Attic Insulation Quandary

I live in a duplex with a flat roof that has an attic that is under- insulated, about R 15-19, in an area where summer temperatures in the 90s are not all that uncommon. The attic, such that it is, is only about 24 inches tall total, with HVAC ducts present.
To make the summers less unpleasant, I'm grappling with how best to cost-effectively add insulation. I'm inclined to do this myself, unless there is an overriding reason to get a contractor. Here are a few ideas:
1) add another layer of unfaced fiberglass batts. Nasty work given the space, but feasible. With the ducts there, only about 2/3 of the space is accessible. So it won't be very orderly. How problematic is it if the extra insulation is rather haphazardly added? Does this defeat the purpose?
2) blow-in or foam insulation. Does anyone have some general guidelines of cost per sq ft to have a contractor do it? Is this at all a feasible DIY project?
3a) exterior insulation. There are 3 ft walls extending above the edges of the roof on three sides, so except from a back alley, the roof is entirely invisible. One option would be a couple layers of polystyrene (or comparable product) applied on top of the roof with tar as weatherproofing. This strikes me as less cost effective than options one or two, but there are no space constraints.
3b) A second exterior option would be to build a plywood false roof (with tar weatherproofing) above the regular roof and place fiberglass insulation inside. I think this would cost less than 3a but would be time consuming.
What do you think? Any thing I've missed? Any feedback would be much appreciated.
Perry
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I had it done to my last house. Too long ago to be relevant about cost today, but given the space, I found it easy to just let the pro do it. Comfort and payback was quick.
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wrote in message

couple months ago. Call it half a buck a square foot. Labor is most of the cost- the material, wholesale in bulk like a contractor buys it, is quite cheap. Given how large I am, and how shallow my attic is (with trusses in the addition, to boot), with almost no floorboards, hiring it out was a no-brainer. They were in and out in a single morning. To blow takes 2 people, and I live alone. Doing it with batts would have taken me several days, and not covered as well. Plus, they also cleaned up and added more of the soffitt air channel things, essential for ventilation. The truck-mounted blower is much more efficent than the little ones you rent at the home center. The only part it made sense for me to DIY was the 1x8 fence around the attic access hole, and the stiff foam lid that lays inside the fence over the hatch. The fence keeps the loose stuff from raining down when you open the hatch, and the stiff foam is easier to manuver than the fiberglass batts they offered to lay over the hatch. I happened to have all that on hand, so all it cost me was an hour's time to screw together.
aem sends...
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Thanks for your advice. I was at Lowe's today, priced out the cellulose insulation and am all but decided that this is the price - effective way to go (about $360 plus tax). I do have some more questions, though, which I'll ask in a new thread.
Perry
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:>
:>> 2) blow-in or foam insulation. Does anyone have some general :>> guidelines of cost per sq ft to have a contractor do it? Is this at :>> all a feasible DIY project?:>> :> :> I had it done to my last house. Too long ago to be relevant about cost :> today, but given the space, I found it easy to just let the pro do it. :> Comfort and payback was quick.
What are such companies called? I'm in Arizona, and have so-so insulation in a peaked-roof house attic.
    -- Andy Barss
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Look in your local Yellow Pages under Insulation Contractors.
--
Larry Weil
Lake Wobegone, NH
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