Is a vapour barrier necessary with havelock insulation?

[tj-grant]

We will be using havelock for insulation. Wood battons to reduce heat transfer. We are removing all factory windows and doors, raising the roof, reskinning, and adding sealed rv windows where desired. So, we will be combating all leak prone areas (aside from the roof fan and solar panel mounts i guess..).
Anyways, do i need a vapour barrier?
Am i trying to keep the condensation water from coming inboard, the warm air from rising to the metal bus skin? If using the vapour barrier, won’t it prevent the insulation from breathing and releasing moisture resulting in sopping wet wool insulation?? Wth is the point of the vapour barrier?????

 

[Mr P]

Steel is an excellent vapor barrior. As such, your barrior is on the outside of your wall. Any air on the inside that touches that steel shell can allow condensation, IF the air inside is warm and moist and the steel shell is cool. Goals of "insulating" should be to A) stop that air flow, stop thermal conduction/radiation/convection. That way, the shell can remain cool and no air reaches that surface.

Really old houses were built very, very "breatheable". Air flowed, leaving moisture, but later air dried it out. New homes are built so "tight" that air (containing moisture) is not allowed there to begin with.

 

[nikitis]

You do not want a vapor barrier with Havelock. It needs to breath. If you add anything other than the steel of the bus, mold will develop.

It needs to breathe.

 

[Bjorkinman]

Oh man here we go. I was going to use Havelock but went with closed cell spray foam instead and couldnt be happier. Video
Watch this video.

 

[nikitis]

Closed cell is the best option, but also costly. I went with polyiso because there are deals often where it's half off because the country is oversaturated with it and there are warehouses full of it and nobody is buying it. I was able to do 2 layers throughout my whole bus for $240 total. And it has roughly the same R value as closed cell if you do 2 layers of it.

Havelock is only slightly better than the default insulation the manufacturers put in. If you aren't ever going to be in extreme conditions it's totally fine though. Just let it breathe.

Closed cell is the vapor barrier itself and not needed. Polyiso boards also don't need a vapor barrier because there will be space between the rivets if you do a roof raise. If you don't do a roof raise and it can lay flat against the walls, you may want to do vapor barrier with polyiso.

 

[Rucker]

You could do a little searching on the relevant terms in this forum. There have been many, many conversations on this over the last few years.

In short, if you don't use closed cell foam, you must use a continuous vapor barrier on the inside of the bus, between the warm, humid interior air and the Havelock.

 

[tj-grant]

Oh man here we go. I was going to use Havelock but went with closed cell spray foam instead and couldnt be happier. Video
Watch this video.

Yes,yes.. the age old discussion. I have watched this a few times and I’m just not convinced that it’s “safe”. I think it has many practical advantages — and some disadvantages if we’re being honest — over wool insulation but the possibility of hazardous chemicals and allergens being directly linked to spray foam is well documented and not just “imagined”. Chuck has done some amazing work but I’m not convinced. I’m not knocking people who do use it. It’s just that for us, we feel more comfortable being exposed to as little chemicals as possible (living on a diesel burning monster and all). I used to build boats and we’d be using polyester and polyurethane products. They are heavily toxic, require precise mixing, can have many mistakes resulting in sly cover ups or total rehauls, and face continued chemical changes after curing due to climate changes. Which happens when you travel…
So ya. I’m still researching of course, maybe I’ll be swayed the other way. But whatever the end choice will be i want to know how to do it right.

 

[Bjorkinman]

Yes,yes.. the age old discussion. I have watched this a few times and I’m just not convinced that it’s “safe”. I think it has many practical advantages — and some disadvantages if we’re being honest — over wool insulation but the possibility of hazardous chemicals and allergens being directly linked to spray foam is well documented and not just “imagined”. Chuck has done some amazing work but I’m not convinced. I’m not knocking people who do use it. It’s just that for us, we feel more comfortable being exposed to as little chemicals as possible (living on a diesel burning monster and all). I used to build boats and we’d be using polyester and polyurethane products. They are heavily toxic, require precise mixing, can have many mistakes resulting in sly cover ups or total rehauls, and face continued chemical changes after curing due to climate changes. Which happens when you travel…
So ya. I’m still researching of course, maybe I’ll be swayed the other way. But whatever the end choice will be i want to know how to do it right.

