Target R values for surfaces?
- Thread starter aernan
- Start date
aernan
Observer
The 3500W webasto. Is that electric or is it a furnace that burns propane/diesel?
java
Expedition Leader
aernan
Observer
One of the books I read said the "dosing pump" on the diesel based heaters ticks. What kind of noise does the webasto make?
I am also planning on using the Webasto 24V diesel heater as well.
java
Expedition Leader
Yep its noisy! A couple tricks, a quick fist clamp holds the pump nicely and is a big rubber insulator. They actually sell a rubber fuel pump mount now also, but I had an extra clamp laying around. A old koozie wrapped around the pump is a trick I read about also. Lots of discussion on boating forums.
Mine is mounted on the frame rail basically under my bed, you can hear it ticking (no koozie yet) but if there is a conversation or something going on you don't notice it much. Just tells me the heat is kicking on when I hear it at night. It fires like 4-6 times at startup then once every few seconds when the heat is running.
Why are you doing a 24V one?
aernan
Observer
My base vehicle is a M1078 LMTV it has 24V mains (4x 6T 120 Ah 12V batteries in series parallel). I plan on making my house battery also 24V (Lithium of some form). I would like to do 48V but inverters and DC accessories (fans) are harder to find. I plan on using the diesel heater to preheat the engine coolant for cold weather starting and quick cabin heat. The Cat 3116 engine is mechanical and much to my surprise has no glow plugs. I do have an optional Ether doser to make cold starting easier but I believe a block heater would be a much better option. Instead of an electric block heater I will use the webasto as a coolant heater.
When stopped I plan on using it for hydronics, radiators (heat sink with electric fan for forced air), and heating a calorifier, warming fuel, water, grey water, batteries.
So I hope to use it for all my heating needs with electric heating for redundancy. I could also use any surplus power that I can't store to generate hot water. This will come from the engine driven alternator or the roof mounted solar. I haven't done enough research into generators yet.
When stopped I plan on using it for hydronics, radiators (heat sink with electric fan for forced air), and heating a calorifier, warming fuel, water, grey water, batteries.
So I hope to use it for all my heating needs with electric heating for redundancy. I could also use any surplus power that I can't store to generate hot water. This will come from the engine driven alternator or the roof mounted solar. I haven't done enough research into generators yet.
Joe917
Explorer
Our truck box is 8'X8'X18'
Foam composite construction, 4"floor, 2-1/2"walls, 3"roof.
With 2 occupants (plus cat) we rarely need heat until it starts to approach 0 deg C.
Our Webasto thermotop C is mounted forward under the frame and does make some noise, It is pretty much incidental, you have to listen for it to hear it.
Set up to heat cabin, water and engine in any combination (or heat cabin and/or water from engine).(also no glow plugs).
Webasto controlled by a Heatmiser slimline N thermostat.
Great system, that is plenty of insulation, we have been comfortable down to -20 deg C. Truck would be OK even colder.
Foam composite construction, 4"floor, 2-1/2"walls, 3"roof.
With 2 occupants (plus cat) we rarely need heat until it starts to approach 0 deg C.
Our Webasto thermotop C is mounted forward under the frame and does make some noise, It is pretty much incidental, you have to listen for it to hear it.
Set up to heat cabin, water and engine in any combination (or heat cabin and/or water from engine).(also no glow plugs).
Webasto controlled by a Heatmiser slimline N thermostat.
Great system, that is plenty of insulation, we have been comfortable down to -20 deg C. Truck would be OK even colder.
aernan
Observer
Why did you opt for a thicker floor then roof?
aernan
Observer
Ok good to confirm that. I have used the quick fists before. Making a sound proof cozie sounds easy enough. Thanks for the advise.
Joe917
Explorer
You would have to ask the Italian company that built the box in 1994! Possibly for structure or because it is in contact with the steel subframe.
Victorian
Approved Vendor : Total Composites
Most european expedition trucks use thicker floors and roofs. Mainly because a thicker roof will let you walk on it and thicker floors to allow for internal structure to mount the camper to the subframe. We use 84mm on roof, floor, front and back. 50mm for the sidewalls.
aernan
Observer
Ok that makes perfect sense now. My initial R calcs did not suggest the floor needed be thick but I have read that the ceiling/roof needs to be much thicker to help trap the hot air and it also helps prevent the sun on the roof from heating the ceiling.
Joe917
Explorer
A home (or camper) loses heat primarily through radiation and air transfer.
