Insulating a roof with no crawl space

Just bought a home built in 1950. The roof I suspect has minimal insulation. To make the ceilings high, the builder has put in no crawl space and the rafters are visible from inside the house.
The house is only around 1000 sq.ft. It is in San Jose California.
I looked at the archives of this usenet group, and found discussions on using foam blocks under the composite shingles. This seems fine but it seems like it is like building a new roof, which could be expensive.
I am thinking of the following alternatives:
- Add foam from within in between the rafters and blend them with the architecture. - Erect an awning (maybe I should call this a tent) that will cover all of the roof for the hot summer months. - Put solar panels. They would not only make shade put also generate electricity for me. However, I hear that solar panels and convertors etc. can be very expensive. - Or, put a solar water heating system.
How would one insulate such a roof?
Thanks!
Deguza
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Exposed rafters so you actualy see the roof deck or whatever finish product is attached? Spray foam would be best, there are R 5 and R 7.2 foams, then finish the ceiling. How thick is the open area in inches to insulate, you want what is appropriate and maximum in R value for your area.
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On Thu, 8 May 2008 05:29:57 -0700 (PDT), ransley

I wonder if these techniques that have been suggested may be hard on the roofing shingles (if they are heat sensitive, such as your typical asphalt shingles)? I know here in New England (not a hot spot) that roofs that have an insulated deck tend to have much lower shingle life than roofs which have some ventilation built into them.
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Yes I wasnt thinking, it will have some effect. I dont know what the procedure is on SIPS construction, if venting is used and how shingles last. But for metal, slate and tile it would not matter. I dont his utility costs but they will likely double soon and that may be more important. Venting could be done by running a spaced sheeting away from the roof deck, but at what cost, maybe a different type of roof material would be better.
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Yes, I believe that is what I am seeing from within inside the house. The rafters are at least 6" down from the roof.
I can create with 2x2's cells in between the rafters and put foam blocks then cover the cells with plywood, then stain them to match the original ceiling color and the exposed rafters.
I wonder if I can use reflective bubblewrap top of insulation instead of foam. (Here is what I am talking about: http://www.btubusters.com/attic-ceiling-detail.html ). I hear that the R values of these are very good.
Here something similar to my ceiling:
http://www.loghomebuilders.org/files/images/log-home-master-bedroom-cathedral-ceiling-jj35.preview.jpg
In my case rafters run in the other direction and the distance between the rafters is far greater. That's why I think I would need to create cells.
If I were to go with cells filled with foam, is there any ventilation neede between the foam and the ceiling?
Deguza
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While searching for insulation on the net I found a real good page:
http://www.eere.energy.gov/consumer/your_home/insulation_airsealing/index.cfm/mytopic510
Deguza
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That is a good site, bubble wrap -reflextic? See if there is an independant lab, a real one, that verified their claims on R value, I dont believe them. The question is what Zone are you in and what is the optimal for your zone, I put in R100, it sank to R 70 but it goes from -20f to 100f where I am. www.energystar.gov might give you a starting point as to what you need. I dont know you weather but I thought it was a mild area
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Thanks for the link, it has much better information.
Yes, where I am the weather is relatively mild. However, builders 1950's did absolutely nothing to insulate the house.
I am the type of guy who can stand cold (my room temp is around 65 to 68 during the winter), but cannot take any heat --literally, not figuratively :)
When temperatures rise during the summer, interior in an older uninsulated house around here goes to 80 to 85. (When I cook or use my computer, it is more like 85.) This really bothers me. I should add here that the home does not have an airconditioner.
So my goal is to lower the interior temperature during the summer as much as possible.
Deguza
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Bubble wrap is not recommended as the R-vale is over stated and needs an air gap to get the radiant barrier to work. With lower temperatures the radiant transfer is substantial. The demonstration they show with the infrared lamps is not realistic. The temperature of the heat lamp is over 300 deg F (that is as high as the thermometer I have will go). Since radiation is expediential as the temperature increases the demonstration is not real.
As for foam, one needs to check with their building code as to what is allowed per the fire code.
I would do nothing less than 2 of foam, would prefer 4 or more. As the years go on the cost of energy is only likely to go up. I am of the mind set that we should be taking societal benefits into account and not just the immediate dollar savings. If you find a good source for societal cost please let me know. Since your goal is comfort Id highly recommend the 4 if it can be installed.
Regardless of the foam being on the top or bottom of the roof deck it will raise the roof temperature (the energy absorbed from the sun has to go somewhere).
Andy
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