Window covering/insulation on the OUTSIDE of glass?

[TheArgobus]

We currently do not have any covering for our windows for privacy or insulation. My primary concern is insulation, so wouldn't it make sense to make some sort of canvas or thick covering, secured with buttons, to go on the outside of the bus? That way it blocks most sunlight/heat on the outer side of the glass. Has anyone done this? Am I not considering something important? This would also be used while driving.

[DeMac]

Your description sounds like ezSnap's product,
https://ezsnapdirect.com/products/rv-shades/

Their claim: "Thermo-Weave™ RV Sun Screens block up to 90% of the sun’s heat & UV rays, without blocking your view."

Snaps hold more consistent than magnets. The weave captures less air at highway speed, reducing the chance "sail" off.

[peakbus]

While these are interior mounted, they have made a Huge difference in reducing heat and light (and cold) into our bus. Attached with strong magnets, they are easy to install and store. Pretty much throw them toward the window and they'll hang on. Made by thisvanlife.net in Idaho. He actually enjoyed making these, as most van windows are weird shape and my skoolie windows were all nice rectangles.

[Flowergarden]

My only thought with the exterior mounted shades is that someone could easily unsnap the coverings ;with snaps or magnets) to peer into the bus.

[DeMac]

Originally Posted by Flowergarden

My only thought with the exterior mounted shades is that someone could easily unsnap the coverings ;with snaps or magnets) to peer into the bus.

Our windows came with factory tint. To the bottom pane (rear windows only) we added Velimax window clings, which block 100% ultraviolet, infrared & visible light)



Matte finish on the inside, glossy black toward the exterior.

From outside, with factory tined upper and lower panes appear identical. Just can't see through the bottom pane.

[TheHubbardBus]

I'm sure you could probably gain some additional benefit by mounting reflective coverings outside the windows, but I'm not sure I'd consider it worth the compromises and inconveniences. Plus it won't buy you anything in the cold. If you maintain an air gap between the windows & interior-mounted reflective 'curtains' ( especially if they're continuous and/or create a decent seal around the edges), I think you'd be happy. Think about what a hassle it may become just to let a little light in or open a window for fresh air or ventilation.

[Rucker]

Originally Posted by TheArgobus

We currently do not have any covering for our windows for privacy or insulation. My primary concern is insulation, so wouldn't it make sense to make some sort of canvas or thick covering, secured with buttons, to go on the outside of the bus? That way it blocks most sunlight/heat on the outer side of the glass. Has anyone done this? Am I not considering something important? This would also be used while driving.

Timely topic. I'm currently building the inside window coverings on my shuttle bus for both heat and cold insulation. This is one of the hardest design challenges I've faced.

I love the idea of an external covering. So far I've just picked up some sun shades, though I haven't figured out how to install them.

For cooling using an outside covering, protection from the rays of the sun (insolation) is controlled with any sun-blocking material sheet, tarp or covering, any color, pretty much, and works well as long as there's an air gap of 6" or greater with free air flow between the shade material and the outside of the bus to allow convection.

Shades won't insulate, as hubbardbus notes. Nor will they prevent conduction, or the heating through direct contact with outside air, so expect the inside walls to be about the same temp as the outside air temp at a minimum in hot weather.

An insulation blanket over the windows should have a light-colored outer surface to reflect sunlight. It should have some R value. Even with that the blanket will still absorb heat through direct insolation and conduction of the outside air temperature, and transmit it through the bus wall and ceiling according to the material's R value. I'm not sure you can make a blanket with enough R to make a difference without also making it both unwieldy to deploy and difficult to store.

Also, the thermal mass of the blanket will retain heat, and continue to transmit that heat through the bus walls and ceiling similar to how a solar panel continues to radiate its absorbed heat downward from a day baking in the sun. Since this somewhat defeats the purpose of the blanket, removing it after the sun's rays are gone is probably a good thing.

A sun shade is probably better bang for the buck.

