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Originally Posted by knna  Fully agree, but although he expressed it wrong, because it isnt ventilation related, he was right in one sense: reflectix tends to make a hot air layer between it and the wall, reducing cooling (not ventilation). |
I suppose there are some configurations where this might possibly be true, but in most cases the reflectix (an insulator) will reduce the amount of heat reaching and absorbed by the wall of the enclosure (where it will be re-radiated by black body emission). There's a few percentage points of light reflectance, accompanied by a correspondingly few percentage points of heat retention. Ventilation is less expensive than lighting so economy favors reflectix.
If the enclosure is adequately lit but overheated, then white paint might be better, but if the room is underlit and overheated (as is often the case) than reflectix plus improving the ventilation system to provide proper air exchange is a better choice.
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Originally Posted by knna And it have another disadvantage in a very small cab, depending of the lighting: specular reflection, increasing the risk of hot spots, especially using HPS. |
White paint does provide more diffuse reflection than reflectix, and reflectix provides much more diffuse reflection than plain mylar. However, although uneven lighting is not optimum, I am little concerned about photoinhibitive damage caused by specular reflection unless an encosure is already seriously overlit.
I am not aware of any reason that practical lighting/ventilation requirements should not scale linearly with the size of the enclosure.
penguin