Greenhouse lean-to a porch/veranda

Hi guys and gals.

I'm in the design stages of a new house and am picking my brains without a solution in sight.
The southern side of the house will be a porch / veranda.


The house will be one floor with a vented attic.
I want to put a lean-to greenhouse on this side over the winter or maybe permanent tops with removable sides for summer.
The idea is to shelter the porch over winter and also do some season extension in the greenhouse - double win.

What i have difficulties with is the GH attachment to the porch.
There are posts holding the roof there, how do i attach the GH ?
I could attach it somehow but it won't be airtight since the porch roof has venting spaces (cold roof).

Please share some ideas, any ideas on how to achieve this.

hmm....I'm not an engineer, but I would say it depends on the house as to whether it can handle being a supporting wall. I would assume it would, but just a consideration. Then, there's the difference in shrink and swell of the GH versus house because soil and slab move differently. So, if it were me, I would make the GH stand alone w/a gasket sort of thing connecting it to the house so neither would push the other much.

But, just my 2 cents.

You could cut some pink foam insulationto plug the venting spaces.
That would be reversible for the summer.
I attached an awning frame made of  1 1/2" PVC pipe  to the fascia board of my house.
I recommend checking the electrical and plumbing sections for what suits your situation, lots of pipes straps and hangers out there.
Mine has snow fencing screwed to it to support tarps in the summer and clear plastic in the winter.
Your drawing looks like it might be perfect for a subterranean heating and cooling system like this one:
https://www.permaculture.co.uk/articles/how-build-solar-greenhouse
Using a fan it takes the hot humid daytime air from the peak of the greenhouse and pushes it through buried perforated drain pipes.
The humidity condenses in the cool pipes, depositing a lot of heat energy.
When it's cold in the greenhouse the process is reversed.
Looks like you might be digging out where the greenhouse will be anyway,so a SHCS greenhouse might be a good fit.

Hey, great feedback.

Funny thing is, after posting, it hit me : why not make the "porch roof" less protruding and place the GH cover underneath it.
That means there's no need for porch posts.
Whatever posts will be will actually support the GH framing.

Also, i could keep a height distance between the roof and GH covering so the vents are outside and i can use this space to install a retractable awning.
Need more shade - extend the awning more, need less, roll/retract it back.

This should also decouple the GH structure from the house structure as they will be independent.
The only remaining thing would be how to secure the awning against winds and how to close the GH to the house walls (preferably so it's easy to take apart seasonally).

Hola, we just finished our lean-to greenhouse extension. Wrote all about it on the blog if anyone is interested in making their own - it's attached to the side of a stone cabin, we converted the old woodstore

https://peaceandpollen.net/2019/11/29/building-a-lean-to-greenhouse-on-a-stone-cabin/

When I attached my greenhouse to my rafters (it was removed due to a house addition), I just used plywood gussets.

By plywood gussets I mean 1/2 inch, or 3/4 inch plywood, cut in a shape that matches the angle of the rafters you are using. I cut (2) one on each side and nail into the rafter tails of your home, and the new greenhouse rafter (assuming you are using framing lumber to make the greenhouse). Just keep in mind you MUST use plywood and not boards, because boards will split. And I do not recommend oriented strand board because it does not do well with moisture. But you can make a ton of gussets with just a little bit of plywood, so the cost is next to nothing...

As for ventilation, you could make pivoting blocks between the rafters to stop/allow ventilation in the attic of the home like most livestock barns do for summer/winter ventilation, but I would not bother. I would seal the soffit up tight, and then just make my vents bigger in the gable ends of my home. That is what I did.

But again, I make some assumptions here.

Here is a picture of "plywood gussets" on my barn. They are so simple, I know with words it seems like a bigger deal then they are.