Design of a drug warehouse with temperature control features
We are rebuilding a drugs warehouse in an area where the temperature can reach 45 degrees and the drugs should be stored at less than 30. We have the chance to spec a building that will keep cool enough using passive cooling design features. I am not an expert in this and I would like some help with the specs. The building will be built by local contractors so can't be too complicated or sophisticated. We are looking at a two roomed building about 5m x 15m.
I have been working in Darfur and I have used a brick building with iron bars at the windows, no windows, and a wooden door. The roof had inside a simple cartoon chalk ceiling and over the usual corrugated iron high up and quite large to give maximum shadow.. I take you do not count in electricity, so did I. If you would have water or not is the next issue, with water you can get nice cooling by just keeping the roof little wet by a continuous drip of water. If no water, nor electricity, the most available ventilation under the most extensive shadow is the only way to get some cooling. In Darfur that was a nightmare when there were sand storms, and they were frequent. All had to be cleaned from the sand. Double roofing does some help. Watch the winds, it may be blown away if not properly done. I Have no idea of how or where you can get passive cooling design features. It sounds like income generating projects and conflict resolution techniques. But I keep my eyes open Regards, Giorgio Francia
We set up a cold chain in Ethiopia using solar fridges. Other drugs were in a white washed container with high thorn bush sides and roof with big overhangs to to act as a shade. Prop the roof at least 0.5 m above container to allow air flow. Regards, Gordon Browne
In my own experience, MSF would build pharmacies with high roofs and ceilings with ventilation near the top - barred windows (and meshed against bats). With corrugated iron roofs they also had a reinforcing bar cage below the ceiling to prevent people prising open the roof to get at the drugs. A good overhang of roof, to prevent direct sunlight coming into the windows also helps. Ventilation above the ceiling at either end (again meshed) keeps down the temperature above the ceiling. A light colour for external walls would help.
A container would work with a grass roof above it to insulate - again a good gap between the container roof and the grass roof with plenty of overhang.
We had a similar RedR TSS inquiry about 2004 for a document building in East Timor. Simply you can dig a hole to about 1.5 or 2 m where the ground temperature is stable. Infill with clean regular sized large boulders for heat mass, but still with air flow. Then using a low power or convection system air is drawn / forced to the bottom of pit and stabilised and then drawn off at the top of pit. An old document "the Owner Built Home" circa 1972 by Ken Kern describes in more detail. Hope this assists.
The temperature experienced in any space is a combination of the ambient air temperature and the radiant heat exchange with the surroundings. If the surroundings are warmer than you, you gain heat; if colder, you lose heat - this is why sitting next to a window feels cold in the winter in N Europe. So the trick with passive designs is to pay attention to the temperature of the building fabric, as reducing the air temperature takes some active measures.
The first principle of passive temperature control is thermal mass. A large thermal mass reduces the swings between night and day temperatures, giving you a cooler temperature during the day. The simplest thermal mass to add is through walls. (You can also increase effective thermal mass by part burying a structure, but this can bring lots of flooding issues). A wall thickness of 1m or so is a good rule of thumb without calculation - what you are trying to achieve is a 12 hour delay between external and internal temperature peaks. (At night the air will be cold, so it does not matter if the internal wall surface is warmest then). Cheapest way to build walls is probably a brick or block skin with an infill.
Second feature is limiting thermal gain by the walls in the first place by using an overhanging roof to shade the walls. You can limit indirect gains by planting shrubs around the building (outside the overhang) to limit radiant gain from the surrounding ground.
Third feature is limiting isolation (sun shining through the windows) and radiant heating from the ground outside. This means using small windows (typically narrow slits that are just enough to provide lighting inside.
Fourth: To limit thermal gain from the roof you need two things:
4.1 A ceiling. This should be as high as possible (so that you get less heat gain from the warm air trapped under the roof effectively radiates less energy downwards), and ventilated (to allow warm air to pass through).
4.2 A ventilated roof space. Spaces under thatch roofs can be quite cool (as they are porous), but thatch brings a whole lot of maintenance issues. Mixing thatch and CGT sheets requires a complicated roof structure, unless directly overlaid with all the corrosion problems that that brings.
Options for ventilated CG roofs are using a "Mozambique" roof where the two parts of the roof have a vertical gap of 0.3m or so at the ridge that is fitted with a ventilator all along it, or fitting ridge ventilation all the way along the roof. Monopitch roofs are not recommended because of solar from the wall. You need to have fairly generously sized vents to encourage a good air flow.
As this is a drug store you will need to screen vents to prevent bat and rodent entry.
