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Old 07-10-2008, 08:58 AM   #21
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Well I plunked down $250 for 2000 sq ft of the stuff and just for kicks started to put a few pieces up in the attic. I swear by the Hammer of Thor, that is tough work! The ambient temp was 116 when I started around 6PM, and working with the material by yourself is definitely not the quickest way to do it. Hopefully as I get more up this weekend I'll notice some improvement.

The hardest part of the job is just getting around the attic without stepping through the ceiling, tripping over the A/C ducts, running into the trusses, or hitting your head on roofing nails.

Upon searching other home improvement forums, the usefulness of the radiant barrier material seems to be hotly debated. I am hoping that this project is not an exercise in snake oil installation...
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Old 07-10-2008, 09:18 AM   #22
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IMHO a couple of wind driven turbines on the roof coupled with another 10 or 12 inches of blown in insulation would be a better investment. Turbines evacuate the hot air and added insulation restricts migration of the heat downward. This is what I did several years ago in Northern Virginia. Enlisted a friend to feed the hopper, use provided by HD with the purchase of the insulation and two turbines professionally installed (today it would have been a DIY deal). The reduction in electric bill was, as I remember, not that great but the home was quieter and the work added, in some small part, to resale value. I believe the radiant barrier will actually raise the temperature of the roof material and the impact is not going to be positive on the life of the roofing material. BTW IMO the time to be doing attic work is winter or EARLY in the morning (before the Sun rises).
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Old 07-10-2008, 09:35 AM   #23
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I believe the radiant barrier will actually raise the temperature of the roof material and the impact is not going to be positive on the life of the roofing material.
This is what the Florida Solar Energy Center has to say on this topic:

"Will heat build up in the roof and damage my shingles?

It's extremely unlikely. The Florida Solar Energy Center has measured the temperatures of roof shingles above attic radiant barriers on hot, sunny summer days. Depending on the color of the shingles, their peak temperatures are only 2-5 F higher than the temperature of shingles under the same conditions without a radiant barrier.

Roofing materials are manufactured to withstand the high temperatures to which they are frequently exposed. A 2-5 F increase in peak temperatures that normally reach 160-190 F should have no adverse affect."

Reference: FSEC-EN-15
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Old 07-10-2008, 09:44 AM   #24
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I am hoping that this project is not an exercise in snake oil installation...
From FSEC: FSEC-EN-15

"When will I see a payback from an attic radiant barrier?

Two things affect the performance of a radiant barrier system the level of insulation in the attic, and the geographic location of the home. A simple answer to the question is that a radiant barrier system reduces the heat flow into the house from the attic by approximately 40 percent. Attic insulation levels have a large effect on the amount of heat flow that is reduced, in other words, if you have little or no insulation in your attic, a 40 percent reduction is very significant, but if your attic is insulated to R-30 or better, there is very little heat flow to reduce. The more of your energy bill that is concerned with heating, the less desirable having a radiant barrier becomes. When you are using your heater, any heat gain from the attic is desirable. There may be a reduction of heat loss through the roof during winter nights, but the climates where testing has been performed do not lend themselves to demonstrating this, as there is very often a brief or non-existent winter. A very helpful website for guidance to the cost effectiveness of installing a radiant barrier is found on Oak Ridge National Laboratory's Web site, http://www.ornl.gov/sci/roofs+walls/radiant/rb_02.html.
In Florida, computer studies conducted in the development of the Florida Model Energy Code indicate that a typical attic radiant barrier installed in a Florida home will offer a six to seven year simple payback and a 15 percent to 19 percent return on investment."
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Old 07-10-2008, 10:05 AM   #25
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IMHO a couple of wind driven turbines on the roof
Add in a car radiator fan @1800 CFM and a 20W solar panel and the turbines work even better.
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Old 07-10-2008, 04:32 PM   #26
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Add in a car radiator fan @1800 CFM and a 20W solar panel and the turbines work even better.
This brings up an interesting problem. If there is any type of power ventilation, placement is important. Studies have shown that the power ventilators often cause air to be drawn in through other nearby high vents, and cause relatively little air to be drawn in through the soffit vents. This can significantly reduce their effectiveness of ventilating the attic.

