Insulation - Cutting Poly-Iso

[cargovanconversion]

I've been meticulously documenting my van conversion as a reference tool for others, for them to know what every little step of a conversion really means and whether they might be able to do it.
Currently I'm working on the sub-floor and have just published part three of the installation.
I've been laying poly-iso boards between the ribs of the floor of my Ford Transit.



You can read about all the details, see photos and view the video here.

Or part 2: Paper Plywood Templates

Or part 1: Tie Downs & Wheel Wells

Enjoy!

Van Williams

[font="Helvetica Neue",Helvetica,sans-serif]Save[/font]

 

[Oberneldon]

Excellent details on your conversion!

 

[MrNoodly]

Since air gaps are a good thing in insulation, wouldn't it be advantageous (and a lot less work) to just lay the poly-iso in large pieces?

 

[highdesertranger]

air gaps are good if they are sealed off. if they are not sealed the cold air moves right in. that's why double pane windows must be sealed 100% or they don't work. highdesertranger

 

[BradKW]

Since air gaps are a good thing in insulation, wouldn't it be advantageous (and a lot less work) to just lay the poly-iso in large pieces?

Plus, having unsupported polyIso as the floor probably wouldn't work out too well in the long run...

 

[cargovanconversion]

Since air gaps are a good thing in insulation, wouldn't it be advantageous (and a lot less work) to just lay the poly-iso in large pieces?

Specific to my conversion (Transit LWB MR) where I don't want to compromise full standing height inside the vehicle, I feel that I don't have another 1/2 to 1-1/2 inch to spare to put a layer of insulation on top of the floor.
Filling the spaces between the floor ribs with poly-iso is an attempt to maximize insulation, where more is needed.

Van Williams

 

[AngryVanMan]

I've been following your project for awhile now Van Williams, great work and a nice presentation of the details  When I stumbled across your website I was quite impressed!

This doesn't pertain directly to floor insulation as shown, but as for air gaps being advantageous for insulation as mentioned, there is a small caveat - particularly in vertical air spaces.  If the space is deep enough, a convection current can be set up in the space where air against the warm side of the space begins to rise to the top, and falls back down along the cold surface.  This creates a flow very similar to a heat pipe, and is quite effective at increasing the losses from one side of the space to the other, which is not good.  Insulation materials primarily trap air, restricting or eliminating draft potential by also stopping or restricting this air flow.  These types of materials are usually great at limiting conduction losses.  Radiant barriers need an air gap to be effective, but this is a different can of worms.  Convection currents become an ever larger concern as the temperature difference between the inside and outside surfaces increase, and as the distance between them increases.

 

[cargovanconversion]

I've been following your project for awhile now Van Williams, great work and a nice presentation of the details  When I stumbled across your website I was quite impressed!

This doesn't pertain directly to floor insulation as shown, but as for air gaps being advantageous for insulation as mentioned, there is a small caveat - particularly in vertical air spaces.  If the space is deep enough, a convection current can be set up in the space where air against the warm side of the space begins to rise to the top, and falls back down along the cold surface.  This creates a flow very similar to a heat pipe, and is quite effective at increasing the losses from one side of the space to the other, which is not good.  Insulation materials primarily trap air, restricting or eliminating draft potential by also stopping or restricting this air flow.  These types of materials are usually great at limiting conduction losses.  Radiant barriers need an air gap to be effective, but this is a different can of worms.  Convection currents become an ever larger concern as the temperature difference between the inside and outside surfaces increase, and as the distance between them increases.

Thanks for your remarks about the website!

I agree about the convection issues. A bit off subject, but relevant: I have always been convinced that more attention should be given to ventilation over insulation. With the inclusion of a floor vent and roof vent, optimal use of natural convection could substantially lower temperatures and humidity inside the vehicle. As you described, natural convection needs a temperature differential, distance between inlet and outlet, height difference. P.S I just finished my somewhat unique floor vent. Will publish that in detail in about a week on my website CargoVanConversion.com

Van Williams

 

[BillTheCat]

What type of insulation would you recommend that would provide for an air flow between the skin and the inside walls that won't trap moisture and will allow for natural air flow to keep it dry between these two surfaces? Maybe I'm misunderstanding something but I read you need the ventilation but you also need to seal it so it won't ventilate. I'll be in a wide range of humidity and temperatures and want something that will work. The best I can come up with is to allow for airflow between the outer skin of the van and the inner walls of the living area.

