[Chance]

Since ribs and miscellaneous van structures made of steel also conduct heat very well, trying to make insulation "perfect" between ribs and structures has diminishing return. Additionally, a lot of heat transfer also occurs through windshield, doors, firewall, windows, etc., so even if we double the insulation in cargo area, we won't cut heat load in half. There is a point where adding more insulation does very little.

And then there is cost. Unless there is limited cooling and or heating capacity, how much do you save? What's the cost difference between buying and operating an 11,000 vs. 13,500 BTU/hr AC, or a larger heater? I doubt it's much. On the other hand if you are trying to cool or heat off battery power, where energy supply is more limited, then added insulation is more important.

I think professional van converters know from experience where to draw the line on amount of insulation for the majority of buyers.

 

[orton]

[QUOTE=Chance;123873]Since ribs and miscellaneous van structures made of steel also conduct heat very well, trying to make insulation "perfect" between ribs and structures has diminishing return. Additionally, a lot of heat transfer also occurs through windshield, doors, firewall, windows, etc., so even if we double the insulation in cargo area, we won't cut heat load in half. There is a point where adding more insulation does very little.

And then there is cost. Unless there is limited cooling and or heating capacity, how much do you save? What's the cost difference between buying and operating an 11,000 vs. 13,500 BTU/hr AC, or a larger heater? I doubt it's much. On the other hand if you are trying to cool or heat off battery power, where energy supply is more limited, then added insulation is more important.

I think professional van converters know from experience where to draw the line on amount of insulation for the majority of buyers.[/QUOTE]

The object is to get as much insulation as possible with reasonable effort and cost.

There are several things that can be done to reduce the need for insulation. One is to let van get cold at night inside and heat van in the morning before you get up. A zero degree sleeping bag and a 12 volt heating pad and wearing a balaclava works. Did this in Sprinter and it worked very well. No heater noise and much reduced refrigerator running. Electrical use is about the same because refrigerator does not run.

A second approach which I will try in the Transit is to partition off the sleeping area. Why try to heat the whole van interior when you only occupy a small part of it. Just heat or cool the part you are in. You can reduce the heat loss in half if you reduce the volume in half. The Transit will have curtains with Thinsulate drapery insulation on each side of the sleeping platform. 30" above floor to ceiling and 5" wide. Be interesting to see how much of the heating pad heat will be retained inside the sleeping volume. Stay tuned.

Cost of heating the interior with a heater is not an issue to me. What is an issure is the noise that goes along with an operating heater. Hard to stealth city camp with a heater running. Heater cycling also affects my sleep.

 

[Chance]

....cut....

The object is to get as much insulation as possible with reasonable effort and cost.

....cut..... Just heat or cool the part you are in. You can reduce the heat loss in half if you reduce the volume in half.

....cut.....

What is "reasonable" effort and cost depends greatly on the consequences of not doing more.

For me, the consequences of less insulation may be my heater running 70 versus 50 percent of time, and since we stay mostly at campgrounds, there is little incentive for me to add more.

I agree segregating floorplan can save energy, but it may come at cost of making RV feel smaller. An insulated wall at typical bulkhead location could reduce HVAC loads significantly but affects general mobility and access.

By the way, the load is not proportional to "volume". May be more or less. If design is uniform throughout, it's more a function of surface area than volume. In the case of front cab area, load is high by comparison to insulated house area.

 

[lkruper]

What is "reasonable" effort and cost depends greatly on the consequences of not doing more.

For me, the consequences of less insulation may be my heater running 70 versus 50 percent of time, and since we stay mostly at campgrounds, there is little incentive for me to add more.

I agree segregating floorplan can save energy, but it may come at cost of making RV feel smaller. An insulated wall at typical bulkhead location could reduce HVAC loads significantly but affects general mobility and access.

By the way, the load is not proportional to "volume". May be more or less. If design is uniform throughout, it's more a function of surface area than volume. In the case of front cab area, load is high by comparison to insulated house area.

One thing I read is that a building (arguably also a van) is like a chimney. Heat rises and the biggest bang for the buck is to insulate the roof.

