Its really a toss up between those two materials and comes down to the owner's preference and willingness to do the routine maintenance on the frame.

Aluminum usually would cost more than the appropriate lumber but aluminum lasts virtually forever and would not rust or rot even under extremely wet conditions. In terms of maintenance, you probably just need to hose down the aluminum or give it a good scrubbing every now and then.
Heat transfer for aluminums can be an issue, but are easily addressed if constructed properly.

Wood is also an excellent material for the frame but you need to make sure you get the ones that are designed for outdoor use that can withstand the elements. I'm not a lumber expert so I dont know exactly what is needed but they are along the lines of pressure treated wood.
In terms of maintenance, you probably would be regularly applying protective stain on the wood. And if a piece does rot out, then it needs to be replaced.
Good quality wood that is designed for outdoor use should last a good while though.

Greetings,

Cedar, cypress, Ipe?

I do not like treated lumber in any enclosed area.

Of those my best option would likely be cypress.

Other wood options.

Thanks again.

BestÂ

Frank

Hi
In my climate i would'nt consider anything BUT aluminum lol.Have not checked but woods that will last must be in the ballpark of aluminum anyway?? I'm always shocked at how much wood has gone up every time I buy some lol
My aluminum structure has withstood 4 hurricanes 3 floods ,termites and carpenter ants lol Has been up almost 25 years and still looks almost new except for the occasional algae lol gary

I used redwood and treated the top with a sealer. Then after I did that I was about to do the sides but decided to just staple a roll of poly on the sides. This helps 2 fold. First it acts like a buffer of air to keep the inside cool or warm. Then it keeps water from splashing on the wood and extends it's life. If I would of thought of the plastic on the inside earlier I would have used regular wood instead of redwood.

Gal steel is cheap, easy to weld and should last a long time too.