View Full Version : under floor... ventilation ?

04-06-2017, 12:03 AM
just about to build a new freezer, 8m x 15m on the floor

(I build it, fridge engineer does fridge stuff)

I've done a few before, thats no problem

but every time I've taken a freezer down the floor panels have been soaking wet, thats with my freezers and a couple of others

so I was thinking maybe I should put some kind of mesh down (few mm thick?) so the floor can be allowed to... drain?

ok, the inside surface of the panels is -20'C, but the floor is above freezing, in the middle of the insulation will be halfway temp etc. etc.

worth it or is it a silly idea?

or was I just unlucky with the ones I've taken down, and they're not normally wet ?

concrete slab has under floor heating installed to stop ground freezing/heaving, water at 15'C, circulates 24/7

04-06-2017, 01:22 AM
Do you re-seal after pull down?
Usually pull down procedure with room temps, then raise above zero, re-seal joints due to contraction of everything.


know.com/pluginfile.php/28738/mod_resource/content/1/TB139.A.Cold%20Store%20Pull%20Down%20Times.pdfjj (http://lms.i-know.com/pluginfile.php/28738/mod_resource/content/1/TB139.A.Cold%20Store%20Pull%20Down%20Times.pdfjj)



05-06-2017, 01:02 AM
I haven't re-sealed after pull down in the past - not sure if fridge engineer I use did (we do the donkey work/labour, he does all the technical stuff)

I'll make sure to re-seal this time

two of the rooms I've taken down were fairly new (couple of years) and had been put up by professionals - both times the floor panels were so wet we seriously struggled to pick them up (we're guys who do manual labour all day long)

one of those is the one being re-built now, the panels have been standing for two years, so they're good and dry now

I have no idea how the water got into them

B G Scott
05-06-2017, 11:14 AM
Check that the vapour barrier on the warm face is intact, moist air penetrating the insulation can be the cause of saturated panels.
I am assuming that these stores are made from modern materials and built by a reputable company.
I also note your comments about the panels being "dry now" but check the insulation if the moisture in the panels has frozen at some time you may have compromised insulation value and compound the problem by re-using the base panels.

13-06-2017, 03:16 PM
hi Scott

do I need a vapour barrier on the floor under the floor panels ? (floor panels, not insulation/concrete)

I haven't see that before, I can easily add some

this freezer was originally paid for by walls ice cream and apparently cost 80,000 - tho the guy I bought from could be fibbing a bit there - 8m x 13m and 2.5m high, with 2 separate/identical 30hp systems - one is backup incase first one failed / down for maintenance - it was a very nice/clean/tidy install, looked like no expense spared

thanks again for help


B G Scott
13-06-2017, 04:44 PM
The vapour barrier is applied to the warm face of the panels. IE. the outside of the panels.
But this should be on the insulation not the cladding but unfortunately for you with injected panels this is almost impossible to retro fit as the blown insulation will be adhered to the cladding which I would assume if the store is of modern construction would be steel sheet.
If I were faced with this problem I would either source new panels for the floor or add new insulation to the base and ensure that it was well vapour sealed.
I think it would be very unwise commercially to reinstall the panels knowing they have been compromised in the past, this will come back and bight you.
If as I suspect the panels of the floor are steel clad on the outside (the part in contact with the floor) inspect them to see if there is any movement between the steel and the insulation if there is I would not re-use them.

14-06-2017, 09:10 AM

yes, you're right, the floor panels are steel sheet either side with blown insulation in the middle

if I check the panels and they're ok, could I put (thin) insulation down on the floor, then vapour barrier and then the floor panels on top ? - would this fix the problem (if the panels are ok)?

I don't want to add much height to the floor, I've bought the building next door and knocked a hole through the wall, the freezer door will be right up against the hole in the wall, I already have a bit of a ram going into the freezer... if I add too much height to the floor the ramp will be too steep - I'll have to dig out and lower the concrete floor (13m x 8m) - that's a lot of work/expense I don't want right now.... but if it has to be done then it has to be done :-o

B G Scott
14-06-2017, 10:34 AM
If you add insulation to the base, you would have to select it very carefully, the weight of the store and its contents could crush the insulation and the store could distort.
Once again I would advise you to inspect the existing floor panels an check that the base steel sheeting is still adhered to the insulation.
Any panels that shown a breakdown between the insulation and the steel sheets should in my opinion be discarded.
On the basis that you will have invested a considerable amount of money and effort to get to this stage in the project replacement of the floor panels with new ones would still be my preferred choice.
I would also reiterate the point I made before, if the floor insulation was so wet it indicates cellular damage, in all probability caused by the moisture entering the insulation, freezing, with the resultant damage to the cellular structure of the insulation.
They may have "dried" out to visible inspection but if the damage is as you indicated in your original post then my feeling is that the integrity of the insulation has been comprised and I would not re-use the floor sections.
Go to a specialist cold store refurbishment company and get the floor replaced, this will extend the life of the store and reduce the operating cost.
If as I suspect the panels are defective, imagine the cost and disruption if you had to dismantle the store to rectify the issue at a later date.