Canadian winters - HELP

[MorinBumkins]

Hey guys, I'm so glad I found this site! My wife and I are building out a 97 Thomas Saf t Liner 36', which we need to be living in by winter.

I think I have my plan sorted, except for one thing, INSULATION!

I am terrified of condensation and cold, as we lived in a mobile home years ago that was moldy and wet and we were very sick from it.

We live in North Bay, Ontario Canada and temps range from -30 to +30 C.

My current best plan is to lay 3 to 6 inches of aluminum backed isopolycyanurate foam board on the roof outside, and then cover with an EPDM RV rubber roof sheet.

This is because I'm 6 foot 2 and we can't do a roof raise, so I want to avoid insulating inside the bus.

I have read that one guy did this and it worked, but I can't find any reviews on it or others that did it.

We also plan on having a diesel air heater at the back of the bus, and a tiny woodstove at the front.

Walls and floor will be insulated inside.

Help! Lol I do not want to be in a wet cold bus come January!

Thank you thank you thank you in advance.

[ABBus]

Hello,
I'm from Canada too, and just wanted to wish you good luck!
S

[peteg59]

-30C, WOW!!!

Not much works in that cold, unfortunately.
Your wood stove will be your saving grace, as batteries won't work and diesel fuel doesn't flow well either. Might want to upgrade from "tiny" wood stove to a larger variant, to be your "primary" source of heat?

Hopefully you'll be stationary for the winter, as it will be difficult at best to keep an insulated "skirt" around the bus if you're constantly on the move.

Good luck and post pics when you get setup...

[MorinBumkins]

Originally Posted by ABBus

Hello,
I'm from Canada too, and just wanted to wish you good luck!
S

Hey there! Where are you from? Did you live in your bus in winter? Give me the deets!

[ABBus]

Originally Posted by MorinBumkins

Hey there! Where are you from? Did you live in your bus in winter? Give me the deets!

From New-Brunswick, and yes, we live full-time on our bus, but in much warmer places (in Mexico, right now).

[Gyrkin]

Originally Posted by peteg59

-30C, WOW!!!

Not much works in that cold, unfortunately.
Your wood stove will be your saving grace, as batteries won't work and diesel fuel doesn't flow well either.

Batteries work just fine and diesel fuel (if you get winter blend) flows just fine at those temperatures, and even lower. A wood stove will keep even an un-insulated bus warm at those temperatures. You will use a lot less wood if you insulate it, but even a big 40 foot bus isn't that much space to heat. I don't live in my bus, but I have camped in some pretty cold temps. It's not insulated at all, and even a modest fire in the wood stove keeps it warm.

[musigenesis]

If you insulate outside the roof but inside the walls and floor, your metal ceiling will still be cold (especially right above the windows) thanks to the high thermal conductivity of steel (which is about 300X worse than wood and 1500X worse than XPS) and you will probably have severe condensation problems there (condensation caused by your warm and moist interior air coming into contact with the cold metal).

[joeblack5]

Not sure if that is correct. Insulation on top of the roof up to the window will result in very little steel exposed to the outside.
On the other hand the inside steel is completely exposed to the warm side. Because the conductivity of the metal is high heat will flow easily towards the cold



So more "warm" energy can flow thru the ceiling towards the cold window pillars then the cold side can reject.


Obvious there will be some cooling but not that dramatic as for instance a window itself.

With a window the heating square surface and the cooling square surface is the same.. so the temperature drop will be more significant.


We have done some limited insulation on the outside of the roof of Dory and I think with some care it could work reasonably well.


Good luck,


Johan

[o1marc]

Some insurance companies have big issues with wood burning stoves.

[musigenesis]

Originally Posted by joeblack5

Not sure if that is correct. Insulation on top of the roof up to the window will result in very little steel exposed to the outside.
On the other hand the inside steel is completely exposed to the warm side. Because the conductivity of the metal is high heat will flow easily towards the cold

So more "warm" energy can flow thru the ceiling towards the cold window pillars then the cold side can reject.

If the metal of the ceiling is not cold enough to cause condensation problems, that will only mean that you're losing a large amount of heat to the outside, which will flow through the metal of the ceiling to the ribs and the side sheeting where it will then conduct/convect to the outside air. In my opinion, to keep warm without a massive internal heat source, you want no incursions of metal from outside to inside, and the headliner (if left in place) represents a very severe one. If the headliner was removed and the space between ribs packed with foam board or spray foam, the thermal bridging problem would be substantially less (and perhaps this is what OP is intending to do - I took their post to mean they were intending to leave the headliner up).

I agree that windows represent a similarly enormous heat loss, but that's a separate matter (and that's why I plan on covering all of mine with XPS foam board inserts in wintertime).

[MorinBumkins]

Originally Posted by musigenesis

If the metal of the ceiling is not cold enough to cause condensation problems, that will only mean that you're losing a large amount of heat to the outside, which will flow through the metal of the ceiling to the ribs and the side sheeting where it will then conduct/convect to the outside air. In my opinion, to keep warm without a massive internal heat source, you want no incursions of metal from outside to inside, and the headliner (if left in place) represents a very severe one. If the headliner was removed and the space between ribs packed with foam board or spray foam, the thermal bridging problem would be substantially less (and perhaps this is what OP is intending to do - I took their post to mean they were intending to leave the headliner up).

I agree that windows represent a similarly enormous heat loss, but that's a separate matter (and that's why I plan on covering all of mine with XPS foam board inserts in wintertime).

