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Discuss water requirements, "soil" (growing media) and suitable planting containers

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By specialkayme
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#407607
ChefDean wrote: Wed Apr 06, 2022 7:30 pm The insulation is the point. It creates a barrier between the plant and the 90°F outside. There will be some heat bleed through, but, since heat rises, it will not stick around. Even a white plastic pot will conduct more heat directly into the media due to its thinner walls that aren't insulated.
I'm not sure how much of a barrier to heat gain the Styrofoam is providing. Considering that peat moss itself has an insulation value comparable to Styrofoam (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8585433/), but the mass of the peat moss is several times more than the Styrofoam. But while the insulation on the side may slow down the time for the roots to get exposed to increased heat, it's likely doing very little compared to the energy absorption that's occurring relative to the peat moss (black) that's directly exposed to the sun's rays.

If that was the goal, planting in a larger (and/or deeper) pot would make much more sense than wrapping a pot in white Styrofoam.
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By ChefDean
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#407611
specialkayme wrote:I'm not sure how much of a barrier to heat gain the Styrofoam is providing. Considering that peat moss itself has an insulation value comparable to Styrofoam (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8585433/),
You're comparing apples to oranges. The link you shared is talking about peat that has been bound in resin and made into panels. They will remain dry and protected from the elements, so will provide a good, physical insulative property. While we're talking about wet media that will have a cooling effect from evaporation, which removes heat from what it is evaporating off of, surrounded by white styrofoam. With evaporation, think sweating, same process. You sweat on a hot day, it cools you as it evaporates. Plus the white styrofoam will reflect much more heat than it will absorb, conducting virtually zero heat through to the media. White pots will reflect a lot of heat too, but will conduct more heat into the media simply due to its thinness and lack of insulative property.
With styrofoam, the water, media, pot, and plant will heat up regardless, but up to the temperature of the surroundings. Heat absorbed by radiation will increase with direct exposure to some degree
Styrofoam will block most heat from radiation, only a small fraction will migrate into the system. Any excess heat, above the temperature of the surroundings, will be transferred from the system to the surroundings via evaporation. The top of the media, if left exposed, will heat up more in direct light due to the darker color, but only the top portion. But that will be countered to a point by the previously mentioned evaporative effect removing heat from the media, keeping the roots at the temperature of the surroundings because no more heat is being conducted in from absorption of solar radiation. Plus, the OP said shade cloth is used, which lessens direct exposure.
A Zeer pot that was mentioned by another member would be a great idea. Essentially a swamp cooler between the surroundings and the system, taking advantage of the properties of evaporation to keep it from overheating.
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By specialkayme
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#407629
ChefDean wrote: Thu Apr 07, 2022 3:59 pm
specialkayme wrote:I'm not sure how much of a barrier to heat gain the Styrofoam is providing. Considering that peat moss itself has an insulation value comparable to Styrofoam (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8585433/),
You're comparing apples to oranges.
Not exactly. The link provided an example of the insulative properties of peat moss in one application. Not all peat moss operates the same, just like not all styrofoam operates the same. But their overall summary indicated:

"The results show that peat moss is a promising resource for production insulation panels, because their thermal conductivity and mechanical stability are comparable to other insulation materials."

I never said styrofoam is the same as peat moss, nor did I compare the resin application method described in that paper to be the definitive composition used for measuring peat moss' r-value. Instead, I said "peat moss itself has an insulation value comparable to Styrofoam", which when compared to the above quote appears to be consistent.
ChefDean wrote: Thu Apr 07, 2022 3:59 pm While we're talking about wet media that will have a cooling effect from evaporation, which removes heat from what it is evaporating off of, surrounded by white styrofoam.
Which gets back to the point I indicated. If that's your goal and theory, a larger pot full of more peat moss (with more thermal mass, more insulation capabilities, that is wet and has a cooling effect) will do significantly better than wrapping a plastic pot in a thin layer of insulation (styrofoam or otherwise).
ChefDean wrote: Thu Apr 07, 2022 3:59 pm Plus the white styrofoam will reflect much more heat than it will absorb, conducting virtually zero heat through to the media.
Which is true when the sunlight is exposed directly to the styrofoam. But it isn't in this application. Sunlight and solar radiation is exposed directly to the peat moss that is facing the sun. The styrofoam acts as insulation AGAINST increases in temperature from the ambient temperature radiation that's occurring around the pot (bouceback heat from concrete, for example), but also works to RETAIN the temperature inside the pot that was absorbed through direct contact with the sun, slowing it's release out into the ambient temperature.