 

[Almost There]

What type of insulation would you recommend that would provide for an air flow between the skin and the inside walls that won't trap moisture and will allow for natural air flow to keep it dry between these two surfaces?  Maybe I'm misunderstanding something but I read you need the ventilation but you also need to seal it so it won't ventilate.  I'll be in a wide range of humidity and temperatures and want something that will work.  The best I can come up with is to allow for airflow between the outer skin of the van and the inner  walls of the living area.

IMO there is absolutely no need to worry about providing air flow between the skin of the van and the inner finished wall. Trapping of moisture in there to the point of causing a problem is greatly exaggerated.

There is sometimes a problem with some people who don't provide for good air flow IN the van when using various appliances such as heating water, cooking and using a propane heater.

I cook and heat water with the roof vent wide open, at least one of the upper side windows in the high top open and both the front windows are always cracked to the level of the bottom of the rain guards. I have no moisture build up from the kettle or cooking as long as I do so. Should I try to heat water with less ventilation, then yes, I can see moisture accumulating on the inside of the van (NOT in the wall cavity).

Decide what you want to protect yourself from and plan accordingly. If you want to keep the van cool then consider a radiant heat barrier (coupled of course with DEAD air space). If you need to plan for cold weather then insulate. If you're planning on being where it's virtually a rain forest, then a lot of good air flow IN the van needs to be planned for.

 

[cargovanconversion]

What type of insulation would you recommend that would provide for an air flow between the skin and the inside walls that won't trap moisture and will allow for natural air flow to keep it dry between these two surfaces?  Maybe I'm misunderstanding something but I read you need the ventilation but you also need to seal it so it won't ventilate.  I'll be in a wide range of humidity and temperatures and want something that will work.  The best I can come up with is to allow for airflow between the outer skin of the van and the inner  walls of the living area.

I could not have said it better than Almost There.

Remember, everybody's situation is different and there is no single solution for a myriad of insulation issues. Insulation and ventilation have to be dealt with in similar ways and with the same vigor.

BUT:
I have a 2016 Ford Transit with factory windows and recently started to work on the walls as part of my Murphy bed/desk combination.

Being concerned about condensation on the windows, which WILL happen sooner or later, I found out, that in that case, the water would not collect at the bottom of the windows to be removed or where it could evaporate. This condensation would drip into the wall cavity, down the skin of the vehicle. On top of that, Ford neglected to incorporate any weep holes as they did in both front doors.

​

I'm working on a solution for it, but it illustrates a possible situation where you have to be concerned about wall cavity moisture. Though I think of it as the exception on the general rule.

I may create some weep holes myself, and very likely keep a dead airspace between the skin and the (Poly-Iso) insulation. Prevention of condensation is number one, but if it occurs, it has a way to drip down without reaching the insulation and escape through the weep holes or dry out. As far as I know, this situation only occurs in the Ford Transit with its factory windows and should have no bearing on you if you have another vehicle or setup.

Van Williams

[font="Helvetica Neue",Helvetica,sans-serif]Save[/font]

 

[Almost There]

The only times I have condensation on the windows is when the van is closed up tightly because of rain/snow and I'm creating heat inside, either by my presence and/or a heater going.

I have both factory windows in the cargo van and aftermarket windows in the high top. I've also had vans before with RV style windows in the living area.

I have window ledges beneath the high top windows and I simply mop the moisture up with a paper towel.

In 40 years of owning vans and knowing hundreds of van owners across the continent I have never experienced or heard of a problem where the interior wall was damaged because of dripping moisture from condensation.

Lots of problems from roof leaks in to pink fiberglass insulation from improper installation of holes in the roofs and problems with aftermarket window seals leaking, yes, but not from condensation in the walls themselves. Pink fiberglass insulation was commonly used in the 70's ad 80's.

Sometimes, anticipating and trying to prevent a problem is more trouble than it's worth!

 

[cargovanconversion]

The only times I have condensation on the windows is when the van is closed up tightly because of rain/snow and I'm creating heat inside, either by my presence and/or a heater going.

I have both factory windows in the cargo van and aftermarket windows in the high top. I've also had vans before with RV style windows in the living area.