Adequate soffit and ridge/gable/hat vents allow for natural convective airflow that is not subject to mechanical failure, costs very little, and has reduced potential to draw conditioned air from the dwelling through the hundreds of gaps and cracks existing in the typical home.
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Old 07-12-2008, 12:56 AM   #27
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Well I plunked down $250 for 2000 sq ft of the stuff and just for kicks started to put a few pieces up in the attic. I swear by the Hammer of Thor, that is tough work! The ambient temp was 116 when I started around 6PM, and working with the material by yourself is definitely not the quickest way to do it. Hopefully as I get more up this weekend I'll notice some improvement.

The hardest part of the job is just getting around the attic without stepping through the ceiling, tripping over the A/C ducts, running into the trusses, or hitting your head on roofing nails.

Upon searching other home improvement forums, the usefulness of the radiant barrier material seems to be hotly debated. I am hoping that this project is not an exercise in snake oil installation...
Please keep us up to date as you go along on this. The radiant heat in a Southern clear-sky attic is incredible. When I replaced two HVAC units and adapted and reconfigured ductwork, I would start out about 7 AM, and work till it was just too hot for me. And that was early in a year! By 10 AM, if I was down on the attic floor, closed my eyes, and swiveled my head around in all directions, I could feel the radiant heat strongly on my face if I faced the roof surface that the sun was shining on. The underside of the roof deck was like a fire at a moderate distance.

What product are you using for the barrier?
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Old 07-12-2008, 02:29 PM   #28
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I've been working on the project for a few days now and I think it's going to save me quite a bit of money - after working in the 120 degree attic (it's 100 outside), I have been cured of my desire to travel to the middle east, or anywhere that might be described as the "desert". I brought a metal ladder into the attic to reach certain areas and it's now too hot to even touch it without burning your hands.

Too early to tell if it will actually save me any money on my electric bill.
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Old 07-13-2008, 07:29 PM   #29
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I bought one of those indoor/outdoor thermometers with a wireless remote and stuck the transmitter in my attic. It allows me an objective measure of how hot it is up there (without sticking my head through the access hole). I also installed a two speed gable fan with a thermostatic switch. I wired it so I can run it in any mode - hi/lo, auto/manual. It quickly cools the attic from 140 degrees to about 110 on a very hot day. I've noticed that my upstairs is noticeably cooler when I have the fan running - the ceiling even feels cooler.

I have a trussed roof support as well and I bought some used 1/2" plywood (thanks craigslist) and made a 2 foot wide track in the "V" of the truss that keeps me up off the insulation, but allows for headroom. I can crawl all over my attic on this track now, which really helped when I installed some tubular skylights.
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Old 07-13-2008, 08:41 PM   #30
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I have a trussed roof support as well and I bought some used 1/2" plywood (thanks craigslist) and made a 2 foot wide track in the "V" of the truss that keeps me up off the insulation, but allows for headroom. I can crawl all over my attic on this track now, which really helped when I installed some tubular skylights.
We had a chicken/egg problem with the attic being too hot to put in flooring or tracks, and the lack of flooring made it tough to put in the insulation to bring down the temperature.

But now that the attic is cooler, our winter project is the "infinite attic storage system"...
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Old 07-13-2008, 09:09 PM   #31
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This brings up an interesting problem. If there is any type of power ventilation, placement is important. Studies have shown that the power ventilators often cause air to be drawn in through other nearby high vents, and cause relatively little air to be drawn in through the soffit vents. This can significantly reduce their effectiveness of ventilating the attic.

