Shielding neutrons works best when you slow them down and then capture them. Neutrons don’t have charge, so they don’t interact strongly with heavy materials the way gamma rays do. The most effective way to slow a neutron is to collide it with a nucleus that has a similar mass to the neutron—that’s a proton. Hydrogen nuclei are basically protons, so a neutron loses a large fraction of its energy in each elastic collision with hydrogen. A series of such collisions rapidly slows the neutron to thermal energies. Once neutrons are slowed (thermalized), many materials with high neutron absorption at these energies can capture them, removing the neutrons from the environment. Hydrogen-rich materials provide both roles—moderation and some capture—making them highly effective neutron shields. This is why substances like polyethylene or water are preferred for neutron shielding, in contrast to heavy metals like lead (which are great for gamma shielding but not for slowing neutrons) or plain aluminum or concrete, which are less efficient moderators.

Thermography shows surface temperatures: hot areas on the image indicate where heat is entering or escaping. When you see a lot of thermal energy around the windows but not at the roof, it points to the windows being weak points for heat transfer. That means the windows are not energy efficient, letting inside heat escape, while the roof is better insulated and not contributing to heat loss. So the best-supported conclusion is that the windows are not energy efficient, but the roof is.

Foam is typically used as a thermal insulator because its cellular structure traps a lot of air, and air is a poor conductor of heat. The many tiny air pockets disrupt heat flow by both conduction and convection, giving foam a very low thermal conductivity. That combination makes foam excellent at slowing heat transfer, which is exactly what an insulator should do in walls, appliances, and coolers. Copper conducts heat readily, so it’s not an insulator. Glass provides more resistance than metals but doesn’t match foam’s insulating performance for bulk insulation. Ceramics can withstand high temperatures and can insulate in some contexts, but for everyday insulation, the lightweight, gas-filled cells of foam make it the more effective choice.

Frequency in the electromagnetic spectrum increases from microwaves up through visible light, then X-rays, and finally gamma rays. Since energy per photon scales with frequency (E = h f), higher frequency means higher energy. Among these four, microwaves have the lowest frequency, visible light is higher, X-rays higher still, and gamma rays the highest. So the increasing-frequency sequence is microwaves, visible light, X-rays, gamma rays.