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00:00five percent that's how many british homes have air conditioning and every july the other 95 of
00:06us lie on top of the duvet at two in the morning wondering how a country built for drizzle got
00:11this
00:11hot but here's the thing that fan in your cupboard isn't a weak machine it's a misused one number
00:1912 is the trick nearly everyone gets exactly backwards number three costs nothing and works
00:25entirely while you sleep let's count down the 15 fan tricks that cool a whole british house without
00:31a single unit of air conditioning number 15 point the fan out of the window not into the room this
00:39is the one that stops people dead because it feels wrong you're hot so surely you want the fan blowing
00:45air at you but a fan does not make cold air it has never made cold air all it does
00:52is move the air
00:53that already exists and the motor spinning inside it actually adds a small amount of heat to the room
00:59blowing hot air around a hot bedroom is just stirring soup turn it around sit the fan in the
01:06window at night facing outwards and it becomes something else entirely it stops being a personal
01:13comfort device and becomes an extraction system it grabs the stale body warmed brick warmed air that
01:20has been sitting in that room all day and throws it out into the street and the house pulls cooler
01:25night air in through every gap it can find to replace it terraced houses in particular respond to this
01:31beautifully because they've got a front and a back and very little in between one fan in a back bedroom
01:38window facing out will quietly empty the entire upstairs of the day's heat in about 40 minutes you won't
01:45feel a breeze on your face you'll just notice around midnight that the room has stopped feeling like
01:50a greenhouse number 14 the frozen bottle in the bowl everyone's nan knew a version of this and it
01:58survives because it works you take a washing up bowl or a roasting tin and you fill it with ice
02:04or better
02:05still with two two liter pop bottles you filled with water and stuck in the freezer the night before
02:10you set that in front of the fan low down and you switch it on what happens next is proper
02:16physics
02:17rather than folklore air passing over ice is chilled by contact and it's also dried slightly because
02:23moisture in the air condenses onto the cold plastic you get cool dry air coming off the back of that
02:29bowl
02:30and you feel it immediately usually within 30 seconds on a still august evening in a south-facing sitting
02:37room it's the difference between comfortable and unbearable frozen bottles beat loose ice for one
02:43reason they don't melt into a puddle on your carpet and you can refreeze them every night forever a bag
02:49of ice from the garage costs a couple of quid and lasts an hour two old lemonade bottles cost nothing
02:55and last all summer the limitation is honest this cools the person not the house the ice will keep a
03:02chair
03:02a sofa or a bed comfortable for perhaps 90 minutes it will not touch the temperature of a room but
03:08when
03:09it's half past nine and you just need to fall asleep 90 minutes is exactly the 90 minutes you need
03:15number thirteen two fans opposite ends one in and one out here's where it starts becoming a system
03:23rather than a gadget one fan blowing out is good two fans working against each other on purpose is
03:31dramatically better put one fan in a window at the cool side of the house usually the north or the
03:37shaded side facing inwards pulling air in put a second fan in a window at the far end ideally the
03:45hot side facing outwards pushing air out you've now built a wind tunnel through your own home
03:52the incoming fan pressurizes the outgoing fan depressurizes and every room between them is dragged
03:59through a current of moving air whether it wants to be or not the trick that makes it sing is
04:04leaving
04:05the internal doors open along that route and closing every other window in the house people
04:10instinctively fling every window open in a heat wave don't open windows everywhere means the air has
04:18a hundred lazy routes and takes none of them properly two windows open and the rest shut means all that
04:25airflow is forced down one corridor at speed you'll feel it on the landing a proper draft in a british
04:32house in august with no cooling equipment of any kind two fans from argos 40 quid the pair running at
04:39perhaps a hundred watts between them an air conditioning unit doing a fraction of that job pulls a thousand
04:44watts and adds 300 pounds to your summer electricity bill number twelve get the height wrong and you waste the
04:53whole night here's the first pattern break and it's the one almost nobody gets right hot air rises
05:00everybody knows this almost nobody acts on it in a hot bedroom the air near the ceiling can be four
05:07or five degrees warmer than the air near the skirting board that's a real measurable stratification and it
05:14means the two windows you choose matter enormously the rule is simple your extraction fan goes high
05:20your intake goes low if you have a sash window that's a gift because you can drop the top pane
05:26down for the hot air to leave and lift the bottom pane for cool air to arrive all in the
05:31same frame
05:32if you've got a fan in an upstairs window facing out and another downstairs facing in you're working
05:38with the house's natural chimney effect instead of fighting it reverse it and you're pushing warm air
