House renovation: comments needed on new heating, thermal stores, boilers etc.

llatsni

Hi all,

I'm finally at the point where we're about to start renovating and extending the house! I've been trying to get my head around thermal-store / heat-bank systems and while I'm fairly sure they are better than un-vented or traditional-vented solutions for our needs, I do have some questions.

- Ground floor: ~70m2 (rads, shower room, utility room)
- First floor: ~40m2 (rads, bathroom)
- New extension: ~34m2 (kitchen, underfloor probably)

I'd like to use a Gas boiler as the main heat source, and a wood burning stove as a supplement, but have the option of solar in the future. I definitely want control over the three areas listed above separately, and I would like high (mains?) pressure hot water throughout the house.
The most logical place for the "plant room" is in the ground floor utility.
I've used a popular heat bank system designer and it's given me some ideas of what's needed, but the prices seem a bit crazy.

Questions:
- Has anyone here got a setup for a similar home?
- Will a stove at the same level as the store be problematic?
- Is there any way of making UFH work with wooden flooring, or should I just suck it up and go tiles?
- Anyone found cheaper stores / systems than that popular system designer site?

All comments and questions welcome.
Paul

oikster

If you can make a decision as to exactly what you are going to do with regards to your system layout some cylinder manufacturers offer a bespoke service which often turns out quite a bit cheaper. If you can design a store using the designer there is no reason you cant do it in reality. A word of warning on heat banks and thermal stores with regards to stratification,very important but has to be taken into consideration at design stage. The plug and play units you are looking at include a lot of kit and this is reflected in the price.

llatsni

Thanks Oikster, I'll definitely talk to some of the suppliers about bespoke systems.

I did talk to an installer this evening who mentioned something that's thrown me a bit: he said thermal stores are the only thing to go for for mixed heat sources where gas is NOT the primary. Where gas is the primary or the sole source, unvented is the best.

Anyone any thoughts on that? Is that correct advice?

oikster

I can understand where gas or oil are the sole sources that this is the case. But a heat bank is designed to distribute whatever heat is thrown at it. It is also designed to control and prioritise heat sources. So literally any heat source can be used effectively.

Outkast_IRE

llatsni wrote: »

Thanks Oikster, I'll definitely talk to some of the suppliers about bespoke systems.

I did talk to an installer this evening who mentioned something that's thrown me a bit: he said thermal stores are the only thing to go for for mixed heat sources where gas is NOT the primary. Where gas is the primary or the sole source, unvented is the best.

Anyone any thoughts on that? Is that correct advice?

I would word it differently................
A thermal store is techincally always the best option as it allows an oil/gas boiler to run at 100% load until the thermal store is satisfied no on/off cycle as such, this will lead to an increase in efficency in itself.

However if gas/oil is intended to be your main heat source then the investment in a buffer/accumulator would be hard to justify as the gain in efficiencies would take a long time to pay back.

The game changes entirely though when you start looking at multiple heat sources, where multiple heat sources are concerned then the accumulator/buffer tank is the best option. And i will give you a typical example build at the moment.

The Homeowner wants
1. A stove.
2. Solar Panels.
3. Oil or gas or wood pellet burner ( anything else really )

If someone wants a boiler stove chances are they light it regularily, you connect it to a gravity coil on the buffer anytime you light the stove it contributes to heating the buffer.

You put a bank of solar tubes on the roof, any glimmer of sunshine and these contribute to the buffer.

Finally you set your oil/gas/whatever heat source to run in the evening and heat the buffer if the other two havent already done that, this leads to a decreased run time on the oil/gas and it will run at maximum efficiency when it is running.

oikster

But Outkast there is a vast difference between a buffer and a heat bank.

Outkast_IRE

oikster wrote: »

But Outkast there is a vast difference between a buffer and a heat bank.

His iniital question is about heat bank / thermal store ....... not sure the issue isnt a buffer/ accumulator tank a thermal store ?

llatsni

Outkast are you talking about an unvented system with a buffer?