Not that you asked, but I'm doing inside insulation panels. They are based on a Lauan underlayment panel slightly larger than the overall window dimensions including the aluminum flange of the window. On the outboard side of the panel is 1" polyisocyanate with one or two layers of reflectix, depending on the window depth, then an outer layer of corrugated plastic sheet material, all covered by vinyl fabric. The various layers add up to maybe R-8 since there are no air gaps between the layers. The panels are designed to fit snug against the glass to minimize condensation.

On the inboard surface I have another layer of 1" polyisocyanate around the perimeter of the window covering the metal flanges. I put that insulation on the inboard side to reduce the overall thickness of the insulating panel. The panel is sealed around the outside edge with a rubber gasket to reduce air leaks. The panels are designed to reduce the amount of conducted heat from the window and the aluminum flange.

Yesterday it was 104 degrees outside, and the flange peaked at 149 degrees on the inside, the wall 121. Clearly a sun shade would reduce this solar gain, but the combination of solar shade and insulation panels should bring the inside wall surfaces somewhere near convection rates. I hope to test that out soon and experiment a little to see how much of the heat gain is handled by shading versus insulation.

Today it's supposed to go to 115 in my part of the central valley of California, so I'm going to get more 'before' measurements.

[Hutchy]

Originally Posted by peakbus

While these are interior mounted, they have made a Huge difference in reducing heat and light (and cold) into our bus. Attached with strong magnets, they are easy to install and store. Pretty much throw them toward the window and they'll hang on. Made by thisvanlife.net in Idaho. He actually enjoyed making these, as most van windows are weird shape and my skoolie windows were all nice rectangles.

nice, what did he charge to make them?

[Flowergarden]

Originally Posted by Rucker

Timely topic. I'm currently building the inside window coverings on my shuttle bus for both heat and cold insulation. This is one of the hardest design challenges I've faced.

I love the idea of an external covering. So far I've just picked up some sun shades, though I haven't figured out how to install them.

For cooling using an outside covering, protection from the rays of the sun (insolation) is controlled with any sun-blocking material sheet, tarp or covering, any color, pretty much, and works well as long as there's an air gap of 6" or greater with free air flow between the shade material and the outside of the bus to allow convection.

Shades won't insulate, as hubbardbus notes. Nor will they prevent conduction, or the heating through direct contact with outside air, so expect the inside walls to be about the same temp as the outside air temp at a minimum in hot weather.

An insulation blanket over the windows should have a light-colored outer surface to reflect sunlight. It should have some R value. Even with that the blanket will still absorb heat through direct insolation and conduction of the outside air temperature, and transmit it through the bus wall and ceiling according to the material's R value. I'm not sure you can make a blanket with enough R to make a difference without also making it both unwieldy to deploy and difficult to store.

Also, the thermal mass of the blanket will retain heat, and continue to transmit that heat through the bus walls and ceiling similar to how a solar panel continues to radiate its absorbed heat downward from a day baking in the sun. Since this somewhat defeats the purpose of the blanket, removing it after the sun's rays are gone is probably a good thing.

A sun shade is probably better bang for the buck.

Not that you asked, but I'm doing inside insulation panels. They are based on a Lauan underlayment panel slightly larger than the overall window dimensions including the aluminum flange of the window. On the outboard side of the panel is 1" polyisocyanate with one or two layers of reflectix, depending on the window depth, then an outer layer of corrugated plastic sheet material, all covered by vinyl fabric. The various layers add up to maybe R-8 since there are no air gaps between the layers. The panels are designed to fit snug against the glass to minimize condensation.

On the inboard surface I have another layer of 1" polyisocyanate around the perimeter of the window covering the metal flanges. I put that insulation on the inboard side to reduce the overall thickness of the insulating panel. The panel is sealed around the outside edge with a rubber gasket to reduce air leaks. The panels are designed to reduce the amount of conducted heat from the window and the aluminum flange.

Yesterday it was 104 degrees outside, and the flange peaked at 149 degrees on the inside, the wall 121. Clearly a sun shade would reduce this solar gain, but the combination of solar shade and insulation panels should bring the inside wall surfaces somewhere near convection rates. I hope to test that out soon and experiment a little to see how much of the heat gain is handled by shading versus insulation.

