Why is a condensing boiler more efficient than a conventiona

Why is a condensing boiler more efficient than a conventional boiler?

Solution

Condensing boilers are water heaters fueled by gas or oil. They achieve high efficiency (typically greater than 90% on the higher heating value) by condensingwater vapour in the exhaust gases and so recovering its latent heat of vaporisation, which would otherwise have been wasted.

Conventional hydronic-heating-loop design practices represent an interrelated effort to prevent direct-fired boilers from condensing in heat exchangers.