I think I'd rather take my chances with the possible chemical leaching from the closed cell. What I am very much against is the impact that mold will have on my family. We live in the southeast and in the summers it's not uncommon to see 90+% humidity. Most buildings around us have mold in some form and my wife and I are highly reactive (her especially, chronic illness and brain disfunction for about 3 weeks and me with extreme anxiety and brain fog). We keep a dehumidifier running in the bus almost constantly and air it out whenever the outside air is pleasant. The vapor barrier is what really sold me on the spray foam, not to mention the added rigidity to the structure of the bus, and R20 all around. I was going to do Havelock as well but in the end chose foam. So far, after spending about 20 sleeps my wife has had only health improvements vs. life in our stick home and she is very sensitive to things like glade plug ins. On a side note, I was concerned about the EMF from our inverter which lives under our bed but so far she's also been fine with that. Time will tell. Best of luck whatever you choose - and I respect the concern for your health fully.

 

[tj-grant]

I think I'd rather take my chances with the possible chemical leaching from the closed cell. What I am very much against is the impact that mold will have on my family. We live in the southeast and in the summers it's not uncommon to see 90+% humidity. Most buildings around us have mold in some form and my wife and I are highly reactive (her especially, chronic illness and brain disfunction for about 3 weeks and me with extreme anxiety and brain fog). We keep a dehumidifier running in the bus almost constantly and air it out whenever the outside air is pleasant. The vapor barrier is what really sold me on the spray foam, not to mention the added rigidity to the structure of the bus, and R20 all around. I was going to do Havelock as well but in the end chose foam. So far, after spending about 20 sleeps my wife has had only health improvements vs. life in our stick home and she is very sensitive to things like glade plug ins. On a side note, I was concerned about the EMF from our inverter which lives under our bed but so far she's also been fine with that. Time will tell. Best of luck whatever you choose - and I respect the concern for your health fully.

We live on Vancouver island. Very humid environment. The construction of the house we live in is not ideal. We deal with mold all the time. That’s my biggest concern with the havelock. It’s easier to flush out any residual gases than it is to flush out moisture. I am partial to the added rigidity, but not the inaccessibility after curing. It’s a toss up either way. I’m not fully sold on either option.

 

[TheHubbardBus]

Great discussion. Nice to see everyone's reasoning, and how no one solution is going to work for everyone.

I never seriously considered havelock mainly because I didn't see anything that made it 'better' than any other competing product, with the exception of being 'natural'. Almost all the data comes from the manufacturer. It's not widely adopted as a conventional building material so it has very little track record for long-term performance / problems. It's supposed to naturally fire resistant in test condtions, but I have my doubts, and it's far less fire-resistant than competing products like mineral wool (rockwool). It's supposed to be mold resistant but again - I have my doubts (serious doubts, here, considering it's organic, and I've watched at least one YouTube video where mold was cited as an issue by a van builder who used it) - and again... other products exist that are better in this regard. R-value is 'meh'. Cost is excessive.

Even if it is a suitable alternative in traditional building (residential), a school bus conversion is far from a forgiving environment. It's literally about as hard on insulation as you can get, and from every angle (vibration, condensation, temperature extremes, need for fire resistance, etc).

@tj-grant, you say it's a toss up between two options. Why just these two? If you wish to avoid spray foam there are countless other options available to you, pretty much all of which would do as good a job or better than wool in terms of thermal insulation. You may LOL ('cuz it's funny), but we used ALL the following in our build (in various places, for various reasons): rockwool, fiberglass, foam rubber, XPS, EPS, Polyiso, & 3M Thinsulate. Pretty much everything but sheep's wool and spray foam (haha)

I get the off-gassing thing, but many other products are effectively inert. Especially when you consider the VOCs of literally everything else you'll use in the build. The stuff behind my walls is the least of my worries in that regard (the walls themselves - plywood - are much more a problem!)

