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Discussion Starter · #1 ·
I've got a 50G "Clear For Life" aquarium with full wooden stand and canopy. Under the canopy I have two Fluval 3.0 LED lights. My room temp is always 69-74 depending on warmer/colder month. I have my heaters set, using an Inkbird controller, to 75. The heaters have almost never run in the past several months since setting up this aquarium! The water temperature in the winter hovers around 78 and the summer it hovers 81.

My hypothesis is that the LED lights produce heat (while not hot they do produce a lot of warm), which bottles in due to the canopy and warms the water, and that maybe acrylic is such a good insulator it prevents heat loss of the aquarium water. The LEDs are laid flat against the top acrylic, I am not using a stand.

This issue is not a problem! The temp is fine for my inhabitants and is stable. But I am curious as to the cause of the perpetually higher than room temp water temperature and no need for heating. Is acrylic this insulating?
 

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The lambda value for acrylic is higher than that of glass. Acrylic has a lambda of 0.19 W/m.K (watts per meter per Kelvin). The specific value for glass depends on how the glass was treated and whether the glass is double glazed. To replicate the insulating properties of glass, the acrylic sheet has to be significantly thicker than the glass.
Probably should have an air gap for the face of the led.
 

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Discussion Starter · #3 ·
Probably should have an air gap for the face of the led.
thanks for the post, i guess this means it is more of a “canopy effect” that bottles in heat and less about the insulating effects of acrylic.

What would be a reason for an air gap? My aquarium is deep so I intentionally do not want the lights raised. In several months there has been no damage or discoloration of the lights nor acrylic top.
 

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I use 80mm PC fans in my canopies and they keep the led lights nice and cool to the touch . I am hoping the fans will increase the lifespan of the lights . I build my canopies and they are open back . I just mount a fan on the top edge in the back and let it blow in over the lights and out with the heat . Has worked well for years . I would second the suggestion to raise the lights at least a little so air can circulate around the lights . I do believe acrylic is a better insulator than glass just from my experience .
 

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After my own research I find you are correct . I was basing my opinion on my tanks . I would like to see the page you linked , but I get a "redirect" warning when I click it .
 

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After my own research I find you are correct . I was basing my opinion on my tanks . I would like to see the page you linked , but I get a "redirect" warning when I click it .
Yea it Is a pdf link. I'll update it correctly
Thermal Properties
PLEXIGLAS® SHEET: U-FACTORS
The amount of heat conducted through Plexiglas® glazing is slightly lower than for glass of the same
thickness. The values tabulated below are U-factors for vertical
(windows) and horizontal (skylights) Plexiglas® glazing. R-values = I/U-value. U-values are largely
unaffected by the color of Plexiglas® sheet.
See mixed signals.
Maybe I'm just not understanding the terminology here..

Now that I read it in "English" I concede you were right..

1. Better insulation
To tell which material has better insulating properties over another, engineers determine the thermal conductivity, aka, lambda. A higher lambda value means the material can conduct more heat and thus the less it insulates. The lambda value of plexiglass (0.19 W/m.K) is higher than that of ordinary glass. To replicate the superior insulating properties of glass, plexiglass glass sheets are made to be thicker. Although glass is a better insulating material, acrylic comes with a host of benefits.
My bad..
 

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Similarly, is plexiglass a good insulator?

When using plexiglass with a glazing applications, it has a high resistance to smudges and scratches while still maintaining stunning clarity. Acrylic and plexiglass have high thermal values and insulate buildings better than glass, helping to improve the efficiency of your structure.

Similarly, does plexiglass keep in heat? Plexiglas for Keeping Out the Cold. Windows are responsible for a great percentage of heat loss in wintertime. Plain, single-pane glass windows are inexpensive, but also ineffective at keeping heat inside the home and stopping cold outside air from entering.

In this manner, is acrylic a better insulator than glass?

The lambda value for acrylic is higher than that of glass. To replicate the insulating properties of glass, the acrylic sheet has to be significantly thicker than the glass. Therefore, in comparing a sheet of glass and an equally thick layer of acrylic, the glass will insulate better.


Glass has an R value of approximately 0.14 per inch thickness
Celluloid (Lexan, Plexiglass?) has an R value of approximately 0.7 per inch thickness
[source: Bob Vila Home Improvement Forums]
U value is the inverse of the R value. (U-value = 1/R-value)
Using this equation and the values above, the the U value of plexiglass is approximately 1.4 per inch of thickness. The U-value of glass is 7.0 per inch of thickness.
So, if these values are correct, then Plexiglas is approximately five times as resistant to heat transfer by conduction as glass.

confusing ..
So as I understand it now.. Plex is more resistant to heat transfer (2 way street)
Therefore less heat will transfer from the light to the tank.
Conversely less heat will leave the tank than w/ glass.
As to the initial topic either way an air gap (low conductivity) will help keep heat out o the tank.

tanks can retain heat 20% better than glass tanks which means that your aquarium heater may not have to work so hard in an acrylic tank as it would in a glass tank of the same size.
 

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Yes: acrylic is a much better insulator than glass, both in terms of conduction and convection. You can test this yourself. Touch a glass tank and touch an acrylic tank. The acrylic tank surface that you touch will be closer to room temperature (the side you are on) than the glass. During the early 80's, immediately following the energy crisis, there was mass purchasing of acrylic glazing to replace glass and/or to use it on the interior of windows to take advantage of it's superior insulation. Incidentally, there is no such thing as "Plexiglass." The correct trademark of this brand of acrylic is "Plexiglas", with one "s."
 
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