Back to the OPs point though. If the pots are getting too hot, what are they getting too hot from? Sitting in the sun? Adding a thin layer of insulation around the outside of a pot that is angled away from the sun is going to do very little to reduce the temperature of the pot's media, as the styrofoam isn't reflecting any solar radiation or heat that would have made it into the pot and is only retaining more temperature (warm or cold) that the media exhibited on it's own. If the pots are getting too hot because they are sitting on a warm heating pad (concrete block, for example), insulation between the hot element and the pot would help that. If the pots are getting too hot because they are sitting in a warm environment (120 degrees), insulation on the outside of the pot is likely to do little to prevent the heat from being absorbed through the top of the pot anyway (if I put a styrofoam cup of water in the oven at 120 degrees the water will still get warm, but all of which is really beyond the point here, as the OP said it was 90 degrees and they're having problems).
ChefDean wrote: Thu Apr 07, 2022 3:59 pmThe top of the media, if left exposed, will heat up more in direct light due to the darker color, but only the top portion. But that will be countered to a point by the previously mentioned evaporative effect removing heat from the media, keeping the roots at the temperature of the surroundings because no more heat is being conducted in from absorption of solar radiation.
Which if correct would mean the evaporative properties of the peat moss is controlling the temperature on it's own, and the styrofoam is doing nothing to reduce the temperature of the peat moss. Hence there would be no need for the original question, as the evaporative properties of the peat moss would be adequately reducing the temperature down to acceptable levels, with or without the styrofoam (unless, as mentioned above, the pot itself is the source of the heat, such as reflecting solar radiation, in which some insulation would be better, but I'm assuming the OP isn't putting their pots under a mirror).

There may be a quick way to answer this though. Take two solo cups and fill them with water. Wrap one in a piece of space blanket material. Put both out in the sun on the grass in your front yard. Come back an hour later and take the temp of each cup of water. See if the space blanket wrapped cup has a lower temperature.
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By elaineo
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#407638
Styrofoam only traps heat if the potting soil is warmer than the outside air temperature. This is physically impossible if the soil is wet, because it takes more energy to heat up water than to heat up the air. If you are still worried about styrofoam and heat retention, poke some holes in the sides of the styrofoam cup. Problem solved.
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By ChefDean
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#407656
No one is disputing anything you've said, but you're still comparing apples to oranges, and doing a sideways dance while doing it. I won't go into a long winded diatribe about it, but you're comparing a dry peat moss, sealed in resin, to wet peat moss open to the sky, discounting the heat dissipation effects of evaporation. Peat moss stops being an insulator when wet as wet peat will actually absorb more heat due to water being a better conductor. But heat rises, and evaporation transfers that heat to the air. You would need much more peat than what's in a pot to start factoring in the effects of thermal mass. You're also discounting the OP's use of shade cloth when the sun is most intense, and his previous use of styrofoam as a pot with much better results than his current pots. Hence his quest for advice.
Also, his environment will likely be much different than North Carolina, and the added insulation and reflectivity of styrofoam may not be seen as necessary for your area, but would be beneficial in his. Where I go to Mexico often, I know a margarita stays cold longer in a styrofoam cup vs a plastic one, so no need for a test with a space blanket. Especially since a space blanket was never a question of the OP.
He already knows styrofoam will serve his needs, he's just looking for advice, other options that may be better.
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