Insulating the "cab" area

[paulnack]

Hey all. I've been racking my brain on thermal calculations, and I thought I'd externalize my madness and include you.

After doing some math, I realized just how severe the heat transfer through the driver section will be, compared to my insulated walls and floors. Here are some numbers to give you an idea:
2.5" spray foam walls and ceiling: 22.5 watts/ deg C
3" rigid insulation floor: 6.8 watts/ deg C
9 double-pane RV windows: 16.4 watts/ deg C
Windshield, door and driver window: 34.8 watts/ deg C
Dash and driver floor: 67 watts/ deg C

This is for an 11 row front-engine flat-nose with an 18" roof raise. You can see my efforts to insulate in the list above. I am assuming the exterior surface is at ambient temp and I am excluding heat from solar radiation, because my roof will be shaded by decking/ solar panels. Also, for the dash area I assumed an R-value of around 0.5. With all that being said, it will take around 10,000 BTU to cool the interior ~25 deg F (I live in FL).

When you consider that mini-splits should be oversized by 150% to 200%, I'm looking at an 18k BTU system. No thanks, I think I can do better. Obviously, the point of focus is the cab area. Not much can be done about the windshield. I could install a new door, but I really want to keep the original. So my question to you all is:

What have you all done in an effort to insulate your dash areas??

Also, if anyone is interested in my thermal calcs (including solar radiation) I will be happy to share more detail.

 

[Dead pirate]

I have a push, but i removed tbs whole dash. Spray foam where i could, and plastic from the outside. There was a lot of wind coming in. It list heat quickly and made driving uncumfortable. It's a lot better, but it can always use improvements.

 

[ol trunt]

I use a snap in partition to isolate the "cab" area in my little bus. It is made of the clear plastic used in convertible tops and has a zippered door way. I also have an old fashion roll up shade above the windshield that when lowered provides trapped air insulation as well as privacy. Not very sophisticated but it sure slows the heat loss. Jack

 

[Twigg-SKO]

A thermal curtain you can pull over the entire width behind the driver's seat, is a common solution.

 

[Rovobay]

A thermal curtain you can pull over the entire width behind the driver's seat, is a common solution.

I like that idea and may use it myself.

 

[Twigg-SKO]

I like that idea and may use it myself.

A local seamstress should be able to sew one up for a reasonable price.

It's one area where I might have Reflectix sewn in, and you can get the top curved to fit the ceiling profile.

A couple of layers of cotton duck or light canvas, with Reflectix in the middle, should do a decent job.

 

[paulnack]

Thermal curtain is a great, easy to employ, solution. My only reservations with the curtain are that it will make the space feel smaller. The cab area may be unusable as living space, but it still lends to the impression of openness, as does being able to see out the windshield. Maybe I can add a window with the "convertible top window material mentioned by Jack. Hmm....

 

[kazetsukai]

I'm interested in the OP's thoughts since we're doing a reverse-layout (bedroom in front) build.

I plan to delete the front door, extend the floor over where the door stairwell was, turning the stairwell into under-storage. On top of that will be pink panther 1.5 inch firm insulation under plywood, with vinyl floor on top of that in the entire cab area. I'm going to also cover the existing metal walls with 1.5 inch insulation and wood walls, so the only original exposed surfaces will be the main window area...

I think I could get away with a thermal curtain over the windows only... thoughts?

Also, I'm keeping the original ceiling panels- my thermal imager showed the problem points to be where the ribs contact, so I may put something over the existing ceiling if I can afford the room.

 

[paulnack]

Kazetsukai, if your bedroom is going to utilize the front entryway, does that mean you are deleting the driver area? ...making the bus immobile? What config is your bus- FE, RE, dognose?

My personal outlook is there's no such thing as too much insulation, but I want to be able to climate control off-grid in extreme conditions. Windows are tricky, really the only option is to cover them when you need the insulation. Some people use curtains, others make removable inserts with rigid foam insulation. I'm going as far as to replace them all together with RV windows. The thorn in my heel is the dash, likely 80% of the insulation work for only 20% of the gain. That rule never fails...

The conditions are very variable bus to bus, and depending on your needs. My best advice is do some rough calcs and see where you stand. Calculate the heat transfer in watts for each section (roof, windows, metal walls, floor) and see where the most heat is being transfered. You can also sum the numbers for all surfaces and it will give you a good idea how much A/C or heat you will need.
Q = U * Area * delta T
Watts = (Watt / m2*degC) * (m2) * (degC)
where U = 1 / R and, delta T = difference between inside and outside temps.

Yes, that's the R-value advertised on so many insulation products. Keep in mind- many R-values are "per inch", thickness matters, and to convert American R-values to (W/m2*degC) divide by 5.678. For single pane glass- you can use an R-value of about 0.14 W/m2*degC.

There's also solar irradiation... that's a bitch. White roof paint goes a long way, as does anything you will mount on the roof with an air-gap underneath.

 

[kazetsukai]

Kazetsukai, if your bedroom is going to utilize the front entryway, does that mean you are deleting the driver area? ...making the bus immobile? What config is your bus- FE, RE, dognose?

