House Earth Bank

A house earth bank is a long mound of soil raised near a dwelling to take the force out of the wind before it reaches the walls, so less heat is stripped off the building in cold weather. Anything that slows wind across a piece of ground is a windbreak; most are rows of trees or shrubs, and this one is made of earth. An earth berm is packed against a wall to steady the temperature inside; this stands clear of the house and works on the air.

Two things decide whether it helps: how tall it is, and how much air it lets through. Height sets the reach - shelter runs eight to fifteen times the barrier's height downwind, halving wind speed, with some effect as far as thirty times the height. So a bank that shelters a house at any real distance has to stand as tall as a mature hedge, in compacted fill at a slope gentle enough to mow. Solidity works against it. Guidance calls for a barrier that lets air through, roughly a quarter to two-thirds solid depending on what it is for. Earth is entirely solid, and a solid barrier gives deep calm just behind itself and then loses it, because the low pressure in its lee drags the fast air back down.

Its best work is as the base under a hedge, supplying height the plants would take years to reach while they supply the openness earth cannot. Built close around the house it puts the dwelling inside the drift of snow, dust and litter it creates, where 45 to 90 m (150 to 300 ft) of standoff is what the figures call for. Run all the way round it has no direction, so it cannot block a cold wind without also blocking a summer breeze, and across a slope it dams the cold air draining downhill on still clear nights, holding it against the house and making the coldest nights colder. An arc left open on the cold quarter and on the downhill side avoids both. Until cover takes hold the bare fill erodes in the weather it was raised to intercept. Upkeep is cover on both faces, slopes mown or grazed, the gaps kept clear, and the base cleared of what the wind drops against it.