All attics are ventilated. Good insulation (R-30+) above the ceiling makes venting the attic much better and less of an energy hit. Good ventilation in the attic also prolongs your roof from overheating, especially for standard composition roofs.
Unfortunately, my house is 90% cathedral ceilings: upstairs Master Bed & Bath, (2) Bedrooms, Bonus Room. I have a small attic above the hall way and one bathroom upstairs. I have to calculate the free area of the vents see how much fan (CFM) I can use. It may not be enough to make a big enough difference. But you must have good outside air quality to use a whole house fan and little or no allergies.
I am thinking to put a drop insulated ceiling the 2 bedrooms for better comfort and less heating in the rooms. 75% of the room capacity is above 8 ft.
For us, the dual-pane windows was more for:
1. Air (Dirt) Infiltration during Santa Ana’s.
2. Temperature Comfort
3. Building Aesthetics
4. Noise Control
5. UV Control
6. Energy Savings
Our payback for our windows is something like 11 years and we paid only $10k for the windows, much less than most would have. We had quotes up to $30-40k. Last year electric bill for winter (3 mos) is $100 per month. $50 in summer with fans & no AC. Our gas averages about $40 per month. We might be saving $25 per month due to the windows, probably less.
Invest $10-20k SCE, SDG&E, &/or Sempra and offset your energy bills from the income, inflation proof.
Its kind of like using a Discover card, pay yourself.
