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Comment by gowld | Hacker News Reader

Why don't we run radiator water pipes across the chimney, to bring that heat back to the house?

The house I grew up in in Scotland did exactly this.

We had fireplace powered central heating -— radiators throughout the house linked to pipes behind the firebox. In the morning I’d wake up to ice on the inside of the windows, and by my teenage years it was my job to head downstairs and light the coal fire first thing in the morning. It worked well once the fire was up and running.

This was in the ‘90s btw, I’m not _that_ old.

This is a very old problem and there are solutions, like the Franklin stove [1]. However, we don’t really use fireplaces as a primary source of heat anymore. Their use is really more decorative. If they were really intended for heat generation, so one of the other posts mentioned, we would use a completely different design.

[1] https://en.m.wikipedia.org/wiki/Franklin_stove

Wood boilers are common enough. Pipes and radiators won't do all that much good if you aren't moving the water, and at that point it makes sense to optimize the whole thing for heating water with the minimum required fuel.

There are designs that do this or things like it. In the US, though, it seems fireplaces are mostly an aesthetic feature and not a practical one.

My father did that a long time ago in a house that had baseboard heat. Made a fire grate out of plumbing pipe, ran the baseboard water through that. It worked, when it did. It would also somehow get air in the lines and start banging from time-to-time. I was a kid, so I don't know if the monetary savings offset the pain in the arse, or not.

In parts of Europe (definitely Germany) heating with water based radiators throughout the house is normal. And that goes from individual houses to big apartment complexes (I lived in a 52 unit one with a central furnace). It's totally normal to let the air out of your radiator from time to time. And they (or you in the individual house case) fill up the water in the 'closed' system from time to time.

Different places, different 'customs' i.e. systems we are used to. All have their pros and cons and sometimes it's just that we don't know that different systems exist.

Radiative heat actually makes you feel significantly warmer, so you can set your heating to a lower temperature and still feel the same warmth compared to airflow heating. This is the reason why floor heating is very efficient, because you have a large heat mass with radiative heat that sits at your feet (which typically get cold first). So it provides the same comfortlevel at significantly lower temperature.

Which is why it is better to make a quick but strong draft in your home than keep window constantly slightly open. With a quick exchange of air, your walls remain warm and continue to radiate heat. Having a window constantly slightly open means air exchange is slow but constant and the area of the wall around the window cools down significantly.

Same in France. There's variations in how the water's heated (gas, fuel oil, electricity) but it's the default form of heating everywhere.

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