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Natural insulation for walk-in cooler
I am struggling to find viable options for a natural insulation, to create a walk in cooler. This cooler is for commercial use, and must meet the sanitation codes for inspection. 3 sides are of a conventionally framed shed. With t-111 shell. One side ( interior non existing wall) will be the door, and interior wall for an adjoined kitchen, also to meet kitchen code. Condesation, is my largest concern. Where, how, and what vapor barriers to use. Keeping in mind, practical ability to clean. Tile, for example is too time consuming to clean. HELP

Edit: the interior size of the cooler is hopefully about 12x8. Working with about 14x10 footprint. Currentlty raw 2x4 airspace avalible on the 3 existing walls. The 12-14ft walls are parralell, one being the interior of the larger structure. It will be cooled with a coolbot hacked window unit.

Your insulation and your cleaning surface do not have to be (and are not usually) of the same material. A person could use straw bales, or cordwood, for the walls, for instance, and then clad those walls with something that is impermeable to moisture and further clad that with something that is easy to clean.

It seems as though the main concern is finding good vapor barriers and a surface that cleans well. Do you have a natural builder helping you?
I am very familiar with natural building techniques. And have used most or many. But refrigeration is an artificial enviroment, which lends itself to artificial materials. Because it is not what nature intends. I have lived in a home with cordwood walls. And they suck. We are talking thousands of dollars of produce on the line. I have not experienced a par to artificial substrates, unless it is a living space. Where it is nowhere near the needs of refrigeration. I personally think it is an unique niche for a builder. And cannot find any realistic information on the subject. Read: not a root cellar. A real commercial cooler
Natural materials breath. Plastic sheeting does not. I am Not looking to insulate a plastic box. That's easy. I am looking for ideas to make a nice breathing cooler
Chad, lets back up to your OP. You mentioned sanitation codes and this is commercial. First off, in most of the US commercial has to be designed by a licensed Architect not that they always know what they are doing but it is the law of the land. Second, if that is not the case please post the sanitation code you are referring to. In that same code be it local or IBC is international commercial code, it should specify a barrier CL 1, 2, or 3, not that it is correct but that law of the land again an inspector will verify per stamped print.

When it comes to public safety fed law mandates professionals do the design not anyone off the internet or a non-pro DIY. That is a good thing for the most part. If it is not being enforced it may still be a good idea to follow it for obvious reasons.
Terry, the code is from usda, not building code. I am using loop holes to fall under "cottage law". So to clarify, it is not the structure that's being inspected, but the condition of the kitchen and ability to clean. My question, I guess, is how to build a refridgerated envelope, within a natural building. It's looking more and more, that I must sacrifice some space, and build a freestanding cooler, opposed to using pre-existing exterior walls. OR sacrifice using natural material on proportions of said walls. I think I found the solution, which is to create an artificially climate controlled air space between the vapor barrier and natural wall. While providing a throu way vent inside the cooler with a humistat.
To elaborate, unglazed clay tile, with air channels. Surrounding the cooler. They will help cool in the summer, caputing and evaporating any condensation before it reaches a natural insulation, and if too moist, warm air from the mechanical condenser of the cooler will draw excess moisture, expelled to an outdoor vent. Via humistat and small fan. If anyone can think of why this wouldn't work, feel free to comment. Its why I asked. (thin hollow clay block, arranged so the holes create ducts)
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I have demolished several old coolers that were insulated with redwood bark and sawdust. Cedar would probably work too.
Thanks dale! That's more of the response I was looking for. If you don't mind, could you elaborate as to how and where they used saw dust. And since you were the person deconstructing the coolers...was there any evidence of rot or mildew-mold? (I understand the qualities of said wood, but have doubts)

I sacrifice my pie to you, because you gave the only answer, and not another question.
Thank you sir. The best cooler was built with two 2x4 walls set about a foot apart, for a total thickness of about 20 inches. Both sides were sheeted in plywood. The roof was made of 2x10 with about 20 inches of ground bark on top, covering the framework. The balloon framed walls were open to the mound of bark on the roof. Settling of the wall material could be filled from the roof.

There was no rot. I don't recall a vapor barrier.

The material was kept clean, and I gave it to a landscaper. My best guess is that the cooler was built in the 50s.

Edit - There was no plastic vapor barrier. There was a thick aluminium sheet, about 4 times thicker than the stuff used as kitchen wrap. This was on the cold side, under the plywood.

Edit - There was no plastic vapor barrier.