05:43downwards against its own buoyancy the fan will run all night use the same electricity make the same
05:50noise and shift perhaps half the air people wake up in the morning look at the fan and conclude that
05:56fans don't work in british houses fans work brilliantly in british houses victorian and edwardian builders
06:04assumed you'd use the stack effect which is why the houses have tall ceilings and windows that open at the
06:10top we've spent a hundred years forgetting what the building was designed to do number eleven the damp
06:17sheet this one has a genuinely long history and it comes with a warning so stay with me you take
06:23a bed
06:24sheet an old one soak it in cold water wring it out until it's damp rather than dripping and hang
06:29it
06:29across the open window in front of the fan air is pulled through the wet fabric as it passes water
06:36evaporates evaporation takes energy and it takes that energy out of the air itself so what arrives
06:42on the other side is measurably cooler than what went in it's the same principle as sweat and the same
06:48principle as those enormous evaporative coolers used in arizona warehouses your grandmother hanging
06:55washing on an error in front of an open window on a hot day was running an evaporative cooler and
07:00calling
07:00it laundry now the warning and it matters in britain specifically this trick works best in dry heat
07:07britain's heat waves are often humid muggy sticky affairs and when the air is already carrying a lot
07:14of moisture the water can't evaporate efficiently and you get very little cooling and a clammy room
07:20in a dry still 30 degree afternoon a damp sheet at the window is transformative in a thundery close
07:27humid evening it makes things worse check the humidity before you bother if it's under about
07:33fifty percent hang the sheet if it's seventy percent and the sky is the color of a bruise skip this
07:40one
07:40and go to number nine number ten your ceiling fan is probably spinning the wrong way if you've got a
07:47ceiling fan and more british homes have them now than ever go and look at it there's a small switch
07:53on
07:53the housing usually on the side above the light fitting that switch reverses the direction of the
07:59blades and about half the people who own one have never touched it or noticed it summer setting is
08:05anti-clockwise when you're stood underneath looking up the blades push air straight down creating a
08:11column of moving air that hits you and lifts the sweat off your skin that's what you want in july
08:17winter setting is clockwise and it runs slow the blades pull air up the middle and push it gently
08:24out along the ceiling and down the walls which shifts the warm air trapped at ceiling height back
08:30down into the room without creating a draft on a cold day with the heating on that can genuinely take
08:37a couple of degrees off what your thermostat demands so there's an object in the room capable of
08:43doing two entirely opposite jobs correctly for about eight watts and the switch that chooses between
08:49them is invisible unless you go looking most people find the reverse switch by accident 20 years in while
08:57dusting the pitch of the blades matters too if they're nearly flat they're decorative if they're
09:03properly angled 12 to 15 degrees they'll move real air cheap fans skimp on the pitch because flat blades are
09:11quiet and quiet cells number nine open the loft hatch second pattern break and this one is close to free
09:19on a hot british afternoon the loft above your head might be sitting at 45 50 even 55 degrees dark
09:27slates no shade baking since eight in the morning that colossal reservoir of heat is separated from your
09:35bedroom by a few inches of insulation and a plasterboard ceiling and it's radiating downwards
09:40all night long this is why upstairs rooms stay hot until three in the morning long after the outside
09:47air has cooled to 18. so at night once the outside temperature has genuinely dropped below the
09:53temperature inside open the loft hatch and put a fan on the landing pointing up into it you're now venting
10:00the hottest part of your house into the sky through the ridge tiles and eaves two rules first only do
10:06this
10:07at night and only once outside is properly cooler than inside otherwise you're pulling the oven open
10:13second close the hatch before the sun gets going in the morning or you'll spend the day inviting that
10:19heat straight back down there's a professional version of this called a whole house fan common as
10:25anything in america almost unheard of here that mounts a large fan directly in the ceiling and dumps the
10:32house's air into the loft they cost a few hundred pounds installed and use about a tenth of the
10:38electricity of air conditioning britain has spent decades insisting it doesn't get hot enough to need
10:43one coningsby hit 40.3 degrees in july 2022 and the argument ended number eight turn the fan off when
10:52you leave the room this is the one that offends people so let me be precise about it a fan
10:58does not
10:59cool a room it cools a person the mechanism is that moving air strips away the thin layer of warm
11:07humid air clinging to your skin and accelerates the evaporation of sweat which pulls heat directly out
11:14of your body it's a wind chill effect on a human being the air temperature in that room is not
11:20one
11:20degree lower if anything thanks to the motor it's marginally higher which means a fan blowing at an empty
