Why Vent?

[trestles]

I have read on others post, one from Chad, that you can fill the open areas with the spray-foam insulation, so why not just do that and forget the vents altogether? I can't imagine the spray-foam insulation adding much weight to the board but maybe I am wrong, or maybe there is another reason?

Thanks,

Hank

[josht]

The spray foam may not add a lot of weight, but its more of a hassle to put in the board. You have to be really careful that you have plenty of space so that the foam doesn't expand too much and cause the board to burst. Some people would just rather drill one or a couple holes and make some vents.

Josh.

[trestles]

As long as you don't put the deck on too soon I see no risk in over expansion since you have plenty of time to let the foam expand and file it down before you put the deck on.....seems much cleaner and easier in my opinion.

[wyatt]

I have not done a foam filled one yet, so I can't speak to the benefits yet...but I plan on making one like that, if for no other reason that to see what the benefits and draw backs are to both. The only down side I can think of for a foam filled board, is if their are any voids in the foam, and you get leak in the board, you are probably not going to know it until it has done some damage to the wood, and if you do realize there is water in the board, you have to drill a hole in it anyway to get it out, but that's the only issue I can think of without making one. I say give it a shot.....and let us know how it works out

[simonz]

Hi all. I have used expanding foam in my sup but i dont think i will be using it again. I think its more hassle than its worth i hafe got some very slight bulging in my board plus you do get voids and these can fill with air and expand and contract as i have found out the hard way.

I would use a non expanding foam. Also unless you buy a fire resistant foam it is very flammable

Next time i won't be using any foam just vents.

[trestles]

Simonz,

Thanks for the feedback, it makes sense that could happen, guess I will stick with using vents.

Hank