Fridge insulation: top sides or bottom?

[Tim Good]

Q: Since You pay more attention to insulate the roof of a room to retain heat, does it stand to reason that the bottom of a fridge would be more important to insulate than the sides and top?

(I appreciate all sides are important but I’m curious if the differences in heat / cold transfer is as significant as in room when retaining heat for example)

 

[geem]

Yes. We have 6” on the bottom but only 4” on the sides and top

 

[neilf39]

I put as much as would fit around the space so for me that was 100mm on the bottom and 2 sides and 50mm on 2 other sides. Its a top loader and the manufacturers lid is only about 30mm of insulation. The more you put all round the more efficient it will be overall. I would have put more if it could have gone in the space to have 150mm all round.

 

[rogerthebodger]

I fitted 150mm all around but left gaps ar the back where the pipes when into the fridge.

Once I filled the gaps with spray in foam the fridge was for more efficient.

Also consider that it not just the cold leaking out its also the warm/hot inside the cabin leaking in.

Any sun on the top of the fridge will also affect the fridge power consumption

 

[ithet]

Also consider that it not just the cold leaking out its also the warm/hot inside the cabin leaking in.

Being scientifically pedantic, it is only the heat leaking in. Cold is lack of heat.

 

[BabaYaga]

Being scientifically pedantic, it is only the heat leaking in. Cold is lack of heat.

Exactly so. Rising temperature inside the fridge is actually a case of passive cooling. What is being cooled is the space surrounding the fridge.
To try and answer the OP: Put the thickest insulation on the side of the fridge that is most hot.

 

[RupertW]

Being scientifically pedantic, it is only the heat leaking in. Cold is lack of heat.

With holes where pipes come in as per the earlier post it is cold air leaking out

 

[rogerthebodger]

Heat transfers consists of one of three types conduction , convection or radiation.

Each have their different mechanism.

So are reduced buy different ways. Insulation is used to reduce conduction but will not help radiation and convection is mainly due to cold/hot air movements (opening door or loss through gaps where pipes/gaps are found) .

 

[Daverw]

As you say, heat rises so the bottom will get warmer but how much spac have you got below for the heat to actually rise, either way you cannot really have enough thickness on sides or bottom within limits.

 

[geem]

In steady state once all the food is cooled down it is remarkable even with a very well insulated fridge how much temperature difference there is between the bottom and the top of a top loading fridge. 7 or 8 degC is quite possible. Opening the top loading fridge even in the Tropics doesn't lose much coolth. Insulation is everything. I use Cellotex or Kingspan rigid board readily available from builders merchants. Fill any voids with builders foam to glue the layers together

 

[Neeves]

As Roger implies there is no one answer. If the top of your fridge is exposed to warmth, sun shining on the top, then you need to insulate the top, more than other locations. If your compressor is not well ventilated and the warmth sits in a locker on one side of the fridge, or bottom (as would be most installations) then you need to remove that heat (hopefully replacing it with cooler air) and maybe increasing the insulation on the locker side facing the fridge.

Most installations will have a minimal space for extra insulation, unless its a custom installation, as modern boat builders will minimise 'empty' space in favour of storage space.

Jonathan

 

[rogerthebodger]

Shiny foil will help reflecting radiated heat which is why I made the inside of my fridge and freezer from polished stainless steel.

The main heat transfer is through conduction which is reduced by low R value thermal (conductivity) and the thicker the better

Losses by convection is mainly due to the opening of the door and cod air being replaced by warmer air. This is why a top loader fridge is better from that aspect

 

[geem]

Shiny foil will help reflecting radiated heat which is why I made the inside of my fridge and freezer from polished stainless steel.

The main heat transfer is through conduction which is reduced by low R value thermal (conductivity) and the thicker the better

Losses by convection is mainly due to the opening of the door and cod air being replaced by warmer air. This is why a top loader fridge is better from that aspect

Yep, I made mine from polished s/s as well. Its also super easy to clean with an insulated drain outlet and and valve that allows us to drain any water out. In addition the compressor and condenser are located in a separate cupboard well away from the fridge where they get excellent natural ventilation and dont heat up the space close to the fridge