Adequate soffit and ridge/gable/hat vents allow for natural convective airflow that is not subject to mechanical failure, costs very little, and has reduced potential to draw conditioned air from the dwelling through the hundreds of gaps and cracks existing in the typical home.
Air is stupid...it doesnt know where you want it to come from or where you want it to go.

In some cases if you create too much negative pressure in the attic, you can draw conditioned air from the living space, which of course is replaced by unconditioned air through every crack and crevice.

The laws of unintended consequences are quite strong when any ventilation product is deployed...
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Old 07-14-2008, 06:19 AM   #32
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We had a chicken/egg problem with the attic being too hot to put in flooring or tracks, and the lack of flooring made it tough to put in the insulation to bring down the temperature.

But now that the attic is cooler, our winter project is the "infinite attic storage system"...
That is a neat system and would work in my garage (which currently is uninsulated). Wonder if I can find some scrap metal strapping to make them myself (for less than the $129)?
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Old 07-14-2008, 08:37 AM   #33
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Do pay note to yet another possible unintended consequence...in many cases the trussing systems used in homes are not engineered to hold uneven weight bearing loads pushing down in the middle of the system...in particular in unsupported garage ceilings. They're made to hold a roof UP.

In my old neighborhood it was very popular to put in the stairs and the full storage floor and fill it up with stuff that people will never use again. Almost all of these had a bowed roof over the garage.
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Old 07-14-2008, 08:39 AM   #34
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That is a neat system and would work in my garage (which currently is uninsulated). Wonder if I can find some scrap metal strapping to make them myself (for less than the $129)?
I think it would be tricky to make those yourself, as it appears they are stout enough to support the 2x2s (and the board over the stud bay, and a guy with a box of Christmas ornaments) without any other fasteners.

If you've got more time/enthusiasm than money, you could accomplish the same result by screwing 3x2's to the sides of your truss bottoms. Temporarily shim them up so they are in the same spot as the Infinite Storage hangers would have put them: 3/4" below the tops of the truss bottom piece. Then, just screw the floor pieces (3/4" OSB would be cheapest,3/4" plywood would be lighter and easier to handle) to the tops.

Waiting for Winter is a good idea.
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Old 07-14-2008, 08:47 AM   #35
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Do pay note to yet another possible unintended consequence...in many cases the trussing systems used in homes are not engineered to hold uneven weight bearing loads pushing down in the middle of the system...in particular in unsupported garage ceilings. They're made to hold a roof UP.
True. I built a shop and added deep shelving up near the ceiling for storage. I hung the shelving with wood that went up to to the top of the trusses, rather than hanging them from the bottoms. That's what the engineers at the truss company recommended.

Also, (obviously) if you think you might ever want to insulate the garage, do it before you put the flooring in. Even just 3 " of cellulose or fiberglass (R-13 or so) will make a big difference compared to an uninsulated ceiling.
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Old 07-14-2008, 08:57 AM   #36
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Insulation is an amazing thing. We have a 3 car garage with bedrooms over top of it. Uninsulated garage doors that take direct sun all afternoon and get too hot to touch and I'm sure the builder put no insulation in the front or side walls. 6" of fiberglass in the garage ceiling/bedroom floor.

Used to get up to about 120-125 out there in the summer. The bedrooms over the garage got plenty warm late in the day.

When we stucco'd we put on an r-4 layer of foam first and we replaced the garage doors with insulated ones.

Maybe hits outside air temp (90ish) by very late in the day now. Noticeable difference in the bedrooms above.
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Old 07-14-2008, 08:59 AM   #37
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I finished putting up the first 1000 sq. ft. roll of foil. The attic still hit 125 yesterday afternoon, but most of the foil I've put up so far is on the east side of the roof. I would say that the part of the roof under the foil "feels" cooler while I'm standing up there, but that may just be my imagination.

When I finish the radiant barrier, I'm thinking of adding a bit more insulation to the attic. Any thoughts on the following questions:

1) Is there any problem with adding a few inches of cellulose insulation on top of ~10 inches of rockwool insulation?

