Maybe this radiant energy stuff does not belong here. I started it by trying to give the original poster an idea for room cooling, but it ended up clogging up the original poster's question. Maybe this side track should get moved to its own post?
Foil might really have some effect in RV windows where the sun shines in. However the sun doesn't shine in my attic and what good would superior reflectivity be after a layer of dust dulls the sheen. Just like the EdenPure heaters there may be a sliver of truth there somewhere but is there enough benefit to outweigh the cost?
Check out some of the DOE articles as well as those from Cal Tech, MIT and others. You'll have to dig around a bit for them.
Also note that the "sheen" does not matter. You can put either side as the reflecting side except mylar-foil which is coated on one side. It's marked so you won't go upside down.
Once I read a study about dust on the material and it was inconclusive. I suppose if it is a flat-on-floor installation, you'd have to vacuum it once in a great while. I have some that has been flat in an attic for over 25 years and there is no dust on it. (Don't remember ever seeing dust, so I checked when I read your post, Eddie_T) Attic ventilation currents must vacuum it out by convection before it settles.
Quote From Above Post:
"The sun doesn't shine in my attic"
The
visible light from the sun is certainly not in your attic, but the
energy is, thanks to radiation and conduction of energy.
The sun
radiates energy onto the roofing materials. All the layers of the roof
conduct energy to each other. The bottom layer (in the attic)
radiates energy into the attic.
We want to "bounce" it back out before it heats the ceiling materials for the room below.
Aluminum can "bounce" 97% of it out.
You can put the aluminum across the floor or across the bottoms of the rafters for a lower temperature attic. (Follow ventilation & perforation guidelines no matter the meothod)
That is how your house heats up on a sunny day. The radiant energy strikes your roof and the layers of roofing material conduct into each other until reaching the bottom layer. The bottom layer then radiates the energy into the attic space.
The whole thing begins again when the energy in the attic radiates to the ceiling's mass insulation and building materials. The radiant barrier's job is to keep the ceiling material cool so they don't radiate heat into the rooms below. When it is saturated, it saturates the ceiling materials and heat radiates from the ceiling into the room below.
In winter, it works backwards. The barrier's job is to block emission from the ceiling's insulation & building materials. Aluminum blocks all but 3% of emitted energy.
To Illustrate Radiant Energy Where The Sun Does Not Shine With An Experiment:
Take two cardboard boxes that are the same color.
Place one upside down on the pavement or other flat surface where the sun
IS shining
Place the other upside down on pavement or other flat surface where the sun
IS NOT shining
After about 4 or 5 minutes, lift an edge of a box and stick you hand under it.
When you do the second box, you will feel a tremendous temperature difference, yet no visible sunlight shone into the box.
You can also do the same experiment by using one box with pure aluminum inside the lid and one without. Put both in the sun & check the temperature difference inside.
Then...
Repeat but with a heat source inside each box. Check the temperature on the outside of the box. The heat source inside experiment illustrates that radiant barriers are not only high reflectors, they are low emitters.
Another Example:
I have two skylights 5 feet apart. They are on the same side of the same pitched roof. Both face south. Inside, they sit on top of curbs, forming a box. On one, I have a white shade which is at the bottom of the curb box, about 6" below the glass. On the other, a radiant barrier home made shade installed the same as the white shade window.
The difference in temperature on the floor below the windows is remarkable.
Fun Fact: Aluminum is not only a 97% efficient at reflecting and emitting radiant energy, but it is also a very good conductor. In the above skylight example, if one were to hold a hand just below the aluminum shade, you'd feel not heat (radiant energy) If you touch the shade, it's hot (conduction of energy).
The Magic of Physics!
Paul
PS: The question of cost versus benefit in the quote above is easy to answer for radiant barrier. I live in a hot-in-summer and cold-in-winter climate (Detroit). Immediately after installing the barrier over only the first two rooms, our next air conditioning power use dropped considerably, even though the days were much hotter the subsequent month. The temperature in the rooms below where I was working dropped noticeably even before I was done installing the barrier.
In some hot climates, radiant barrier is often accepted as the only insulation required. (Once mass insulation is saturated with radiant energy, it's not useful. The energy is radiated or convected to the space it was protecting.)
Our winter heating gas usage also dropped dramatically, but 4 rooms were done by winter. I studied "Heating Degree Days" from the previous years' gas bills versus the post-foil bills. It was colder in the post-foil year- the one with the lower costs. One of my brothers laid perforated across his attic floor. He said his gas energy use dropped enough to pay for the materials in 2.5 months His summer temperatures in the living areas dropped. His cost for a 4,700 ft-sq attic = $760.00. Time = 2 Hours.
Is Edenpure one of those heaters that claims to get more BTU than the others for the same wattage? Unless the laws of physics have changed since I was in school, watt can only yield 3.41221 BTU no matter how overpriced the heater is.
