years, will the back boiler save me the cost of heating the hot water through the wood burner vs the combi boiler ?

Any advice would be greatly appreciated.





]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=12958&Focus=216353#Comment_216353 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=12958&Focus=216353#Comment_216353 Tue, 06 Jan 2015 01:05:17 +0000 Peter_in_Hungary
Also if you are planning on selling the house in 5 years then there is a lot to be said for a standard heating system that all understand, the combie boiler doing CH and DHW with the feature wood stove in the lounge sounds great. The general public get frightened by what is seen as complicated heating systems.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=12958&Focus=216357#Comment_216357 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=12958&Focus=216357#Comment_216357 Tue, 06 Jan 2015 08:26:37 +0000 DarylP
If you have the wood for free, and the space to store/season it, then by all means invest in the hardware to utilise it as a major fuel source...
But, if not, forget it!
Use mains gas as your fuel source, and perhaps the WBS as a 'feature'.
The extra/over to purchase/install the plumbing for a back-boiler/TS will buy you a lot of mains gas kWhs....

Good luck]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=12958&Focus=216359#Comment_216359 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=12958&Focus=216359#Comment_216359 Tue, 06 Jan 2015 08:37:04 +0000 Beau ]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=12958&Focus=216370#Comment_216370 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=12958&Focus=216370#Comment_216370 Tue, 06 Jan 2015 13:21:59 +0000 theloneboarder I was hoping that the simple option was the best and it seems like you agree. I guess that if the back boiler was installed then I would feel that I had to use it to, even if I didn't necessarily want the WBS on.
Beau, I like the idea of a bit of extra piping around the WBS as I might as well make use of the heat that's coming from it. It may not make a huge difference but its only going to be a few pence for a bit of extra pipework so def worth it.

BTW, is it worth having the expansion vessel ? I was led to believe that it's a good idea to have one to prevent the boiler coming on every 2 minutes to warm the UFH. I was told that, as the vessel holds a decent amount of hot water, the UFH will take it from this and the boiler will only heat the vessel when it's temp drops (which should be less frequent than without it). Is this a long the right lines ?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=12958&Focus=216380#Comment_216380 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=12958&Focus=216380#Comment_216380 Tue, 06 Jan 2015 16:17:44 +0000 SteamyTea Posted By: theloneboarderBTW, is it worth having the expansion vesselI am not a plumber, but isn't that what a buffer tank does rather than an expansion tank. An expansion tank if really just that, it allows for thermal expansion of the fluid.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=12958&Focus=216390#Comment_216390 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=12958&Focus=216390#Comment_216390 Tue, 06 Jan 2015 18:08:36 +0000 Nick Parsons https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=12958&Focus=216395#Comment_216395 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=12958&Focus=216395#Comment_216395 Tue, 06 Jan 2015 18:35:08 +0000 CWatters https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=12958&Focus=216398#Comment_216398 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=12958&Focus=216398#Comment_216398 Tue, 06 Jan 2015 19:19:07 +0000 theloneboarder Are they worth while ?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=12958&Focus=216406#Comment_216406 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=12958&Focus=216406#Comment_216406 Tue, 06 Jan 2015 21:48:24 +0000 SteamyTea https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=12958&Focus=216415#Comment_216415 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=12958&Focus=216415#Comment_216415 Tue, 06 Jan 2015 22:55:38 +0000 ringi
However some combi boilers can have there max output for heating reduced, so making the system more stable.

--------------

I would expect that if a boiler would modulate down to 3kw (e.g. Vokera Linea 1) and you use a TPI based thermostat you may get away without a buffer tank. Or just put a control system that stops the boiler running for 1 minute out of every 20 minutes, while keeping the UFH pump running.]]>