Greenfield central heating: Zoning decision to make - your opinions?

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New Member
Dec 11, 2023
Belgrade, Serbia
Hello friends,

I hope this is the right forum to post this question, I am new here. I'd really appreciate your input, since it's the first time having to decide on a central heating system.


I recently bought a house in the countryside, and it currently has no central heating system. Due to my geographic location (Serbia, Central Europe, which basically only has coal deposits), I'd like to stick to wood logs. It's abundant, it's local, and no geopolitics. Petroleum and gas are imported, coal stinks, pellets are low-quality here and electricity is too expensive.

With a 1200m2 plot, I have some space to spare to season my firewood, so I was planning on a pyrolythic boiler with appropriate accumulation (more on that later).

I've made a small sketch because I must come to a decision how I'd like to zone the house:

The house was built by two brothers, who split it through the middle. The house itself has about 250m2 of effective living space to warm (blocks 1-4), so probably I'll settle for a ~35kW system. G1 and G2 are two garages. I intend to use G1 as the "boiler room" and run a smokestack along the left side of the house.

Planning is as follows: 1 - living room, 2 - sleeping quarters, 3 - kitchen, dining, etc., 4 - guest quarter.

So, 1 & 3 will be used during daytime, 2 at nighttime, and 4 sporadically.


1) We plan on creating a passage between the 1 & 2 areas. The house as a whole has External Wall Insulation, added on at a later point, but because it was built left and right side relatively independently from one other, the right-hand side of the house has a bit better insulation (an additional layer of wood panel + mineral wool indoors). This makes as far as heating is concerned the left- and right-hand side of the house distinct.

So, one would think to do two zones and split along the center line. But on the other hand, the use of 2 & 4 will be markedly different, making me think whether it's better to zone 1+2+3 together and 4 separate.

Thus, I see two zoning scenarios: (I) where zone A is 1+2+3 and zone B is 4, and scenario (II) where zone A is 1+3 and zone B is 2+4.

(I) 4 is isolated from the rest of the household.
(II) Zoning takes into account difference in isolation + can turn off zone A in its entirety at night.

(I) Not easy to turn off heating in 1+3 at night due to having to keep heating on in 2.
(II) Difficulties to handle the impact of having or not having a guest at 4 on 2. Where to put the thermostat? Say, we want to keep 2 at 18C. If there's no guest, you don't have to heat 4, so you want to have the thermostat in 2. If there is a guest, maybe it's granny who needs 26C, but I don't want to sleep in 26C. In that case, the thermostat must be in 4, and we should somehow turn down the radiators in 2...?

Which one would you choose and why?

Of course, I can choose 3 zones: 1+3, 2 and 4. But that takes again more investment (zoning is installed in pairs)...

2) I understand that compared to a traditional log furnace, a pyrolythic system comes at higher up-front investment, increased maintenance, and increased requirements on firewood quality. Since I have no prior experience and aside from those factors: If the wood is seasoned right, can I indeed expect a halving of the amount of firewood I'd use compared to a traditional boiler?
I'm reading around the Internet that with a traditional boiler you expect 35-40% efficiency, whereas with a pyrolythic boiler, you expect 85%.

Sorry for the lengthy post. I'd be happy to hear your thoughts!

Kind regards,
I have a boiler with storage and cast iron radiators with TRV's to control the temps.
I have no zones, temperature is set with the TRV's and it stays there.If a room isn't used you turn the TRV to zero
TRV's are not powered so if you lose power they will still function and all you need is power to the circ pump to continue heating your home which is nice at -40C when the power goes down.
My bedroom is in the top floor and all interior walls and floors are insulated so you can truly maintain various temperatures in all parts of the house.
I prefer a very cold room to sleep in, my bedroom is always cold even though it's the highest room in the house.
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Hi @salecker, thanks for your feedback! Yes I can see how that's a useful and simple approach. However, I'd have many TRVs to regulate. When you go to sleep at night, do you manually turn down all TRVs throughout the house (except for those in your bedroom which can be kept at a constant setting)?
Also, what's controlling your circulation pump in case of heat demand? Or is it simply running continuously, even if no TRV is below its threshold?

No i never touch the TRV's once winter has set in
I leave my upstairs bedroom door open during the day which brings the temp up for getting into bed, my Girlfriend isn't a fan of going to bed in the cold.When i go to bed i close the door and the room cools off overnight.
I have one TRV in the upstairs bathroom, one on the upstairs bedroom, one on the mail floor of the house that controls 8 ft of cast iron rad. Those rads provide 75% of the heat for the mail floor. Then there is one for the bedroom/bathroom on the main floor.
The basement is one area at the moment.
Nothing in a TRV to go bad. Zone valves do fail, but not often
Thanks for your clarification. Can I ask what causes your upstairs bedroom to cool down at night? You wrote you have accumulation, and you don't touch TRVs. Is your accumulation simply losing capacity overnight?
All the walls and floors are insulated inside the house
I did that to be able to have a cold room to sleep in. Seeing the main bedroom was upstairs i hoped that insulation would allow me to control the heat.
The insulation also deadens the sounds
I didn't have any way to find the btu outputs of the cast iron rads, so i took wild ass guess's as to how many i need.
So far even in a prolonged -40C or colder stretch of weather everything still performed great. Even the temps for my bedroom stayed the same.
The 8 ft of cast iron rads really pump out the heat at those temps,my house is open design with a super high valeted ceiling that is open for over half of the house.
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