Underfloor Heating with Electric boiler & Stove

[Curtis]

Hi folks,

 

I'm at the point in my house design that i need to figure out heating and hot water options.

 

The plan is to insulate the house well and use triple glazed windows and the Mrs wants underfloor heating so i need to work out what else i can tie into this system to help keep electricity costs down.

 

I plan to have a solar array and a battery bank (not sure size yet), i'm not keen on air source heat pumps so i thought i would try and tie in my wood burning stove to help generate hot water which is sent to my hot water boiler which can service my normal hot water and also my underfloor heating.  If the fire is not on then the boiler will be heated by electricity where some of this will come from my solar via my batteries (if the sun has made an appearance that day).  

 

Is this system even possible or is this a completely sxxt plan?

 

Any recommendations for systems / models of boiler, underfloor heating and stoves would be appreciated.

 

Cheers

[Mr Punter]

The stove will pollute massively.  Do you have a free source of timber?

 

https://www.bbc.co.uk/news/business-59546278

[Curtis]

5 minutes ago, Mr Punter said:

The stove will pollute massively.  Do you have a free source of timber?

 

https://www.bbc.co.uk/news/business-59546278

 

Yea i have a few acres with some trees although not a massive supply but my plot is next to a large forrest so i'll be "acquiring" wood at every opportunity!

[ProDave]

This system works best with a stove heating a large thermal store which will supply hot water and run the under floor heating.

 

With the solar PV, install a diverter to send excess PV to an immersion heater.  Unless you have a LOT of PV you will probably find batteries unnecessary.

[Roundtuit]

Why not ashp?  Tried and tested technology;  all you need to do is build airtight and insulate well.  I'm sure a wood burner can be linked to a thermal store, but I'm not convinced the extra messing about is worth the effort.

Edited January 11, 2022 by Roundtuit
typo

[Curtis]

2 minutes ago, ProDave said:

This system works best with a stove heating a large thermal store which will supply hot water and run the under floor heating.

 

With the solar PV, install a diverter to send excess PV to an immersion heater.  Unless you have a LOT of PV you will probably find batteries unnecessary.

 

Do you mean two different systems?  Stove to a thermal store tank for the underfloor heating and then diverted PV to an immersion heater tank for hot water?

 

2 minutes ago, Roundtuit said:

Why not ashp?  Tried and tested technology;  all you need to do is build airtight and insulate well.  I'm sure a wood burner can be linked to a thermal store, but I'm not convinced the extra messing about is worth the effort.

 

One of my pals has one and they do not like it, they've said their electricity usuage has shot up because the unit goes into frost protection mode to stop the unit freezing because we can get harsh winters up here (NE Scotland) .  Not sure if his set-up / installation is not good or if this is a true representation of ASHP's.

[ProDave]

1 minute ago, Curtis said:

 

Do you mean two different systems?  Stove to a thermal store tank for the underfloor heating and then diverted PV to an immersion heater tank for hot water?

No 1 big thermal store that provides both the heating and hot water, and that same tank can be topped up using an immersion heater and surplus solar PV.

 

You need something like this because a stove generates a lot of power and is "unctontrolable" so needs plenty of capacity to absorb it's heat output.  Being a large tank means the stove only needs lighting perhaps once a day or even less.

[billt]

In our previous house we had a gasifying log boiler with a large thermal store and lots of solar thermal collectors. If run hot with dry wood, as it should be, it doesn't create much pollution and presumably you don't have near neighbors to annoy. (Unlike all the houses near us who all have gas ch but still burn wet wood and coal and create lots of pollution.)

 

However in a new well insulated house (as it should be if it's a new build) it's a bad idea. It will be expensive to install, messy to run and stands a good chance of over heating the house.

 

Solar thermal and PV are useless for heat in the winter especially in the north.

 

ASHP is a much better option if you can get it designed  and configured correctly. I wouldn't take a sample of one as a guide. Various contributors here have ASHPs which apparently work well, but the system must be properly designed.

