UKH

Do the rules of human wind chill factors apply to objects such as buildings?  I think of 'human wind chill' being best explained 'increasing wind speed increases the rate of heat loss of a person to a rate equivalent to that lost to a lower temperature'.  If this increasing rate of heat loss affects buildings as much as it does people, then could it be that a house in a relatively warm but windy place (like Land's End) could actually cost more to heat than somewhere colder but less windy (like central Europe)?  Are there any rules of thumb out there which can be used?

Wind cools people down by:

Blowing away sweat (houses don’t sweat)

Blowing away air next to the skin which has been warmed by the bod and replacing with cold air (houses, if well insulated, are typically cool to the touch)

So I think wind will not have the same effect on a house as a person?

The heat transfer coeffiecient tends to increase with an increase in fluid flow speed, so yes same rules apply.

However, it won't be the rate limiting step of the heat loss to the surroundings, so will make a neglible difference. The heat transfer coeffiecient from the surface of the building to the air is already very high, hence it feels cold to the touch, as Jack says.

What you are describing is Forced Convection:

https://www.sfu.ca/~mbahrami/ENSC%20388/Notes/Forced%20Convection.pdf

The temperature of a house's exterior walls is typically a lot closer to the environmental temperature than the interior temperature due to the insulation provided by the bricks (take a look at Conductive Heat Transfer for details of this).

Depends on the starting temperature of the object. windchill will cool objects faster then if there was no wind but the object will never get colder then the air temp. so in this regard yes windchill does affect objects too.

I tend to think about it this way: if you took a hot piece of metal and put it in a room to cool down then that will take a while because the air around it be heated and will linger (well slowly rise due to convection) and effectively help to insulate the object from the cold air around it, if you pointed a fan at the metal then it'd take the hot air away faster and replace it with cold air, speeding up the cooling process until the metal is the same temperature as the room. 

anyway that's how i understand it!

Yes same rules of physics apply. 

Remember back to school science... and beakers of hot water with "Aluminium ears" (increased surface area), damp cotton wool jackets (to simulate sweating in animals or just wetness in objects) etc 

A big factor would be humidity of the air too. -40 in Arctic is Ok if dry, deadly if humid

Your example is correct, but even if the fan blows air at the metal which is at the same temperature as the air that is displaced (ie infinitely long metal and air flow), the rate of cooling will also increase. 

The increased air velocity results in increased mixing of heat in the direction perpendicular to the air flow. This generally has more effect than the change in air temp you describe, as generally the change in air temp is tiny.

Wind Chill doesn't apply to buildings and other inanimate objects as they do not have a temperature in the same way as warm blooded animals.

Objects at a higher temperature than the surroundings will lose heat until their temperature becomes the same as the surroundings. This will happen more quickly if air is moving over the object but they won't get any colder than the surroundings.

Warm blooded animals 'try' to maintain a constant temperature so continue feel the chilling effect.

Dave

Ok so it may not be called wind chill, but wind still effects rate of heat transfer until equilibrium?

Unless the inside of the buildings are heated.  Most of us like the buildings we live and work in to be warmer inside than the ambient temperature outside much of the time.  Our houses are generally cooler inside and better insulated than our bodies, but nevertheless they do "have a temperature".

Unless the object is wet, in which case evaporative cooling may ultimately reduce it's temperature below that of the air.  If it happens to be raining much of the exterior wall of a building exposed to the wind is also likely to be wet because rain does not necessarily fall vertically on a windy day.

Some good answers here. 

This is fairly obvious - but air exchange is likely to be more meaningful than windchill. My house is not very airtight. The leakage is just enough to ensure adequate ventilation and prevent damp. When it's really windy there is a lot more exchange of air and heat. I can hear the chimneys roaring, and feel draughts from windows. 

Do humans get colder than the surroundings?  

Wind does make a difference in cold places.  In warmer places less I expect.  