 

[perchancetodream]

Insulation - thoughts on the first condensing surface concept

Water vapor will condense as soon as it encounters a surface with temperature below the dew point. The best strategy is to prevent that from happening by making sure any surface air can get to never reaches dew point. Insulation moves the dew point from the metal van skin to somewhere in the middle of the insulation thickness. But with batt insulation, water vapor tends not to condense on fine fibers, but continues to move through until it reaches the cold inside surface of the van skin, where it will condense. With fully adhered closed cell foam and spray foam, air cannot reach the cold metal, and the inside surface of the foam is above dew point - no condensation. When insulating with batts or pieces of rigid foam, meticulous sealing is necessary to minimize air movement into the space between van body and interior finish. A small hole or open seam allow LOTS of air and its moisture to enter the concealed space. Far more than vapor diffusion. Polyethylene and reflectex vapor barriers are not the answer. First, they're far too easily punctured and torn. Penetrations for wires, anchors, electrical boxes are hard to seal. Second, since moisture WILL get into the concealed space, there must be a way for it to dry off later, ideally by sun shining on the exterior heating up the concealed space and driving water vapor through a vapor permiable interior finish. Otherwise, trapped moisture = inevitable corrosion, unless you never camp or cook in cool climates.
Spray foam is totally adhered, but has its own special problems. Tendency to get between ribs and exterior skin, then expanding to cause ripples. Tendency to plug weep holes. Hard to go back and run new wiring. Tricky to mix perfectly for 100% reaction with no residual outgassing (urethane is a potent sensitizer). So it seems the best solution is fully adhered flexible closed cell foam wherever possible. Polyethylene from foambymail or Kflex / Armorflex duct soundproofing insulation. Contact cement - use a proper respirator! Hard to reach rib cavities could be stuffed with batt insulation then wrapped with vapor permiable house wrap (Tyvek) with all edges sealed. Generally not worth the trouble - the thermal conductivity of the rib dwarfs heat loss through the air space inside it. Finish with plywood. I'm not so sure polycarbonate or FRP or load protection polypropylene panels are such a good choice due to zero vapor permiability. Thought about Homosote as an option, but suspect it can't hold up to road vibration. Maybe marine hull liner, but I'd want to know its vapor permiability first. Then there's the question of outgassing from the contact cement...I think this drops off quickly because the quantity and thickness is minimal once the solvent evaporates. It might be worthwhile to investigate carpet and flooring adhesives with "green" indoor air quality (IAQ) ratings. They're water-based, but I can tell you from experience, they are VERY sticky...and get all over everything just as easily as contact cement.

 

[lkruper]

One thing I did learn from doing the insulation in my sold Sprinter is to thermally isolate the 80/20 framework. ....

This stuff (http://www.jetsongreen.com/2010/02/aerogel-ultra-thin-super-insulation.html) is very expensive but it might not be cost prohibitive for reducing conduction from metal bridges and you could also claim bragging rights that your van is built like a Nasa Spacecraft!

 

[orton]

What is "reasonable" effort and cost depends greatly on the consequences of not doing more.

For me, the consequences of less insulation may be my heater running 70 versus 50 percent of time, and since we stay mostly at campgrounds, there is little incentive for me to add more.

I agree segregating floorplan can save energy, but it may come at cost of making RV feel smaller. An insulated wall at typical bulkhead location could reduce HVAC loads significantly but affects general mobility and access.

By the way, the load is not proportional to "volume". May be more or less. If design is uniform throughout, it's more a function of surface area than volume. In the case of front cab area, load is high by comparison to insulated house area.

Reasonable effort may be different for different people. For me I will fill all the openings that I can.

I simply do not want to listen to a heater turning on/off.

No problem with partitioning off the sleeping area. Two insulated curtains put up on each side of bed. Removed during the day. We do know the heating load will be significantly less. Something like 1/8 the volume and surface area. Do not need to be an engineer for that evaluation.

 

[Chance]

One thing I read is that a building (arguably also a van) is like a chimney. Heat rises and the biggest bang for the buck is to insulate the roof.

I worry more about how roof insulation affects air conditioning at noon on a sunny day. While true that heat rises, when it's 20 F outside and the heater has to work hard to keep van comfortable in the 60 to 70 F range, I don't see the fact that heat rises inside a small van making a big difference in comfort or heat load.

