Reflectix + Spray Foam combination?

[JThomas]

I'm making plans for insulating my mini bus for all-year living in northern Michigan (Lower Peninsula) where the temperature ranges from +/-0* F to +/- 90*. My situation involves already having amassed roughly 200-300sqft of Reflectix, none of which I've had to pay for - it came with our fresh basil at work twice a week. I've also found out spray foam would seem to be the best option overall, and considering the cold winters here I don't want to lose out.

My thought was to combine the two in order to save some money on spray foam and/or make an even more efficiently insulated bus with the addition of a radiant barrier. My questions:
1 - Is this indeed the case? (Reflectix + spray foam better than just 2" of foam)
2 - Would my Reflectix be better used doubled up somewhere? The floor? The ceiling?
3 - Any other advice?

ALSO: How crazy is it to keep most of the windows instead of covering/insulating over them considering my climate? '95 Thomas Bus

[brokedown]

I'm making inserts for my windows using reflectix glued to 1" XPS foam and plywood on the back (to match the wall). They pop right out when you want windows. Your windows will be the biggest loss of heat (and cold).

Outside of layering against glass, reflectix is worse than basically any other option. I used a lot of it on my short bus. It's better than nothing, but not by much.

Closed cell spray foam has a great R value and will out-perform the other options. It's harder to work with and more expensive than other options.

Polyiso is good in warm temperatures but its R value drops big time in cold temperatures.

XPS is probably the best balance of R value, cost, and ease of use.

[JThomas]

Thanks for all the advice and insight!

[EastCoastCB]

Reflectix is the placebo of the insulation world.
Its just mylar with bubblewrap.

[Yukon Cornelius]

Originally Posted by brokedown

I'm making inserts for my windows using reflectix glued to 1" XPS foam and plywood on the back (to match the wall). They pop right out when you want windows. Your windows will be the biggest loss of heat (and cold).

This is likely the best use of reflectix, we have cushions for putting in aircraft windows to keep the sun from beating in through the thick windscreen and turning the metal tube that is an aircraft into a tube shaped oven.

Having little panels you can pop in and out with ease and store just as handily will definitely help with temp control, they'll also double as room darkeners if you so choose to use them as that.

[JThomas]

Originally Posted by brokedown

I'm making inserts for my windows using reflectix glued to 1" XPS foam and plywood on the back (to match the wall). They pop right out when you want windows. Your windows will be the biggest loss of heat (and cold).

Thinking more and more about doing this, I think it's a great compromise.

I'm assuming you framed in your whole bus to hold the plywood/insulation? I've been trying to weigh the options of a frame/no frame, not sure I want plywood or some other, thinner option that might not require studs. I assume durability and rigidity are your sacrifices for weight?

[Daisyfuel]

Hey , has anyone tried to spray foam under the floor of a bus , between the supports , would that be possible or would it not stick or is their another reason that wouldn’t work ???
Thanks ��

[Brewerbob]

Originally Posted by brokedown

Polyiso is good in warm temperatures but its R value drops big time in cold temperatures.

I don't know what Polysio is but I don't know if I buy that about any material. How the hell can anything be good for insulating heat but not cold or vise versa??? Maybe some kind of exotic alloy of metals but nothing a skoolie person is ever going to touch much less buy. I'd even put money on the space shuttle tiles are just as good at keeping your fingers warm with liquid hydrogen as it does keeping your fingers cool with a torch on the other side.

Originally Posted by Daisyfuel

Hey , has anyone tried to spray foam under the floor of a bus , between the supports , would that be possible or would it not stick or is their another reason that wouldn’t work ???
Thanks ��

There is a lot of stuff under there that ought not be covered; wires, fuel lines, bolts... etc.

[o1marc]

Originally Posted by Brewerbob

I don't know what Polysio is but I don't know if I buy that about any material. How the hell can anything be good for insulating heat but not cold or vise versa??? Maybe some kind of exotic alloy of metals but nothing a skoolie person is ever going to touch much less buy. I'd even put money on the space shuttle tiles are just as good at keeping your fingers warm with liquid hydrogen as it does keeping your fingers cool with a torch on the other side.

There is a lot of stuff under there that ought not be covered; wires, fuel lines, bolts... etc.

Insulation in different forms have different capabilities. The insulation in your oven is not the same as in your fridge. They are intended for specific heat ranges. So an insulation designed for high temp areas may not perform as well at extreme cold temps.

