Have you ever opened up a wall and discovered a scorch mark that would make the biggest pyromaniac in the world weep for joy? I have. Invariably it is the result of repair in a tight space that required a soldered joint. In the course of completing the repair the plumber or erstwhile DIYer had such a hard time heating the connection hot enough to get a good seal that the stud it was located near either scorched or actually caught fire. After the flames were beaten out, the wall was sealed up, and no one was the wiser until you opened the old wound back up.
Whenever plumbing repairs need to be made to copper pipes there is a good chance that the space where it is to occur will be tight. In order to cut the chances of melting insulation or scorching studs there are flame resistant pads that can be purchased and placed behind the location where the soldering will occur. The only issue with these things is the need to grow a third hand in order to hold it in place while you operate the torch and hold the solder in the correct location. You can also try putting in a strategically located screw or nail to hold it, but if you can't solder well because of the location you probably don't have room to do this and then undo it when you are finished.
You can also try using fittings that are pre-soldered to cut your torch time and free up one of your hands to hold the flame shield in place. (Watch out for burned finger tips. They suck!) These units are about 2-3 times more expensive than regular fittings, but they do allow for soldering in some very awkward locations where holding a spool of solder in place while you work with a torch is almost impossible. The re-pipe of my townhouse is a great example. There were at least 3 spots where the plumber HAD to use these fitting or else do some major demolition in order to have room to do the job. (For the full story send a check for $4500 to.... )
You can try to use compression fittings to solve these issues as well, but again if you are tight for space I'm not sure how, exactly, you intend to use a wrench to tighten the fitting properly. Also you should check with your local municipality to make sure that you are allowed to use them where your repair spot is.
Another heat-less solution is epoxy. There is definitely a two part copper fitting epoxy out there, but the set and cure time is extremely long compared to other fixes, and if you blow it and don't get a good seal you are up the creek trying to redo the repair. Imagine having to clean or burn off a bad epoxy job in a tight spot... not pretty.
At last there is a new solution for those who are working in a tight space and trying not to burn down the house. Shark Bite fittings are here to save the day. These babies are not cheap, but they are easy. They are the high end escort service of the plumbing world. These fittings require no solder, no tightening, and have not setting time for them to work. Just press in the copper until you hear the "click" and you have a good seal. Even better, if you need to take it apart later for some reason (No, I can't think of one either) you just follow the instructions and the joint will come apart easily. Then you can reuse the same fitting to put it back together again when you are ready. I have already mentioned the cost of the fittings being high (up to $5.00 of more per piece), but when you NEED to get it done quickly, easily, and don't want to drop the $12-$60 for a torch set up or mucho $$$ for a plumber these babies start to look very reasonably priced indeed. Especially when you consider demolition and clean up needed to make sure you have the space you need to complete the repair with other methods.
One little extra note: These fittings will also allow you to connect your copper pipes to CPVC or PEX lines with no threaded joints! Just push the different pipes into their respective ends until you hear the magic "click", and you are done.