And in my experience, if you camp without a heater the inside of the van will approach the outside ambient temperature in a relatively short period. In that case there isn't much heat to rise anyway.

 

[Chance]

Reasonable effort may be different for different people. For me I will fill all the openings that I can.

I simply do not want to listen to a heater turning on/off.

No problem with partitioning off the sleeping area. Two insulated curtains put up on each side of bed. Removed during the day. We do know the heating load will be significantly less. Something like 1/8 the volume and surface area. Do not need to be an engineer for that evaluation.

What heat source will you have in sleeping area when stealth camping?

 

[orton]

What heat source will you have in sleeping area when stealth camping?

12 volt heating pad under sleeping bag. Warm your body not the whole van. Power used remains about the same. Because interior is cold the refrigerator runs less so you trade the heating pad power used with the less refrigerator power used. Also less noise from refrigerator. Very quiet.

Not for everyone. Found I never ran heating pad higher than its # 2 setting. It has 7 levels of heat. It is on/off with higher settings on longer. The problem is your body is warm but your head is out in the cold air. A balaclava solved that problem but looks a bit weird.

I sleep on a 54" wide bed platform 30" above the floor. On Transit I will have two removable insulated curtains that go from the platform up to the ceiling. I will find out if that enclosure retains some of the heating pad produced heat. The bed platform will be a composite panel that includes 1/2" of rigid insulation. The front curtain will be split to allow entry without removing curtain. Both curtains will be removed during the day. Sort of a tent within the van. I think it will retain some of the heat. We will see.

The other "air conditioning" that works well to keep van interior close to the outside ambient air temperature is a hole in the van floor and a ceiling vent. Open floor hole and ceiling vent and hot air rises to pull cooler air from under van up past the refrigerator coil and out the open ceiling vent. I seldom needed to turn on the ceiling fan. Just needed both to be open.

 

[lkruper]

I worry more about how roof insulation affects air conditioning at noon on a sunny day. While true that heat rises, when it's 20 F outside and the heater has to work hard to keep van comfortable in the 60 to 70 F range, I don't see the fact that heat rises inside a small van making a big difference in comfort or heat load.

And in my experience, if you camp without a heater the inside of the van will approach the outside ambient temperature in a relatively short period. In that case there isn't much heat to rise anyway.

My experience in the Roadtrek in the mid-twenties when we ran out of propane confirms your experience. At my cabin we generally heat with just a fireplace. I have an infrared thermometer I use to see the temperature at various parts in the cabin as it heats up after starting a fire. The heat builds up at the ceiling and works its way down to the floor, always remaining warmer. We have 9' ceilings. Also, I see a difference at maintaining a comfort level after the cabin has warmed up ... we do not heat it at all between visits.


After I blew insulation in the attic and insulated below the floor I did notice that it appears to heat more quickly, and even though we let the fire die out at night we generally only have a delta of 10 to 15 degrees lower in the morning.


That being said, a van has much less mass to retain heat which would explain why it reaches ambient temperature so quickly. Also, the cold will work its way up from the floor in a way that does not happen with a conventional building.


We maintain comfortable temperatures with lots of air penetration and not much insulation in the walls (if any) at the cabin and the windows are original single pained glass from when it was built. So my answer to that is to burn LOTS of wood. I think we burn more than 1/10 of a cord of seasoned hardwood per day when we are there.


My preliminary conclusion in making a comparison to a van is that the key to comfort at extreme temperatures is to have the ability to furnish massive amounts of heat or cooling.


One option that might work, but would be very costly and also not very livable would be to make an airtight box inside the van and use some of the space age high-tech insulation. The insulation alone might run 3-5K. Still, in reading what some ppl spend on Lithium batteries as an option on a Roadtrek, that price is affordable to some!


But back to reality, I wonder if one of those small marine coal/wood stoves might not put out enough BTUs to provide enough heat in almost any condition we might encounter. There is a brand I saw online called Tiny Tot (think 6" diameter X 12" vertical fire box) which does not appear to be very expensive.... under $500. Some others go up to 4K installed. I realize that there is a fire danger, but we have control over what we put into the metal box (ie van) that is combustible. Also, wooden boats are also flammable and no one thinks twice about using them there. Most campgrounds sell firewood for use in a fire pit and lump coal is pretty cheap and lasts quite a while in a controlled burn.


