Adding Insulation to Walk-In Walls

Good Morning Coldspot,

If you worked on the unit 10 to 15 years ago and the equipment was already 10 to 15 years old, this equipment may be 20 to 30 years old.

If my guess on the age is close, this equipment is now very inefficient.

I am guessing that replacement is not an option due to expense that being why you posed the question.

Is this walk-in located indoor or outdoor (I have seen both)?

What type of jacket is on the walk-in now, aluminum, SS, sheet metal?

I would go with some type of vapor barrier making sure not to block any vents, ducts and/or devices.

I too am appalled at my electric bill and I don't even have a walk-in freezer

The Walk-In walls are enclosed in an unconditioned space.

The wall panels seem to be a Stainless Steel alloy - there is absolutely no rust.

The question is, can there be any disadvantage to adding 2" of the pink insulation board Home Depot sells, and then covering that with 1/2" OSB.

It is one of those deals that even if it did not do a lot of good, it would make the owner feel better. He will have his own employees put it up, or do it himself. The cost of covering the walls is nominal.

If it is the age of the compressor, he might spring for one or rebuild this one. However, I guess that would mean a shut-down which few small business can afford.

Incidentally, I did pump it down and the valves seems to hold back head pressure. I do not know how one would check compressor performance, except compare run times historically. Without a history, which there is none, it is pretty tough I think.

<...can there be any disadvantage to adding 2" of the pink insulation board Home Depot sells, and then covering that with 1/2" OSB...>

It needs to be discussed, at least, with the site's fire insurance company before work starts.

Good thought, your no slacker.

your you're

Usbport - Very good suggestions, you've got my GA.

radio shack has cheap thermo guns . approx $60.00. they won't don't give a if image, just a temerature reading. they're accurrate. check for condensation in the insulation.

I've noticed with the walk in freezers in every shop I've been to, they are continuously humming.

Having to chill the walk in space seems to make all the difference, although I haven't thought through why. All that air in the open area, seems to take more energy to chill than the solid product.

Any physics to explain that?

As to physics, the thermal capacity of air is tiny by comparison with the goods, so cooling an empty fridge or freezer is quicker and cheaper than cooling a full one. That is to say, as long as the door is kept shut. If the door is opened, the cold air escapes and is replaced by warm. If the fridge/freezer is full, there is less cold air to escape, and the thermal capacity of the goods ensures that the temperature does not rise as much. Much therefore depends on how often the door is opened. In theory an airlock or antechamber might achieve some savings, but opening and closing two doors in sequence would probably be too much of a nuisance in practice.

That makes sense...

I bet these systems use sensors of the air temperature, rather than the temperature of the goods, to determine when the coolers cut in or out. Low thermal capacity of air, and prompt changes in temperature when doors are opened, means that the air temperature is constantly fluctuating, and the sensors therefore cause it to run continually.

So maybe a change of sensor system, to respond to changes in temperature of the goods, instead of the air, would be one way to cut unnecessary energy usage in the cool room?

The question is, can there be any disadvantage to adding 2" of the pink insulation board Home Depot sells, and then covering that with 1/2" OSB.

If you are wanting to add to the outside then there should not be a problem. If it is to be inside then I would have to ask what is being stored in the cooler. This may not be allowed for food products but I am not sure of this. You mentioned earlier that the lining is currently stainless steel.

I added an insulation blanket to my water heater and was laughed at by the furnace technician. He said I don't need that for a heater located in a basement. I left it on. I figured extra insulation had to help.

I would recommend modifying one and setting up an hour meter or electric usage meter to verify any improvement. I would even do a side by side comparison with another unit of similar size before and after the addition of the insulation. That way you have a base line reading on each unit as they probably will be different. And as the weather is changing this would help rule out or at least limit the ambient temperature as a factor in improved efficiency.

Somewhere in the engineering dept of the compressor mfg there is a graph of the amps at given suction and discharge for a given voltage. The trick is to see if anyone still has can find the info. Low current means not much work being done, thus long run times to make up the difference.

I think your comment about making the owner feel better is right on, since the pink stuff has such a low R-value compared to what he already has, I don't think it will make much difference. -- JHF

Instal pressure gauges at compressor suction & discharge ports, crack open service valves. If discharge pressure is less than specified for given refrigerant, compressor is inefficient, to be replaced. If suction pressure is higher than manufacturer's data, condenser has become inefficient (water/air cooled). If sight glass shows bubbles, refrigerant to be charged. However, very energy efficient equipment are available world over & a 30years old machine definetly should be replaced.

Coldspot, yours is an interesting and intriguing story. Riveting.

Is there something you would like to ask us?

Coldspot,

What is the internal space temperature when it is running and what is the setpoint temperature that the chiller eqpt is meant to be obtaining. Does it ever switch off when the temperature is reached ?

