Most folks probably already know this, but I think it bears repeating that fiberglass is a very poor insulator that supports mold and that loses a significant portion of it's 'R' value when subjected to extreme heat or cold. It's called thermal drift, and it happens when you need it most. This also effects a lot of the foam products, but not to the extent that FG suffers.
Reflectix and the "bubble wrap" core products have an 'R' value of basically 1, and that's just for the air layer that it creates. The Mylar like surface reflects most long wave radiation (those are the frequencies that we feel as heat), but there are other products out there that do the same thing, in the same thickness, but that add a lot more 'R' value.
Something else that needs some clarification is that Styrofom is a name brand Extruded Polystyrene (XPS) product made by DOW Chemical, usually blue, but they make other colors too. It has never been used to make food service cups. The stuff we know as "styrofoam cups" is actually Expanded Polystyrene (EPS), and the two products have very different properties.
XPS and Polyiso foams are very similar and both get an initial 'R' boost over EPS thanks to the gas that is used to create the tiny bubbles that form the foam. Problem is, they de-gas throughout the life of the product, causing more of that "drift" mentioned with FG. EPS starts out at a lower relative 'R' rating but its rating remains stable throughout its lifetime. EPS can absorb more moisture more rapidly than XPS, but it can also lose that moisture more quickly too, so if both are kept wet for an extended period of time, the XPS, as well as the Polysio, will take much longer to dry out, so double edged sword.
I've seen a lot of comments about insulated vs. non-insulated floors and where to put what. Looking at a heated van or any vehicle, in the real world, where air is circulating all around it, and most importantly, wind is stripping heat from all sides, above and below. The heat will move like water or electricity. What I mean by that is that it will take the path of least resistance to its flow or movement, so your greatest heat loss will occur at your envelope's weakest point, or in this case, lowest 'R' value surfaces of your envelope. So if you insulate the heck out of your roof, and maybe not so much the walls, and do nothing with those big expanses of glass in your windshield and windows, the greatest heat loss will be through the glass, and in a van with an un-insulated metal floor, through the floor as well. As a matter of fact, your heat loss will be so huge that the vehicle will very quickly take on the temperature of the ambient outside air. The only thing your vehicle provides then is a way to keep the wind off of you. It's just a matter of too many Btu's leaving faster than your body can replace them.
So if you resort to adding Btu's artificially, you're always going to be spending money to keep warm, and wouldn't we all rather not have to do that? The answer is all math, ya just need to slow that heat loss down to a point where you reach an equilibrium with your ability to keep up. If you reduce it far enough you'll soon find yourself comfortable in shirt sleeves, even with it freezing outside, but that takes a lot of attention to detail.
With insulation covering the glass, most RV and mobile home type single pane windows also provide direct heat loss conduits (that also work like radiators in the summer) because they have no thermal "break" in their frames between the outdoor and indoor environments, so in the summer, something that keeps the window frame from catching direct sun is a big help, and in the winter, something on the inside that gets in the way of the frames wicking heat to the outdoors will help.
The issue of the un-insulated floor is I think best understood if you just look at the effect of wind chill. It works the same on your van as it does on your face, so wind whipping under your vehicle's belly is going to strip heat the same as it does blowing across your glass, walls, or roof. The point being that a uniform layer of insulation throughout is the best solution when pure heating and heat retention is the goal.
In a high heat environment of course that changes a bit, as long as you're not trying to air condition the space, and as long as you don't arrive in the heat of the day and park over an already super-heated substrate. If you're short on dough and just need help hiding from the long wave radiation, the Mylar type covering of the bubble wrap will be a huge help, but so will a couple cheapo "Space Blankets". Better yet the roof rack idea with a space blanket laminated onto a piece of plywood would work even better, since any heat that gets absorbed by the plywood will have air on both sides cooling it, so the sun never touches the roof, and nothing from the plywood can conduct heat since there is no path. In that instance you could probably succeed in eliminating nearly all of the long wave radiation completely, so then your awnings become the next most likely suspect for limiting heat gain from your walls, other than the ambient air temperature itself.
Heating, cooling, and controlling moisture in a big aluminum or steel beer can on wheels absolutely has some unique challenges, but the basics of thermal dynamics are constant, we just have to be observant in addressing what applies where. If I were trying to prepare for both extreme heat and cold possibilities, my goal would be to create an igloo cooler on wheels, with a uniform layer of insulation on every square inch of my living space. With that accomplished you could literally heat your space with a candle (but don't do that 'cuz it'll eat up all of your air!). If you're in a van you might also look at trying to reduce the size of the space that you're trying to keep warm, so maybe a removable bulkhead or plug made of foam board turned into a composite panel (cover with FG screen and paint both sides with latex paint) that could be used to close off the front from the cargo area? Just spit-ballin'...
Reading recommendations for operation of combustibles in enclosed spaces to try and keep up with large heat loss deficits completely creeps me out and makes me worry for peoples' safety - I don't care how many times you've gotten away with doing it. Whether it be alcohol, propane, butane, or any other fuel. Better insulation all around will keep you comfy with none of that, so cheaper, safer, and more comfortable in the long run, plus you save space by not having to lug around a heating solution.
And for the record, 100% complete combustion rarely occurs with any of the stoves being used, so remember, the first product of that problem is carbon monoxide, which you can tolerate in low doses for a long time, but the effects can become cumulative and extremely debilitating short of death. Also, the "alcohol" fuels often contain all sorts of other compounds, none of which are good for living things. Here's a quick list of Crown Fuel constituents (REI sells them):
Methanol 65% - 75%
Ethanol 20% - 30%
Isopropanol 0 – 5%
Methyl Isobutyl Ketone 0 – 1%
By-products of incomplete combustion of most of these is also not healthy in any way.