I also wonder if perhaps burning a good clean charcoal might even be stealth enough. If not, one could find a place to park next to a BBQ joint!

 

[perchancetodream]

Ventilation hole in floor

The other "air conditioning" that works well to keep van interior close to the outside ambient air temperature is a hole in the van floor and a ceiling vent.

orton, regarding that hole in the floor - how did you handle controlling exhaust fumes, road splash and critters?

 

[Chance]

What is wattage on heating pad(s)?

 

[orton]

orton, regarding that hole in the floor - how did you handle controlling exhaust fumes, road splash and critters?

http://sprinter-source.com/forum/showpost.php?p=145056&postcount=9

Opening has a screen. Only problem with driving with it open is dusty roads when it needs to be closed. Excuse the Rube Goldburg design but it does work very well. A lawn mower starting cord is used to ope/close the vent.

 

[orton]

[QUOTE=Chance;124385]What is wattage on heating pad(s)?[/QUOTE]

Electro Warmth 36" x 60" heating pad is 6.2 amps DC max. One pad

 

[perchancetodream]

Excuse the Rube Goldburg design but it does work very well. A lawn mower starting cord is used to ope/close the vent.

You wouldn't happen to have a dog named Grommet?

 

[orton]

You wouldn't happen to have a dog named Grommet?

No but I like the name for next dog.

 

[mactweek]

Back to the insulation conversation. I am more concerned about keeping the interior cool in the sun, especially if I use a solar panel and can't park it in the shade too much. I have a roll of prodex (like reflectrix) and I am not sure whether to attatch it to the interior or exterior walls, or even both. I understand the need for an air gap, and I may use foam board or thinsulite in the walls. I will use foam board under the floor. I guess I could temporarily attach a section each way to the ceiling and compare temperatures.
Any suggestions?
This will be a long wb hr in red should arrive next week,. I plan a moderate conversion, refrigerator, fantastic fan sink, with fresh and greywater tanks, a rear bed and cabinets that I can remove or get out of the way when needed for hauling stuff. I might do propane but a camp stove will suffice at first. A removable porta-potty is a must. we like to boondock, but camp minimally. Our former class b was great but we never used the shower, hot water or furnace, and it had no insulation. We like sleeping cool and found that making coffee in the morning heated up the van sufficiently most of the time.

 

[orton]

I am more concerned about keeping the interior cool in the sun, especially if I use a solar panel and can't park it in the shade too much.

You can keep the van interior close to the outside temperature with a floor vent combined with a open roof vent. With both open, air will flow from under van through the floor hole and out the ceiling vent without powering the ceiling vent.

http://sprinter-source.com/forum/showpost.php?p=145056&postcount=9

If floor hole is located behind the refrigerator the air flow will also reduce the run time of the refrigerator. Also useful at night so you do not have to keep front windows down slightly. Also works well for air flow when it rains. Needs to have cover to stop air flow in cold weather and with dusty road conditions.

 

[Chance]

Back to the insulation conversation. I am more concerned about keeping the interior cool in the sun, especially if I use a solar panel and can't park it in the shade too much. I have a roll of prodex (like reflectrix) and I am not sure whether to attatch it to the interior or exterior walls, or even both. I understand the need for an air gap, and I may use foam board or thinsulite in the walls. I will use foam board under the floor. I guess I could temporarily attach a section each way to the ceiling and compare temperatures.
Any suggestions?
....cut....

I may not be understanding your question in the right context, but if I am, the only way to cool a van in the sun is to have an air conditioner.

If you have enough solar capacity, you may be able to power a small air conditioner that will cool your van somewhat if insulated very well -- and if you don't have too many windows.

If you don't have an AC, then excessive amounts of insulation won't help much more than a normal amount. That's because you'll have to circulate outside air through van to get air temperature close to outside ambient. And since moving air is easy you can move more as needed. The easiest way is to open windows or doors. Fans work too. But in no case will adding lots of insulation make the van significantly cooler once steady-state is reached. Insulation will mostly delay the inevitable for a few minutes.

On the other hand if you are trying to cool the van with a 5,000 BTU/hr AC as I do, then insulation (or lack thereof) is critical.