In a house we take care of air transfer by making the building as airtight as possible. Then we can use an HRV to bring in fresh cold air and exhaust warm stale air. HRV's recover something like 70% of the heat, they are not practical for a vehicle. Radiation is equal in all directions. We put extra insulation in roofs because it is easy and costs less to put it there than build thicker walls. It has nothing to do with warm air rising. Thicker roof insulation will help reduce heat transfer in the summer from the roof.
Window R values don't make much of a difference in overall performance as they are usually only a small percentage of the building envelope. Probably even less important in a camper, with the one note that single pane windows will sweat in the cold.
In a house we take care of air transfer by making the building as airtight as possible. Then we can use an HRV to bring in fresh cold air and exhaust warm stale air. HRV's recover something like 70% of the heat, they are not practical for a vehicle. Radiation is equal in all directions. We put extra insulation in roofs because it is easy and costs less to put it there than build thicker walls. It has nothing to do with warm air rising. Thicker roof insulation will help reduce heat transfer in the summer from the roof.
Window R values don't make much of a difference in overall performance as they are usually only a small percentage of the building envelope. Probably even less important in a camper, with the one note that single pane windows will sweat in the cold.
Betarocker
Adventurer
We build Passive Houses and there is a point where insulation becomes too costly for only minimal more gains. What is critical is air tightness and thermal bridging. A small structure like a camper will not take much energy to heat it compared to a house. Foam has an R value of 5 per inch, regardless if it is expanded or extruded sheet stock, or 1/2 pound or 2 pound spray foam. Expanded sheet and 1/2 pound spray are considered open cell and do not have air barrier properties; the other two types are considered air barriers.
Dew Point is something which needs to be addressed. When we build a Passive House, the exterior skin is a vapour permeable material, R30 Roxul or Cellulose in a 10" thick wall structure, the vapour/air impermeable layer of sealed and taped OSB or Plywood, and then a 2x4 service wall which is filled with Roxul, and then whatever wall finish is specified. The building science recommends at maximum 1/3 insulation inside the air barrier. Any moisture in the exterior portion of the insulation has a way to diffuse out to the exterior so there is never a chance of water droplets forming in the cavity due to the vapourizing and condensing cycle which occurs inside a typical wood framed home.
Taking the science into account, retrofitting a metal bodied van or trailer is not as simple as just spraying the walls with closed cell foam because there isn't enough insulation to fully create a thermal cocoon. Any moisture inherently trapped between the foam and metal skin has no means to be evacuated and can lead to rusting. A layer of Roxul with a thin layer of 2 pound foam to make an air barrier will allow the humidity to bounce around in vapour form eventually finding a way out in the drainage ports throughout the bodywork. Roxul has the benefit of after getting wet, it will revert back to its R value once dried. Fiberglass batt once wet can never regain its R value.
The SIPs (structural insulated panels) material Victorian uses to build his structures are scientifically the best option for a camper. Air tight, a good compromise of R value to wall/roof/floor thickness and dew point issues minimized. due to no air entrainment. The drawback is that designs can be drawn with an Etch-A-Sketch, meaning very rectangular.
Dew Point is something which needs to be addressed. When we build a Passive House, the exterior skin is a vapour permeable material, R30 Roxul or Cellulose in a 10" thick wall structure, the vapour/air impermeable layer of sealed and taped OSB or Plywood, and then a 2x4 service wall which is filled with Roxul, and then whatever wall finish is specified. The building science recommends at maximum 1/3 insulation inside the air barrier. Any moisture in the exterior portion of the insulation has a way to diffuse out to the exterior so there is never a chance of water droplets forming in the cavity due to the vapourizing and condensing cycle which occurs inside a typical wood framed home.
Taking the science into account, retrofitting a metal bodied van or trailer is not as simple as just spraying the walls with closed cell foam because there isn't enough insulation to fully create a thermal cocoon. Any moisture inherently trapped between the foam and metal skin has no means to be evacuated and can lead to rusting. A layer of Roxul with a thin layer of 2 pound foam to make an air barrier will allow the humidity to bounce around in vapour form eventually finding a way out in the drainage ports throughout the bodywork. Roxul has the benefit of after getting wet, it will revert back to its R value once dried. Fiberglass batt once wet can never regain its R value.
The SIPs (structural insulated panels) material Victorian uses to build his structures are scientifically the best option for a camper. Air tight, a good compromise of R value to wall/roof/floor thickness and dew point issues minimized. due to no air entrainment. The drawback is that designs can be drawn with an Etch-A-Sketch, meaning very rectangular.
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