Anybody install a radiant barrier?

[il d00d]

We're getting into unbearably hot season here in Houston, so I am looking at my home cooling options.  I know there are some construction folks here on the board, so I am looking to find if a DIY radiant barrier would one, help noticeably, and two whether this would be a fools errand/honeydo for me to undertake.  In other words, if you have done this before, would you do it again or pay someone to do it?
Looks like there is a new tax credit for bubble insulation, so score one for cost.   I am looking to install this on the underside of my roof, by the way, so that heat it reflected before it hits my ductwork.
Any info on estimated cost, time, materials and tools would be appreciated     Thanks in advance...

[rgramjet]

http://www.ornl.gov/sci/roofs+walls/radiant/index.html

This link has some good Radiant barrier info.  I have a friend that just built a house and they sprayed an aluminized coating to the underside of his roof sheathing....Ill ask him what he thinks of it.

Good luck!

[il d00d]

I like the sound of spraying.  That sounds like a lot less time in a hazmat suit, in an attic, in Texas, in Summer.  Thanks,  lemme know what your friend thinks

[Sinister]

il d00d:  Is your roof already insulated?  If so, I would (along with the radiant barrier, which can't hurt) insulate my ductwork and then vent my attic space. 

Good luck.

[il d00d]

Well, the ceiling is insulated.    The area between the joists that hold up the roof have no insulation, which is typical for houses here.  Duct work is also insulated, but it is in the crawl space in the attic, so it is cooking in the heat up there.  This is also typical for houses here, and I admit it doesn't make much sense.  One of the radiant barrier suppliers likens this to making ice cream in an oven - sounds about right, come July and August.
After doing some reading, I have come to understand that insulation is an air flow barrier - it prevents air from the respective areas from mixing when you don't want them to.  The radiant barrier, in theory does not affect air flow, but how much outside heat transfers into the attic to begin with.  I do have plenty of venting - all around the eaves, and at the top of the roof line.  I think my bases are covered there.  Now, I think I will be set if I can just control how hot my attic gets.

One other thing I was looking at was windows.  This is a 50+ year-old house and I have windows that might as well be perforated.  Does anyone have any FHE installing more efficient windows?  In this case, since they are so goddamn expensive, I would want to know about how long I can expect them to take for them to pay for themselves in energy savings.

[Scottish]

I have no experience with this radiant barrier. However it seems to me that if your roof is that hot already, and this stuff works as advertised and actually does reflect heat back out through the subroof and shingles with some efficency. Perhaps you should be concerned with your roofing material. Now I know it wouldn't pass code if it could create cumbustable temps. But if you have asphault shingles it would seem the extra "radiated back from inside" heat could decrease the life of them, perhaps even drastically. If you have a tiled roof I don't think this would be a concern. But it is something to think about. I'd look for some early customers and see if there are any complaints.

[Ddan]

I have no experience with this radiant barrier. However it seems to me that if your roof is that hot already, and this stuff works as advertised and actually does reflect heat back out through the subroof and shingles with some efficency. Perhaps you should be concerned with your roofing material. Now I know it wouldn't pass code if it could create cumbustable temps. But if you have asphault shingles it would seem the extra "radiated back from inside" heat could decrease the life of them, perhaps even drastically. If you have a tiled roof I don't think this would be a concern. But it is something to think about. I'd look for some early customers and see if there are any complaints.

The radiant barrier won't increase the temps on the roof,  it will just restrict the flow of heat further into the space.

If the house is already vented at the soffit and ridge, anything you can do to increase the chimney effect will help.  A reflective membrane along the bottom of the rafters should help pull air in the soffit vent, along the underside of the roof deck and exhaust it out the ridge vent.  Moving more air is better so gable vents could also be part of the fix.

[rgramjet]

A powered attic ventilator will substantially reduce the heat build up.  Maybe one in each crawl space?  These are often thermostatically controlled.  Probably the least expensive solution.

[hypurone]

Firstly, DO THE WINDOWS!! Dual pane vinyl units are the shit and WILL make a huge difference, been there done that. I would recommend getting the Low-E coating for all windows that follow the suns' path.

As for the attic thing, I am having a product called Eagle Shield installed this Saturday. It goes down over your existing insulation. It is a two sided thermal reflective barrier that can breathe for moisture evap.

They had a really cool demo box with 2 heat lamps that had your normal attic setup on one side and the addition of the product on the other. They fired it up and within 10 mins the diff in temp was ridiculous. I put my hand up to the heat lamp and got a feel for the heat, then put some of this stuff between my hand and the lamp and couldn't feel a damn thing. They are based out of Texas or make the stuff there or something. Just look em up on the interwebs.

I would def pay someone to do any kind of insulation or work in the attic around insulation, that shit is nasty.

I am getting a 1800.00 tax credit (direct and full. not a percentage based on this or that bullshit) It depends on the size of the install. They have an 18 month same as cash payment plan too!!   

[rgramjet]

If you dont have the $$ for new windows right now, try heavy insulated curtains.  They block the radiant heat from coming through.  Just keep those suckers closed!

[NAKID]

In my house in Phoenix, I put in a solar powered attic fan. Worked well. Never had to think about it. Didn't cost me anything to run it and it was rated at 1800cu-ft/min...

[hypurone]

In my house in Phoenix, I put in a solar powered attic fan. Worked well. Never had to think about it. Didn't cost me anything to run it and it was rated at 1800cu-ft/min...

+1 I'm getting one of those too. Forgot to mention that part.   

[Sinister]

Well, the ceiling is insulated.    The area between the joists that hold up the roof have no insulation, which is typical for houses here.  Duct work is also insulated, but it is in the crawl space in the attic, so it is cooking in the heat up there.  ...I do have plenty of venting - all around the eaves, and at the top of the roof line.  I think my bases are covered there.  Now, I think I will be set if I can just control how hot my attic gets.

I would insulate your roof joist bays, and add an active ventilation component to your attic (a fan).  This is a cheap way to partially "condition" the attic space; somebody mentioned a fan out the gable, which is a good idea.  The passive venting is okay, but isn't sufficient.