RE flatnose. I'm deleting the door (sheet metal over it, framing under that, insulated with R13 fiberglass, maybe reflectix), the stairwell (covering it wth sheet metal level with the floor, 1.5 inch R7 firm insulation over that, then plywood + vinyl flooring).

Windows are tricky, really the only option is to cover them when you need the insulation.

I'm in the process of deleting all of the windows, I expect to finish putting the sheet metal over them today, then I'll frame and insulate over them (same R13 fiberglass as in the walls, maybe reflectix).

The thorn in my heel is the dash, likely 80% of the insulation work for only 20% of the gain. That rule never fails...

Really. I had to redo the internal coolant loop for the defroster (the original owner removed the heaters when he removed the seats- leaving not evne the defroster). On a side note, I had enough BTUs pumping out with the 3 replacement heaters I installed that even in 30 degree weather with no insulation on the walls, or windows, after about 40 minutes it would get uncomfortably warm. I'm guessing there's some overkill there... I might want to isolate that loop from the engine coolant loop with a heat exchanger for the warmer weather.
Anyway, it _looks_ fairly simple to frame over and insulate underneath/behind the dash... I'm going to be covering most of everthing though.

There's also solar irradiation... that's a bitch. White roof paint goes a long way, as does anything you will mount on the roof with an air-gap underneath.

I can speak to this... Installed Henry's tropicool (stole that from ROLL WITH IT) before it got cold last year- before the ceiling would get too hot to touch in the sun, now it is cool to the touch. Major difference.

 

[2martins]

RE flatnose. I'm deleting the door (sheet metal over it, framing under that, insulated with R13 fiberglass, maybe reflectix), the stairwell (covering it wth sheet metal level with the floor, 1.5 inch R7 firm insulation over that, then plywood + vinyl flooring).


I'm in the process of deleting all of the windows, I expect to finish putting the sheet metal over them today, then I'll frame and insulate over them (same R13 fiberglass as in the walls, maybe reflectix).


Really. I had to redo the internal coolant loop for the defroster (the original owner removed the heaters when he removed the seats- leaving not evne the defroster). On a side note, I had enough BTUs pumping out with the 3 replacement heaters I installed that even in 30 degree weather with no insulation on the walls, or windows, after about 40 minutes it would get uncomfortably warm. I'm guessing there's some overkill there... I might want to isolate that loop from the engine coolant loop with a heat exchanger for the warmer weather.
Anyway, it _looks_ fairly simple to frame over and insulate underneath/behind the dash... I'm going to be covering most of everthing though.


I can speak to this... Installed Henry's tropicool (stole that from ROLL WITH IT) before it got cold last year- before the ceiling would get too hot to touch in the sun, now it is cool to the touch. Major difference.

"I might want to isolate that loop from the engine coolant loop with a heat exchanger for the warmer weather."

How would one do this? I was considering running it under the bus to the front. How do most people do this?

 

[2martins]

"I might want to isolate that loop from the engine coolant loop with a heat exchanger for the warmer weather."

How would one do this? I was considering running it under the bus to the front. How do most people do this?

Are you going to add RV windows later and enlarge another door or do you have another normal entry door? Have you found RV windows at a reasonable price anywhere?

 

[paulnack]

Kazetsukai, sounds like you've got it all figured out then! With a rear-engine, your dash will probably be simpler than mine. And as for the fiberglass batting, I believe it's only R13 as long as you maintain its original thickness (3.5"?). If it gets squeezed, its R-value will drop proportionally.

2martins, I got double-pane windows from RV scrappers on eBay for around $150 each average. Oddball sizes, but sometimes they have more in stock if you contact them.

 

[kazetsukai]

"I might want to isolate that loop from the engine coolant loop with a heat exchanger for the warmer weather."

How would one do this? I was considering running it under the bus to the front. How do most people do this?

I can't speak for anyone else, but...

The original seats mounted to the floor in the middle and to a metal lip on the walls. That lip was about as thick as a 2x4, so I framed on top of it. Because of that, I have about a 2x8 channel running along the entire wall on both sides of the bus.

I ran 5/8" coolant hose through that channel (in the cab) to the front. I considered going under the floor but it was more of a pain than I cared for- I had previously tried to re-route the bus electrical for the rear lights underneath and ran into several issues. I'm on the verge of redoing all of it inside the cab again...

Anything under the cab had better be ready for the weather and the elements. The little electrical I ran underneath is all in PVC conduit I wouldn't recommend doing it any other way. Assume its going to fail at some point and think about how you're going to replace it when it does- I can get at the coolant hoses any time I want fairly easily.

 

[budbud7]

Kazetsakai you said that you were going to eliminate your door and replace with sheetmetal. What type of sheetmetal, thickness, are going to use? I know a lot of people on this forum remove their windows and replace with sheetmetal. I would like to do that also.

