condensation on top of the ply crown board.

[user 6228]

I'm getting clear condensation through a ply crown board under 25mm polyurethane foam insulated roof in a wooden hive. The condensation shows as a circular damp patch in the middle of the board about 75% of the diameter. there is mold growth at the edges of the board
As I suspected (and as stated in building regs) untreated plywood isnt a vapour barrier

 

[drstitson]

is there a gap between top of crownboard and the insulation/roof? is the space ventilated?

 

[tonybloke]

is there a gap between top of crownboard and the insulation/roof? is the space ventilated?

obviously not!

 

[Monsieur Abeille]

Can I ask if the floor is solid or open mesh?

As I suspected (and as stated in building regs) untreated plywood isnt a vapour barrier
Dont understand this, are you not saying it is a vapour barrier?

As I understand it, having top insulation encourages the vapour to the cooler sides, however if your entire hive is polyurethane, I guess that negates that effect?

 

[Monsieur Abeille]

Can I ask if the floor is solid or open mesh?

As I suspected (and as stated in building regs) untreated plywood isnt a vapour barrier
Dont understand this, are you not saying it is a vapour barrier?

As I understand it, having top insulation encourages the vapour to the cooler sides, however if your entire hive is polyurethane, I guess that negates that effect?

Sorry, just re-read the post and I see that the condensation is on top of the board

 

[user 6228]

obviously not!

Obviously jumping to conclusions?
There is space and ventilation above the insulation.

 

[tonybloke]

the ventilation can't be effective then, or there would be no moisture apparent?

 

[oliver90owner]

And it's only September. Imagine the state of it in the middle of the winter. Mine are all dry, btw, so don't know what you have got wrong.

 

[drstitson]

Omf?

 

[user 6228]

I'm not asking a question I'm supplying information about the permiability of plywood.

 

[drstitson]

 

[tonybloke]

 

[oliver90owner]

That makes three!

 

[drstitson]

perhaps the condensation has got in somewhere critical and caused de-lamination!

 

[oliver90owner]

perhaps the condensation has got in somewhere critical and caused de-lamination!

You might be right, but the thread was about 'leaky' crownboards!

 

[Finman]

Two reasons to condensation in inner cover

1) inner cover strucure is too cold
2) you have too much spare to too few bees. Bees are down stairs and lft it too cold.
--- take extra space off.


Make a new respirating inner cover. It move moisture out.

Make a frame 7 cm high
hit 10 mm x 50 mm wood panels to the frame

you get a low box. Then use someting moisture penerable insulation in the box.
5 cm high is good. Keep ventilation space open between insulation and rain cover.

Yuo will se that moisture penetrates the cover structure.

I use foam plastic matress as inner cover insulatr. They are all recycled matresses
mice do not love that material.

 

[user 6228]

is there a gap between top of crownboard and the insulation/roof? is the space ventilated?

if you ventilate the space between non porous insulation and the crown board sufficient to carry the vapour load you have compromised the value of the insulation...
You ventilate above porous insulation unfortunately porous insulation products (sheep or rock wool) have half the insulating performance
~0.4 w/m.
The condensation in my case is caused by insufficient(no space for any more) non porous insulation above thin porous wood, but we all knew that didnt we?

As regards delamination it probably has started to delaminate(new in may) but what would you expect subjected to moisture and heat, Its not marine ply. its not coated.

My point is thin untreated plywood supplied in wooden kit hives is conducive to condensation problems. It should be made vapour tight.

better still get rid of thin wooden hives

 

[Finman]

.
In this case there is a profound problem, because it is summer still and warm weathers.
Condensation problem should not occur this time.

I suppose that there is too much space in the hive, too much ventilation and the hive is cold.

 

[itma]

Would it make sense to have an "insulating wooden hives, how do do it properly" thread? (and maybe another to separate the insulate yes or no question from practical details)

 

[user 6228]

.
In this case there is a profound problem, because it is summer still and warm weathers.
Condensation problem should not occur this time.

I suppose that there is too much space in the hive, too much ventilation and the hive is cold.

"I suppose that there is too much space in the hive" no its full of bees
" too much ventilation " No, brood box is a"made in Finland" polystyrene foam one with just the supplied open mesh floor and entrance.

"the hive is cold" No,the top of the brood frame is between 39C and 41C

Condensation does not require cold Weather or Winter, only a surface below the dew point temperature.

Being Finnish I trust have you seen the condensation on the door window of a Sauna