Good info Dale, I'm getting ready to put a net-zero natural spec home to market with no plastic, foam, or vapor barriers, house wraps, osb, glues, etc, 100% breathable including the polished and sealed concrete floors.....I'm making a public presentation at a local home show on a 60 inch 4K 3D monitor of it in a week. All my suppliers think it is incredible, and all do not understand it. It is double wall construction. It is very interesting changing (or trying) the way people think and VERY time consuming. I hope to get many sold
BTW Chad I'm super busy getting ready to write alot but you might look @ evaporating desiccants or molecular sieves like alumina zeolite aggregates w/a clay or lime binder as plaster. Super interested in your project, I just know too well how codes are you did not define which call for plastic barriers, especially commercial hence the questions before wasting my time, sorry I was not of more help.
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I forgot to mention the best parts, tomorrow starting with my 26 year old son and then Thursday with our 10 employees around his age I get to explain how to better design natural homes to the next generation of builders. I could not ask for a better b-day present since I turn 56 tomorrow ...Funny part is I demanded no cell phones at this all hands meeting, imagine this generation having no cell phones for two hours, with the attention span of a gold fish? Wow!
In Mount Vernon there is an ice house used to store ice blocks cut from the Patomac River in winter, so they had ice in summer. The ice was packed in saw dust in the ground with a drain hole back down to the river. I do not recall anything special about the building, I think it was just a simple shed construction. The key was the saw dust insulation packed around the ice blocks in the ground.

I seem to remember reading about ships that carried ice from ice houses in new england, to southern states during the summer. Again, the ice blocks were packed in saw dust.

So I think the advice above, about using saw dust for wall insulation, is a very good idea. I'm not sure how saw dust compares to rock wool or sheep wool insulation for R-value, but would be considerably less expensive if you lived near a saw mill, and wasnt concerned about termites or fire proof qualities. Using double walls as recommended above eliminates thermal conduction through wood, which is a real concern in high R-value applications.
Back when my Grandfather built his chickenhouse for commercial broilers he used "Sawdust Cement". It was a product invented if you will, by the University of Maine. Instead of using rock for aggregate, it used sawdust. It did so for insulating purposes, and reduced weight on a timber framed structure. It lasted until 1994 when the barn burned around it.

Maybe it is something to consider using?
I just googled "r value of sawdust" and am not sure it is such a good idea after all. One post says to add lime to keep it dry and critters out. Some say it harbors lots of mold (although the post above indicated no mold in the walls when using foil). And another article indicated sawdust was R-1 per inch, which is 25% or 30% of wool, or rock wool. I guess it is better than nothing, but would do more research.
Sawdust around ice blocks is not just a simple R value. It also dried the surface of the ice (wet ice melts faster than "dry" ice because water conducts heat faster) and cooled itself as the water evaporated off.
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R Scott wrote:Sawdust around ice blocks is not just a simple R value. It also dried the surface of the ice (wet ice melts faster than "dry" ice because water conducts heat faster) and cooled itself as the water evaporated off.

Good info and insight Scott. Many that know no better try and relate steady state r-values that do not apply. Enthalpy is far less understood. The reason I went to a double wall has nothing to do with u-or r-value or I can easily do that with single wall construction and the way most construct double they thermally conduct. Most do not understand "dynamic thermal conduction or r-value" or the conditions that real value is obtained and therefore advise inaccurately. Enthalpy works to create two independent enthalpy interior/exterior systems that can react to their respective boundary condition requirements. So in the case of a "natural material for a walk in cooler" a desiccant like aluminosilicate zeolite in a plaster would provide the evaporation cooling by phase changing a liquid vapor to a gas that heats the zeolite by heat of adsorption, that is an open loop (no sealed vacuum) system. Same happens with certain clays, limes, woods, etc, with high intracrystalline voids but not as fast. Materials of lower moisture content indexes (MCIs) don't perform as well, concrete is not as good as these materials despite the myths. Also zeolite is not damaged by the process. We just described a great way to manage indoor humidity with water vapor in liquid, condensation, or vapor form that cools a room and lowers HVAC requirements at a fraction of the cost. The desiccant, like zeolite retains 100% of it heat of adsorption with no loss.

At night when it gets cold and the dry hvac is running or the next day when the zeolite sees solar heat it reverses its process, converts a gas to a liquid that releases vapor or condensation back to the atmosphere for humidity buffering. Great part is as the heat is increased so is the amount of vapor. The desorption of heat and vapor is slower than adsorption for night time. The heat of condensation is released to it's surroundings lower heating bills. The cycle repeats.

Since these materials are chemically stable and insert there is no microbial growth in the presences of liquids and heat, unlike many plastics, foams, glues, used. These dynamic mass systems can accommodate any environmental conditions.

An entirely different independent system that handles a different set of exterior conditions can be designed on another wall/wythe. Airflow is the best insulator between the two wythes. Has nothing to do with r-value that would be HIGHLY misleading as usual. The math is complex, one has to assume an adiabatic process to quantify the dynamic hygrothermal systems. It should be obvious that adding a vapor barrier would ruin the process most would advise that know no better, same for house wraps that would ruin the systems. The same design can be applied to walls, roofs, foundations
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