Warm air, or Hot Air heating, is where heated air is recirculated from the house, through a heating bank, and then back into the house again.  It uses a network of ducts, usually in a ‘tree and branch’ formation in a domestic property.

The heat bank could be heated directly by Gas, LPG, Electricity or Oil (indeed, there are a few other options as well).

Installed correctly, using the latest equipment, warm air has the ability to be arguably the most efficient way to heat a space.  This is because there is only one transfer of energy, from the original fuel to the air. Radiators, for instance, involve burning a fuel, heating water, and then exposing the water in some metal tins (aka radiators) to the air in the house.  That’s one more transition.

This is why most commercial spaces are heated using air (when was the last time you bumped your trolley into a radiator in Sainsburys?).

In the 1950s -1970s domestic central heating was often of the warm air type, mainly because it was cheaper than other systems to incorporate at the construction stage – and sometimes because wacky 1960s architects loved lots of floor to ceiling wooden windows, ruling out radiators.

This Lennox heater had lived a long, and hard, life


Our customer in Bromley had an old Lennox heater, and like most Lennox owners, wanted to replace it with another one, because it had soldiered on reliably for so many years.  The fan in the old one was pretty worn out, or so it seemed, but when we removed it, it hadn’t been cleaned for around 15 years and was almost blocked, meaning the servicing technician conveniently ignored this part.

New unit in place

We fitted a new Lennox G61MPVT condensing warm air unit, with an efficiency in excess of 94%.  The new unit was flued via the garage to outside, and was configured in the safer ‘room sealed’ mode.

Outside flue termination, after routing through the garage

We also added an additional ceiling supply register in the master bedroom, and replaced the existing register to ensure they matched.



Additional ceiling diffuser fitted to ductwork, to replace one was incorporated within an ensuite bathroom some years ago


Our customer Martin. Thanks for the lovely teas & coffees!

A new Trion electrostatic filter finished the job.

Trion micro particle air cleaner

Finally, we specified the Honeywell Lyric T6 wireless thermostat, which our customer can control locally, or from afar using his Android phone.

Honeywell T6R Lyric internet connected thermostat

As usual, our ductwork was a professional job rather than the pile of cut steel sections and gaffer tape so often found in the gas replacement sector!

Does your replacement warm air look like this?


Honeywell T6 thermostat receiver