I'd be worried about snow coming from your upper roof down onto the GHS roof and crushing it.

Snowload is a consideration but we rarely get that much at a time. The 3 season porch roof slants away from this spot, the roof on the back of the house slopes towards it but it is a really low pitch and we don't get snow dropping off. In either case, I would frame it up with ceder tone green treated for looks and strength. The 25mm polycarbonate is touted to be incredibly strong as well which is why I was leaning towards that for the roofing at least. Thoughts? I'm still pretty new to all this. Thank you for taking the time to respond!

Im sorry I didn't see this, didn't have notifications set up. I am not sure on prevailing winds, I guess from the west? I am about 30 min. south of Mpls-St Paul Minnesota. In terms of framing, I agree which is why I was looking at cedar toned treated lumber framing like in my last picture above. The ground is stamped concrete here so the area wouldn't be for any in ground gardening, more a spot to overwinter some decorative or fruit trees or do some container gardening for plants or some cool weather crops and to maybe start seeds towards the end of winter. So if thats the case I wouldn't need to worry too much about water or drainage. I have electricity out there although I would add more outlets. Might even experiment with a couple of barrels of water hooked up to a flat plate solar heater for some thermal mass.

Actually, I wasn't thinking of inground growing. I was really after the ability to do in floor radiant. west facing is good and bad, depending an terrain. good because of sun, bad because well, west wind in MN can really drag heat efficiency out of a greenhouse. Doable? eminently. how much of this are you looking to do yourself?

Wow! I was just looking into the radiant heating system idea last night. I have two uncles who work at Uponer (formerly Wirsbo) and I was going to talk to ask them their thoughts on this. My thinking, and I don't yet know if it would work or the logistics of it, but since these two areas need heating and they are stacked on top of each other, if I couldn't run a 2 zone hydronic radiant heat system for them.

I found a couple online distibutors for polycarbonate panels that were way cheaper (including shipping) than some of the retailers I was looking into before. I sent them emails last night and one got back to me and am now leaning towards a 25mm 5 wall "x" polycarbonate panel. R value is about 3.7 and a 4x8 sheet would run about $140 before shipping.

I'm in construction (flooring/stone work) so I know my way around the toolbox. I was planning on doing most of it myself along with a brother in law who owes me several years worth of favors and a contractor buddy who owes me a favor or two.

Ok, so you know what you're doing and how to get everything lined up.

So now you just gotta nail down specifics of what you want. How you are going to heat and what you need for that. Where do you want water access. Any plans for misting? Propagation chamber? Electric. How are you going to vent?

But really, most of those questions are up to you. As far as skin material...and i'm calling the polycarbonate panel covering a skin...any kind of insulation factor you can get, the better. I know someone in ct that used triple wall panels, and carefully cleaned then taped the cut ends, and barely uses any heat in winter.

Just a thought...how's the sun in summer? Those panels can really warm up what's behind them when the sun shines, so i'd at least consider using shaded panels on the roof. Pro, summer shade, con, winter shade...but that's your call.

Thank you Wayne,

I can build just about anything but to be honest a lot of the gardening stuff is new to me (2nd year gardener) so I am kind of figuring that out as I go. You've given me a few things to think about and look into such as the misters & propagation chamber, etc so thank you! I was planning on a few of the automatically opening roof vents incorporated into the polycarbonate roofing.

My plan was to remove the vertical wall panels and store them over the summer making the lower section a screened in porch area. I was figuring on making those angled P.C. roof panels permanent and was just planning on leaving that as is over summer, maybe some interior curtains running between the joists on cables that I could block out some summer sun or maybe a seasonal exterior awning over the p.c. roof? I am planning on planting a red maple outside this area which would eventually add shade to this section and the back of the house in the summer but still allow full sun in the winter.

Again, thank you for your thoughts and help, Ive asked around quite a bit around here but it doesn't seem like many people know enough about greenhouses to help me out in this application. I greatly appreciate you taking the time out of your day!

So what are the things you currently do that you want to do more of? What are those things that you'd like to get into?

Things require a certain amount of space. Give yourself adequate space for those operations.

Don't skimp on framing. If anything, put in extra. Because plants can hang from the ceiling as well as sit on benches or shelves. And there's going to be mechanicals that usually run overhead.

JR Johnson is a greenhouse supply place in the twin cities. They might be able to give you some pointers...like on motors and automated controls for the vents.

The biggest problem I see here is taking the panels off and storing them every year. You have to be sure to mark the UV protected side so that you put it out to the sun when you reinstall. Otherwise, if you put the wrong side out your panels will not last very long. It is the UV protection that gives them their longevity. Also, I would be concerned a little about the holes your screws go through. You want to make sure when reinstalling that you are not making them larger every year. The holes should be predrilled before installation slightly larger than the screws you are using. This is to allow for contraction and expansion of the material. This is the reason why you have to use the 1" neobonded washers with the screws. If you keep making the holes larger the washers may not cover the hole and you may get some leaks. If you are careful not to increase the size of the holes when reinstalling you should be OK.

So that was 2 years ago, any pics of what you two did ?