Only some thoughts ...

The roof of my sunshed covers a 5' by 20' 3-sided structure. Those 3 walls and the roof are insulated. The sloping south wall extends another 4' so that the entire building is 9' by 20'. The south wall is redwood 2 by 4's covered by uv-resistant plastic film.

Interior walls are foil-covered insulation board. Because of the sun angle, this design really gathers winter sunlight. All that is about to change as the sun follows a path, ever higher.

By mid-April, that 9' tall roof would completely shade the interior, north wall. However, there will be a central bench covered with plants catching that sunlight. By July, sunlight will only fall on about one-half of that central bench. It's about 40" above the floor. The sloping, plastic-covered south wall is allowing for a fair amount of sunlight under the bench. There is also a low, narrow shelf directly under the south wall. It is in sunlight throughout the year.

All that interior summer shade helps keep the sunshed a little cooler through the summer ... not that there is much going on in there through the summer. That won't be true in your case, with the tomato plants. I imagine that you will have these on the floor and that there will be no bench or shelves. I also imagine that those plants will take over the entire south part of the greenhouse as they grow towards the light. Plan for access - hopefully, the shaded area on the north side of the plants will stay open for you but you will have to reach all sides of them to harvest fruit.

Steve

You might consider using polycarbonate roofing panels instead of metal. Metal blocks all light, which is not what tomatoes need. White polycarbonate panels transmit a fair amount of light, yet have a cooling effect. They go on like metal panels, so are just as easy to install. Cost is about the same. Polycarbonate is strong, so hail shouldn't be a problem.

Thanks for the input - here's what we ended up with: grey uv polycarbonate roofing, low-e windows and west facing door, and clear acrylic double east facing doors. I was worried that we might be blocking too much of the transmissible light, but seems like we're doing ok - all the plants are thriving. The low-e windows and roofing definitely keep things cooler in the greenhouse than a typical greenhouse. It feels warm in there, but there aren't any of the scorching/burning rays. I had been away the night before and didn't open up the greenhouse until 3:00 pm, the outside temp was 80, and the greenhouse was at 93. We did end up buying a vent with thermometer that we haven't hooked up yet, but are planning to soon. It gets the warmest at the end of the day when the sun is shining through the east double doors of clear acrylic. But that is happening as the outside temp is starting to drop and it heats the sand and flagstone floor, so we're still at 60 degrees in the morning.
We've got 18 tomatoes, 5 peppers, 3 basil and some hanging flower baskets that are all thriving. I do have everything on benches in 3 gallon containers with the tomatoes wrapped with twine attached to the rafters. I put everything on the benches because the windows don't go all the way to the floor and I wanted the starts in the light. Also because I've had issues with my dirt before and I wanted an 'easy' fix if something went wrong and needed to be cleaned out.

Your greenhouse turned out very nicely indeed, ladypant, and seems to be working well for you, too. Thank you so much for the update!

I can envision a circle of raised beds being built around it in the future. What a nice set up! I imagine that you will be spending many happy hours in that greenhouse and will make use of it for years to come.

I am quite envious of those that have the room, skill and $$ to put in a greenhouse. Do you ever lend out your husband and his building skills?!? (j/k)

Holly