Frost Heave Prevention and Floor Insulation in Cold Rooms

Hi Everyone
I hope you might be able to help me with this

We install cold rooms within warehouses/shops etc and currently have a rule that any freezer temperature room over 9m2 will require an underfloor heater mat. We also specify that any room (chill or freezer temperature) above a void (ie a basement, upstairs etc) would also require underfloor heating. I do not understand the purpose of heater mats on a ground floor installation where the room would have (for example) a 100mm thick Polyurethane floor (incorporating 12 or 18mm thick plywood on top for strength) being situated onto a concrete floor.

If frost heave is due to cold tracking through to the sub floor is this not prevented by the insulated floor? The cold does not track through the cold room wall panels of the same thickness.

So my questions are:

Why is underfloor heating necessary on a ground floor coldroom installed onto a solid floor (ie concrete) when the room has insulated floor panels?

If it is required, is the 9m2 rule based on any science or is it completely made up? No-one knows from where this rule came...

Is underfloor heating required on any cold room installation above a void or is it dependant upon the thickness of the floor upon which it is installed?

thanks very much in advance

Chris

Welcome to the forum Chris!

First, the flow is always from the warm side to the cold side. But it works as well to assume that it is the other way and imagine that the cold tracks through the insulation.

Insulation SLOWS down the transfer of heat, it does not eliminate it.

Ice formation does not occur on the outside of the wall panels because the panels are in a warmer environment, just as though they were heated. I had this problem with a wall of panels installed in a medium temp room. They were installed improperly up against a office wall. Being medium temp there was no ice, but moisture condensed none the less.

The same is true of an unheated floor. Usually not an issue unless it is below freezing. If left unchecked it will freeze under the floor down much deeper than you could imagine. I have seen floors heave so bad the building structure was damaged.

I will leave it up to the others to comment on the necessity of heating floors under 9m2.

I would always allow for a heated floor in a low temp walkin, not just prevent ground frost heave, but to prevent slips from spills freezing. Also if the super heat setting is low on the evaporator due to certain products being stored, the humidity will be higher and condensation could build up on the floor and freeze.

In my 45 years working in freezer rooms i have yet to come across one where water on the floor doesn't freeze solid. chilly willy how hot do you set your underfloor heating and how much more HP needed to attain minus temps?

Allow for at least 15 w (0.0211 eHP) per square meter additional heat load, using either single or multiple trace heating cables or zoned glycol circulated through pipes spaced around 450 mm apart, with multiple sensors spaced around 20 square meters. Ideal for insulated or uninsulated floors as it allows time for mopping up, or condensation freezing and causing a death trap for the unsuspected.

I always specify these where the client has experienced their staff genuinely slipping, or just putting in a claim, or just as a general precaution against floor damage in the long run. But it usually does just stay as a specification due to the initial outlay cost and the slightly higher running costs.

Another option would be to use a studded or modular sub floor system that is isolated from the ground, with a ventilated floor void, and just allow for the full cubic ambient.

They usually just choose a standard insulated floor.

Even in medium temp rooms where beasts are wet wrapped, this could also be considered due to the recommended -2 deg + 4 deg C.

Hi everyone
thank you for your replies - and NH3LVR thank you for your example of installing a room up against a wall, that is something I hadn't considered!
This subject has been a source of debate in my company for a long time, but I think it would be sensible to suggest ALL freezer temp room s should have frost heave prevention.
thanks again