How does insulation work?

Question

I've been helping my dad sheet rock our basement and we needed to replace some insulation. Some insulation had aluminium foil facing the "living space", and others had brown paper.

How does insulation help keep the heat inside our houses?

Answer 1

The aluminum foil and the brown paper have the same purpose: condensation barrier.

Insulation helps keep heat from being conducted through the walls by preventing the air in the wall from moving.  Air is a poor conductor of heat when it doesn't move.  Air is fairly good at conducting heat when it moves.  That is why you car's radiator has a fan behind it.

Answer 2

The insulation you are referring to is pretty simple to understand. It is thickness dependent like the blanket on your bed. It works by making it hard for heat to conduct through. It does not trap air (cheap air filters are made from fibers of glass just like insulation). It works giving heat a lot of mass to soak into. It basically absorbs the heat and stores it so it can not move from one side through to the other very quickly.

The kraft paper on one side is used as a moisture barrier and to help hold it in place when installed. It gives installers something to staple to the wall or studs. The foil facing is used again as a moisture barrier but is more useful as a radiant barrier. It works by reflecting heat much as a mirror reflects light. This means that heat has a much harder time getting into the insulation which in turn, keeps the insulation from working so hard.

The kraft paper is now considered a fire hazard in most areas and is against most fire codes now a days. It should be installed so that it does no have direct contact with an open airspace. The foil facing should face the airspace and is almost always rated as a class a fire rating. In a basement wall, you probably don't have an airspace as you would in an attic so I wouldn't worry about fire ratings too much. If the insulation will be totally enclosed after the wall is sheet rocked, then you can use either the kraft paper faced or unfaced insulation. I am from the Dallas area though and don't have a lot of experience with basements in general.

Typically, the thicker the insulation, the higher the R-Value.

Answer 3

the foil acted just like how aluminum foil works keeps the heat to the inside of the house, the brown paper was used as a heat sink i believe. Anyways insulation is like cotton candy tons of open spaces in it the air travels into these open space s and is traped when you place the new plastic coatin and drywall on. That trapped air becomes dead air shich act like a heat sink to keep either the heat in and to take it out during the warmer months

(take physics classes they have a little blurb on thremal transfer and heat conduction it out ines it in there)