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Discussion Starter #1
In my haste to get started building before really getting into these forums, I installed my floating subfloor using 3/4" plywood on top of Reflectix the same way this guy did:


I don't really care about the negligible R-value on the floor vs polyiso. My bare feet walking on it on a cold night as I laid it down on the subfloor seems to support that idea that it was indeed better than walking on the cold metal floor.

I know a lot of people have said that Reflectix under load will eventually go flat. Now that I have that idea in my head, I'm worried about continuing to build and they prove to be right when I have the opportunity (while still being a pain) to fix it now. I responded to his video, and he said he hasn't noticed anything though it's only been a year.

Has anyone actually had this happen or is it just kind of a theoretical problem? I'd like to keep the interior height as maxed out as possible, but if I'm asking for trouble doing it this way, maybe I should just bite the bullet and put down some 1/2" polyiso under the 3/4" plywood.
 

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You're first mistake was following the advice of a uTuber! I think you'll be ok but if it were me I'd pull it out and go with the polyiso. It's now or never tho.
 

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If you don't care about the added insulation qualities of foam board, there's no reason to change out the Reflectix. It won't hurt anything, it just won't do anything.
 

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I think if you want to keep the same height, just leave it. I have 1" polyiso under 1/2" plywood and vinyl flooring. The floor is still on the colder side when its below freezing outside. Also you can consider the 3/4" ply will add some insulation value too. I wouldn't use the reflectix for anything but maybe DIY window insulation.
 

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If you are going with the 1/2 polyiso, think carefully about running electrical/water/propane in a channel in the polyiso. I ended up with two channels for my layout. If you do run them mark them clearly on the plywood.
 

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Discussion Starter #7
Thanks for the replies. My wife really wants to put in panoramic windows like a passenger van, and if she gets her way it's probably going to be a rolling igloo anyway.

I might assess how much of a PITA it will be to replace it. My biggest fear is that it's going to go flat and crinkly years down the road. As KOV says, it's now or never. I might just reclaim the space by attaching the ceiling straight to the ribs instead of furring strips.
 

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You're first mistake was following the advice of a uTuber! I think you'll be ok but if it were me I'd pull it out and go with the polyiso. It's now or never tho.
Yea, this. I haven't seen a single YouTuber for van builds that was doing literally anything correctly. EVERY.SINGLE.VIDEO is an exercise in how to do something wrong 😂

If you don't care about insulation, then just keep what you have. It's not doing anything at all being there, positive or negative.

If it was me, I'd put in some insulation. R3 from a 1/2" Poly board is better than R0 from nothing. Then 3/4" plywood on top of that. And then the vinyl floor on top of that. It'll still be cold, but not as cold. In the winter, I go a step further and have some custom cut carpet that I put down. Not only does that insulate it further, it helps contain stuff into the little ridges when you step into the van with shoes full of snow. They sell these in much bigger sizes and you can cut them down to fit your layout: TrafficMaster Black 24 in. x 36 in. Fiber and Rubber Commercial Door Mat-60-885-1907-20000300 - The Home Depot
 

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Thanks for the replies. My wife really wants to put in panoramic windows like a passenger van, and if she gets her way it's probably going to be a rolling igloo anyway.

I might assess how much of a PITA it will be to replace it. My biggest fear is that it's going to go flat and crinkly years down the road. As KOV says, it's now or never. I might just reclaim the space by attaching the ceiling straight to the ribs instead of furring strips.
Buy a bunch of these and make some good window covers for the nights. It only costs a few bucks at a seamstress to cut them to your measurements and sew on the edging strips. I used snaps from Amazon to attach them to the van vs the shitty suction cup crap it comes with. 2 of these will take care of all the windows and fans (not including the cab): Do it Yourself Quilted Window Insulation Kit

Also, when you install the ceiling, make sure to account for squeaking. If you install planks directly to the ribs without glue or some sort of isolator, they will eventually squeak, as the whole van is flexing when you move on uneven ground (think pulling out of a parking lot onto a road).
 

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I think you'll be ok but if it were me I'd pull it out and go with the polyiso. It's now or never tho.
I agree -- I'd pull it up and lay down some polyiso. If you have the plywood done, you could use it as a template. I adhered the foam board to the plywood using spare primer paint. $60 for polyiso and done. One or two days of work for a properly insulated floor seems a reasonable use of your time.
 

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Discussion Starter #11
I ended up ripping out the reflectix and going with polyiso. Thanks for all the advice. Next time I'll just stay off youtube. :)
 

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So put carpet on the plywood and move on.
This. In my prototype build, I temporarily slapped on a few pieces of rubber-backed entrance doormat carpet. $9 - $12 CAD for a 3 ft x 4 ft piece, primarily to protect the bare unpainted plywood against accidental spills. It turned out to be warm and comfy for bare feet.
 

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I built a wooden framework and used Havelock wool.
It is amazing how this wool transformed our big metal box on wheels into a quiet ride!
Cleaned the floor with Acetone and glued the frame down with marine adhesive.
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20200726_114436 (2).jpg
 

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Discussion Starter #14
I built a wooden framework and used Havelock wool.
It is amazing how this wool transformed our big metal box on wheels into a quiet ride!
Cleaned the floor with Acetone and glued the frame down with marine adhesive.
Very cool. I'm too far down the polyiso road to turn back now. I've thought about adding a layer of something soft like thinsulate to help with sound deadening before the walls and ceiling go up, but the conventional wisdom around here seems like anything but polyiso against the walls is either a melting/fire or mold risk, or at least that's what they say.
 
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