Greenhouse orientation question, very early planning stage

Hello! I've been a permies member for awhile now, but this is my first post. We are starting to set up some infrastructure on our newish property (been observing the land and making plans going on 2 years while doing a complete remodel on a severely broken house). Anyway, it's finally time to get my garden area staked out so I can get someone to disc it up and pile a bunch of organic material in there to overwinter. BUT, I can't layout my garden boundaries until I at least have the footprint for my greenhouse laid out. Also waiting on the greenhouse footprint and fenced garden boundaries is the food forest for which I have potted trees and shrubs anxiously awaiting their final locations. Winter is coming and I still need to get some house things finished so I don't have a ton of time to keep researching on my own.

I've read that the glazing on a greenhouse should be directly south (true south, not magnetic south). But someone on another greenhouse thread mentioned orienting it 16 degrees southeast for some reason that I don't recall. I'm working in a pretty tight area (we have 18 acres all together, but I have a lot of things to squeeze into zone 1 and I have topography to deal with).

So what is the consensus on orientation of the greenhouse? Should the glazing wall be exactly at true south, slightly off in any direction? I'm near Pittsburgh, PA, USA for reference. About 40 degrees N, zone 6a.  I have my preliminary plans drawn up in CAD and plan to use a variety of passive heating/cooling systems, including making it a dual purpose chicken coop/greenhouse... but I'm a real newbie with all of this, so I'll surely be asking lots of questions along the way. For now, I just need to layout the footprint so I can mark out my row garden and food forest areas. Greenhouse coop won't actually be underway until next year (at least).

I remember my friend took some drone photos for us last year, North is around 1 o'clock in this photo... the greenhouse will be where the little white square nearest the house is (currently a dilapidated shed that is serving as the current chicken coop). The fenced garden will be above the greenhouse/coop and the food forest will be to the left of that up to the edge of the woods. We have a lot of invasives control (oriental bittersweet and multiflora rose) to do in the woods to the left and we'll be loading up the newly open spaces with fruit and nut producing thicket species. But that should probably all be in it's own post, I'm just excited to finally get started on the fun stuff!

Welcome to Permies Melissa!  Will your greenhouse be all glazing or will it be a passive solar design with insulation  possibly on the N, E and W sides?  Is your intent for some season extension or to grow through the winter?

If your greenhouse has glass or glazing on all sides, the orientation likely doesn't matter that much.  If it's passive solar, where the sun only comes in well from one side, the orientation becomes more debatable.  I'd say true South if you want maximum winter solar gain.  SSE to South facing if you just want an extended growing season and seed starting.

Apologies if two replies come through, I tried a few min ago with a pdf of my preliminary plans but it got hung up trying to upload.

It will be a passive design with glazing only on the south side. North, East, and west sides plus the roof will be fully insulated. I'd like to be able to use it as a 4 season greenhouse. If only to overwinter some citrus or other warmer zone dwarf trees in there.

I would orient a greenhouse like that slightly SSE, so that it gets sun as soon as possible in the morning to start warming up.

I have one word of advice from my experience with a little seed-starting greenhouse.

Beware of shade. It looks like you have some trees and structures nearby where you are intending to build your greenhouse. Check the shade on these and imagine how it will change throughout the year and as the trees grow. A shaded out greenhouse acts kinda funky... ask me how I know.

My greenhouse is shaded out by a giant persimmon tree and a mulberry tree that I pollard. I get really leggy starts if I do them when the foliage is in. It works well enough in the winter when the limbs are bare and I've pollarded the mulberry.

L. Johnson wrote:I have one word of advice from my experience with a little seed-starting greenhouse.

Beware of shade. It looks like you have some trees and structures nearby where you are intending to build your greenhouse. Check the shade on these and imagine how it will change throughout the year and as the trees grow. A shaded out greenhouse acts kinda funky... ask me how I know.

My greenhouse is shaded out by a giant persimmon tree and a mulberry tree that I pollard. I get really leggy starts if I do them when the foliage is in. It works well enough in the winter when the limbs are bare and I've pollarded the mulberry.

Thank you, I am definitely aware of the shade factor... topography is actually helpful in my case here. The greenhouse location is a higher elevation than the nearby house and garage, and the wooded area to the left is mostly down in a gully (so even lower elevation than the house). The one tree I am starting to watch carefully is a mature chestnut just to the left of the house, but I checked it the other day at noon when the shadow was directed toward the greenhouse area and the shadow fell short by at least 15 feet. I'll keep watching it, but my hope is that if the sun gets low enough in the sky for the tree to cast a shadow on the greenhouse that it will at least be without leaves by then. I also need to consider if we are even going to keep that tree... we've collected some chestnuts this week to see if we like them, the location is not ideal for dropping 'spike balls' where the kid's swing set is, but that's just a seasonal nuisance, so we will see. The tree near the corner of the current shed/coop has a terrible lean to it and needs to come down regardless.

yeah...  shade...  It's amazing how far those shadows reach in late December.  

I can see Glenn's point about heating up a bit earlier in the morning.  I'm guessing it is a couple degrees either way if you go S or SSE.  If you go true south you get a bit more overall heat collection so the innards of the greenhouse will pick up a tad more heat during the day.  Maybe that will carry through the night better?  Or it might just be better to give up a couple degrees of early nighttime heat in order to gain those two degrees earlier in the morning.  Perhaps a horse a piece...

I marked up my drone photo a bit (maybe it is completely illegible, but hopefully it is helpful). I realized there are a few trees in the photo that aren't even there anymore or won't be by the time we get to building the greenhouse. Notably, the giant one in the purple circle, it was a three trunked wild black cherry that split and came down last year. The ones in the red circles will also be gone soon if they aren't already. The one in the orange circle is the chestnut that I'm keeping my eye on. I'm guessing we are likely to lose more trees in the future food forest areas as we tackle the oriental bittersweet. It's already mostly thicket to begin with, and the trees that remain are being strangled by bittersweet. I see this area as an eventual food forest/thicket without any really big, tall trees. We have lots of plans, as you can see... but we are going one step at a time, and since the bittersweet battle will likely be years long, we'll have plenty of time to watch and re-evaluate what food forest plants we add back into that area.  

Since I'm sharing.... here are my very preliminary plans for the passive greenhouse/coop. I am a real newbie to all of these systems, so I'm sure much of this is wrong and will need to be modified, but I'm a long way from the build. I am hoping that the general layout/footprint will pretty much stay the same though. I will be trying to accomplish a lot with this structure so hopefully it will work! **Sorry if it is blurry, I converted the PDF to a jpeg since the I wasn't able to upload the pdf when I tried last night so image quality is fairly poor.

As far as orientation, I think it would suite the site better to angle it about 10 degrees toward the southeast from straight south and it sounds like that will get me some earlier morning sun which will be okay. Thanks for the help, I'm looking forward to sharing more as we are finally going to be able to start getting some of our permaculture systems going on this new property!