[brokedown]

Originally Posted by Brewerbob

I don't know what Polysio is but I don't know if I buy that about any material. How the hell can anything be good for insulating heat but not cold or vise versa??? Maybe some kind of exotic alloy of metals but nothing a skoolie person is ever going to touch much less buy. I'd even put money on the space shuttle tiles are just as good at keeping your fingers warm with liquid hydrogen as it does keeping your fingers cool with a torch on the other side.

There is a lot of stuff under there that ought not be covered; wires, fuel lines, bolts... etc.

Polyiso is the typical single or double faced white foam you see at the hardware store. Nothing exotic that's for sure. It just happens to perform differently based on temperature, which also isn't particularly rare.

https://buildingscience.com/document...endent-r-value

[Brewerbob]

Originally Posted by brokedown

Polyiso is the typical single or double faced white foam you see at the hardware store. Nothing exotic that's for sure. It just happens to perform differently based on temperature, which also isn't particularly rare.

https://buildingscience.com/document...endent-r-value

I googled the Polysio. I'll have to read thru the temp dependent stuff.

[Brewerbob]

Well that link sucked. Thx anyway. I was more interested in the why (physics) and not just the observed of just polysio.


The above is the reason I ddin't do well in Calc. Who the **** cares what happens as X approached zero? I want to know what happens AT zero (and why).

[brokedown]

Well the important thing isn't why it does it, it's that it does it.. But here's a friendlier link: https://www.ecohome.net/guides/2254/...not-to-use-it/

I'm using mostly XPS in my bus.

[Brewerbob]

Originally Posted by brokedown

Well the important thing isn't why it does it, it's that it does it.. But here's a friendlier link: https://www.ecohome.net/guides/2254/...not-to-use-it/

I'm using mostly XPS in my bus.

If it wasn't for that damn Calc II class, I'd have a 4 yr engineering degree.


Thx again for a lousy link!! The gf sees this and I'll be stuck using the rock wool because hippy dippy.



As for what I am using, I've already decided on the spray foam for the sealing of holes if nothing else. My plywood subfloor was nailed to the steel from the factory. Plywood is gone now but the 100s of pinholes are not. The spray foam will take care of those, the bolt holes and the smaller rust holes that I didn't patch. It's more expensive but the up side is that when I accidentally end up with 16" of the stuff, my bus will double as a barge.

[Brewerbob]

All kidding aside, I do thank you for the link. If the bank pulls their heads out of their @sses, I'm going to closing next week on a house that needs siding. It was built in 1895. Somewhere along the way, it picked up asphalt shingles for siding over the lap board. I want to do vinyl siding over the lap board and was thinking about adding some of the XPS to it. Probably the 1 inch. Maybe 1 1/2 inch. I've no idea what's inside the walls. The roof has 12" of bat tho.* I need to go check the prices of the XPS vs wool. If the wool isn't too much more, I'll go with that.



*Which reminds me.... Note to self: get a list and pics if possible of the rehab work that was done by previous owner.

[brokedown]

I suppose I should have mentioned that I already have spray foam and I'm using XPS for areas that couldn't be sprayed. The floor has 1", below the chair rails gets 1", the windows get 1" inserts, etc.

I saw people recently gluing coins to their floors to seal the holes. Not sure how great of an idea that is.

[o1marc]

Originally Posted by brokedown

I suppose I should have mentioned that I already have spray foam and I'm using XPS for areas that couldn't be sprayed. The floor has 1", below the chair rails gets 1", the windows get 1" inserts, etc.

I saw people recently gluing coins to their floors to seal the holes. Not sure how great of an idea that is.

What negative can you see from gluing pennies to the floor?

[thrifty1]

It’s a felony ;)

[o1marc]

Originally Posted by thrifty1

It’s a felony ;)

I'm not defacing them in any way, therefore not a crime.

[Brewerbob]

Originally Posted by brokedown

I'm using XPS for areas that couldn't be sprayed.







The floor has 1", below the chair rails gets 1", the windows get 1" inserts, etc.

As I plan the same, ...Couldn't be sprayed or couldn't be reached? Windows makes sense that you don't want to spray but I'm not keeping mine. Did you have any spots that couldn't be spray because you couldn't get to them?

Originally Posted by o1marc

What negative can you see from gluing pennies to the floor?

Penny pops loose because 1) the glue sucks (not enough, dirt, whatever) 2) different expansion rate (dunno if that's a problem with such a small surface area) 3) vibration.... 4) etc.


Whatever reason, if one does pop loose, you now have water, dirt, moisture being trapped and not allowed to dry on your floor. That's my justification for spray foam. If you just can't afford it and you're out of kidneys to sell, then For pinholes, the "rubber paint" would work. That won't seal a bolt hole tho.