[The Rooster]

Theoretically, the aluminum foil dosen't need to be on the outside of the house. Most of the heat absorbed by your house through the roof from the sun is not through the conductunce of heat from the roof downward into the home, it's the invisible ultraviolet radiation that passes right through the roof into the house.

Using white paint will reflect a lot of the visible light and lower the surface temperature of the roof, and through conductance (or lack thereof), somewhat lower the temp in the attic, but it won't stop any of the infrared light passing right through.

Ever see an infrared camera work? They see right through walls, doors, and can see engine heat through car hoods. Space Telescopes take photographs of stars through dusty, gassy nebulae with ultraviolet cameras. The reason it works is because the energy in that wavelengh, passes through most solids, liquids and gasses with ease.

Aluminum has the property of reflecting roughly 97% of all radiant (ultraviolet in this example) energy, so your idea is very sound, just impractical as it'll be subject to the elements and pissy neighbors.

Three types of heat;

Conductance: This is how heat travels through solids. Your walls, studs, joists and even fiberglass insulation are all conductors of heat. (Fiberglass insulation just happens to be a very, very poor conductor, which is why it works...for conductance.) However, fiberglass is a very poor insulator against radiant heat...which is what you mainly need to insulate against.

Convection: This is how heat travels through a liquid or gas. Heat rises for this reason: As a liquid or gas is heated, it expands and thus becomes "lighter" and moves to the top of the medium (air/water/whatever)

Radiation: This is in the form of invisible light. Every object not at absolute zero radiates heat in this fassion. Hotter objects radiate more heat (Like the sun, a lightbulb, a heater, fireplace, etc)

(Technically radiant energy has no heat, it must be absorbed by an object, then that object gives off the heat...this is how heat gets from the sun, through the frigid vaccuum of space to warm the planet...the space between the sun and earth is cold, but there is a lot of energy in the form of radiation (light of variying wavelenghts) from here to the sun.)

So since what we really need to block from the sun is radiation, though it may be easier, putting aluminum foil on the outside of the house isn't necessary. I propose this idea...if you can somehow find a way to apply it in your tiny attic;

Staple your aluminum, shiny side out, to pieces of cardboard. Do this to both sides, as in the winter time, you'll also retian the radiant heat you create inside the home and reflect that back down into your house.

Then, using 2" nails, hammer your cardboard into the underside of your attics joists, but hammer the nails in only 1", leaving the cardboard/aluminum foil suspended and creating about a 1" air gap. For better performance, find a way to add additional layers that don't touch each other.

It's important that the foil not touch anything but air as much as possible. From what I read, it'll need a minimum of 3/4" of air space to work, and the more, the better. Also the single aluminum panel wont do anything for convection, however, a few layers an inch apart can reduce most of the heat loss through convection.

You can buy products that are already made for this purpose, but cardboard and aluminum foil is way cheaper, if that's the route you want to go.