Poyiso + Cold weather

[birdman86]

Lots of searching and all I can find is comments pointing out that polyiso loses R-value in cold weather. But at the same time, it's a really good moderate weather insulator, and easy to install.

I'd like to be able to camp for ski trips (say -25C/-13F at night with risk of colder) with a heater buddy and vent. If I build up say 2-3" of polyiso do you think that'd be thick enough to rule out the reduced R-value?

My original plan was to use roxul & furring strips, then use poly to hold it in before putting up plywood walls - that way poly's got a good warm insulated layer between it and the cold winter outside. But I'm convinced the poly needs to be glued down pretty much completely otherwise it'll squeak like a ******** so ruled that one out. Now trying to decide if putting the poly directly on the van wall and just building it out as a 2-3" layer would work, ie contact with the van walls won't be enough to kill the r-value all the way through. Ughhhhh dilemmas!

 

[Paddy]

2-3" of polyiso seems like a LOT of R. I haven't heard it reduces R at lower temps but that doesn't seem logical. I would suspect that propane kept outside at that temp may lose its ability to flow however.

 

[Bbasso]

I've done low temps with a mildly insulated van and the Mr buddy heater didn't cut it for me...
I stepped up to the EsparD4 and haven't worried about being cold again.

 

[luthj]

The R value reduction with polyiso is not as bad as some data would lead you to believe. This is because the polyiso will have a temperature gradient with the middle being the average between inside and outside.

For a van, the biggest losses will be from the uninsulated cab and the glass. Honestly you won't have much trouble with 3" of polyiso vs other materials. If you can get the windows and cab insulated that will be an order of magnitude more improvement than switching to another material from polyiso. You could also go with expanded polystyrene, though it is more expensive. Don't forget to insulate the floor!

With no window coverings my Espar D2 (2kW) is good for 45f above ambient in my van. This is with 1" of spray foam and 1.5" of thinsulate. With window coverings I have not hit any practical limit for cabin heating (I have not camped sub zero with it). I have about half the glass installed compared to a passenger van. So for a well insulated van with average window coverings, you can expect good results from a 2kw heater. The biggest issue is ventilation losses, especially with an unvented heater. For a poorly insulated van the 9,000btu (2.6kW) heater buddy would probably be inadequate in sub zero temps.

How warm do you need the cab? Just above freezing? Say 40F? Or do you need/prefer a 70F cabin?

 

[birdman86]

I'd like it to be as comfortable as possible so 70 would be nice. My van is one of those ones with windows all down one side and the back, cargo panels on the other. The plan is to build some kind of reflectix wrapped insulation cushion for each window to seal that stuff up, won't be perfect but as good as I can without permanently closing them right off. Then I'll have some kind of barrier between the cab and cabin, probably one (or two) of those heavy thermal curtains with as good a fit as I can manage.

EPS has a lower R-value than poly at regular temperatures though if I recall right? At the end of the day the van is a mountain bike hauler so it'll be more summer focused, I just don't want to rule out the occasional ski trip due to insulation.

 

[luthj]

EPS does have a lower R value. If you have thermal curtains for the cab, and well sealed window coverings, 2-3" of EPS or polyiso would be plenty (assuming insulated floor) with a 2kw or greater heater. 50-60F differentials should be possible as long as you keep the venting as low as reasonable. The moisture from the unvented heaters is going to be noticeable though. Your gear may not dry out. If you can swing the cost a D2 can be had for about $1k from heatso.com (make sure to get the altitude sensor). It will keep you warm and dry. I have one in my van, and it is phenomenal. Uses very little power, its quiet too.

Having good insulation is helpful in the summer too. It will keep the thermal gain down combined with a roof vent and window coverings it will allow the van to stay within a few degrees of ambient.

 

[IdaSHO]

At -13F, you will have propane issues if the tank is outside, especially if hitting high altitudes in those temps.
It gets incredibly hard to light, and the heat put off is diminishes quick.

We regularly see down to near -20 F and high altitudes in our travels every winter, so when designing our camper, the propane compartment was certainly an important component.


The result is a setup that seems un-effected by cold all-together.


The compartment is sealed, but not insulated from the interior space, and insulated from the exterior.
A small vent is provided to the outside to handle the venting needs.

But the compartment remains warm, absorbing cabin heat, even well below zero.

 

[birdman86]

EPS does have a lower R value. If you have thermal curtains for the cab, and well sealed window coverings, 2-3" of EPS or polyiso would be plenty (assuming insulated floor) with a 2kw or greater heater. 50-60F differentials should be possible as long as you keep the venting as low as reasonable. The moisture from the unvented heaters is going to be noticeable though. Your gear may not dry out. If you can swing the cost a D2 can be had for about $1k from heatso.com (make sure to get the altitude sensor). It will keep you warm and dry. I have one in my van, and it is phenomenal. Uses very little power, its quiet too.

Having good insulation is helpful in the summer too. It will keep the thermal gain down combined with a roof vent and window coverings it will allow the van to stay within a few degrees of ambient.

Interesting...I haven't reached the point of researching heating systems yet, what does the D2 run on? 12V control, heating fuel from the gas tank? Big gas tank in the van, so that could be a good option. Are there any cold weather ventilation solutions out there? Rust is my biggest fear with this whole project... And just to be clear, these D2's don't create moisture like a propane heater does?

For the summer I've got a maxxair fan and going to put one or two deck plates in the floor, so in theory I think that'll be pretty good. Just stuff the floor vent with some rockwool or something when not in use.

 

[luthj]

The Espar D2 uses diesel fuel or kerosene. It needs 12V power to run, but uses only 2.8 amps on high, and 0.7 amps on low. Some specs on the PDF linked below. The espar B2 and B4 heaters use gasoline for fuel. They are more expensive though. I have seen several installations where a separate diesel/kerosene tank was used to provide fuel for a D2/D4 heater when the vehicle did not have an onboard diesel tank. On high power the D2 only uses 0.07 gallons per hour of diesel, so its quite reasonable on fuel. Secondary 2-3 gallon tank will last for a number of days.

http://www.pro-west.ca/pdfs/airtronic_D2-D4-D5_spec_sheet.pdf

As far as venting, cracking a window and opening the vent fan is usually enough to help keep the moisture under control and keep you breathing.

 

[Bbasso]

The Espar I have provides dry heat, very welcome in a damp climate. (Snow, cold rain...winter)

 

[Paddy]

Go for the D2! Away more better than non vented propane for several reasons. I got my kit off eBay for 700$

 

[luthj]

Remember if your are camping above 3500ft, you need an altitude sensor. Otherwise the unit will coke up over time.

I have ordered this kit from the UK, with the pound lower, its a great deal at $718, shipping is very reasonable. It even comes with a muffler, which many kits don't have. Trust me, you want the muffler.
http://www.heatso.com/eberspacher-airtronic-d2-12v-2-2kw-heater-kit/

Here is the altitude kit for $185.
http://www.heatso.com/eberspacher-high-altitude-kit-22-1000-33-2200/

Here is a 2.7 gallon fuel tank for those with gasoline vehicles.

http://www.heatso.com/plastic-fuel-tank-10-l-capacity-blue/

The prices from this vendor are very good right now. The Webasto diesel cooktops are only $1,100$!!!!!