Yeah, I was planning on leaving the headliner. But I guess it would be better to do both then, right, remove headliner and insulate inside with say 1", and then put another 4" or so outside.

[musigenesis]

Originally Posted by MorinBumkins

Yeah, I was planning on leaving the headliner. But I guess it would be better to do both then, right, remove headliner and insulate inside with say 1", and then put another 4" or so outside.

I've been meaning for a couple of years now to set up some experiments to evaluate the effectiveness of various insulation configurations, including partly insulating on the outside, but I've never gotten around to it. My thinking (unconfirmed by any measurements) is that if you essentially sandwich the roof sheeting with insulation inside and outside, the temperature of the roof (because of the very high thermal conductivity of steel and the fact that the roof is still fully connected to the rest of the bus' uninsulated external skin) is going to be a lot closer to the outside air temperature than to your internal air temperature. If this is the case, then the external roof insulation will not provide much benefit no matter how thick it is.

The proof is the pudding, but I'm too tired to make pudding!

[MorinBumkins]

Originally Posted by musigenesis

I've been meaning for a couple of years now to set up some experiments to evaluate the effectiveness of various insulation configurations, including partly insulating on the outside, but I've never gotten around to it. My thinking (unconfirmed by any measurements) is that if you essentially sandwich the roof sheeting with insulation inside and outside, the temperature of the roof (because of the very high thermal conductivity of steel and the fact that the roof is still fully connected to the rest of the bus' uninsulated external skin) is going to be a lot closer to the outside air temperature than to your internal air temperature. If this is the case, then the external roof insulation will not provide much benefit no matter how thick it is.

The proof is the pudding, but I'm too tired to make pudding!

Very good point, and just what I needed to hear. So I guess my next question is, is 2" of XPS, plus foam core reflective barrier (1/4") going to be enough interior insulation?

[MorinBumkins]

Originally Posted by musigenesis

I've been meaning for a couple of years now to set up some experiments to evaluate the effectiveness of various insulation configurations, including partly insulating on the outside, but I've never gotten around to it. My thinking (unconfirmed by any measurements) is that if you essentially sandwich the roof sheeting with insulation inside and outside, the temperature of the roof (because of the very high thermal conductivity of steel and the fact that the roof is still fully connected to the rest of the bus' uninsulated external skin) is going to be a lot closer to the outside air temperature than to your internal air temperature. If this is the case, then the external roof insulation will not provide much benefit no matter how thick it is.

The proof is the pudding, but I'm too tired to make pudding!

Now, what if I was to remove the exterior sheeting, and the interior sheeting, put 6 inches of insulation in, and EPDM rubber sheet it on the top.

[musigenesis]

Originally Posted by MorinBumkins

Very good point, and just what I needed to hear. So I guess my next question is, is 2" of XPS, plus foam core reflective barrier (1/4") going to be enough interior insulation?

If your biggest concern is cold weather, a reflective layer is without value. Most heat transfer is due to conduction and convection; radiative heat transfer only starts to be a little relevant when it comes to shielding your interior from the high temperatures a roof will get to if it's sitting out in direct sunlight (which could be 140-150°F or higher). Even then, a reflective layer needs an air gap of at least 1" between itself and the hot roof - and even if you could manage this gap, it would still be more effective to just pack that gap with foam insulation.

My own insulation is 2" of XPS all around, but I'm only looking to survive Philadelphia winters where the temperature at worst gets down around 0°F. Even with all my windows uninsulated, I found that a 1500 watt electric heater got the interior close to 70°F with the outside temperature at around 30°F (sorry I'm not doing the Celsius conversions here). With my windows completely covered with 2" XPS foam inserts and my 5000 kW diesel air heater, I'm fairly confident I'll be able to handle 0°F but I don't know yet for sure.

I would not be totally confident about handling -30°F with this setup, but I dunno. Maybe 2" XPS and two diesel air heaters would do the job. I do think the completeness of the insulation is a very important factor - you don't want things like uninsulated windows, doors, emergency exit hatches, or the uninsulated front of the bus providing easy escape routes for your heat (this is mainly why I built a fully-insulated bulkhead wall behind my driver's seat).

[musigenesis]

Originally Posted by MorinBumkins

Now, what if I was to remove the exterior sheeting, and the interior sheeting, put 6 inches of insulation in, and EPDM rubber sheet it on the top.

I dunno. I want to say this sounds a bit wonky, but I dropped part of my floor 3" to avoid having to raise my roof, so wonky is possibly where it's at.

[MorinBumkins]

Originally Posted by musigenesis

I dunno. I want to say this sounds a bit wonky, but I dropped part of my floor 3" to avoid having to raise my roof, so wonky is possibly where it's at.

Dude, wild. How? Photos? I need to know lol

[musigenesis]

Originally Posted by MorinBumkins

Dude, wild. How? Photos? I need to know lol

You can check out my build thread, although it's pretty long at this point. Here's an imgur album summary of the floor rebuild. It's not really a practical thing to do for a healthy bus, but my bus was badly rusted and I had to rebuild that entire section of the floor anyway, so I did it in a way that gained me some useful extra headroom in the kitchen and shower.

[newhorizons]

Are you replacing the windows?

[newhorizons]

We built campers for a number of years. We tested them to -20f. We sprayed them closed cell foam. Could you put ribs cut out plywood over the roof and then spray that with closed cell. Then sheath it with 1/4 baltic birch plywood. 1/4 is really strong when you bend it. That is how we did our campers. Then coat it with silicone roofing. It is rolled on, very easy to apply.