I was scrabbling around looking for a fan at 1:30 this morning, found the tall oscillating one but the base broke off when I picked it up :-(
Are these air coolers that take water or frozen ice blocks worth looking at or are they a waste of time?
I live in a chalet bungalow and I don't think there is any insulation in the dormers, can that silver sided insulation that comes in slabs be retro fitted by sliding it up from the side?
Thanks.
<shiver> (sorry, memories of last year's terminally inane "swamp cooler" thread)
Most people's experience of these types of evaporative cooler, is that they tend to work well in very hot and very dry climates. This is because the process of evaporating liquid consumes energy and drops the air temperature, and the added humidity can be desirable.
In the UK, we normally get oppressive heat and humidity as a package. That tends to have two effects on the performance of these types of cooler; firstly they can't as easily evaporate water since the air is already close to saturation. Secondly, the added humidity is unwelcome, because it pushes the environment even closer to saturation making any natural cooling you can get from sweating even less effective.
Possibly, if you have the access space, and there are no noggings in the way. If there is no insulation at all, then even a relatively thin layer of insulation can make a big relative difference.
Alternatively, if there is space (say 35mm), just boarding over a dormer cheeks with insulation backed plasterboard could make a reasonable improvement. (then fill and redecorate the new wall surface)
The spray-water cooler, agreed. The water is just as warm as you are, the only effect is from evaporation. Which doesn't happen if the humidity is high enough.
The ice-block ones do actually have cooler water, but there's three problems:
1) You make the ice block in the freezer, which is maybe inside your house. The freezer just pumps the heat back into the house (not the case if your freezer is in a garage or similar) 2) The surface area of an ice block isn't great, so you don't get a lot of conduction into the air. 3) You're still introducing extra humidity into the airThat said, I haven't tried one to know how effective they are in real life. I think an ice pack would be better since it'll conduct directly to you.
Worth saying there's a difference between insulation for warmth and insulation for overheating. In the winter, most of your heat comes from convection (people, boilers, radiators, etc). In the summer, a good chunk of your heat comes from radiation (the sun beating down).
The foil blocks radiation, blocking gaps stops convection, the foam stops conduction. Ideally your system does all three, but you can get a good way from reducing summer heat by just reflecting radiation. Foil is good for that, but white things are good too. The 'foiled bubble wrap' style insulation is good for radiation but not so good for conduction (hence why it's used on spacecraft - no conduction or convection in vacuum).
I saw a stat that silver is only 5% more reflective than white (in the context of window blinds), and I've put up white blinds which made marked reduction in solar gain compared with blue blinds that were there before.
So if you're worried about overheating from direct sunlight, painting the outside white can make a big difference. Won't do anything for the gas bill though.
Theo
swamp coolers are OK ....
oh right...ok in the near of jockland ....tee hee
Well, evaporating water only works if the humidity in the room is low. Once you reach saturation at the current temperature and air pressure, nothing happens. After all that is how sweat works and the same problems exist. Only proper air conditioning using a coolant can really cool down a room or a car. Brian
Many thanks to Brian and the others for the replies :-)
I will get myself an ordinary fan and let it play over my hot sweaty body!
I spent last night downstairs , 5 degrees cooler than upstairs.
The answer is it depends. There are multiple designs of swamp cooler, with effectivenesses ranging from very good to waste of time. It won't surprise many that the ones usually seen in retail stores here tend toward the latter end - single stage, direct rather than indirect, not enough evaporation, resulting in little temp drop. At the other end, 2 stage systems that evaporate the water outdoors are far better.
Do they work? They cool the air a wee bit. If you're hot enough to be sweating you won't experience the difference, as they reduce your evaporation. But if it bring the temp down to where you don't need to sweat, then yes the improvement in comfort is nice.
Should you buy one? If you want evaporative cooling for a week or 2 just use wet towels and a fan.
In heatwaves I've sometimes sprayed the roof with water. Makes quite a difference.
Don't fanny about with them. Get a split Aircon system and luxuriate in cool comfort or use it to provide heat in the winter. It's a bigger initial cost but worth it in the long run.
In the evening after a hot day, open the loft hatch, so that the hot loft acts like a chimney to draw cooler air up from downstairs. This assumes that there are decent vent tiles in the ridge.
Bigger initial cost and much bigger running costs unless you have solar PV panels. Bite the bullet and upgrade the roof insulation.
A beneficial side-effect of solar panels is that they stop radiant heat from hitting the roof tiles in the first place which can make a dramatic difference to loft temperatures.
Invariably useless in the UK. Can work OK in some arid dry hot regions.
The most effective combination in a very small space are the rigid 3mm thick polystyrene foam with a foil backing. Aluminium facing inwards and the insulation facing the outside world. It cannot ultimately stop all ingress of heat but it can slow it down considerably.
I did this to my S facing garage doors and the workshop is now bearable even on the hottest summer days although the doors get insanely hot (too hot to touch) and paint on them fails more quickly.
It is more subtle than that. If you want to reflect heat away then matt pigment white paint is much better than aluminium foil.
You can easily test this with a kitchen sin experiment. A4 white paper vs A4 aluminium foil. The latter will get mad hot in direct sunlight. Although foil reflects more light it is also very bad at emitting lower energy thermal IR to radiate heat away (whereas a white paint is essentially a black body in the thermal IR band).
There are now designer materials that are both a black body for thermal IR and a mirror for visible and near IR light. They are still a bit too expensive for consumer use but they are getting closer now:
Popular science version:
A thin insulating layer and a mirror finish on the inside surface will also make a big difference to how quickly the room gets hot and so how hot it gets. It is most important on the S and W facing walls.
More insulation is better but you need an airspace against the foil.
Experienced one on Monday, a Convair. It turned a very small area from too hot to nice & cool. Their abilities are much more restricted than heat pump ac, but they work fine under the right circumstances. However if you buy a unit at random & use it without any understanding of what they do & how, odds are not on your side.
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