David Mark

Wyo -

From what I've read, it needs a minimum of R30 on sides. top and bottom. However you get there. That could include bales of straw, a double wall filled with wood shavings such as used for animal stalls, a base of wood pellets (like for pellet stoves), etc. Henry David Thoreau describes the winter of 1847 when a huge pile of ice was covered with straw and a tarp - no building - and lasted not just the summer but into the fall and the next winter.

Important point here is minimum volume of ice to make this work. Again, smallest dimensions I've seen for traditional ice houses call for at least 20 tons of ice. I am not saying smaller cannot last through summer, but I am guessing it won't. A much higher R-value would help.

As to why size matters so much, it's about mass versus surface area. A cube of ice three feet on each side has a surface area of 54 square feet and volume of 27 cubic feet, for S/V=2.0. More surface area means faster melting. Take dimensions up to 5x5x5 and its 150 square feet and 125 cubic feet for S/V=1.2 (and ice weight of 3.6 tons). At 10x10x10 the S/V=0.6 and weight = 29 tons.

From historical accounts of big, commercial ice warehouses in Maine, they expected 5% meltage by June (remember, still cold in Maine in June) and 20% by end of August. We are talking buildings with two feet of sawdust between the double walls and outside dimensions of 80 feet wide, 40 feet tall and 300 feet long. They used horse-drawn ice plows to cut the ice six inches deep, pry bars to finish the breaks, and steam-powered conveyor belts. Blocks were roughly 1x2x2 feet and 200 pounds each.

Nelfson -

George Washington tried snow - it did not work. He had slaves gathering snow, and then pounding it into his cellar to pack it down. Problem is, cannot get close to the density of ice. In subsequent years he sent his slaves out in boats on the Potamac River to bring back pieces of ice.

Ken and Dave -

Thanks for posting all the math. A few comments - As a historian researching ice cellars and ice houses, I've learned that once you dig past a meter or so, the year round soil temperature in central New England is around 50F. So, huge amounts of work do dig a pit or cellar, without huge benefit. Prior to 1805 it was all cellars (Washington at Mount Vernon, Jefferson at White House and Monticello), but after Frederic Tudor commercialized the process of storing and shipping ice it was all in above ground buildings - initially brick or stone, but then wood.

For the cellars, before filling, bottom filled with a foot of gravel and two feet of sawdust on top of that (packed to less then a foot once ice added). Then planked first or ice directly on top of sawdust. As filled, a gap of one foot left between walls and ice, to be filled with packed down sawdust. Or, an inner wood wall built and the space between the wood wall and the outer stone-lined pit wall filled with sawdust.

A common design for small ice houses was a double-walled wood building 10-20 feet wide (all inside dimensions), 10-15 feet high, and 15-30 feet long. If you look up ice house and Tobyhanna, PA, they have an ice house that holds 50-60 tons, and is filled every winter. The gap between the inside and outside walls about one foot, filled with sawdust.

I've seen mention of Amish using expanded polystyrene block 18-24 inches thick (about r=5 per inch). Have to allow for drainage at bottom and venting at top so that any warmer air can escape.