One caution -- greenhouses heat up real good in the daytime (sometimes a lot a lot more than you want them to, unless you have expensive thermostatically-controlled venting and fans!), BUT they do not hold the heat at night. So you get giant temperature swings. (Greenhouses for growing plants are usuaklly heated at night with propane or etc).
Large, meaning REALLY large, thermal mass in the greenhouse helps reduce temperature swings. A deep gravel-bed floor, cement or gravel-filled cinderblocks everywhere there's room, and/or large black-painted drums of water (sealed) will help. However you still have to be prepared for too hot and too cold.
In fact, if your userID means you live in Texas
(e.t.a. - duh, I looked at 'from', yes it does ), I would say that a greenhouse would prolly be a baaaad idea, even with fully open ends for ventilation, for most of the year,
OTOH you could use the frame of a prefab greenhouse if you came upon one cheap, and cover it w/mesh or (if ground predators are not a problem) shadecloth, and anchor it really well, and it might make an awfully nice run, that could be partly covered w/translucent fabric for more 'greenhouse effect' during the colder months.
JMO,
Pat
