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maple flats
12-11-2017, 10:58 AM
Many have asked what I suggest to use as a fill/insulator in an arch, mainly under the flue pan. Some suggest sand, I do not, it is far heavier and insulates poorer than vermiculite. While I bought mine from a different source my wife recently got a new catalog for her greenhouse supplies and I see they have better prices that what I paid back in 2009. Here's a link: https://www.martinsproducesupplies.com/peat-moss-potting-soil/horticultural-vermiculite-perlite
The 20# fine vermiculite will be your best price but shipping gets pricey. They sell a 20# bag for $15.80 and shipping is 22.99 to my location (zip 13421). I checked a few other vendors and they wanted more for the vermiculite and then charged over $38 shipping per bag. Martins is in Shippensburg, PA 17257 if you are close enough to drive there.
Back when I got mine, I bought 3 bags of 6CF at $21ea and I picked them up in Syracuse, NY. That place has since been bought out. I got mine after pricing the biggest size bag that Lowe's sold and did the math on how many I needed to fill under the raised flue section on my 3x8 arch. Lowes price was just north of $500, I paid $63 and drove 25 miles to get it. I filled my arch flue section to 1.5" below the flues, then I dry laid half bricks on top. That resulted in a 1/4" space under the flues. Any cracks were filled with dry refractory cement, then I lightly misted that 3 or 4 times over the span of a day. Then I put the pans on and added enough water to start a small fire. After the fire burned out, I drained the pans because it was well below freezing. I did that 3 days in a row, to help cure the refractory.
You must put something, either fire brick or refractory over the vermiculite or it will be sucked up the stack. My bags were sold as 6CF, but I think they weighed in the 20# range, Martins can likely help you for volume.
Good luck to those just setting up a new arch.
If anyone finds a better price for vermiculite, please post it in this thread, to help others find the best price. A retail outlet will not be priced right, but other greenhouse suppliers may, or just other locations that may be closer for others to drive to.