11:27sitting room is doing nothing but heating your house and costing you money every fan in your home
11:32should be either pointed at a body or pointed out of a window there is no third useful position and
11:39there's a limit that comes up rarely here but matters once the air is hotter than skin roughly 35
11:45degrees a fan blowing on you starts delivering heat to you faster than evaporation takes it away and in
11:52that situation for elderly or vulnerable people especially a fan can make things actively worse
11:58rather than better that's not scaremongering that's why heatwave guidance changed after 2003
12:06for the ordinary british summer though the rule holds cleanly fans cool people windows cool houses use
12:14each for what it actually does and you stop wasting both number seven shut the curtains before the sun does
12:21the damage there's no point extracting heat all night if you're letting it flood back in from six
12:26in the morning sunlight coming through a south or west facing window is not a subtle thing direct sun
12:32through single glazing can dump several hundred watts of heat per square meter into your room
12:38that's a small electric fire running all day aimed at your sofa no fan on earth can outrun it
12:45so the discipline is this curtains and blinds closed on the sunny side from the moment the sun reaches
12:52the glass until it leaves not the whole house just the side taking the hit which moves round through the
12:59day pale lined curtains are far better than dark ones because the pale side facing out reflects the light
13:06back before it's converted to heat blackout blinds fitted tight to the frame are better again
13:13better still is anything outside the glass because once the heat is through the window it's already
13:18in the room this is why mediterranean houses have shutters and we have net curtains a cheap external
13:25awning or even a garden parasol angled at the window outperforms the most expensive blind money can buy
13:32then at dusk the whole thing flips curtains open windows open fans on closed by day open by night
13:41most british households do exactly the reverse out of habit and then wonder why the house never cools
13:47down number six close the internal doors and shrink the problem you cannot cool a whole house evenly
13:55and trying to is why so many people fail think about what you actually need you need one room comfortable
14:02in the evening and one bedroom sleepable at night that's it the spare room the hall the box room full
14:09of
14:09christmas decorations none of it needs a single watt spent on it so you zone shut the doors on
14:15everything you're not using now the volume of air your fan has to shift has dropped by two thirds and
14:22the same machine is suddenly three times as effective in the room you're actually sat in
14:26put a rolled towel at the bottom of the door if it's a bad gap it sounds fussy it's the
14:32same principle as
14:33fire door and it works just as well on hot air as it does on smoke the bit people miss
14:38is the corridor
14:40a closed door either side of a landing turns that landing into a proper channel and a fan at one
14:45end
14:46of a narrow hallway generates a genuinely fast moving current because you've cut the cross section the air
14:52has to travel through half the space double the speed for free zone by day open up by night for
14:59the
14:59whole house purge it's two different modes for two different jobs and the switch happens at sunset
15:05number five use the extractor fans you already paid for third pattern break and it's sat in your
15:11bathroom right now every british home built or refurbished in the last 30 years has extractor fans
15:18in the bathroom and usually over the hob they're there for building regulations for condensation
15:24for mold nobody thinks of them as cooling equipment they absolutely are an extractor fan does one thing
15:31it takes air from inside your house and puts it outside that's precisely what you want at 10 o'clock
15:38on a hot night switch on the bathroom extractor switch on the cooker hood open one window at the far
15:44end of the house and you've built a passive extraction system out of hardware you've
15:48already got and already paid for they're not powerful individually a bathroom fan might shift 15
15:54liters a second but they run for pennies they're already wired in they're silent enough to leave on
16:00and they're pulling from exactly the spots where heat and moisture collect worst have a shower leave the
16:07fan running for an hour afterwards instead of the standard 15 minute overrun and you're extracting warm
16:12damp air continuously while you sleep the cooker hood is the real prize and it leads directly to the next
16:19one because the kitchen is the hottest room in the house and there's a reason for that nobody wants to
16:24hear number four stop making heat in the first place you cannot fan away heat you're still manufacturing
16:31run through your house and count the oven on for an hour is a 2000 watt heater with a door
16:38the tumble dryer is a heater with a drum and it vents most of that warmth straight into the utility
16:43room
16:44unless it's a proper condenser plumbed outside the kettle the toaster the dishwasher's drying cycle
16:50every one of them turns electricity into heat that ends up in your air then the quiet ones old halogen
16:57down lighters the sort still fitted in thousands of british kitchens run at 50 watts each and get hot
