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Old 05-09-2012, 12:05 PM   #46
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feasability of replacing AC flex ducting by myself?


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Originally Posted by rdc View Post
I got a huge reduction from opening up the blower side of the condenser and cleaning that - there was about a 1/2 millimeter layer of matted stuff covering a large part of the condenser grill. So make sure you check that. Who knows who may have run your AC without a filter? That saved me $100/mo in electricity.

I don't have any other results yet as I'm in the middle of revising my design, now that I've seen the plenum. But I'm targeting 20% reduction of cooling bills in the summer. I will also benefit from everything being clean.

Regarding trunk duct: I read bobinphx's message as being against trunk and in favor of Ys like you already have. Pick a duct traveling from your air handler going to a Y or a register and remove it and have a look inside the plenum. If its clean then you can just replace the duct. Your earlier pic of the duct looks clean, a good sign. My mesh is clogged with dust. BTW, triangle is not a plenum, its a distribution box. You can buy those prefab cheaply at the AC place I mentioned. Ask for ductboard triangle box.

I will also blow cellulose into my attic. I have already sealed it and built dams around the bottom of my rafters. But have to redo duct first. I will be lifting it up in the air also. I am adding a bit of floor joists on top of the attic rafters to build a raised floor in a few spaces so I can still get around after the insulation is added. Make sure you use wide strap to hang the duct, and support enough so it doesn't sag. Strap available at AC supply. I will hang the strap with wire and eyehooks screwed into the rafters.

Radiant barrier - I'm installing some because its cheap enough DIY and easy enough to install and it looks good when you sell the house. I dont expect dramatic results from it, but it does have some effect. The idea is that your roof absorbs sun's heat and radiates that into your attic, heating up insulation which then spreads into interior. Barrier will reflect the radiated heat back to the roof. For installation options see attic foil dot com. I'm using their stuff and it works well.
Hey thanks for the tips, do you mind elaborating on how your are going to build a raised floor? id like to build something like that in my crawl space if i can. otherwise you would have to crawl through the new cellulose i imagine. also what are these rafter dams you are talking about? are you talking about these?



i dont know about your system but my air handler is currently sitting on the top of the raters, im not terribly comfortable lifting it up, so i thought id build some sort of dam around it? ever seen something like that?

re: radiant barrier,
i understand the concept of reflecting radiated heat, but i guess im not convinded hot wood emits enough heat to necessitate a reflective surface. i could be way off though, as is frequently the case. ill have to take a look at that website when i get a chance.

i would think that creating a ventilated envelope of air between he roof sheathing and the attic would be better? it seems like ive seen something like that done with polystyrene foam boards that took air up the soffit vents and out the attic vent.
regardless i think ill just roll it all back up, and reinstall it later, no sense in not using it i guess.

thanks.

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Old 05-09-2012, 12:23 PM   #47
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feasability of replacing AC flex ducting by myself?


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Old 05-09-2012, 09:08 PM   #48
rdc
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feasability of replacing AC flex ducting by myself?


Queequeg152, that picture is correct for what I did for ventilation, stapling those foam channels up there, and I also put cardboard beneath them to block the insulation from falling into the soffit.

Re lifting the air handler, no, I'm not going to do that. I will build a short wall around it with plywood. My floor will be 2x8s spaced 12-16 inches apart, held in place by 2x4s nailed to the rafters and cross-braced. I will put plywood on top after I blow the insulation. I will also build a short wall around the attic opening. My water heater is up there too so I have to be able to get around.

The radiant barrier I'm using is nailed to the bottom of the rafters, so it works as you described, creating an air channel where soffit air can flow up to the ridge vent. You can also just lay that sheet on top of your insulation. I'm not familair with the Lo/Mit that Doc Holliday is recommending.

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