Copyright 2018, Michael Bryant
...are they any good?
Another tricky one. I have to say, it all depends on which condensing boiler...
Condensing boilers have come of age at last. The good ones are very very good in my opinion. Just fitted one in my own house and I'm really pleased with it!
Condensing boilers are a new(ish) type of boiler that extracts more of the heat energy from the gas flame by allowing condensation to occur inside the heat exchanger. This requires a special heat exchanger resistant to the corrosive affects of the condensation, hence the extra cost of a condensing boiler. The best ones have stainless steel heat exchangers instead of the cast iron of an old style boiler.
Condensing boilers can use as much as 91% of the available heat energy in natural gas, compared to 50% to 80% for conventional types of boiler. Have a look through the SEDBUK boiler efficiency database at www.sedbuk.com
If you are considering a condensing boiler they will reduce your gas bill but they also have a few drawbacks...
1) Pluming. The exhaust gas from a condensing boiler is rather unpleasant. It smells more than ordinary boiler flue products and it contains condensation which make it look like wispy white smoke. This means that the location of the flue outlet needs careful consideration to avoid it being a nuisance. There have been rare cases where outside walls of houses have been damaged by dampness caused by condensing boiler flue gasses.
2) Location. Substantial amounts of condensation collect inside the heat exchanger and this is disposed of via a pipe to drain. Consequently condensing boilers need to be fitted where there is access to a drain connection.
3) New technology. Any new technology tends to be less reliable than conventional tried-and-tested equipment. I doubt if condensing boilers will prove to be any different. Finding a heating engineer to repair one may also prove more difficult as they are not widely understood by all heating engineers yet.