Having it connected to your house might be a good idea in winter but probably not in summer. In winter you could potentially get some heat gain into the house by day to balance out the loss at night.

Do you really want something in the greenhouse when it's 115 outside? It will be a huge load on central air to cool that space in summer. And central air is not the best way to cool a greenhouse. Evaporative cooling and shade cloth are much less expensive.

I'd probably be thinking about having it covered in winter and then removing the greenhouse covering during the frost free period.

It would help to know your location, crops, size of the greenhouse, and your goals.

My house does not have central air - purely swamp cooler. That is why I thought it would be good for the greenhouse, because I have to have an "exit point" for the swamp cooler anyway, and the area I would install the greenhouse is actually where we usually keep open anyway in the summer, to get best airflow in the house. I will still garden outside, but this is just to maximize my space and ability.
I like the idea of covering it in the winter - but, how do you get enough sunlight, when doing so?

My location is southern Utah, size of the greenhouse would be under 100 square feet, and my goals is to just provide enough vegetables, herbs, etc to at least get me by. I do not know what does best in a greenhouse environment. I am now VERY limited on what I can eat - no starch or preservatives. As a result, my crops have to change drastically. No more beans, corn, potatoes, cauliflower, beets, ginger, etc.... I will rely heavily on greens, would love to have plenty tomatoes and peppers, and wish there was a way to grow things like squash and cucumbers in the winter!! Really, I am still trying to figure all of this out.

In my garden I have always had onions, garlic, greens, carrots, tomatoes, potatoes, asparagus, peppers, watermelon, squash, pumpkins, cucumbers, kale, leeks, and the list goes on... I know I cannot do all of that in a greenhouse, but I am open to doing ANYTHING possible, which does not contain starch.

tarabelle:

The warm season vegetables in winter are really difficult. You could get it warm enough in there during the day but providing enough heat at night would be very expensive. Now greens are another matter all together and would be a great winter crop in your climate. You just need enough heat at night to avoid freeze damage. So you could heat only enough to avoid teens and below.

Your idea of using the greenhouse as an exit for your homes swamp cooler might work. You need enough air movement to exhaust the greenhouse air about once a minute. This along with a summer shade cloth could keep the greenhouse cool enough for crops. But you will still need a way to cool the greenhouse in the cooler months. My sunroom and greenhouse will both reach 130F from now until spring if I don't run exhaust fans or dump the hot air in another fashion.

A poorly designed greenhouse will be a waste of money. And with a 130F annual temperature range your greenhouse will be too hot or too cold much of the time without a good design. My temperature range is about 10F to 100F in a normal year with lots of sunshine. I need large exhaust fans, an evaporative cooler, and a good heater to make my greenhouse usable all year. Attaching yours to your house makes it harder to design.

If you want a greenhouse that is sure to work I'd build it separate from the house and include all the temperature controls above: exhaust fans for one air change per minute, a wet wall opposite the fans, and a good heater.

Great info, fruitnut - thank you. It looks like I may just need to use my current garden area for the greenhouse, and move my garden to a different location.

What do you grow in the winter? I kind of assumed I would be limited to mostly greens, but, I am HOPING I can make other stuff work. I do not want to be eating lettuce and spinach for every meal! ;)

Right now I have cauliflower, radish, spinach, kohlrabi, carrots, peas, and chard. But my main crops are year around fruits: apricot, nectarine, sweet cherry, fig, blueberry, grapes, persimmon, kiwi, plums/pluot, and citrus. All in the same greenhouse. I don't do vegetables in the greenhouse in summer. They do fine outside under row covers. You could grow all this in your greenhouse at somewhat more expense because of your greater temperature range.

The design of your greenhouse to do all of the above is critical. If your summers are dry enough you might get by with an open greenhouse during that period. Covered with a heater in winter and uncovered during the freeze free period. Mine is covered all year to protect from rain induced rot of some fruits. The design is dependent on crop, climate, and your objectives.

If I were in Page AZ, a climate I'm familiar with, I'd have a covered in winter and open in summer setup for some crops. It hardly rains there all year.

So helpful! Thank you! Yes, my climate is very similar to Page, AZ :) An area I am also familiar with, and love!

I don't know much about gardening in your climate, but I think I can offer at least a few suggestions.

I imagine that in the winter you will have a lot of sunshine and the potential for a nice warm greenhouse. The trick will be to retain the heat at night. This is very doable. I'll list a few tactics and you can search this forum and other places for more details on the things that interest you.

For winter heat retention, you can make a trench around your greenhouse foundation, down below the frost line and fill the trench with sheets of styrofoam. This method is described here and is also described in Shane Smith's book, A Greenhouse Grower's Companion (or something like that). That is a book you should buy right now!

Also in winter, you can create microclimates within the greenhouse. By uncovering things during warm days, then covering crops at night you can get a lot more bang for your buck from your greenhouse. See Elliot Coleman's book, The Four Season Harvest. That is another book you need.

Some people have had great luck keeping areas of the greenhouse warm by putting black water buckets underneath the row covers.

Overall, there is some dispute about the value of using water as thermal storage. Well, no one disputes that it works but if you do the math it would take a lot of water to actually keep the greenhouse warm. But it is nearly free to fill your extra space with water containers.

Soil heating cables are another tactic. These can also be used under a frost blanket in the winter.

As for the timing of growing and what you can grow, you will have to experiment. I bet you can get a very long season from your greenhouse. I imagine you could have tomatoes until Thanksgiving and you could get them started again in late Feb. As you probably already know spinach is incredibly healthy and has a million uses. You will be able to grow spinach all winter. Carrots also do well. As long as they are past the seedling stage once winter arrives they will generally make it through the winter. I have carrots in my unheated Montana greenhouse 12 months a year.

If I were in your shoes dietarily speaking, I would focus 70% of my energy growing the best food possible. But save 30% of your efforts for canning, freezing, pickling, and otherwise preserving your harvests. That is by far the easiest way to have tomatoes in January. And there are all manner of ways to preserve your produce. See the harvest forum for endless ideas and recipes.

The design of your greenhouse is going to be very important here. A well designed and well built greenhouse has huge potential. But if you rush, skimp and compromise, you will regret it. Build the very best (and largest) structure you possibly can.

The last thing I will say is that having a productive greenhouse is tremendously satisfying! There is value way beyond the actual spinach and carrots - the whole system is fun and uplifting and rewarding. So enjoy the journey! Take your time and do lots of homework now that you are in the planning stages.

Karin