My girlfriend keeps the AC on all the time. House is usually 65*F-70*F and the seeds do fine. I have a small little setup in our closet for germinating seeds that hasn't failed me yet. Its just four one gallon fabric pots filled with a good seed germination mix (like Fox Farm Light Warrior or Miracle Gro Seed Starting Mix) and a 200w CFL bulb + hood on an adjustable hanger.
I pre-soak the medium and let it drain for about five minutes so it's not to wet and at the same time I soak my seeds for 3-5 minutes for good luck. After that sow the seeds in the medium about 1/2" deep or three times the depth of the seed. I turn the light on and leave it on 24/7 until the seeds sprout. I average 2-3 days. Anything that doesn't pop on the forth day I assume I sowed to deep and I grab a tooth pick and carefully pull back the soil. It's rare but it does happen and I'm usually good about saving the seedling when it does occur.
Even though the house is freezing, the light gives the seedlings enough warmth. I haven't needed a warming mat and I never pH my water. Although I would if I was going to put them in a hydroponic setup, but since they go outside in my garden I keep things simple.