Sometimes when it's very very hot and dry, evaporation of sweat can cool the skin to lower than air temperature

Of course on cold sunny days the temperature experienced can be warmer than the actual air temperature.  The mean environmental temperature is sometimes expressed as 2/3 air temperature and 1/3 radiant temperature

So on a slightly different note would wafting a towel at a piece of warm rock cool it down? 

Ok I see what you mean, but I meant through wind chill. 

Yes, if the surroundings are hotter than 37C. 

They effectively do if they are wet, and especially if they have wet porous stone walls.  Making the walls hydrophobic or sealing them completely reduces the evaporative cooling and makes them lose noticeably less heat. 

At 37 deg C I wouldn't be worried about wind chill.  

Is the house on a treadmill?

Sorry, couldn't help it *hangs head in shame*

Only dead ones?

Dead ones will become the same temperature as ambient.

Wafting a towel can have amazing effects.

"Ginzberg is 74 and he marries a much, much younger woman. Soon, they’re having some problems—the young woman is just not being satisfied. So they decide to go see the rabbi for advice. The rabbi hears the problem, strokes his beard thoughtfully, and says to Ginzberg, “Let’s try something they say in the Talmud. Go find a nice, handsome young man. Have him come in while you’re making love and waft a towel while you’re performing.”

So Ginzberg and his wife find a handsome young man, and they bring him into the bedroom with them. Ginzberg starts shtupping his wife, and the young man wafts a towel. They try this a couple of times, but it still doesn’t work. Nothing. The wife just isn’t satisfied. So they go see the rabbi again, tell him what happened. The rabbi says, “Okay. Jewish tradition says we do anything to satisfy our wives. Go back and try again, but this time reverse roles. Murray, you waft the towel. The good-looking young man, he gets into bed with your wife. Let’s see what that does.”

They go home, go back to the bedroom. Ginzberg picks up the towel, the handsome young man gets into bed with the wife, and they start having wild, passionate sex. The wife starts screaming, going absolutely crazy, has an incredible seven-minute orgasm. When it’s over, Ginzberg grabs the young man’s arm and says, “You putz—that’s how you waft a towel!”

From the stage production of Old Jews Telling Jokes.

Given that temperature in some parts of the world have hit 50C they'd have to

Thanks for that, but there's some heavy maths there for a non-mathematician like me!

A quick google for 'forced convection heat loss from a house' came up with this:-

https://www.engineeringtoolbox.com/convective-heat-transfer-d_430.html

Looks like the air-heat transfer coefficient doubles from near calm to force 8.  I'll do some sums later - need to work out the surface temperature of my house first...... pumping some guessed figures in for the gable end of my house results in a heat loss of 5kW rising to 35kW in a force 8.

That seems unlikley

The thermal conductivity of your wall (Watts/m2/deg C) will be a composite of all of the layers, bricks, insulation, plaster etc and the film of still (on a calm day) air on the outside and inside of your house.

For a human with bare or lightly covered skin the film of still air will be very significant, for a moderately well insulated house much less

If you want to make a good guess make sure you consider the total heat transfer resistance:

https://www.engineeringtoolbox.com/overall-heat-transfer-coefficient-d_434....

I imagine its fine to just consider heat transfer from the inside wall surface to the outside air to (slightly over)estimate heat loss, ie just conduction in the wall and convection outside. It will probably show that the wind speed doesn't matter much.  

Also many older houses have a suspended wooden ground floor which is open to the exterior via ventilation bricks to protect against dry rot. Even if draughts into the rooms are prevented, there is likely to be inadequate insulation over the flooring. In addition there are often uninsulated, copper pipes serving hot water to central heating radiators in the subfloor space which is fairly near exterior temperatures......winds will probably improve the ventilation but increase any heat loss.

I had something even better than that - my house has suspended timber floors. It also had un-insulated central heating pipes which actually sagged into the lake which forms in the subfloor void in winter as the water table rises. I wondered why my downstairs rads would stop warming up in February after prolonged rain until I lifted a trap and saw the 'tidemark' on the sleeper walls!