 

[kazetsukai]

Kazetsakai you said that you were going to eliminate your door and replace with sheetmetal. What type of sheetmetal, thickness, are going to use? I know a lot of people on this forum remove their windows and replace with sheetmetal. I would like to do that also.

I used 18 gauge over the windows... I think its plenty thick to delete the door with as well.

I just opened a thread on my build....
http://www.skoolie.net/forums/f11/kazetsukais-build-22680.html

 

[EastCoastCB]

I used 18 gauge over the windows... I think its plenty thick to delete the door with as well.

I just opened a thread on my build....
http://www.skoolie.net/forums/f11/kazetsukais-build-22680.html

18ga is perfect for bus bodywork.

I keep a few sheets around for deleting windows, hatches, etc.

 

[2martins]

RE flatnose. I'm deleting the door (sheet metal over it, framing under that, insulated with R13 fiberglass, maybe reflectix), the stairwell (covering it wth sheet metal level with the floor, 1.5 inch R7 firm insulation over that, then plywood + vinyl flooring).


I'm in the process of deleting all of the windows, I expect to finish putting the sheet metal over them today, then I'll frame and insulate over them (same R13 fiberglass as in the walls, maybe reflectix).


Really. I had to redo the internal coolant loop for the defroster (the original owner removed the heaters when he removed the seats- leaving not evne the defroster). On a side note, I had enough BTUs pumping out with the 3 replacement heaters I installed that even in 30 degree weather with no insulation on the walls, or windows, after about 40 minutes it would get uncomfortably warm. I'm guessing there's some overkill there... I might want to isolate that loop from the engine coolant loop with a heat exchanger for the warmer weather.
Anyway, it _looks_ fairly simple to frame over and insulate underneath/behind the dash... I'm going to be covering most of everthing though.


I can speak to this... Installed Henry's tropicool (stole that from ROLL WITH IT) before it got cold last year- before the ceiling would get too hot to touch in the sun, now it is cool to the touch. Major difference.

What kind of replacement heater did you use? I also bought a RE bus with no coolant lines to the front and it seems like it might be easier to just put an engine powered heater up front and skip the lines. BUT, does that mean that my engine will be more subject to overheating because it does not have that long run of coolant hose to cool off? How much of that system is designed to heat and defrost the driver and how much is to COOL THE ENGINE? I know people that have problems with their engines overheating turn on the heater to help cool it down. I live near the desert and it gets REALLY hot in the summer and REALLY cold in the winter. Perhaps the best option for me is a set of coolant lines inside and out and the ability to switch between them? Although I'm not sure I have read about anyone with undercarriage storage actually having run their coolant lines underneath. IIRC, my coolant lines are 1". I figured I should replace with the same size lines. Ryderfleet website has the best coolant hose lines I've seen by a LOT. You have to buy in 50' intervals but with a 40 RE bus this isn't an issue.

 

[kazetsukai]

What kind of replacement heater did you use? I also bought a RE bus with no coolant lines to the front and it seems like it might be easier to just put an engine powered heater up front and skip the lines.

I used three of these:
https://www.jegs.com/i/JEGS-Performance-Products/555/70602/10002/-1

And one of these for the bathroom:
https://www.jegs.com/i/JEGS-Performance-Products/555/70601/10002/-1

They each have three speeds out of the box using 3 positive wires + 1 negative wire. You power the wire for the speed you desire. I have them hooked up for computer control via relays. Details here:

BUT, does that mean that my engine will be more subject to overheating because it does not have that long run of coolant hose to cool off?

Bus drivers don't pump heat into the cabin in hot weather, do they? Its an easy, "free" source of heat during the winter and has little do with cooling the engine if anything.

I know people that have problems with their engines overheating turn on the heater to help cool it down.

I have enough heaters that cranking them all to the max will probably cool an overheating engine, at the expense of frying me.

Perhaps the best option for me is a set of coolant lines inside and out and the ability to switch between them?

Better solution: Use a liquid-to-liquid heat exchanger instead of running your coolant lines inline with the engine. You'll need another coolant reservoir for the internal line and a booster pump, and there is another advantage: you can put a diesel (or propane) water heater on the second loop and have dual-mode heat using the same heaters (this is what I'm doing).

Although I'm not sure I have read about anyone with undercarriage storage actually having run their coolant lines underneath. IIRC, my coolant lines are 1". I figured I should replace with the same size lines.

Mine were 1", I ran 5/8" and I'm perfectly fine.

Seriously, I was fine. No insulation, bare metal walls, stock windows: between the 4x heater cores it'd get into the upper 70's in 30 degree weather. I couldn't pull that off with my wood stove....

Ryderfleet website has the best coolant hose lines I've seen by a LOT. You have to buy in 50' intervals but with a 40 RE bus this isn't an issue.

I bought 100' in 50' lengths locally from a couple of O'Reilly's auto parts stores. Cleaned 'em out.

When I get home I'll take pics of the coolant loop and post them on my build's thread.

 

[Ninjakitty]

Are you going to add RV windows later and enlarge another door or do you have another normal entry door? Have you found RV windows at a reasonable price anywhere?

What do you consider reasonable?