Reflectix and the "bubble wrap" core products have an 'R' value of basically 1, and that's just for the air layer that it creates. The Mylar like surface reflects most long wave radiation (those are the frequencies that we feel as heat), but there are other products out there that do the same thing, in the same thickness, but that add a lot more 'R' value.
Something else that needs some clarification is that Styrofom is a name brand Extruded Polystyrene (XPS) product made by DOW Chemical, usually blue, but they make other colors too. It has never been used to make food service cups. The stuff we know as "styrofoam cups" is actually Expanded Polystyrene (EPS), and the two products have very different properties.
XPS and Polyiso foams are very similar and both get an initial 'R' boost over EPS thanks to the gas that is used to create the tiny bubbles that form the foam. Problem is, they de-gas throughout the life of the product, causing more of that "drift" mentioned with FG. EPS starts out at a lower relative 'R' rating but its rating remains stable throughout its lifetime. EPS can absorb more moisture more rapidly than XPS, but it can also lose that moisture more quickly too, so if both are kept wet for an extended period of time, the XPS, as well as the Polysio, will take much longer to dry out, so double edged sword.
I've seen a lot of comments about insulated vs. non-insulated floors and where to put what. Looking at a heated van or any vehicle, in the real world, where air is circulating all around it, and most importantly, wind is stripping heat from all sides, above and below. The heat will move like water or electricity. What I mean by that is that it will take the path of least resistance to its flow or movement, so your greatest heat loss will occur at your envelope's weakest point, or in this case, lowest 'R' value surfaces of your envelope. So if you insulate the heck out of your roof, and maybe not so much the walls, and do nothing with those big expanses of glass in your windshield and windows, the greatest heat loss will be through the glass, and in a van with an un-insulated metal floor, through the floor as well. As a matter of fact, your heat loss will be so huge that the vehicle will very quickly take on the temperature of the ambient outside air. The only thing your vehicle provides then is a way to keep the wind off of you. It's just a matter of too many Btu's leaving faster than your body can replace them.
So if you resort to adding Btu's artificially, you're always going to be spending money to keep warm, and wouldn't we all rather not have to do that? The answer is all math, ya just need to slow that heat loss down to a point where you reach an equilibrium with your ability to keep up. If you reduce it far enough you'll soon find yourself comfortable in shirt sleeves, even with it freezing outside, but that takes a lot of attention to detail.
With insulation covering the glass, most RV and mobile home type single pane windows also provide direct heat loss conduits (that also work like radiators in the summer) because they have no thermal "break" in their frames between the outdoor and indoor environments, so in the summer, something that keeps the window frame from catching direct sun is a big help, and in the winter, something on the inside that gets in the way of the frames wicking heat to the outdoors will help.
The issue of the un-insulated floor is I think best understood if you just look at the effect of wind chill. It works the same on your van as it does on your face, so wind whipping under your vehicle's belly is going to strip heat the same as it does blowing across your glass, walls, or roof. The point being that a uniform layer of insulation throughout is the best solution when pure heating and heat retention is the goal.
In a high heat environment of course that changes a bit, as long as you're not trying to air condition the space, and as long as you don't arrive in the heat of the day and park over an already super-heated substrate. If you're short on dough and just need help hiding from the long wave radiation, the Mylar type covering of the bubble wrap will be a huge help, but so will a couple cheapo "Space Blankets". Better yet the roof rack idea with a space blanket laminated onto a piece of plywood would work even better, since any heat that gets absorbed by the plywood will have air on both sides cooling it, so the sun never touches the roof, and nothing from the plywood can conduct heat since there is no path. In that instance you could probably succeed in eliminating nearly all of the long wave radiation completely, so then your awnings become the next most likely suspect for limiting heat gain from your walls, other than the ambient air temperature itself.
Heating, cooling, and controlling moisture in a big aluminum or steel beer can on wheels absolutely has some unique challenges, but the basics of thermal dynamics are constant, we just have to be observant in addressing what applies where. If I were trying to prepare for both extreme heat and cold possibilities, my goal would be to create an igloo cooler on wheels, with a uniform layer of insulation on every square inch of my living space. With that accomplished you could literally heat your space with a candle (but don't do that 'cuz it'll eat up all of your air!). If you're in a van you might also look at trying to reduce the size of the space that you're trying to keep warm, so maybe a removable bulkhead or plug made of foam board turned into a composite panel (cover with FG screen and paint both sides with latex paint) that could be used to close off the front from the cargo area? Just spit-ballin'...
Reading recommendations for operation of combustibles in enclosed spaces to try and keep up with large heat loss deficits completely creeps me out and makes me worry for peoples' safety - I don't care how many times you've gotten away with doing it. Whether it be alcohol, propane, butane, or any other fuel. Better insulation all around will keep you comfy with none of that, so cheaper, safer, and more comfortable in the long run, plus you save space by not having to lug around a heating solution.
And for the record, 100% complete combustion rarely occurs with any of the stoves being used, so remember, the first product of that problem is carbon monoxide, which you can tolerate in low doses for a long time, but the effects can become cumulative and extremely debilitating short of death. Also, the "alcohol" fuels often contain all sorts of other compounds, none of which are good for living things. Here's a quick list of Crown Fuel constituents (REI sells them):
Methanol 65% - 75%
Ethanol 20% - 30%
Isopropanol 0 – 5%
Methyl Isobutyl Ketone 0 – 1%
By-products of incomplete combustion of most of these is also not healthy in any way.
