Is interior wall insulation necessary?
We're building a 3500 sf home in the San Diego area, near the beach. Our climate is so temperate that we use our heat only about 2-4 weeks/year, and we don't have a/c because it would probably only be used a maximum of 5 days/yr, if that.
Our home is well-insulated on the exterior walls and roof, but our builder tells us that he did not plan to insulate the interior walls. Since we've got a fixed price contract, it would cost us extra to put insulation in the interior walls, which he thinks would cost us around $700.
I have a couple questions -
1) Is interior insulation standard and is it typically included in a standard bid for a custom (fairly high-end) home?
2) Even if the cost is not included, should we go ahead and do it as an extra? In the big picture, of course $700 is no big deal but I hate to pay for something that's not necessary.
The builder is using 5/8" drywall, which he claims is a bit nicer than regular 1/2" drywall and may help make the house feel a little more solid and quiet...don't know if that's true or not.
There aren't many adjoining interior walls where sound transmission would be a potential problem. The rooms that share a common wall are our daughters' two bedrooms and the office and guest room, and that's about it for the major rooms. The powder room shares a wall with the dining room so it might be a good idea not to hear the toilet flushing during a dinner party, but other than that, I can't think of any other areas that could pose a problem, and I don't know if insulation would make a big difference anyway...your thoughts?
All advice/feedback welcome. Thanks in advance!