pearl

If you ask me Flat White Paint is the best thing for your application.
There might be a primer that you can use to make it stick a little better.

How big is it going to be ?

Good Luck, Oh Welcome to gc.com...............................pearl

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taffy

In my experience Mylar increases temperature.

I would try a flat white paint over a primer of some sort meself, good luck whichever you choose.

taffy

penguin

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.

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

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BluInTheBathtub

It should not matter the paint you use as far as sticking to the metal casement. You should use a good primer made for metal but the key here is to be sure the surface is clean and try to find a product called WilBond. My spelling may be off, this product will "soften" the current coating allowing for a good bond between it and the primer. I used to work for a painter and he swore by it whenever we had to paint metal cabinets and such.

knna

As you said, if direct lighting isnt phoinhibitive, reflection either. Not concern about, just even lighting is more efficient

But there some reason to consider lighting/ventilation depending of the scale. Basically, due to small cabs are often overlit, and have more watts per cubic ft, but cost per unit surface of reflectance material isnt relevant, while in large grows its more relevant.

Of course reflectix is a good choice, but the mix latex flat white paint+barite is far cheaper, more reflective (or same, but not less), not insulator, with far easier manteinance and having a near perfect lambertian reflection.

But ive notice barite is difficult to find in your countries at retail level. Its the only disadvantage. Why about if any of you suggest hydro shops owners to buy 25 Kg bags?

Or better, why about some of you do business with it? (ordering a paint manufacturer a custom production and selling it in bottles to hydro shops? It still would be a cheaper and better choice for "consumers".

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penguin

I agree.



I am not sure why it is desirable to add reflective surfaces to a grow that is already overlit?

Cost of initial installation depends on the application. It may be initially less expensive to add white paint (and possibly barite) to a closet or cab. In larger scale room-within-a-room style grows, reflectix is rigid enough to serve as a wall with a minimum of external support, so may be cheaper than wallboard + white paint. At the same time, it is flexible enough to eliminate 90 degree corners, or build parabolic reflectors. In the longer term, reflectix is easy to salvage, and reuse, and has a much longer useful life than white paint. So taking depreciation into account, the long-term grower may find that reflectix to be much a better investment.

Also, if flat white paint + barite is as reflectiive as aluminized mylar (reflectix), then arguments based on heat retention hold little water. 99% reflective is 99% reflective, and unless the reflectivity of white paint drops off in the IR, then both will reflect radiant heat similarly. So the difference is that reflectix, as an insulator, will inhibit conductive heat exchange between the airspace and the walls more than will white paint. So that keeps the heat in the airstream where it can be exhausted, rather than allowing it to be absorbed and re-radiated by the walls. The latter situation may be desirable in some cases but in most cass the former is preferable.

These are good points, but very arguable. Having used all three (but not barite), I very enthusiasticallly recommend reflectix over both white paint and mylar for most applications.



penguin

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knna

Very good points, penguin.

You are right in the sense it probably depends of the setup what reflective layer to choose.

Reflectix keeping heat in the room is a advantage in some setups, specially in large rooms, but i believe its a disadvantage in cabs.

I painted my floro's reflectors with thermal resistant enamel+barite and i noticed a large improvement since it: although the lamps are at the end of its useful life, im getting higher yield for it.

I prefer painting than attaching reflective surfaces, but this is just my personal preference. Anyway, the white paint+barite option is another excelent option, wich havent been used and worth to be considered.

As said before, barite is very cheap, and its just mixed with latex paint to increase its durability. In this pdf you can see reflectance and durability analysis of different white paint+barite mixes. Instead of using pure BaSO4, wich is more pricey, i choosed to use barite, wich is 93-99% BaSO4 (96% for the barite i buy) and is very, very cheap. Likely this weekend a friend is going to test this cheap mix with a spectroradiometer, in order to see if using barite instead of pure BaSO4 has an impact on reflectance and how much.

knna

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alteredego

Here's a good read. Some of the info may be useful.
Enhanced Materials for Light Dispersion

EDIT
And another good thread.

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knna

Very interesting article, alteredego, thanks for linking it.

I want to take advantage of this new technologies. Im working on a prototype to use solar light to grow indoor (by waveguiding). Consist in a light concentrator (acrilic Fresnel's lens) and a fiber optic wich go to the grow. Either with a IR filter in the fiber optic head, either using IR bloking fiber (depending of price, just the cheaper option). But i want to finish my LEDs prototypes before building this.

knna

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