Another question we get asked a lot, probably only second to what is a condensing boiler is What is a combi boiler A combi boiler is a type of condensing boiler that delivers both hot water and heat for your home.

As it is a type of condensing boiler it will be a high efficiency boiler. What do we mean by Highly Efficient boiler? This refers to how it maximizes the output from the fuel used to drive the boiler. This high efficiency is achieved by condensing water vapour (and so the name condensing boiler) in exhaust gases which recover latent heat that would otherwise have been wasted or vapourised through the flue. In other words, it recaptures water vapour been lost from the system and extracts the heat from it for your use, this is the heat that would in an older boiler have gone out the flue.

For every €100 of fuel, you put into a combi boiler you will get €90+ worth of heat out. This compares very favourably to efficiency rates as low as 60% for older noncondensing boilers.

This high efficiency means your combi boiler will be more environmentally friendly as it needs to use less fuel to do the job. Less fuel when the fuel is gas or oil means less carbon dioxide released into the atmosphere. Less fuels also means less cost for the owner of the boiler.

As the price of fuels rockets a move from a very inefficient boiler to a combi boiler can save you substantial amounts of money. If you have a combi boiler you will not need a hot water cylinder as the hot water is heated directly from the mains. Cold water pipes can be connected directly to a combi boiler so there is no need for a cold-water tank in the attic.  This can be an important consideration where space in a home is at a premium.

Combi boilers are not the only types of condensing boilers. There is also regular and system boilers which have different characteristics from combi boilers but are condensing boilers.