Question on moisture barrier in winter boxes

[PashkaTLT]

Hello guys,

Most of us make those "double ceilings" in winter boxes where moisture will gather and be prevented from just dripping on the center of the palm.

My question is, how much of a gap on the sides of this inner ceiling do you leave? I leave about 1/4" around all sides, but I'm not sure if it's a good gap or not.

[Las Palmas Norte]

For me it depends on the wood dimensions that I use to frame it up. I've just completed one and used 1x4, so a ¾" spacing between sheets of poly.  I have used 2x2 creating an 1½" gap. I can't be certain one is better than another. All this is assuming I understand your question correctly. 

[PashkaTLT]

@Las Palmas Norte

Sorry, I haven't made a picture in my starting post.

Here it is:

[Las Palmas Norte]

I create mine like a double glazed window using 6 mil poly vapor barrier.

[PashkaTLT]

I mean these side gaps, guys:
https://pasteboard.co/EsbEbXEr7DkS.png

[Las Palmas Norte]

I'm unclear as to why you'd incorporate these gaps? Does it serve a purpose?

Here's what I've built. The top is a pitched roof with hinges on the back side. This allows for the roof to be opened during milder spells for ventilation. It can be locked down to prevent strong wind gusts from flipping it open & damaging it. It's just a double walled 6 mil poly design. Maybe in my climate that's enough.

 

 

Here's a much smaller shelter I built and I do have a foamboard panel that I could use over the top if weather does get nasty. It's hinged as well to be opened.

 

 

 

[PashkaTLT]

@Las Palmas Norte

I thought I need the gaps so that moist air will go up through them, condense there between the two ceiling and the internal ceiling will prevent water from dripping on the palm?

[Las Palmas Norte]

I believe moisture will condense on any interior surface regardless of where inside the shelter it is.  I plan on using a fan inside this larger shelter to circulate the air. Generally speaking there's only a few instances each winter where I'll have to completely close the shelters for more than overnight.