I have window ledges beneath the high top windows and I simply mop the moisture up with a paper towel.

In 40 years of owning vans and knowing hundreds of van owners across the continent I have never experienced or heard of a problem where the interior wall was damaged because of dripping moisture from condensation.

Lots of problems from roof leaks in to pink fiberglass insulation from improper installation of holes in the roofs and problems with aftermarket window seals leaking, yes, but not from condensation in the walls themselves. Pink fiberglass insulation was commonly used in the 70's ad 80's.

Sometimes, anticipating and trying to prevent a problem is more trouble than it's worth!

I agree completely with you. Until recently, I had a 25-year old Dodge B-250 with fiberglass in the walls. Still in pristine condition. But the wall also had weep holes and the windows had 'ledges'.

My Ford Transit windows have nothing to stop condensation from entering the wall cavity, as you can see in the following video clip.

[video=youtube]

The wall will contain insulation and I need to keep it dry.

Van Williams

 

[BillTheCat]

Decide what you want to protect yourself from and plan accordingly. If you want to keep the van cool then consider a radiant heat barrier (coupled of course with DEAD air space). If you need to plan for cold weather then insulate. If you're planning on being where it's virtually a rain forest, then a lot of good air flow IN the van needs to be planned for.

Since I will be enjoying many climates, I just want to ensure that over the years, this van doesn't incur problems down the road that could be prevented now while I'm putting it together.

For a radiant heat barrier, would this be something like Reflectex glued to the side or just the polyiso inserted where ever I can fit it into?

Thanks for your insights!!!

 

[Almost There]

Since I will be enjoying many climates, I just want to ensure that over the years, this van doesn't incur problems down the road that could be prevented now while I'm putting it together.

For a radiant heat barrier, would this be something like Reflectex glued to the side or just the polyiso inserted where ever I can fit it into?

Thanks for your insights!!!

Reflectix is a radiant heat barrier, polyiso is an insulation product. Two different materials for two different applications.

Reflectix only works as a radiant heat barrier if it has a DEAD air space provided for it. In a van, attaching bubble wrap to the side of the reflectix that will be facing the metal of the van wall is an effective way of providing the needed dead air space. There are better and less expensive methods of attaching the combination of bubble wrap and reflectix to the vehicle than glueing it to the wall. I used (and recommend) the metal tape that is meant for using with the reflectix.

If you want to protect the inside of the vehicle from the radiant heat of the sun you use a radiant heat barrier. If you want to keep the inside of the vehicle warmer when heating it with a heat source like a propane heater, you use some form of insulation.

If you want both, then you need to provide for both.

 

[cargovanconversion]

Since I will be enjoying many climates, I just want to ensure that over the years, this van doesn't incur problems down the road that could be prevented now while I'm putting it together.

For a radiant heat barrier, would this be something like Reflectex glued to the side or just the polyiso inserted where ever I can fit it into?

Thanks for your insights!!!

Without answering your question, I may address your concerns.
Your questions are legitimate and have been asked many times before. Ultimately, you will get many different answers that will likely make you more confused.

My personal opinion is that if you live in or spend most of your time in a cold(er) climate, you should put an extra effort into more and/or thicker insulation. That said, if you live in a warmer climate like me, moderately apply insulation, which often consists of rigid boards with high R-value and lower rated materials to fill the gaps.

Make ventilation a priority to lower interior temperatures and avoid condensation, which can lead to rust. Make well-insulated window covers and use a cabin curtain. Park in the shade, unless you have solar panels.

But remember, a van has too many doors that open regularly and that aren't sealed well and you can do only soo much…

I will probably use mainly 2 inch rigid Poly-Iso on the ceiling, because that's how thick my roof cross members are and because the roof is very exposed to the sun. The walls likely a 1 or 2 inch airspace against the skin of the vehicle, followed by 1 or 2 inch Poly-Iso. Fill in materials could be specially treated Denim, Thinsulate or even fiberglass bats. Each with their own pros and cons: price, possible moisture issues, R-value, sound insulation properties. Again the floor could be Poly-Iso, but is less important.

If you always travel between campgrounds with utility connections, the above is even less relevant.

Read about it, read some more and read more. Then make up your own mind and don't worry too much: any insulation is probably much more than the average factory made RV contains.

Van Williams