How does it compare now with previous performance ?

I would say, given the age calculated at around 30years, that the compressor is worn and now highly inefficient. Any refrigeration mechanic would soon take pressure readings and be able to confirm this.

Imagine how many miles you would have done driving your car over the last thirty years, and I'll bet you are not driving the car you had thirty years ago (perhaps you didn't even have your license). You would say that car was worn out but you only drive it a couple of hours a day, the refrigeration unit is on all day and running perhaps 25% of that on average (ie. six hours a day). Put a new compressor on it and the lower power bills will probably pay for it quite quickly. You will probably have to change gas though.

On that subject, has the gas been changed and the settings not been adjusted? The wrong gas/settings can be pretty inefficient. Check what gas is in it and look up the temperature you are trying to achieve and see if it possible with that compressor. Again, any good refrigeration engineer (I am not one) should be able to put you straight.

Can you describe the wall/floor/ceiling thicknesses and insulation types? How big is the door, and how long/often is it open? What is the external ambient temperature? How much warm product is being moved into and out of the freezer?

This info will help to estimate the refrigeration load. 5hp seems high. Loss of refrigerant charge would tend to keep the compressor running for long times, but then one would expect to see higher than normal superheat.

another thing to think of is minimizing the "open air" inside the cooler. By this, I mean that a cooler that has nothing at all in it will be much less efficient than one that is nearly full of frozen meat. Of course, you must have space for the air to circulate, but the more that's stored in there frozen, the better (less) it (the compressor) will run. I keep a few jugs of water in my freezer just for that purpose.

I appreciate your jugs of frozen water will have the capacity to keep your other goods at a lower temperature should the compressor fail but I think you will find the energy input required to attain and maintain the volume of water at the low temperature will be greater than an equivalent volume of air.

If the walls and ceiling are well insulated (more is always better of course) have you thought about insulating the floor?

The coldest air will sink to the lowest point, so the floor needs to be insulated even better than the walls do.....

Best of luck......

Getting the cooled space down from the outside ambient air temp. to near freezing is a lot of the heavy-lifting for this unit. There's a cheap, and very efficient diy device that he can add to his walk-in that will do this for a lot less money, and take a lot of the load off his old, inefficient system.

A little outside-the-box, or walk-in thinking here

Unless you can feel or see cold spots around the exterior I wouldn't bother with the external insulation,I would look to the compressor or the refrigerant,It could be that it needs a drain down and refill,Think about it if this were an oven and you were losing heat there would be a hot spot where the heat was escaping, the same would apply to cold.

Given that the age of the freezer is 25-30 years, the most likely insulation is Polyurethane foam. Designed as a chiller the insulation would be 3" thick. typical U value 0.25W/K.m². Designed as a freezer 4" thick typical U value 0.2W/K.m². After 25 years without ground insulation the floor would be suffering from frost heave, so we can assume ground insulation thickness at least equal to the wall thickness insulation. A walk in must be a minimum of 7' high internally so the total surface area is 1300ft² or approx 130m². A commercial freezer is typically run at -18ºC and I will assume an external ambient of 15°C so the Δt is 33°K. Running the maths, the heat loss would be 860 watts (1.1HP) at steady state and discounting freezing new stock or looses through an open door. (If the door is open for long periods, a transparent plastic strip curtain will minimise cold loss without causing too much inconvenience).

I would expect a 25 year old compressor to be running at no more than 50% efficiency so when not freezing additional stock and without the door opening, a 5HP compressor should run about 40% of the time. Any more than this, you have an insulation breakdown or a dodgy compressor.

Today the insulation on a commercial freezer is typically 6-8". Adding another 2" to walls and ceiling will improve the efficiency but by less than 1HP under steady state conditions. You cannot add any extra to the floor without major disruption. Payback on adding insulation will take a long time. Spend the cash on a new compressor for a better return.

It will only suffer "frost heave" if the ground under the floor gets cooled, but the cold gets "stopped" from seeping away completely, enough to freeze.....If something is allowing the cold to simply "seep away" without "containing" it, as could easily happen, you will still lose the energy, but the floor will not get frozen/raised.

Its a simple matter of what is "more", the cold or the warmth.....

Furthermore, if it's a solid concrete floor, the "heave", if it happens, may go downwards without any visible sign that the floor has moved in any way shape or form......especially if the ground was disturbed just before the concrete was poured - building site for example and not properly compacted -, it will just get compressed, but downwards.....

Assuming what you assumed in your post is possibly correct and possibly not......only a proper investigation can prove that.....Remember, throwaway comments are just that.......

I would bore holes and check for proper floor insulation, quick and easy and if found to be either non existent or too little, that is where money must be invested first.........it may allow the old system to run economically enough as it is, once the seepage is stopped.........

Have a great day anyway......