2) I'd only target a few areas of the roof for extra insulation, if I'm only doing 10-20 bags of cellulose can I just distribute it by hand? I'd rather not deal with the hassle of getting a blower (I know its a free rental, but still). I imagine that I could fluff up the insulation in a big plastic tub in the attic, then use a bucket to throw it where I need it. Other than taking longer than with a blower, any problem with this approach?
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Old 07-14-2008, 09:11 AM   #38
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When I finish the radiant barrier, I'm thinking of adding a bit more insulation to the attic. Any thoughts on the following questions:

1) Is there any problem with adding a few inches of cellulose insulation on top of ~10 inches of rockwool insulation?
Nope, absolutely no problem. In fact, (as noted previously) the cellulose will do a lot to increase the insulating value of your already existing insulation by stopping the flow-through convective losses that rock wool and fiberglass are subject to on very cold days.

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2) I'd only target a few areas of the roof for extra insulation, if I'm only doing 10-20 bags of cellulose can I just distribute it by hand? I'd rather not deal with the hassle of getting a blower (I know its a free rental, but still). I imagine that I could fluff up the insulation in a big plastic tub in the attic, then use a bucket to throw it where I need it. Other than taking longer than with a blower, any problem with this approach?
I think you'll be sorry. The blower is easy to handle, the hose is long enough to allow the unit to be placed outside, and the blower does the job of moving the insulation up to you. It also fluffs it up and distributes it more evenly than you can do it by hand. Also, you can shoot the stuff a good distance with the blower, which will save you from having to crab your way all over the attic. Probably not a big deal unless your roof pitch is low.

The job goes very quickly with the blower (it digests a bag in a couple of minutes). It's a good, satisfying project. Wear a good dust mask (N95--with an exhale valve. Spend the 5 bucks). I think you'll find using the blower (if you've got a helper) a lot simpler than hoofing those bags up to the attic and then trying to hand spread the cellulose. But--it's possible to do it that way. Some folks do it.

If I were going to do this by hand, I'd probably use unfaced fiberglass batts. And I hate those things/that stuff.
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Old 07-14-2008, 09:13 AM   #39
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I only tried doing one bag of cellulose by hand, if that helps.

Ends up chunky, you dont get as much coverage, and you'll be covered with the stuff.

If you get a blower, make sure you dont block any vents or cover any recessed lighting thats not rated to be covered with insulation.
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Old 07-14-2008, 09:45 AM   #40
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That is a neat system and would work in my garage (which currently is uninsulated). Wonder if I can find some scrap metal strapping to make them myself (for less than the $129)?
I think the cost of the metal will pale in comparison to the cost of the wood!

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Do pay note to yet another possible unintended consequence...in many cases the trussing systems used in homes are not engineered to hold uneven weight bearing loads pushing down in the middle of the system...in particular in unsupported garage ceilings. They're made to hold a roof UP.
In my old neighborhood it was very popular to put in the stairs and the full storage floor and fill it up with stuff that people will never use again. Almost all of these had a bowed roof over the garage.
We'll have to see what happens with our hurricane-strength trusses. I think our attic storage is living on borrowed time with all the things that are propped between the trusses. I know that in 20 years I'm not gonna want to shimmy across the trusses.

It's an interesting thought about spending the $$ to improve the storage of crap. Some of it is valuable crap-- like spare parts for our 19-year-old stove scavenged from all the ones put on the street a few years ago. But otherwise this is about the only way that we're going to get a good look at all of our stuff. Spouse has floor rugs from houses that she lived in 20 years ago but heaven forfend that we should get rid of them-- we might need them someday! Once we price out the project it might make more sense to actually divest ourselves.

The most popular stupid truss trick around here was replacing shake or composition-shingle roofs with ceramic tile without installing additional trusses. You can actually see the waves on some roofs.
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