Today it's supposed to go to 115 in my part of the central valley of California, so I'm going to get more 'before' measurements.

Fascinating. Your weather is like ours in S Arizona. For now I am trying my first shake down trip with just tinted windows and insulating curtains that are continuous the length of the bus. Then after I discover that I am frying I will explore additional insulation. My bus sides all have 1” of insulation (foam board) that was factory installed and the roof down to the windows has 1” of polysio that I added. It goes over the ribs. I wanted 1.5” (2 3/4” boards) but there is none to be found. So I will try this and move on to 2” (add another inch) if necessary. The windows are all single pane though 😢 so we shall see. I’m eager how your insulated window inserts work out. How will you store them all?

[Rucker]

They will nest but there are twelve of them! They'll stack in the back while travelling, then on the driver's seat when parked. That's the theory.

I've just finished the first full mockup, and I'm actually thinking maybe I only need six, for the side in direct sunlight. Maybe.

The reason I'm thinking six may be enough is because the non-sunlit side is only 5-10 degrees above outside air temp. These things are a bear to fabricate, by the way. I've got a jig and everything; but I may get away with using something a little lighter on the side not exposed to direct sunlight--like your standard youtube fabric-wrapped double layer Reflectix.

I'm guessing I'll make a set of Reflectix-style coverings anyways because the 12K BTUH diesel heater does a good job keeping things toasty when it's 30 degrees outside without any window coverings, and we won't be travelling to much colder places than that.

By the way, 100% of the fabric I'm using I got at Goodwill. Drapery is an easy thing to find there on the cheap.

[musigenesis]

Originally Posted by Flowergarden

My only thought with the exterior mounted shades is that someone could easily unsnap the coverings ;with snaps or magnets) to peer into the bus.

Or, like, unsnap them and walk off with them.

People generally don't insulate outside of the windows of buildings. No reason to do it on a motorhome.

[TheHubbardBus]

Originally Posted by Rucker

Timely topic. I'm currently building the inside window coverings on my shuttle bus for both heat and cold insulation. This is one of the hardest design challenges I've faced.

I love the idea of an external covering. So far I've just picked up some sun shades, though I haven't figured out how to install them.

For cooling using an outside covering, protection from the rays of the sun (insolation) is controlled with any sun-blocking material sheet, tarp or covering, any color, pretty much, and works well as long as there's an air gap of 6" or greater with free air flow between the shade material and the outside of the bus to allow convection.

Shades won't insulate, as hubbardbus notes. Nor will they prevent conduction, or the heating through direct contact with outside air, so expect the inside walls to be about the same temp as the outside air temp at a minimum in hot weather.

An insulation blanket over the windows should have a light-colored outer surface to reflect sunlight. It should have some R value. Even with that the blanket will still absorb heat through direct insolation and conduction of the outside air temperature, and transmit it through the bus wall and ceiling according to the material's R value. I'm not sure you can make a blanket with enough R to make a difference without also making it both unwieldy to deploy and difficult to store.

Also, the thermal mass of the blanket will retain heat, and continue to transmit that heat through the bus walls and ceiling similar to how a solar panel continues to radiate its absorbed heat downward from a day baking in the sun. Since this somewhat defeats the purpose of the blanket, removing it after the sun's rays are gone is probably a good thing.

A sun shade is probably better bang for the buck.

Not that you asked, but I'm doing inside insulation panels. They are based on a Lauan underlayment panel slightly larger than the overall window dimensions including the aluminum flange of the window. On the outboard side of the panel is 1" polyisocyanate with one or two layers of reflectix, depending on the window depth, then an outer layer of corrugated plastic sheet material, all covered by vinyl fabric. The various layers add up to maybe R-8 since there are no air gaps between the layers. The panels are designed to fit snug against the glass to minimize condensation.