You can also fit lower level vents in the walls to encourage cooling through the stack effect, but the danger is of drawing in the very hot ... (more)
There have been a number of responses to this enquiry of which some are very technical and would take a lot of time and effort to put into place. I would like to mention a couple of very simple options.
Double skin roofs which have ventilation at the top to allow the hot air to escape will help to prevent heating due to solar gain but the ambient temp. is still too high so something has to be done to lower it. A simple form of cooling is evaporation.
Many Moorish buildings in southern Spain, and throughout the Arab world I suspect, have a central courtyard with a fountain. The water spray cooled the air which was then circulated through corridors leading off the courtyard to cool the adjoining rooms. This is ok if there is electricity for a pump, there is plentiful, pressurised water supply or there is a handy artesian bore hole in the back garden.
When I worked in Afghanistan I was introduced to 'Afghan air conditioning' A vaguely domed shaped roof had been formed with rough cut branches that still had plenty of smaller branches attached. Onto this was placed what I can best describe as tumble-weed. Scraggy little bushes with very small leaves. At first I wasn't impressed with this 'inadequate' sunshade but when a young lad was given the nod and he threw a few mugs of water on the tumble-weed the drop in temp was amazing.
Finally: Whenever I go camping my milk is left under the car, stood in a billy-can of water and covered with a wet tea towel which is draped into the water. Evaporation keeps it cool.
I hope that some of the above is useful and can be adapted to your situation. Be aware that mossies breed in water and vessels should be emptied periodically to break the cycle of egg laying/hatching. The French didn't know that when they started to build the Panama canal and died in droves.
Regards, Alan Jenkinson
I had a look but my records are not that good as about the time I changed computer but I can remember the basics proposed for East Timor. Dave Hodgson is more an expert but here are the basics that I recall:
In most parts of the world the ground temperature does not change year round at about 1.5 to 2 m down and is fairly constant; the idea then is to draw or push air from the bottom of a clean hole / space about that depth.
In the Timor case I remember we needed a stable temperature in an area with an unreliable electricity supply so the answer was to use a wind cowl (a pivoting intake or wind scoop aligning to the prevailing breeze) to create an air flow air via a large duct which discharged at the bottom of the pit. In the middle east wind scoops (malquaf or badgir) are used to channel air from the higher levels down into living areas and the same principles can apply. From there the air would either flow, or could be drawn by a low power (possibly solar) fan up into the building.
This was proposed by a number of adherents in the 1970s, the one I recall was in Ken Kern's "The Owner Built Home". I recall in that book he also referred to a German patent that used crates of gravel placed in cellars to increase the efficiency and heat mass. Again the principle is fairly simple that the air must flow around the gravel and be in contact with it so a uniform rather than graded gravel would be desirable.
In another book "The Natural House Book" by David Pearson, he provides comparative figures for Australian built earth covered homes indicating the significant temperature stability below ground - as I recall in one example about 12 Deg C fluctuation internally while outside temperatures varied from subzero to mid forties.
The ceiling of the warehouse needs to be ventilated (with screens against bugs and snakes) to allow the hot air to rise and ventilate, thus drawing air from the pit.
In a somewhat different application traditional Khmer houses do this... the tiled roof is unsealed allowing hot air to flow out. The slatted floors which are raised above ground allow any breeze to enter, and even draw air in as the hot air rises and escapes through the vents, such as when two to three families live as an extended family in a large room; the air is drawn through the floor and vented through the roof. This air movement is also effective at minimising mosquito nuisance ( they do not like moving air).
My suggestion would be to use the stable temperature below ground, increase the heat / cool mass and draw or flow the cooled air into the building (may be low power solar fan, heat funnels may work)
I did two missions in South Sudan and my impression there was of considerable heat and quite ... (more)
I know this may sound like a wild card but phase change materials are also great for thermal stability used commonly to keep remote telecommunications equipment cool http://teappcm.com/ I have used them in thermal storage floor slabs and have heard of very cheap non commercial versions Regards, Dave Hodgkin
Mechanical means or physical
1 Twin wall tent; 'fill' the void space with straw/grass; absorbent material; keep wet, circulating system, then get an air blower to push or pull air through the inter-space. This is the same concept to 'Iraqi air con'; yes there is cooling as there is constant heat loss through evaporation
1 Paint the external walls of the tent silver or cover in a good reflective material; glue aluminium foil to external skin
Sorry; this might seems a little 'blue-sky' but could help.
I cannot add anything to John's excellent response.
When considering thermal comfort, passive design, building maintenance and material selection , we often refer to the Building Issues report from Lund, specifically:
More generally from Lund http://www2.hdm.lth.se/bi/report/frame.htm, or:
Lastly, our overview training on climatic design introduces the concepts and is consistent with the training that we developed both for the IASC ESC and the IFRC:
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