Outkast_IRE

llatsni wrote: »

Outkast are you talking about an unvented system with a buffer?

the joy of the buffer is that the systems that connect off from it are your choice, you could have an unvented or vented hot water cylinder connected to it, but as usual if you plan on connecting a stove to the buffer the stove pipework etc must be an open system and i would probably install a secondry safety backup i dont work on stoves too often so someone else here could advise about heat leak radiators and other products designed with stove safety in mind.

This diagram is a decent example

http://www.rvr.ie/Get_Advice/?InfoPage=index.php%3ftitle%3dImage%3aBufferSchematic.jpg

llatsni

Ah, yes I get you now, but why do you think unvented + buffer is better than a thermal-store? Surely it's more complicated? What's the benefit?

Outkast_IRE

llatsni wrote: »

Ah, yes I get you now, but why do you think unvented + buffer is better than a thermal-store? Surely it's more complicated? What's the benefit?

If you can link to the thermal store you were looking at or an example it would be appreciated and i can draw a fair comparison then.

To be honest im not familiar with heat banks............. i am familiar with buffer/accumulator tanks which are a thermal store?

The entire point of the buffer/accumulator is to be a water based thermal store that can take multiple heat sources and allow heat sources to heat them at maximum efficiency

vertico

i have a saey blenheim 12kwish stove and oil fired boiler set up to a traditional heating system.the stove alone will only heat about six rads and thats with a good fire on.
can i change my regular hwc for a thermal store?
will the stove heat the thermal store easier?
possibility of fitting solar panels in the future?
oil when needed to boost thermal store?
any advice??

edanto

llatsni wrote: »

- Is there any way of making UFH work with wooden flooring, or should I just suck it up and go tiles?

Yes, absolutely. We just did a renovation and I didn't want to have tiles in the kitchen/living area, so we found a wooden floor setup that worked grand with underfloor.

You want to get engineered or laminate flooring (not solid - doesn't like the direct heat), and it's crucial that the underlay has minimal insulative properties.

We went with a very hard wearing laminate (graded for light commercial), and it's been working fine with the underfloor. Take the normal precautions with leaving expansion space at all edges, under skirting and kickboard.

During that very hot week recently, I had a little bit of it raise slightly just where it meets the tiles of the utility (hadn't left enough expansion space there, could see it pressed up tight against the tiles), but I cut a few mm off that last board and now it's sitting pretty. Delighted with it - and sure didn't want tiles in the living area.

etcetc

Outkast_IRE wrote: »

If you can link to the thermal store you were looking at or an example it would be appreciated and i can draw a fair comparison then.

To be honest im not familiar with heat banks............. i am familiar with buffer/accumulator tanks which are a thermal store?

The entire point of the buffer/accumulator is to be a water based thermal store that can take multiple heat sources and allow heat sources to heat them at maximum efficiency

Would like to see the link to the thermal store you are talking about also

llatsni

I debated, researched, debated, researched, ad infinitum on all of this and eventually I decided against the thermal store solution in favour of a more basic (but highly efficient) unvented system. The main reason being cost: a proper store system (in my opinion: gas + solid + solar + ???) was many, many times the initial outlay for a very minimal ongoing cost benefit (I do accept that this may change with rising gas prices). And from a practical point of view, running a solid-fuel burner often and long enough to make a dent was not realistic. The guy installing the unvented system really knows his stuff and it should do a good job of managing itself and keeping the bills low. I'll report back again when we get the first one!

Outkast_IRE

llatsni wrote: »

I debated, researched, debated, researched, ad infinitum on all of this and eventually I decided against the thermal store solution in favour of a more basic (but highly efficient) unvented system. The main reason being cost: a proper store system (in my opinion: gas + solid + solar + ???) was many, many times the initial outlay for a very minimal ongoing cost benefit (I do accept that this may change with rising gas prices). And from a practical point of view, running a solid-fuel burner often and long enough to make a dent was not realistic. The guy installing the unvented system really knows his stuff and it should do a good job of managing itself and keeping the bills low. I'll report back again when we get the first one!

Your quite right, its a big capital outlay, and as I said there are some specific scenarios where the buffer is the right way to go. I believe most heat pump companies are now recommending a buffer as it stops on-off cycling.

But for myself if you had the room for a good bank of solar tubes then I would like to see them hooked up to the buffer, could be designed if you wanted to heat hot water cylinder first then the buffer.