On the inboard surface I have another layer of 1" polyisocyanate around the perimeter of the window covering the metal flanges. I put that insulation on the inboard side to reduce the overall thickness of the insulating panel. The panel is sealed around the outside edge with a rubber gasket to reduce air leaks. The panels are designed to reduce the amount of conducted heat from the window and the aluminum flange.

Yesterday it was 104 degrees outside, and the flange peaked at 149 degrees on the inside, the wall 121. Clearly a sun shade would reduce this solar gain, but the combination of solar shade and insulation panels should bring the inside wall surfaces somewhere near convection rates. I hope to test that out soon and experiment a little to see how much of the heat gain is handled by shading versus insulation.

Today it's supposed to go to 115 in my part of the central valley of California, so I'm going to get more 'before' measurements.

I can't wait to see you implement this idea. I'll be following along with great interest. Our plans are similar in theory, but I still haven't come up with a solution I'm 100% sold on. I still REALLY want to utilize aerogel if possible, but not sure if it will be doable yet from a perspective of cost / availability. What I do know is that coming up with a solution similar to yours will make the largest impact possible on the effective r value of the bus as a whole.

What I'm leaning towards is a 2 stage system. Stage 1 being curtains constructed with aerogel sheet as a filling. They'd seal (as well as curtains can) against the top and bottom of the wood framing the windows, as well as both sides of each curtain section (not sure if there would be one section per window or one spanning multiple windows). The exterior facing surface would be a good reflector of radiant heat. The shell would in total be vapor impermiable. And the framing around the windows would be built up enough to create about 2" of air gap between the curtains and the pane.

Stage 2 would be the addition of 2" wide insulated 'seat cushions', designed to fit into each window frame, and held in place either friction and/or the aforementioned curtains. Don't know what I'd use for fill but thinking rubber insulation (like that used for insulating pipes) might be a good choice so long as I can seal them in a manner that prevents the smell from coming out. 2" of that would be ~r8, the 1/4" aerogel ~r2.5, so combined I'm thinking it would make a pretty big diff, especially when cold.

All just high level thinking, though. Not anywhere close to meeting the devil lurking in the details.

[TheArgobus]

Thanks for the replies everyone, this is exactly what I was looking for. I think it does make sense to put them on the inside, mainly for the convenience of access while driving, but also I realize we really only need to put them up on the whichever side is sunny. I'm not really concerned about privacy based on where we go, it's mainly insulation and keeping it dark for baby nap time. I will investigate these options and see what works best.

[jimmythomas]

I cut up a couple of big brown cardboard boxes to block the sun coming in the windows.
It's really cheap and works well enough for me. I think it's about r-15 value.
YMMV.

[peakbus]

Originally Posted by Hutchy

nice, what did he charge to make them?

I think he charged $600 for 13 panels a couple of years ago. Some cover a couple of windows, some only one.

[Rucker]

Originally Posted by jimmythomas

I cut up a couple of big brown cardboard boxes to block the sun coming in the windows.
It's really cheap and works well enough for me. I think it's about r-15 value.
YMMV.

Funny! Should be a short video.

[musigenesis]

Originally Posted by jimmythomas

I cut up a couple of big brown cardboard boxes to block the sun coming in the windows.
It's really cheap and works well enough for me. I think it's about r-15 value.
YMMV.

Wow, just double up the cardboard and you could have R30!

[rebapuck]

Originally Posted by musigenesis

People generally don't insulate outside of the windows of buildings. No reason to do it on a motorhome.

Storm windows.

[musigenesis]

Originally Posted by rebapuck

Storm windows.

Storm windows don't insulate, they block airflow. Insulation lowers heat transfer via conduction, airflow affects heat transfer via convection.

[Millenial Falcon]

I cut 1/2" polyiso panels to fit inside the window frames, which are 1/2" deep (inside the bus). I taped the edges and spray painted one side black for heat gain in the winter. They just pressure fit in the gap with no magnets or anything. The other side I left silver to reflect heat in the summer. If I want more light, I just remove one or more and they stack up fairly small. I usually reverse them once in the spring and fall. They work great on the side windows, but don't stay put as well on the rear windows.