What is the best greenhouse roof.

My son and I are building a greenhouse.  Her has definite ideas about design and materials. He is not a gardener, or a carpenter.  That being said, like his dad he's one of those people who can fix, and build anything. He has been watching YouTube videos on greenhouses.  So far we have a frame built with 2x4's.  It's 5' wide, by 6' 6" long, and 6' 6" tall.  The frame sits on a cement pad for each corner. Brick will fill the gaps between the pads.  I bought 6 ml reenforced greenhouse plastic.
We have two issues to resolve. I was hoping to gain a little wisdom here to help.  One my son wants to use those wavy plastic panels you use on roof's on hole greenhouse.  I want to use the plastic. The panels are 17$ each for an 8' x 28". Then you have to buy the the piece that fill the gaps, of use something.
Issue 2 is the roof.  I want to use plastic. He wants to use those panels.  The roof will be a low slop roof. We live in California zone 9 b, so snow isn't an issue.  Someone also brought up needing something that will filter the light. Hadn't even thought about that.
Just looking for the best affordable option. Thanks

You have the greenhouse plastic, so unless he's buying I would go with that.
It will not last forever, but it should last a good while.
The corrugated plastic and/or fiberglass panels  have a limited life expectancy as well.

A third option is my preference,  shower, storm and patio doors.
Even if they cost a little money at a reuse center, they will pretty much last forever.

Hello,
In my opinion, a plexiglass sheet is the best building material for the greenhouse since it features double-layer protection. A greenhouse constructed of plexiglass will save significantly on heating costs during cold weather because it traps heat. I have heard this from where I work. Please let me know if I am wrong.
Thanks

i built 2 greenhouses.. one i managed to reuse glass form windows and made roofing out of that (got the free windows during "heavy pickup - once a year here you can throw out the big stuff in the spring) we have snow so i had to be somewhat carful - you don't - use glass if you can ... OR

the other greenhouse i just put a sheet of 6 mil over the whole roof (shed roof - i slope) - 9 x 20 feet - i have to replace it every 2 years - i strap it to the roof with 1x2s.. it takes about 3 hrs to replace.. you might do it every year - but it is cheap and easy..

hope this helps - cheers!

I cant speak to what the "best" roof for a greenhouse is, but I built a greenhouse with EMT tubing and those clear plastic PVC panels, and they are about the worst. I assume this is what you are talking about at 17 dollars per sheet. They become insanely brittle after a year or two. In your heat and sun, they will likely be crispy in a year. Mine are still limping along, but if you apply any pressure at all to them, they crack. There are several holes, but it is just a greenhouse, so I dont care that much. As far as sealing the gaps at the ends of the panels goes, i did not really find it to be that important. The extra airflow might even be a good thing.

Now, they do also make a lexan version of those panels - they usually have a square profile instead of rounded corrugations - that stuff is great. It is also about twice as expensive, and I think it will yellow over time. Still, it will easily last for a decade, and retains its toughness even after prolonged UV exposure. I have not used plastic greenhouse film before, but it will wear out a lot faster from what I have heard about it.

I feel like I have also heard talk about some glazings blocking part of the spectrum, but I cant say I have noticed any problems with the stuff I used.

I have a big pile of saved window glass panes, and someday I want to build a real beauty of a greenhouse with metal frame and glass panes. Alas, the to-do list is long. Recycled windows would be a great solution, but you almost need to get the windows first and build the frame to suit.

Anyway, My advice would be to throw on the greenhouse plastic that you have as a temporary solution. When it wears out in a couple years, you can revisit the whole thing with a lot more experience. Maybe you will be sick of looking at your empty, neglected greenhouse; or you might want to build it twice as big!

Carl offers some good advice - i have plexiglass on porch/sunroom roof and it holds up great - expensive though..

those corrugated panels are the worst for sure.. they even need curved support which cost extra- read the reviews on home depot... stay away

you can even skip the greenhouse plastic to start as i did >> dead easy and way cheap.. i can a 10' x 150' roll for 75 bucks cdn.. 6mil though - be sure to use the heavy stuff... you can get the spacers from PT lumber @ hardware stores for free - those thin flat pieces of wood make GREAT strapping

then, as carl also mentioned, you "have" a greenhouse and can then start planning improvement vs neglect

cheers!

A couple thoughts. In the northeast where I live, we are more worried about cold than heat, so we would probably only put a clear wall/roof on the south side. Everything else would be solid. In your climate, I would be more inclined to think about shade cloth.

As for the materials, Glass tends to let in the most amount of light, but is breakable. Plexiglass is next best for longevity, is not breakable, but depending on the type, it can yellow over time in the sun, and reduce the light coming in. There are specific green house and generic use plexiglass. The ones built for Greenhouses tend to have UV protection built in. Then you have your plastic sheeting. There is again generic use and stuff built specifically for Greenhouses. Personally I think it is worth the cost to get Greenhouse specific plastic over the generic, but it really depends on how tight you need to be on material costs... and how easy it is to replace. A smaller greenhouse like that would be much easier than some of these high tunnels that I see people building.

I'm working with triple-wall polycarbonate greenhouse panels right now, and they seem like excellent material. 10 year warranty, 2.5 R value, and way stronger than glass or acrylic... but also more expensive than the other materials you've mentioned.
https://www.menards.com/main/outdoors/gardening/greenhouses/amerilux-multilite-16mm-4-x-8-clear-polycarbonate-triple-wall-panel/1594354/p-1444424087198-c-10122.htm?searchTermToProduct=1594354

ooooohhh - those are sweet!!

i found them here in canada @ home depot.. $$ but tick all the boxes -  i will have to consider them thanks a million matt!

James MacKenzie wrote:ooooohhh - those are sweet!!

i found them here in canada @ home depot.. $$ but tick all the boxes -  i will have to consider them thanks a million matt!

If you do go that route, the "H" channel pieces to connect the panels together is also (you guessed it) expensive. I found that cheap vinyl soffit "H" channel and "J" channel, as well as 3/4 inch aluminum "U" channel are all viable options to fit on the edges too.  Just doesn't look as professional.