 

[tj-grant]

Great discussion. Nice to see everyone's reasoning, and how no one solution is going to work for everyone.

I never seriously considered havelock mainly because I didn't see anything that made it 'better' than any other competing product, with the exception of being 'natural'. Almost all the data comes from the manufacturer. It's not widely adopted as a conventional building material so it has very little track record for long-term performance / problems. It's supposed to naturally fire resistant in test condtions, but I have my doubts, and it's far less fire-resistant than competing products like mineral wool (rockwool). It's supposed to be mold resistant but again - I have my doubts (serious doubts, here, considering it's organic, and I've watched at least one YouTube video where mold was cited as an issue by a van builder who used it) - and again... other products exist that are better in this regard. R-value is 'meh'. Cost is excessive.

Even if it is a suitable alternative in traditional building (residential), a school bus conversion is far from a forgiving environment. It's literally about as hard on insulation as you can get, and from every angle (vibration, condensation, temperature extremes, need for fire resistance, etc).

@tj-grant, you say it's a toss up between two options. Why just these two? If you wish to avoid spray foam there are countless other options available to you, pretty much all of which would do as good a job or better than wool in terms of thermal insulation. You may LOL ('cuz it's funny), but we used ALL the following in our build (in various places, for various reasons): rockwool, fiberglass, foam rubber, XPS, EPS, Polyiso, & 3M Thinsulate. Pretty much everything but sheep's wool and spray foam (haha)

I get the off-gassing thing, but many other products are effectively inert. Especially when you consider the VOCs of literally everything else you'll use in the build. The stuff behind my walls is the least of my worries in that regard (the walls themselves - plywood - are much more a problem!)

We’re going to use xps for the floors. In my research, spray foam and havelock are the most popular/ hotly debated products. I like to be consistent but as long as it’s insulated idrc. And yes, plywood… not sure what to do about that lol. Good point. Not planning on using too much of it but will be using “doorskin” — as we used to call it (1/8” finish ply).

 

[tj-grant]

Edit: just remembered that there is a plywood product available in my area that is glued with soy. I’ll have to do that up again when I’m ready

 

[Mr P]

Edit: just remembered that there is a plywood product available in my area that is glued with soy. I’ll have to do that up again when I’m ready

My 2 cents: anything with a grain base could be a rodent attractant. As a car mechanic I fix plastic fuel lines that mice/squirrels bite into. I think they smell the 10% alcohol content in the fuel. This was not an issue years ago, before ethanol was government mandated to be included with gasoline.

I do not have proof of my theory.

At least test my theory before use.

 

[nikitis]

We’re going to use xps for the floors. In my research, spray foam and havelock are the most popular/ hotly debated products. I like to be consistent but as long as it’s insulated idrc. And yes, plywood… not sure what to do about that lol. Good point. Not planning on using too much of it but will be using “doorskin” — as we used to call it (1/8” finish ply).

XPS is the clear winner for the floors. Compression strength is unmatched and R value high. I've done 4in of it and have zero squeeks, creeks, or sound when walking on them. Solid as can be.

As for walls and ceiling, it's really about climate and costs for everyone and their unique situations as to what you choose. I think we all agree.

 

[TaliaDPerkins]

but the possibility of hazardous chemicals and allergens being directly linked to spray foam is well documented and not just “imagined”

Yes, they are imagined -- because the possibility is apparently never qualified by "if you don't follow the instructions".

 

[TheHubbardBus]

Yes, they are imagined -- because the possibility is apparently never qualified by "if you don't follow the instructions".

Even the simplest chemical reactions, taking place in controlled laboratory conditions, in small and carefully measured quantities, rarely achieve 100% conversion.

I can pretty much guarantee that even professionally-applied spray foam - much less DIY kits - contain unreacted consituent chemicals in the final product. "How much" and "To what, if any, detriment" are valid questions, however.