He needs to replace lights in the bedroom, bathroom, kitchen and basement so 2+1+1+4 = <<2+1+1+4=8>>8 lightbulbs
In the garage, he needs to replace half that amount so he needs 8/2 = <<8/2=4>>4 lightbulbs
All total, he needs 8+4 = <<8+4=12>>12 light bulbs
They come 2 per pack and he needs 12 lightbulbs so he needs 12/2 = <<12/2=6>>6 packs of lightbulbs
#### 6