heat exchanger in coal fire chimney

I've read that you get a build up on crap on the exchanger, though this doesnt strike me as a showstopper, you just use twice the size of exchanger.

Cooling the exhaust will also reduce the updraught, so you may need to have a fan as well. Chimney heat exchange always struck me as a potentially sensible idea, especially considering you can get heat exchangers from scrapyards for next to nada, and it costs very little to add it during build.

Regards, NT

You can ? What should I be asking/looking for ?

Industrial heating and cooling units use large heat exchangers, and land in scrappies when the systems are changed. If you know what a heat exchanger looks ilke, you'll spot them instantly.

Regards, NT