Yes, a greenhouse will help avoid conditions that lead to bud rot. It can because you lower the amount of pest exposure and excess water (rain, snow and God forbid hail) to your buds. Beyond the benefits of not being attacked by as many bugs or being assaulted by precipitation, there's less contamination from the spores that cause bud rot because there's a physical barrier there to block them.
There's a caveat to this though. And that is the need to move a lot of air (both circulating inside and exchanging it with fresh outside air) or you could be facing even more issues.
Having a roof above you plants definitely helps, as long as you keep paying attention to what you and your plants are doing together. And yes, you can grow stuff that is just as good as indoor. Inside of a greenhouse or hoop house the temps, water, wind, pests and humidity (to an extent) can be, controlled. And that is where a majority of the differences come into play between indoor and outdoor. You can even control the light inside of a greenhouse (light dep plastic and supplemental lighting). And when comparing the green/hoop house to indoor there are two other benefits to the hoop house- more space and (unless supplemental lighting is used) free lighting.
I love mine! And I have had great luck so far this year at avoiding bud rot. Just keep paying close attention and you can do amazing things inside of a greenhouse or hoop house.
