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Ask HN: What to do with an existing hydronic house heating system?
4 points by EFFALO 11 days ago | hide | past | web | favorite | 13 comments
Just moved into an older house that has an existing hydronic baseboard heating system installed. It's connected to a boiler that burns heating oil. While the system is quite old, it still works. I've never lived in a house with this type of heating, but from my research I've learned how expensive and inefficient heating oil is, compared to more modern methods of environmental control.

Does anyone out there have any suggestions or experience on how this system can be repurposed to be made more efficient? Given that all this pipe has already been run, I'd prefer to find a way to put it to use over removing it entirely.






my research I've learned how expensive and inefficient heating oil is

Test and measure.

The most common (in the US) type of home heating systems are forced-air. Fans pull cooler air into the system, past a heating element, and then out into the space to be heated. The heated air eventually warms the occupants by convection.

The less common (in the US) approach is radiant heating. Heat up a surface and warm the contents of the space (including people) by infra-red radiation. This is how most of the heat in the universe moves (e.g. the sun's heat across the vacuum of space to the earth).

Hydronic heating via baseboards has several potential efficiency advantages. It is radiant. Radiant heat heats people not air. The transfer mechanism is liquid not air. Water conducts heat more efficiently than air. This is why fiberglass insulation is fluffy full of airspaces and why it loses effectiveness when wet. Finally, radiant baseboard provide heat along the building perimiter, low-near the floor, and without creating drafts (moving air).

Fuel-oil prices tend to fluctuate more than electricity or natural gas because it is less subject to regulation. It is less subject to regulation because natural gas and electricity run infrastructure in the public right of way.

Finally, expensive is relative. That's why test and measure. Fuel oil can be twice as expensive as natural gas. But that might mean $600/month versus $300/month or $150/month versus $75/month. Those are economically divergent against the cost of changing the system.

Ok, the real "finally." If it ain't broke don't fix it. Having a warm house is 98% of what's important. There are lots of other places to spend money that will significantly improve livability. Many of them are going to be easier to accomplish because swapping out heat systems involves lots and lots and lots of tradeoffs, vetting contractors, and living with disruption of significant construction...and of course, swapping out heating systems doesn't make your house better. The fact that the system is still in use is evidence that it is good enough. Good luck.


This is the reason I come to HN. Thank you, sir.

What I've heard is the opposite. If you are going to burn fossil fuels for heat, those oil burning boilers are more efficient than most hot water heaters and furnaces. The hydronic system is also efficient at getting heat in the right place.

To really improve on an oil boiler, you could get a heat pump or maybe active or passive solar. If you have a system that generates hot water you could probably run it through existing pipes.


Most places with boilers are too cold for air to air heat pumps to be viable during heating season. Geo-thermal heat pumps have a wider range but they involve significant site work and require a non-trivial lot size. In terms of expense a typical geothermal heat pump will have a very long payback period. An open loop geothermal heat pump might be practical if there’s a source and sink for the water running through it. Most people don’t have those. But it’s a simple system with a water pump and fan as the only moving parts.

Air source heat pumps can operate all the way down to 0F. I’ve paired one with a hydronic system, with a firewood heated boiler for backup heat, in rural Pennsylvania.

The less reliable power is and the colder it gets during winter months, the more tricky the problem gets.


Typical residential units come with a resistance electrical heating element. It forms the basis of the "emergency heat" functionality. It also begins operating as ambient outdoor conditions exceed the performance of the heat pump mechanism.

I mention this not because this is what your particular system does. I mention it because it is typical for widely available residential heat pumps in the ordinary market.


Yep. The real selling points of heat pumps is comfort, since they can go from aircon to heat and back seamlessly. Where I live geothermal heat pumps are the practical option, but south of Pennsylvania the air source heat pumps are a great option.

To me, they are a no brainer in the Florida peninsula. Above that, I'd start to consider a furnace and an air conditioner as an alternative for better heating aesthetics (quieter and warmer air at the register). Also, sizing the AC properly to prevent short cycling, means a heat pump will not heat as quickly a furnace. With a furnace, short cycling is not an issue.

Someone told me they switched to heating oil because the local market had only one local utility for natural gas which was charging too much. With heating oil there are multiple suppliers who can drive a truck to your house and price competition.

All heaters are 100% efficient in that any leaked heat leaks into the house you are trying to heat. I would look at insulation if you are trying to be more green.


My hydronic system is heated by a tankless and costs almost nothing. Would that be a possible conversion?

My cousins use a black roof with water pipes just underneath to absorb heat on sunny days, and circulate it down to a giant insulated basement water tank that functions as a heat sink. They then use that to supplement their heating system.

Fill your oil tank now while prices are low. If you can get the company to let you pre-buy at todays prices, I would do that too.

In addition to all the other comments, radiant heat doesn't dry out your skin like forced air does.

This was a big plus for me.




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