Installing Reflectix over windows

[rarebear.nm]

Originally Posted by richard5933

I'm guessing that it traps a layer of air against the glass, and this layer get super heated and causes problems.

I doubt that the Reflectix fits tight enough to really trap much hot air. When we put it up there are air gaps around the edges. We've never used it for heat reduction only cold and to block light, both sun, campground and parking lot lights.

Someone interested in the heat build up could use an infrared gun and get temperature readings before and after putting up the Reflectix. Sometimes we've left it up when the RV is being stored just to reduce UV issues inside. Even though it's been hot on some of those days, we've never experienced glass damage. We do have thermal pane windows.

[grindstone01]

Originally Posted by richard5933

I'm guessing that it traps a layer of air against the glass, and this layer get super heated and causes problems.

If that were the case, then you would have invented a newly efficient solar heat collector. Solar heat panels will use a black background to absorb heat and trap it inside the glass. A silver background, like Reflex would just reflect the radiant heat back out of the solar panel. Note the black hot water heating panels in the picture.

[richard5933]

Put the Reflectix in one window and not the one next to it. Let the sun shine on both for a few hours. Check the glass temperature with an IR gun. Then we'll know. My guess is that the temp of glass will be higher on the one with the Reflectix.

[mobilemike]

Originally Posted by grindstone01

Reflex being blamed for heating windows and causing breakage/fogging just defies logic. The silver reflective backing should reflect the heat back out through the glass window. The black film that covers the window will absorb heat, but that will be the case with or with out the reflex.

You are not seeing it but know why.

The sun rays penetrate the window. The window has resistance to the rays. This causes heat in the glass. The rays then bounce off the reflector and travel back through the glass a second time. The glass has resistance and that creates heat again.

So the sun rays travel through the glass 2 times. Heating the glass each time. Generating more heat than is the rays went through the glass only 1 time.

This is why you want to put the reflector on the outside of the widow.

[CLIFFTALL]

I had a huge piece that covered the entire inside of the windshield and driver and passenger windows as well.
I washed the rig and split one side of the windshield in the middle from top to bottom. [emoji20]

[mobilemike]

Originally Posted by rarebear.nm

I doubt that the Reflectix fits tight enough to really trap much hot air. When we put it up there are air gaps around the edges. We've never used it for heat reduction only cold and to block light, both sun, campground and parking lot lights.

Someone interested in the heat build up could use an infrared gun and get temperature readings before and after putting up the Reflectix. Sometimes we've left it up when the RV is being stored just to reduce UV issues inside. Even though it's been hot on some of those days, we've never experienced glass damage. We do have thermal pane windows.

IR heat guns do not read reliably on shiny, or reflective materials. Like windows, polished aluminum or polished stainless steel. You would need to install a heat "target" to get reliable readings.

[jdpm]

Originally Posted by mobilemike

You are not seeing it but know why.

The sun rays penetrate the window. The window has resistance to the rays. This causes heat in the glass. The rays then bounce off the reflector and travel back through the glass a second time. The glass has resistance and that creates heat again.

So the sun rays travel through the glass 2 times. Heating the glass each time. Generating more heat than is the rays went through the glass only 1 time.

This is why you want to put the reflector on the outside of the widow.

Agreed! Never use it dual pane either.

[grindstone01]

Originally Posted by mobilemike

You are not seeing it but know why.

The sun rays penetrate the window. The window has resistance to the rays. This causes heat in the glass. The rays then bounce off the reflector and travel back through the glass a second time. The glass has resistance and that creates heat again.
So the sun rays travel through the glass 2 times. Heating the glass each time. Generating more heat than is the rays went through the glass only 1 time.

This is why you want to put the reflector on the outside of the widow.

So why don't solar panels have a reflective inside vs being black?
According to the chart below, 75-80% of solar radiant heat is passed through glass and a reflective material inside the window will reflect that 75-80% back outside. The remaining 20% radiant heat that is trapped will provide some heat, but not super hot.
I agree that Reflex (any reflector) on the outside would perform best for blocking sun rays.
It's just not practical from the stand point of being exposed to weather (wind) and for appearance sake.
https://www.engineeringtoolbox.com/r...ws-d_1005.html

[mobilemike]

Originally Posted by grindstone01

So why don't solar panels have a reflective inside vs being black?
https://www.engineeringtoolbox.com/r...ws-d_1005.html

Because common solar panels want to trap not reflect the radiation at the receptor cells. Some household solar systems are duel systems that will heat water also.

There are also reflective solar generating systems where mirrors are focused on a point that is super radiated for better efficiency of the cells.