[ProDave]

4 minutes ago, Curtis said:

One of my pals has one and they do not like it, they've said their electricity usuage has shot up because the unit goes into frost protection mode to stop the unit freezing because we can get harsh winters up here (NE Scotland) .  Not sure if his set-up / installation is not good or if this is a true representation of ASHP's.

We are just north of Inverness in a frost pocket (when the news says frost in sheltered glens, that is us) and the ASHP has no problem.  Once it gets below 0 there is little moisture in the air to cause it to frost up, and it regularly works at -10.  the worst temperature fro frosting is just above 0 when it's damp and lots of moisture in the air.

[Curtis]

2 minutes ago, billt said:

In our previous house we had a gasifying log boiler with a large thermal store and lots of solar thermal collectors. If run hot with dry wood, as it should be, it doesn't create much pollution and presumably you don't have near neighbors to annoy. (Unlike all the houses near us who all have gas ch but still burn wet wood and coal and create lots of pollution.)

 

However in a new well insulated house (as it should be if it's a new build) it's a bad idea. It will be expensive to install, messy to run and stands a good chance of over heating the house.

 

Solar thermal and PV are useless for heat in the winter especially in the north.

 

ASHP is a much better option if you can get it designed  and configured correctly. I wouldn't take a sample of one as a guide. Various contributors here have ASHPs which apparently work well, but the system must be properly designed.

 

 

1 minute ago, ProDave said:

We are just north of Inverness in a frost pocket (when the news says frost in sheltered glens, that is us) and the ASHP has no problem.  Once it gets below 0 there is little moisture in the air to cause it to frost up, and it regularly works at -10.  the worst temperature fro frosting is just above 0 when it's damp and lots of moisture in the air.

 

That's 3 people on this thread saying ASHP is a good option so i will definately take a look at this.  

 

I grew up with a coal fire on every day and so i know i will use my woodstove a lot so i wanted to try and utilise the heat to generater hot water as well but only if the set-up of this isn't too complex / expensive.

 

@ProDave  you are literally only an hour or two away from me and so the weather won't be all that dfferent, what systems do you have in place for heating and hot water?

 

[ProDave]

31 minutes ago, Curtis said:

 

@ProDave  you are literally only an hour or two away from me and so the weather won't be all that dfferent, what systems do you have in place for heating and hot water?

5kW monoblock ASHP driving wet under floor heating and a 300 litre unvented hot water tank.  3 bedroom 150 square metre 1 1/2 storey house.

 

Well insulated and air tight to near passive house levels, calculated (and borne out with actual figures) worst case heat loss about 2.5kW

 

I do have a room sealed wood burning stove as well. It will heat the whole house, or rather it MUST heat the whole house, shut the doors so the heat is confined to 1 room and that will very quickly overheat, it only works because the house layout allows the heat to travel to all rooms.  It supliments the heating to use up free wood and reduce electricity usage, and as a backup in case of power cuts. And for those grey wet days when 20 degrees feels "cold" when it is dreary so we use it to crank things up a bit.

[Curtis]

9 minutes ago, ProDave said:

5kW monoblock ASHP driving wet under floor heating and a 300 litre unvented hot water tank.  3 bedroom 150 square metre 1 1/2 storey house.

 

Well insulated and air tight to near passive house levels, calculated (and borne out with actual figures) worst case heat loss about 2.5kW

 

I do have a room sealed wood burning stove as well. It will heat the whole house, or rather it MUST heat the whole house, shut the doors so the heat is confined to 1 room and that will very quickly overheat, it only works because the house layout allows the heat to travel to all rooms.  It supliments the heating to use up free wood and reduce electricity usage, and as a backup in case of power cuts. And for those grey wet days when 20 degrees feels "cold" when it is dreary so we use it to crank things up a bit.

 

Are you happy with the systems? Anything you would change?

 

What make and models did you use?  I appreciate that all houses are designed differently but this would be very helpful as a starting point for my research into what solutions i should use.

 

Thanks for all the info much appreciated