Differences

This shows you the differences between two versions of the page.

--- hvac:insulation [2022/01/17 04:36]
princess_fluffypants [Tips and Tricks]
+++ hvac:insulation [2022/01/21 23:12]
princess_fluffypants [The effect of "Total" R-Value]
@@ Line 21: / Line 21: @@
 -Way stretch carpet is ideal for this.  Because it has some give to it, it's possible to mold it over and around all the sort of crazy compound curves that makes up the van body. Many videos on youtube showing this process, here https://www.youtube.com/watch?v=TON7xuJkQs8 or here: https://www.youtube.com/watch?v=ob9TmLn8D8o
+----
+===== The effect of "Total" R-Value =====
+Total R-Value is the //total// R-Value of a given construction, taking into account all the different R-values of the different sections that it might have. For example, a well-constructed residential wall in a house in a cold climate might have an R-Value of 20((https://www.e-education.psu.edu/egee102/node/2064)) (1/2" plywood, then 1" of Poly-Sty, then a vapor barrier, 3.5" of fiberglass batting with wood studs forming the wall, then 1/2" drywall), while a solid-core door might have an R-Value of 4 and triple-pane windows might have an R-Value of 2.5-3((https://homesteady.com/differences-single-double-pane-glass-8600425.html)).
+Total R-Value is the calculation that works out, when given the square inches/footage occupied by materials of the different R-Values, what the effective R-value of the whole structure will be.
+Vans are really hard to insulate well in the first place, because they've got a metal skin which is connected directly to metal ribs which act as fantastic (or terrible) thermal bridges. A basic van insulation build for the walls will have an R-Value of **~5** ((some sheet insulation like 400 thinsulite, some mini-cell foam for the floor and a basic liner to cover up all of the ribs and make sure we don't have any exposed metal)), and a crazier build for ski bums might have an R-Value as high as **8-10** ((Filling every single nook and cranny with 600 Thinsulite, mini-cell foam and poly-sty sheet for the floors, maybe poly-sty for the walls as well covered with plywood or wood slats or even 4-way stretch carpet)).
+Single-pane windows (Such as used in cars) has an R-Value of 1 ((actually closer to .91)). **This is why you really need to insulate your windows!!!**
+Let's look at some examples of how this dramatic heat loss from windows affects the total insulation of your van using [[https://www.cascadiawindows.com/tools/r-value-u-value-calculator|this total R-Value calculator]].
+Let's say we're insulating a van with windows all around, like a former passenger van/shuttle bus.  In this case, about 35% of the van's surface area is going to be glass.
+We'll start with a typical kinda basic insulation, like what you'd get from the factory or most people who are doing a full build out of their own and not going too crazy.  An R-Value of 5 for the walls, and 1 for the windows.
+{{ :hvac:therm_1.jpg?direct&600 |}}
+Huh!  So in spite of all that insulation work, you got an R-Value of barely over **2**.  You're very chilly at night, so let's say you DO go crazy with the insulation! You spend a thousand bucks on 600 thickness thinsulite, you stuff it in EVERY nook and cranny, you put mini-cell foam pads on all the sheet metal and then cover the whole inside of the van with some sheet poly-sty and then a solid sheet of plywood or wood paneling. You've gotten the R-Value up to 10 (Which is REALLY REALLY hard). Let's try it again:
+{{ :hvac:therm_2.jpg?direct&600 |}}
+Wait so you DOUBLED the insulation on the walls, and it barely made a dent in your total R-Value! Damn. Well, let's go REALLY nuts! Let's build it like we do a house, and do a full wood frame inside with an inch of poly-sty, wood studs spacing out 3.5" of fiberglass batt, plus a vapor barrier and 1/2" of plywood. That can get us up to an R-Value of 20 for the walls (This would lose you a HUGE amount of space inside, but let's just do it as an experiment):
+{{ :hvac:therm_3.jpg?direct&600 |}}
+**WUT?!** You went bat-shit nuts and lost a ton of interior space, and your van is still leaking heat like a sieve because of the massive loss through those windows.
+BUT. Let's assume we do a bit of insulation on the windows. Nothing crazy, just add some window covers with some basic window covers. Even some thick cardboard, wrapped in some $5 fleece blankets that you got from wal-mart and tightly fit into the window openings, covering them completely. This will get the window R-value up to around 3 if you leave a bit of an air gap. Let's see how that changes our calculations, even with our basic lazy van insulation:
+{{ :hvac:therm_4.jpg?direct&600 |}}
+//WILL YOU LOOK AT THAT!// Just by covering the windows, poorly, and insulating the rest of the van to a kinda-mediocre level, you've got NEARLY TWICE the total system insulation as if you did a completely nutso, bonkers, over-the-top insulation job but haven't covered the windows!
+**TL;DR - COVER YOUR DANG WINDOWS IF YOU'RE TRYING TO STAY WARM**
+Speaking of...
 ----
 ===== Windows =====

RV and vandwellers wiki

User Tools

Site Tools

Differences

Page Tools