Polystyrene sheet under aluminium rooves

Beekeeping & Apiculture Forum

Help Support Beekeeping & Apiculture Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

beeno

Queen Bee
Joined
Apr 25, 2011
Messages
5,181
Reaction score
234
Location
South East
Hive Type
National
Number of Hives
5
Is this a good idea or would it cause condensation and rot the wood?
 
No it won't - the more insulation you have the better chance your bees have of maintaining the hive temperature they want ... Why do you think so many people are turning to poly hives and those with timber ones are putting kingspan on top of the crown board ? There's only a few dissenters who still insist that cold bees become 'hard' bees and put matchsticks under the CB... Lots of threads in here .. Just think about it ... Insulating your house loft does not cause condensation.....
 
here we go again :)

Hi derekm,
It is a serious question and I was hoping for your answer. Got some stuff that went under lead roofs, but more like felt for lead to slide on. Should I not bother with something between aluminium and wood then?
 
Unless you fork out on bespoke aluminium covers for your roofs to give you extra depth you are better off putting insulation inside the roof i.e. between the roof and the crown board - if you have battens inside the roof either rip them out or cut the insulation to fit inside them. You don't need an inch empty space between CB and roof unless you're one of these id!ots who believe that a raging gale through the cluster courtesy of gaping holes in the crown board is good for the bees and you definitely don't need roof vents - all my roofs have insulation inside and all but two have no ventilation holes - never had trouble with condensation.
If you are going to put insulation on - don't b*gger about with polystyrene and such like - just get some kingspan
 
Last edited:
Thanks folks. Found it on David Cushman's site. If it is good enough for him then it is good enough for me. Still to have a look at the aluminium though. It might never happen.
 
Hi derekm,
It is a serious question and I was hoping for your answer. Got some stuff that went under lead roofs, but more like felt for lead to slide on. Should I not bother with something between aluminium and wood then?

The interaction of Insulation, ventilation, condensation is a misunderstood topic, here is a simplfied answer by splitting the continuuminto 3 scenarios

1) If you greatly reduce insulation and increase ventilation you get the same humidity and temperature as outside or pretty close. There is none or little condensation and little extra warmth.

2)As you increase insulation and reduce ventilation you now have a warmer cavity with colder spots and surfaces with condensation and the internal humidty falls dramatically as the cold spots are now acting a strong dehumidifier.

3) If the insulation is increased further and the ventilation reduced, the cold spots are removed from inside the cavity. The internal humidity now rises as the dehumidifaction is removed and the condensation now takes place outside.


This is a simplification but is basically the case.
The matchsticks & open feed hole advocates operant in scenario 1
others are somewhere between 2 & 3. I 've gone completely to scenario 3.
 
No it won't -
. . . .the more insulation you have the better chance your bees have of maintaining the hive temperature . . . . . . . . . .
Just think about it ... Insulating your house loft does not cause condensation.....

Maybe, but sealing it all up without the proper ventilation does, See Part F of the building regulations!

Bees generate their own heat.
Insulation with ventilation, (ie slab of celotex/polystyrene on the OUTSIDE) will help to reduce loss of heat.

Closing the vents with insulation on the inside WILL cause damp and increase vulnerability to disease, SIMPLE.
 
Maybe, but sealing it all up without the proper ventilation does, See Part F of the building regulations!

Bees generate their own heat.
Insulation with ventilation, (ie slab of celotex/polystyrene on the OUTSIDE) will help to reduce loss of heat.

Closing the vents with insulation on the inside WILL cause damp and increase vulnerability to disease, SIMPLE.

No it isnt simple...
I suggest you read the buiding regs and the research that went into them in more detail.

If the insulation is carried out with attention to detail the cold spots will not deposit the water to the bees disadvantage.

The way to easily ensure no cold spots above the bees is a drop over cover of Recticel/kingspan
 
Last edited:
Unless you fork out on bespoke aluminium covers for your roofs to give you extra depth you are better off putting insulation inside the roof i.e. between the roof and the crown board - if you have battens inside the roof either rip them out or cut the insulation to fit inside them. You don't need an inch empty space between CB and roof unless you're one of these id!ots who believe that a raging gale through the cluster courtesy of gaping holes in the crown board is good for the bees and you definitely don't need roof vents - all my roofs have insulation inside and all but two have no ventilation holes - never had trouble with condensation.
If you are going to put insulation on - don't b*gger about with polystyrene and such like - just get some kingspan
the kingspan if fitted snuggly the foil surfaces will stop moisture entering the roof space i.e. it becomes "A warm roof".
So JBM is correct. Just make sure its a good fit to the crown board.
 