17:03enough to burn you 12 of them across a ceiling is 600 watts of heating on every evening swap them
17:10for leds
17:11and you've removed roughly 90 of that heat load permanently and cut the bill besides a television
17:17a games console a desktop computer a router a set-top box all of it every watt drawn is a
17:25watt released as
17:26heat there's no exception it's the first law of thermodynamics and it applies to your telly
17:32so in a heat wave cook cold salads sandwiches the microwave if you must which uses a fraction of
17:40the energy and puts almost all of it into the food rather than the room dry the washing on the
17:45line
17:46which is what it's for kill the standby lights it's not glamorous and no fan is involved but it's the
17:52reason a fan works in one house and fails in the one next door number three the 4 am purge
17:59fourth
18:00pattern break and this is the whole game british brick is thermal mass your walls absorb heat all
18:06day slowly and then release it back into your rooms all night slowly that's why a terraced house can feel
18:13hotter at 11 at night than it did at four in the afternoon the house is exhaling the day back
18:18at you
18:20it's also why those same walls kept people alive through victorian winters so it's a feature not a
18:26fault but it means the coldest air of the entire 24-hour cycle arrives at roughly four in the morning
18:33an hour or so before sunrise and it's often 10 or 12 degrees cooler than the afternoon peak
18:39that air is completely free and almost every household in britain sleeps through it with the
18:44windows shut for security the move is to have every fan you own running outwards from about midnight
18:51until seven pulling that pre-dawn air through the brickwork and stripping the stored heat out of the
18:57fabric of the building itself you're not cooling the air you're cooling the walls and cool walls will
19:03keep the house down for hours the next day because they've got capacity to absorb again then at seven
19:09you seal it windows shut curtains drawn the whole house closed like a flask most people fling everything
19:16open at breakfast because it's a lovely morning that's the moment you throw away everything the
19:21night gave you charge the house overnight spend it through the day that's the rhythm and it's the one
19:27your great grandmother followed without ever being told why number two the fan on the landing that
19:34cools the hole upstairs every british house has one spot that decides the temperature of the bedrooms
19:40and it's almost never in a bedroom it's the top of the stairs heat from the entire house rises up
19:46that
19:47stairwell all day and pools on the landing and from there it seeps sideways into every room off it
19:54your stairwell is a chimney with a carpet on it and at nine in the evening the air at the
19:59top of it
20:00is the hottest air in the building so put your best fan there on the landing high up if you
20:06can
20:06on a chair or a chest of drawers pointed out of the landing window or up into the open loft
20:12hatch
20:13leave the bedroom doors open and one downstairs window open at the back you've now got one machine
20:20emptying the single biggest reservoir of trapped heat in the house and every bedroom drains into it
20:26the results embarrass people because it's counterintuitive you put the fan nowhere near where
20:32you sleep and the room where you sleep gets cooler that's because you've stopped treating the bedroom as
20:38a room and started treating the house as one connected volume of air with a hot end and a cool
20:44end
20:44do this from 10 at night until you go to bed then move the fan into the bedroom on low
20:50pointed at you
20:51for the sleeping hours the landing fan cools the house the bedside fan cools you that's the sequence
20:59and it's the whole reason the same fan can feel useless one night and miraculous the next number one
21:05build the loop and stop buying the box and finally in first place the trick that isn't a trick at
21:11all
21:12it's the moment all 14 of the others stop being separate tips and become one machine here's the loop
21:19at sunset curtains open and every window on the plan opens cool intake low at the back on the shaded
21:27side
21:28hot exhaust high upstairs out of the top of a sash or into an open loft hatch with your strongest
21:35fan
21:35behind it bathroom extractor on cooker hood on internal doors open along the route shut everywhere
21:42else oven cold dryer off halogens gone that runs from 10 at night through the 4am purge until 7 in
21:49the
21:49morning and it doesn't cool the air it cools the bricks then at 7 you close the flask windows shut
21:56curtains
21:57drawn on the sunny side doors shut on the rooms you're not in the house spends the day slowly absorbing
22:04heat into the mass you emptied overnight and by the time it's saturated it's dusk again and you open
22:10the loop back up total cost perhaps 80 pounds of fans and a bit of discipline total running cost less
22:17than a pound a week and the reason it feels like a secret is that britain spent a century assuming
22:23it
22:23never got hot enough to need one so nobody was ever taught it try the 4am purge tonight and the
22:30landing
22:30fan tomorrow then come back and tell me in the comments whether your bedroom was cooler at breakfast
22:35because i'd bet the house on it your nan never had air conditioning she had a window
22:40so a sheet and the sense to know when to open it
22:43so
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