I guess if you want to cool your snakes you can, but it might not be necessary. I don't know for sure that boas require cooling to reproduce. I think when the fall and winter months arrive the cages naturally drop a few degrees and that might be enough to do the trick. 
If you still want to "cool" your snakes...... Well, this is just one method. You need to figure out what works best for you.
Cooling should start when the temps start to drop outside. If you live in a warmer climate it's a bit harder to cool, but not impossible. Let a bit of natural cooling take place first. Turn down the heater in your snake room. You might want to set it about 70 or 75. Then you want to turn down the ambient temps. I'd say 80 to 82 degrees should do it. To get that little extra bit of cooling,for a NTL(night time low), you should turn off the room heater at night. Just be sure to turn it back on in the morning. Be sure you still have a warmer side and cooler side inside your cages. Your boas will decide which side they prefer to be on. I've found that my boas start breeding when the temps drop to 82 degrees or less. Breeding stops if they drop below 78 degrees. If the temps get that low they sort of huddle on the warm side. I've had boas continue to breed at temps as high as 85 degrees. Of course, they didn't start breeding until it dropped below 82 degrees. HEY!! Maybe there is something to this cooling thing. I like to keep a hot spot during the cooler months, while the snakes are breeding. I normally keep it between 87 and 92 degrees. Keep an eye on their health. You don't want them too cold. Being cold won't "make them sick", but it will lower their resistance to infection. Try to keep the cage as clean as possible. Don't let it get really nasty. If the cage gets too dirty your snakes will get sick. Be sure to give them an appropriate photo period. Shorten the amount of light as the days get shorter. A little trick to get them more "active" is..... Mist them at night. I've noticed that my boas breed more at night. Misting them stimulates activity.
There's a lot more to breeding boas, but you only asked about the "cooling" part.
BTW this post will SELF DESTRUCT IN 30 SECONDS. Read it quickly and remember what you read. This is top secret info and we must keep it out of the wrong hands. LOL. J/K
Most of this info isn't a secret at all. It's mostly common sense. Well, it's common sense if you've had boas for a while.
Good luck this breeding season. I hope you get some AWESOME LITTERS!!!!
