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Old 04-18-2019, 09:42 AM   #1
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more foam in ceiling or rigid in floor?

So, I'm a tall guy & no roof raise. Maybe next time for that. I will be rubbing my head & slouching some no matter what, which is OK. I've done it my whole life on workboats.

We are DIY spray foaming the walls & ceiling, XPS on the floor. We will be travelling in all climates, hopefully more in warm than cold as I've grown up and lived in cold most of my life. Our primary heat source will be a wood stove.

Where should I put my last inch of insulation? In the floor or on the ceiling? I'll go no less than 1" rigid in the floor. If I go with 1.5 or 2", the extra will probably come off the ceiling. Any one have some post insulation/living experience that left them perfectly happy or bummed that they didn't do something different? Am I splitting hairs?

Thoughts?
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Old 04-18-2019, 10:21 AM   #2
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If heating in cold conditions, put on ceiling.

If aircon used in the heat, put on floor.

If both are of equal concern, do both or flip a coin.
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Old 04-18-2019, 11:01 AM   #3
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If heating in cold conditions, put on ceiling.

If aircon used in the heat, put on floor.

If both are of equal concern, do both or flip a coin.
Yeah, the coin flip is about where I'm at. I'm leaning toward the floor mostly because the extra inch is easier & cheaper to deal with down there.
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Old 04-18-2019, 11:56 AM   #4
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The center of the roof can easily be insulated from the outside..especially if you put solar on top as well. If you spray foam diy then I would spray foam the bottom..relocated some tubing and wiring and stay away from the exhaust.
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Old 04-18-2019, 03:14 PM   #5
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Your woodstove will generate quite a bit of heat which will rise naturally. I have found no problems keeping the ceiling really warm and it seems the floor area is much cooler, especially the first couple of feet up. Might make for cooler sleeping and cold feet. I'd add to the floor in your case, wish I had but may in future.


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Old 04-18-2019, 03:24 PM   #6
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Yes with a woodstove, R-value is less critical than with burning diesel or propane.

Of greater concern would be infiltration of cold air, from incomplete or insufficient vapor barrier.

Cold is not rising up from a lower R-value floor, but entering from anywhere will by default fall to the floor.

Little low consumption fans can even out that thermal stratification issue.
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Old 04-18-2019, 07:10 PM   #7
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Your woodstove will generate quite a bit of heat which will rise naturally.

John
Heat does not rise. If it did, it would only be hot above the woodstove.

Hot air rises. Heat goes in all directions.
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Old 04-18-2019, 10:06 PM   #8
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Heat does not rise. If it did, it would only be hot above the woodstove.

Hot air rises. Heat goes in all directions.

Good catch, my bad! Does the heat need a push from the hot air

to dissipate or move throughout the bus?



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Old 04-18-2019, 10:56 PM   #9
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Radiant heat is like light, travels in a straight line, warms the dark surfaces, bounces off the reflective ones.

Heat conduction travels through a material, including out the other side.

Convection is carried by moving air - heat rises, cold falls, both travel through any gaps in the space "envelope".

Slowing down or facilitating each process requires different approaches.
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Old 04-18-2019, 11:21 PM   #10
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Quote:
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Good catch, my bad! Does the heat need a push from the hot air

to dissipate or move throughout the bus?



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https://www.herschel-infrared.com/ho...nvection-heat/
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Old 04-18-2019, 11:50 PM   #11
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I would ditto on the spray underneath the floor of the bus instead of inside. You don't loose any height and you can add more than one inch. It will also make your ride more quiet and will help keep your feet warmer, which will make the bus FEEL warmer at the same temperature, and seal any cracks you might have missed. Wood stoves are great - when I get further along, I want to do some research into how those work in a skoolie, but it is always nice to have a backup plan for heat, especially if you are going to travel through the winter - double dibs on boon docking in the winter. How about a propane setup as plan B?
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Old 05-01-2019, 03:19 PM   #12
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Someone else mentioned this product, which I will be using on my bus for exactly the same reasons. I'm tall, and I only have 2" of headspace right now. R22 in a single centimeter of space is just what I need!

https://www.insulation4less.com/default.aspx
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Old 05-01-2019, 04:11 PM   #13
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Quote:
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Someone else mentioned this product, which I will be using on my bus for exactly the same reasons. I'm tall, and I only have 2" of headspace right now. R22 in a single centimeter of space is just what I need!

https://www.insulation4less.com/default.aspx
can't happen - the open air space between walls and the membrane is how they come up with that R value - - gluing it right to the ceiling, walls, or floor, would provide next to zero R value
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Old 05-01-2019, 04:27 PM   #14
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Yes this is a scam.

To get even half that performance requires 50x the cost, high tech aerogel, vacuum panels, etc
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Old 05-01-2019, 05:38 PM   #15
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I would ditto on the spray underneath the floor of the bus instead of inside. You don't loose any height and you can add more than one inch. It will also make your ride more quiet and will help keep your feet warmer, which will make the bus FEEL warmer at the same temperature, and seal any cracks you might have missed. Wood stoves are great - when I get further along, I want to do some research into how those work in a skoolie, but it is always nice to have a backup plan for heat, especially if you are going to travel through the winter - double dibs on boon docking in the winter. How about a propane setup as plan B?
Sounds like a lot of optimistic speculation. I don't know that anyone here who's thought of the idea of spray foam under the bus has ever decided it was the way to go and did it. I would not recommend such a fix without first hand experience. Common sense says it not a good idea.
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Old 05-01-2019, 05:41 PM   #16
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Can you spray the underside of the floor?? like add 3 inches ?
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Old 05-01-2019, 05:48 PM   #17
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Can you spray the underside of the floor?? like add 3 inches ?
You mean from under the bus?Crawl under your bus and see if it's something you could accomplish. I see a nightmare working under a bus to coat it.
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Old 05-01-2019, 06:41 PM   #18
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Will you still have many of the original bus windows exposed? Single pane bus windows are leaky and non insulators. You can put hundreds into insulation, but if you're keeping the windows, it'll diminish the efficacy of any insulation project.

I put 1/4" pink foam board on the floor under my subfloor j6st as a thermal break, it's only 1.0 r rated...
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Old 05-01-2019, 08:59 PM   #19
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It seems there’s a lot of different preferences and tolerances for heat and cold. Personally, building a custom floor heat system for my old Motorhome was the best thing I’ve done. Adding a little insulation here and there didn’t seem to help all that much. But in reality it probably helped more than I realize. I put 2” of foam on top of the roof then covered that with solar panels. But it’s the cozy warm feet that I notice the most.
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Old 05-01-2019, 09:07 PM   #20
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The previous owner of my old Motorhome spray foamed under it. They did a very neat job but I dont think I would do it. Id rather buy a rig with plenty of headroom and insulate the inside heavily.
But to each their own.
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