Reply
 
Thread Tools Display Modes
 
Old 01-19-2019, 10:52 PM   #1
New Member
 
Join Date: Jan 2019
Location: Summerland BC
Posts: 1
Year: 1985
Coachwork: chevy
Chassis: shorty
Engine: 350
Roof insulation

Hello there,

I am working my first built and it is a shorty Chevy 1985.
I've already started to do my new insulation but I may have made a mistake.
I want to know what is the best to prevent condensation.
I got a sweet deal on spray foam and foamed the walls and ceiling myself with the plan to put this double reflective vapour barrier on top of it. Unfortunately someone told me that it was probably going to creat condensation between the vapour barrier and the roof. That lead me to do some more research and read that a proper vapour barrier would work but that such a thing is nearly impossible with van conversion. That the best option is to have more ventilation.

My bus already has 2 holes trough the roof for ventilation.. one for the airflow for the condensation from the propane fridge and the other one just has a general opening for air. I am planning to get a mini wood stove for dry heating.


So the big question: What do I risk if i have these layers ( from outside to inside ) for my roof.
Outside metal shell, 1-1.5 inch of spray foam, 1 layer of double reflective vapour barrier, 1/4 inch fir tree planks


Thanks ahead for helping me out.
Chevyshortbus85 is offline   Reply With Quote
Old 01-20-2019, 07:44 AM   #2
Bus Nut
 
Drew Bru's Avatar
 
Join Date: May 2016
Location: Minnehaha Co., SD
Posts: 551
Year: 1996
Coachwork: Amtran
Chassis: International
Engine: DT466
Rated Cap: 65
Quote:
Originally Posted by Chevyshortbus85 View Post
So the big question: What do I risk if i have these layers ( from outside to inside ) for my roof.
Outside metal shell, 1-1.5 inch of spray foam, 1 layer of double reflective vapour barrier, 1/4 inch fir tree planks
Sounds like it should work just fine. I think most spray foam installations are like what you're planning. I wouldn't think you need to worry.
__________________
Our Build: https://dazzlingbluebus.wordpress.com/
Drew Bru is offline   Reply With Quote
Old 01-20-2019, 01:32 PM   #3
Bus Crazy
 
milkmania's Avatar
 
Join Date: May 2015
Location: Oklahoma aka "God's blind spot"
Posts: 2,360
Year: 1989
Coachwork: 1853FC International/Navistar
Chassis: 35' Retired Air Force Ambulance
Engine: DT466, MT643
Rated Cap: 6 souls and a driver
Quote:
Originally Posted by Chevyshortbus85 View Post
*snip*
Outside metal shell, 1-1.5 inch of spray foam, 1 layer of double reflective vapour barrier, 1/4 inch fir tree planks


Thanks ahead for helping me out.
what kind of R Values are being expected from "1 to 1.5" spray foam?
not sure which route I'm taking

I'm learning
R-3.5 to 3.6 per inch open cell spray foam
R-6.5 per inch closed cell spray foam

I know poy-iso foam board is R-5.0 per inch.
__________________
I once complained I had no shoes....
Until I met a man with no feet
milkmania is offline   Reply With Quote
Old 01-20-2019, 05:40 PM   #4
Bus Geek
 
Tango's Avatar
 
Join Date: Mar 2011
Location: Houston, Texas
Posts: 8,462
Year: 1946
Coachwork: Chevrolet/Wayne
Chassis: 1- 1/2 ton
Engine: Cummins 4BT
Rated Cap: 15
You do NOT want to use open cell foam. Open cell = "Sponge".

However...it is excellent if you want to hold lots of moisture in your roof & walls.
Tango is offline   Reply With Quote
Old 01-21-2019, 03:57 PM   #5
Bus Crazy
 
milkmania's Avatar
 
Join Date: May 2015
Location: Oklahoma aka "God's blind spot"
Posts: 2,360
Year: 1989
Coachwork: 1853FC International/Navistar
Chassis: 35' Retired Air Force Ambulance
Engine: DT466, MT643
Rated Cap: 6 souls and a driver
Quote:
Originally Posted by Tango View Post
You do NOT want to use open cell foam. Open cell = "Sponge".

However...it is excellent if you want to hold lots of moisture in your roof & walls.
Got it, thanks
__________________
I once complained I had no shoes....
Until I met a man with no feet
milkmania is offline   Reply With Quote
Old 01-23-2019, 06:56 AM   #6
Bus Nut
 
Yukon Cornelius's Avatar
 
Join Date: Apr 2018
Location: Goose Bay NL
Posts: 381
Year: 1997
Coachwork: Thomas
Chassis: International
Engine: T444E
Rated Cap: 72
I'm skipping the vapor barrier, letting it breath is the concept. Much the same as cabins up here, as the bus will be exposed to hot and cold cycling dependant on usage, and weather I want to any moisture to be able to breath as oppose to trapping it.

Condensation will form on the warm side, so if your spray foam has been done well all you have to worry about is a thin isolator between the spars and your ceiling material. Then from there airflow/cycling/exchanging should help regulate the moisture difference.

disclaimer.....random redneck ravings
__________________
Yukon

Handyman and Shenaniganizer
http://www.skoolie.net/forums/f11/97...ion-22324.html
Yukon Cornelius is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


» Featured Campgrounds

Reviews provided by

Powered by vBadvanced CMPS v3.2.3

All times are GMT -5. The time now is 12:22 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2019, vBulletin Solutions, Inc.