Horsesh 1 t

Neeiiggghh, just not a clue. Hasn't thought about the ventilation at all. There has to be some or the bees would die. The OMF affords more than adequate ventilation; during winter, outside air does not rise any further than the level of the entrance as it is generally colder, so more dense, than the air inside (apart from a small amount of mixing - either by diffusion or from the air currents across and through the OMF). But, of course, there are slight differences of air density between dry and water-laden air which will further complicate the gaseous movements, even if no lateral air movement at all at floor level (there will always be some vertical movement above the cluster, and hence lateral movement at the crownboard). We must not forget that carbon dioxide is more dense than air.

There must clearly be adequate gas exchange between the inside and outside of the hive if umpteen kilos of sugar is converted to carbon dioxide and water as well as removal of the water associated with the 'fuel'.

Top insulation removes the problem of condensation in that area. Adequate insulation on the sides reduces condensation, adequate ventilation (wherever it may be) allows continual removal of 'exhaust gases'. If at the bottom, that ventilation will carry away the minimum amount of heat. If the exchange of gases between inside and out were down to simple diffusion as the means of passage ('combustion air' in and 'exhaust gases' out).

Think here the turbo aspirated engine, perhaps. The energy in the exhaust gases is simply extracted and used to power the induction process, thus increasing efficiency. Less energy lost in the exhaust means more energy available for use, or lower fuel requirement. So gases lost efficiently from the hive reduce the food consumed.

It is not all about simple condensation, but energy efficiency as well.

Up at the roof level, the space outside the hive (above the crownboard) is an entirely different issue and needs only to be dry to avoid damage to the fabric of the 'building'. No different whether a hive or our house. If the space is dry, no problem. If damp, timber potentially rots (is eaten by fungi). Damp in the roof space can arise from either ingress from inside or from outside. So ventilation, to enable avoidance of damp, is a sensible precaution - not always needed, but there when it is.
 
Polystyrene sheet under aluminium rooves
Is this a good idea or would it cause condensation and rot the wood?
Swienty poly hives have an aluminium roof, there is a slab of polystyrene that sits inside it above the crownboard. Crownboard is closed throughout the year, including winter, and only because I got the boards made to be dual purpose and can also use them as feeder boards if necessary - but never have done.
Should I not bother with something between aluminium and wood then?
The insulation goes beneath the roof and fully covers the top of the boxes. The aluminium roof does not come into contact with the boxes, there is slight play so they can be lifted off, but not much.

Or do you mean any atmospheric that may be absorbed by the box itself that you think may rise inwards and upwards, and so damage your crownboard? That didn't happen when I used wooden hives topped with polycarbonate crownboards, then insulation, then roof.

For a budget crownboard, instead of polycarbonate, you could use a sheet of thick polythene. The bees will seal it in place in a week and so stop an in-hive moisture reaching above it. A polycarbonate crown board is a better option, either a piece without a feeder hole or one with the feeder hole closed with another bit of polycarbonate.

Closing the vents with insulation on the inside WILL cause damp and increase vulnerability to disease, SIMPLE.
Possibly, with a thin-walled wooden hive, solid floor, and very reduced entrance, but most people have open mesh floors because that's what's supplied these days. Plenty of air available that way, and the bees are more than capable of moving it around if they want to. But, that said, I've used a solid floor along with thick top insulation and a polycarbonate crownboard. The hive stayed dry during a rather wet winter.
 
Hi everyone. I am not a BK but am familar with building roof design. Condensation will occure when the warm moist air in the BB comes in contact with any surface with lower temp than its dew point tempature. See the physcometric chart in CIBSE guides. If the roof structure is airtight above the BB and the warm moist air is trapped below the insulation then ventilation may not be required, i say may. If air can move up past the insulation and contacts any surface lower than its dew point temp then condensation will occure. Such as underside of the roof. Warm air will always try to move up, like an air bubble in water.

So either make an airtight seal at the insulation level or else provide some ventilation to disapate the warm air once it escapes to the roof void.
if you know the temp and mean %humidity of the bb it would be simple to find the approx dewpoint temp from the phy chart. Letting you know when at risk.

Building control always require a cold roof void to be ventilated unless a breathable membrane such as t*vec is used above it.

That is my building or arcitectural perspective on the discussion. And hope you find it informative. There are many further debates and what if senarios to be had. But above is my understanding of how condensation occures. And would occure in a hive.
I have no bee hive or keeping experience but am interested and learning. I enjoy reading this forum.

Sent from my GT-I8160 using Tapatalk 2
 
So either make an airtight seal at the insulation level or else provide some ventilation to disapate the warm air once it escapes to the roof void.

Sent from my GT-I8160 using Tapatalk 2


Would raising the crownboard with something like matchsticks do the trick then?

What a great idea!


Thanks for your interest, williamtyrone!


Dusty
 

Latest posts

Back
Top