Underfloor heating installations in cold conditions

A reminder to protect pipes and manifold from freezing during cold spells of weather.


This has been an unusually cold and long winter, with proper frost and below zero degrees Celcius temperatures spread all over the UK including London and the South East.  It is likely we’ll still have more of the same.  Therefore there is no reason to have a relaxed attitude towards filling a new underfloor heating system with water – unprotected – and then leave it, assuming the current mild weather will stay with us.


In an ideal situation each ufh system should of course be filled with water on installation date, then pressure tested and left pressurized ready for screeding.  However under certain circumstances it isn’t possible to fill a newly installed ufh system.  This is where doors and windows haven’t yet been fitted, or even the roof may still not have been completed.

In this case an air compressor can be used, to fill the ufh system with compressed air.  Care should obviously be taken to avoid accidents and we’d recommend a lower pressure (4 bar) compared to one used with water (6 bar).



Not every building site makes the expected progress and may have serious delays.  Hence even if you had the ufh installed in summer, will the property be weather tight by the time first frost arrives (which can be already in October in most parts.. most years)?  Perhaps not always…

In these cases it is again important to consider whether to drain the ufh system (temporarily) rather than take any risks.  Of course gaps in the wall can be filled or blocked with e.g. boards.  However always consider the risks.


Many seem to think that once the screed has been laid over the pipework, it’ll protect the pipes from any form of evil.  It obviously helps to protect the pipes to a certain level.   Minus one or minus two degrees for a couple of hours overnight may then possibly not be such a critical issue (assuming the manifold is also protected).  However add another degree or two plus add to the length of the freezing period and you’ll have a disaster on your hands.


So our recommendation is – don’t take a gamble.  Follow the guidelines and respect the weather conditions.

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