hot tin roof

[stoneleighhouse]

Is the hive hotter or cooler under a shiny tin roof.. like the one sold by T****s?

 

[pbh4]

Yes!

 

[blackcavebees]

Yes!

Is that yes to hot or yes to colder ??

 

[Mr greenwood]

Probably

 

[pbh4]

Okay, a less facetious answer! A shiny roof will both radiate and absorb less heat than a dull roof. A matt black roof both absorbs and emits radiated heat most efficiently. What that means is if it is hotter outside the hive than inside, the shiny roof will have a cooling effect. On the other hand if it is warmer inside the hive, it will have an insulating effect. Think of it as slowing down the heat transfer from hot to cold.

That is why thermos flasks (Dewars) are shiny.

There is an article at http://en.wikipedia.org/wiki/Stefan–Boltzmann_law on radiation physics but it does come with a warning that "This article may be too technical for most readers to understand".

The shiny roof will not affect other modes of heat transport, namely conduction (through physical contact with surrounding materials) and convection (hot air rising) but I expect it will make some difference.

Paul

 

[Poly Hive]

So that is the theoretical answer but what is the practical situation?

Anyone geared up to measure?

PH

 

[thorn]

So should I paint my poly nuc black (I've got some spare charcoal chalk paint), white (the remains of a tin of masonry paint) or any colour matchpot my wife brings back from B&Q and instructs me to use? Will the black make the nuc too hot in the unlikely event that the sun may one day shine on Leeds?

 

[Poly Hive]

Frankly it will make no odds but a more subtle shade will assist in disguising it.

PH

 

[Tom Bick]

There is an article at http://en.wikipedia.org/wiki/Stefan–Boltzmann_law on radiation physics but it does come with a warning that "This article may be too technical for most readers to understand".

Paul

That will be me then

 

[barratt_sab]

Frankly it will make no odds but a more subtle shade will assist in disguising it.

PH

Ours are all green, so those using the evil eye of the online arial mapping services have a harder job spotting them.

 

[itma]

A shiny roof disorients unwary (young?) bees, reflecting the sky and causing them to crash onto the roof.
Hence I'd think its probably better to paint them with a matt finish - but I haven't bothered yet!

Yates (in Caveat Emptor) advises putting some insulation (expanded polystyrene sheet) between the roof metal and the roof wood. I've done this on the most recent roof I put together, but I doubt there will be much dramatic difference to see.

 

[madasafish]

I had shiny aluminium roofs on 2 x warre hives but a nice (?) wet spring /summer has left a lovely green patina of lichen .

Free and eco conscious

 

[oliver90owner]

A little thought given to the actual interior temperature gradients and the thermal conductivity of air might be useful for some to consider.

Consider a well insulated roof in the winter, covered with snow, and a well insulated roof in the summer - yes, a proper roof is designed to be a thermal insulator.

Think, so what? Do the bees care anyway? Would any heat absorbed through the roof make any significant difference? Think Spain and other hotter/warmer climates than here? Think it is not even really worth measuring?

 

[alanf]

Is the hive hotter or cooler under a shiny tin roof.. like the one sold by T****s?

A 'tin roof' is seen far more frequently on houses in places that are far sunnier than here such as Australia. In hot sun it reflects more radiant heat than, say, a black felt roof.

 

[user 6228]

Solar heat gain is major problem in building design. There's about a 1Kw per Sq m falling on your buidling or hive .
Any air conditioning system needs to manage that heat gain and that takes effort.
Bees run an air conditioning system in their building , so large heat gains may require larger inputs from the bees to maintain the status quo. Although there may be little outside noticable effect, the bees will have to adjust to the extra 0.5 to 1Kw (size, surface emittance, and aspect to the sun depending).

I have two highly insulated hives one painted green the other ally coloured. The green is hot to the touch the ally coloured quite cool. With a wooden hive the level of insulation is so low , that most of that heat, the bees inside will have to deal with .

They can deal with it, but should you as keeper of bees make them ?

I choose to help them in summer with insulation and reflective coatings.
Your choice is your choice.

 

[itma]

A 'tin roof' is seen far more frequently on houses in places that are far sunnier than here such as Australia. In hot sun it reflects more radiant heat than, say, a black felt roof.

Having lived under such a roof in the tropics for a couple of years, I can assure you that they still get bl**dy hot, and are not primarily specified for their cooling properties!

 

[oliver90owner]

that most of that heat, the bees inside will have to deal with .

I just don't believe it! In fact, utter rubbish. The bees would never need to deal with any where near 'most of it' even if there was a 'beekeeper' with just a metal roof and no crownboard.

Beeks, just consider your domestic hot water cylinder; maybe 60 degrees at the top (3kW heat input?), but how hot is it at the bottom - and I mean here the underneath surface? 'Nuff said?

Even with a kW incoming, most would be reflected away, only half re-radiated inside as infra-red (approx equal amounts from each side) and any conduction to the air would need rapid dispersion with a forced draught as hot air would stay at the top (convection). So to say 'most' is a pure exaggeration.

 

[Poly Hive]

I measured the outside surface temp this afternoon of a poly roof and got 31.2 C

The underside surface was 3 degrees cooler, and this was consistent over a sample of three.

PH

 

[user 6228]

dup post

 

[madasafish]

I just put insulation under the roof. Job done.