- Home
- Doubles
How a Buffalo double is actually heated
Four arrangements, three kinds of occupant. The arrangement decides what is physically possible; who you are in the building decides who can change it. Pick both.
When one boiler serves both flats and the thermostat lives in one of them, that flat is deciding the temperature of the whole building — and it is usually the flat that is naturally warmest, because whoever fitted the thermostat put it where it was convenient rather than where it was representative. The other flat has no control at all and no way to explain why. Nothing is broken. It is simply a system with one brain and two households.
One boiler, one thermostat, whole house
The original arrangement in most of this housing stock, from when a double was one family’s house with grandparents upstairs. The boiler heats everything and one thermostat decides when.
What it means for comfort: the upstairs flat runs warmer than the downstairs one, always, because heat rises and the upper flat sits under a roof and over a heated space. The two flats will never be the same temperature and no adjustment changes that.
What it means for bills: one meter, one bill, and no way to measure who used what. Any split is an agreement rather than a measurement.
What can be changed: splitting it into two zones is frequently possible, and whether it is depends entirely on how the pipes were run — if each flat is fed by its own riser or loop, it is straightforward; if the pipework alternates between floors, it is not.
One boiler, two zones, a thermostat each
The best of the common arrangements. One appliance to maintain, one flue, one service visit — and each flat calls for heat independently through its own zone valve or circulator.
What it means for comfort: each household controls its own temperature. The upper flat still benefits from the heat rising through the floor, so it will call for less, but it is no longer at anybody else’s mercy.
What it means for bills: still one meter unless somebody has fitted separate metering, which is uncommon. The fuel is shared even though the control is not, and that surprises people.
What goes wrong: a zone valve that fails open makes one flat permanently hot; one that fails closed makes it permanently cold while the boiler and the other flat behave perfectly. Both are ordinary repairs and both get misdiagnosed as boiler faults.
Two separate systems, one per flat
Usually the result of a conversion done properly, or of a boiler replacement where somebody decided to split the building for good.
What it means for comfort and bills: complete independence. Each household controls its own heat and pays its own meter, and there is nothing to argue about.
What it costs: two appliances to maintain, two flues, two services a year, and two things to replace eventually. In a building where both flats are let, that is a real running cost against the simplicity.
What to watch: two appliances in one basement means two flues, and in a building that has been insulated and re-windowed since they went in, the combustion air for both is coming out of the same basement. That is worth checking once rather than assuming.
One boiler, thermostat in one flat
Technically the same as one thermostat for the whole house, but with a social problem attached: one household has the control and the other does not, and both of them know it.
What it means for comfort: the flat without the thermostat is either too hot or too cold depending on the habits of the flat with it, and has no way of doing anything about it except a phone call.
What can be changed, in order of cost:
- Move the thermostat to a hallway or a stair that is representative of the whole building rather than of one flat. Cheap, and it removes the worst of the unfairness without changing the plumbing.
- Balance the radiators so the naturally warm flat gets less and the cold one gets more. On steam that is vents and pitch; on hot water it is lockshield valves. Also cheap, and frequently overlooked.
- Split it into two zones, which is the real fix and depends on how the pipework was run.
You live in it and you own it
The simplest position: the decisions are yours, and you also live with the consequences, which tends to produce better decisions than either of the other two roles.
The thing worth knowing is that you are the one who will be told about it — a tenant in the other flat reports the problem to you, and you decide whether it is a fault or an arrangement. That is exactly what this page is for.
You own it and live elsewhere
You have the authority and none of the daily information. Everything you know about how the building behaves arrives second-hand from whoever is complaining, and the household that complains most is not always the one with the problem.
That is worth solving with a measurement rather than with a judgement. We will measure both flats on the same visit and put the figures in writing, which usually ends the conversation one way or the other.
You rent
The heating system, the boiler, the pipework and the thermostat are the building’s, not yours. That is true even where the problem is obvious and even where you would happily pay to fix it.
What helps is being specific: which flat, which rooms, what time of day, and whether the other flat has the same problem. That last answer is the single most useful thing you can find out, because it separates an arrangement from a fault in one sentence.
What to do next
- Find out how the pipework was actually run before pricing anything. It decides whether zoning is a day’s work or a rebuild, and it is a short visit to establish.
- Do the cheap things first. Moving a thermostat and balancing radiators cost a fraction of zoning and solve a surprising share of it.
- Get both flats measured on the same day. Temperatures in matching rooms, at the same time, with the system running. It turns an impression into a comparison.
- If you are replacing the boiler anyway, that is the moment zoning is cheapest, because the controls and the header are being touched regardless.
What to do next
- Commission a measurement, not an opinion. Both flats, same visit, matching rooms, figures in writing. It settles whether you have a fault or an arrangement.
- Establish what is metered. One meter or two changes every other conversation about the building, and a surprising number of owners are not certain.
- Ask what zoning would take before you are forced into it by a boiler failure in February.
- What your lease requires of you is a question for you and your attorney, not for us. We can tell you what the building is doing and what it would cost to change; we will not tell you what you owe.
What to do next
- Report it in writing, with dates. A phone call is not a record. Which rooms, what time of day, and how long it has been happening.
- Find out whether the other flat has it too. If both flats are cold, it is the boiler or the controls. If only yours is, it is balancing, a zone valve, or the arrangement itself.
- Ask where the thermostat is. If it is in the other flat, that explains a great deal and it is worth saying so plainly to whoever owns the building.
- We will not do work on a building without the owner’s instruction, and we would not be able to invoice you for it if we did. What we can do is put the technical findings in writing so you have something to hand over.
Four things that are true in every double
The upper flat is warmer for free, all winter, and the lower flat pays for part of it. No control change alters the physics — only balancing and zoning change who is comfortable.
Whatever the heating arrangement, the combustion air and the flue usually serve the whole building. A tightened-up basement affects both households at once, and that is worth checking once.
On steam it is the vent or the pitch. On hot water it is a zone valve, a circulator or an air lock. The boiler is proving it works everywhere else in the building.
The same rooms, the same time of day, the same visit. It costs very little and it is the only thing that reliably ends an argument between two households about heating.