Passively-cooled larder design

[Jason]

[Jason]

I live by the sea in the far North of England, so it never gets *too* hot, and never gets *too* cold. What we do have, is a cool sea breeze, so the air is seldom still, and fierce gales that blow down from the North. The breeze I could probably make use of, but the gales certainly need to be kept out of the main living area of the house.

For fruit and vegetables, the fridge is too cold (and too dry) and the room is too warm. I would also like to be a little less reliant on energy use to keep things cool, especially when careful design could obviate the need.

-- JJ

[Cicero]

========================== You might consider incorporating unglazed earthenware pipes or tiles into your design. Old fashioned butter and milk coolers were made from clay and had to be soaked in water periodically but worked pretty well. A scaled up version might be possible.

Cic.

[Andrew Gabriel]

I have an alternate loft hatch cover which gets put in place in the summer, which has a rather large fan in it to draw air through the house and expel it through the loft (also cooling the very hot loft). It is under the control of my home automation system. I haven't actually spent much time working out the optimum rule for switching it on, but it currently switches on when the loft reaches 25C. I often switch it on manually in the evening too to draw in the cooler nighttime air.

[Mary Fisher]

Is your house like Woodchester Mansion???

Heavens :-)

The thing is that in past centuries there wasn't central heating. Even our kitchens are heated these days, if the pantry opens off a heated kitchen it will accrue some of that heat.

Our kitchens are smaller than those of the past, in such a house as Woodchester the whole volume of the kitchen and the house itself would be slower to warm in weather such as we've had in the last few days. There's no comparison.

But yes, if you're prepared to compromise from 100% passive there are many ways to keep a pantry/larder cool, not that I'm convinced that a tiny fan would do the dibs.

Mary

[Mary Fisher]

Our house has one of those, it's 3" thick and tiled. It becomes the same temperature as the rest of the kitchen :-(

Water cooling comes to mind ... but do you want a moisture laden atmosphere?

Mary

[Mary Fisher]

Quite. Anything 'passive' will be a compromise.

I would too. I've had to learn to live with it.

Inner city Leeds is comparitively warm. I have nowhere to air-dry hams and can't even keep root vegetables through the winter :-(

Mary

[Derek ^]

Wasn't York famous for hams, just 20 miles away?

How do the Spaniards manage it ?

DG

[Mary Fisher]

25 in fact. But York hams are dry cured, not air dried.

They probably have wind machines these days. You don't think that it's naturally air dried do you? If so, you probably think that sun dried tomatoes are laid out in the sun ... :-)

Mary

[Jason]

Yes, I have one of those. Before we discovered 'Lurpack Spreadable', it kept the butter at just the right temperature throughout the summer. It just needed topping up with water every couple of days.

-- JJ

[Nick]

I think one brand was called something like "Osokool"....

It was a white block of something like a cubic foot, walls about an inch or so thick with a depression in the top into which water was poured to keep the whole thing damp. Evaporation of the water from the porous walls kept the innards about 10 degrees cooler inside...

Nick

[meow2222]

Great idea Jason. This should be one of those desirables for a well designed house.

There are a few options. I'd go with a small fan and differential thermostat for a start. IME this has knocked 4-6C (and occasionally as much as 10C) off evening and night time indoor temp without any insulation. Add insulation and lots of thermal mass, eg cast in situ concrete, and you'll see a temp reduction all day as well.

The diff stat is important, running a fan on a timed schedule did not deliver anything like as much benefit. A cupboard would only need a tiny 3" computer case fan, with 2 exterior holes for air inlet and outlet. Holes should have metal mesh to keep rodents out and insect mesh to keep bugs and debris out.

You'll want the puter fan to be silent, so I'd mount it on rubber bushes so it doesnt use the all as a sounding board. Use a variable V wallwart to power it, so you can select 12,9,7.5 or 6v. This reduces consumption and noise if full power isnt needed, and it probably wont be. A simple labyrinth over the fan is the best way to kill fan noise, so if you find your heavily constructed cupboard doesnt silence it, you can make a very effective labyrinth out of sheet steel with 2 layers of cardboard glued onto it. Or chipboard would probably be easier.

If you want to take the cooling further, there are 2 simple ways to chill it.

1. Take the inlet air through a plastic pipe sitting in a trough of water. A standard ballcock keeps the trough filled. The water evaporates, cooling the inlet stream. The pipe barrier keeps the inlet air dry, you dont want to get the cupboard damp.
2. Bury a plastic pipe underground and bring in the air through that. Temp underground is well below ambient in summer. Cooling a house this way needs an awful lot of pipe, but a small cupboard doesnt.

If you must have something totally passive, larger air holes with one way dampers would work, waiting for the wind to blow through. But this would require more vent area than forced air, plus actuators to keep the dampers shut when required. I'd go with the fan, its much easier.

There are of course other options. Heat pipes act like one way heat valves, and are fully passive, but a fan and stat are a lot simpler and controllable. Heat pipes have been used in custom fridges to provide this type of cooling during winter, reducing energy consumption.

I wouldnt use air from under the house as it'll be damp and musty, not whats wanted. If using evaporative cooling, keep the damp separate to the intake air. Plastic pipe makes a very simple heat exchanger.

Lastly, I suppose another alternative is to run the cold water supply pipe to the house through the larder before it goes anywhere else. This comes in at a nice cold underground temp. If you do that, you'll need a drip tray, as condensation may form on the pipes. Add fins to the pipe for greater heat exchange.

NT

[John Rumm]

Perhaps you need to think along the lines of how people in hot countries use pottery jugs etc to keep liquids cool. The slow seepage of liquid through the material cools the jug via evaporation.

Now you need something that is only permeable on one side, and that side is outside the house.

[Dave]

How about running the incoming water main through the pantry via a matrix of copper pipes attached to a wall?

Dave

[The Natural Philosopher]

Thats no bad idea.

When I was laying the kitchen slate floor a few summers ago...very very hot...and using considerable quantities of water to make cement and wash the cement off the buggers afterwards, the incoming pipes were DRIPPING with condensation..water tends to the diurnal mean of the temp range over several days...

[Mary Fisher]

Yes - and I use that method a lot when under canvas, have done for 60 years.

But it's not the same thing as coolking a larder in a building.

Mary

>

[John Rumm]

No reason it could not be with a bit of lateral thought. Coolroom on the outside of the building with a permeable panel when the window might be, backed with a small reservoir made from something non permeable. The outside surface would support the evaporation and the whole reservoir would then cool. This would give a large cool surface in the room.

You could enhance the evaporation with a double skin on the outside and a solar PV panel driving a fan to add some forced circulation through the evaporating layers.

[Steve Firth]

In most Victorian pantries it's exactly the same thing, no DPC so the pantry is cooled by water evaporating from the porous brick.

[Mary Fisher]

Jason, you've had me searching the house for a favourite book - Elizabeth David's Harvest of the Cold Months (Penguin 1996).

This is a scholarly but readable account of the history of ice making and storage over the world, including India, Persia, the Levant and other hot and dry places. If you can get a copy (Amazon have some used ones) it won't solve your immediate problem but would be worth reading, it might give you some ideas :-)

Mary

[Jason]

I suspect with changing climate (and bigger extremes in the South East) that idea may be something that could be rejuvanated. Imagine every new home being built with an ice-house :-)

-- JJ