Which side of insulation goes down?
James Olson
Updated on April 27, 2026
Thereof, which side does the foil go on insulation?
Foil insulation underlayment is recommended under a metal roof, and in most cases, the shiny side should be facing up, but there's a catch. Foil insulation is a radiant barrier, and it works by reflecting heat from the metal, but for it to do its job, there has to be a layer of air between the roofing and the foil.
Furthermore, how should insulation be installed? Gently push the insulation into the cavity, but do not force it or compress it, which reduces its insulating value. The insulation should fit snugly into the cavity with no gaps or spaces, filling it from top to bottom (or end to end). Fold out the paper flange along one side of the insulation.
Keeping this in view, what happens if insulation is installed backwards?
So if it is installed upside down, the paper moisture barrier can actually keep moisture in-between the paper and the sub-flooring. This can lead to mold issues, as well as structural deterioration. Also, the paper is flammable so not properly installing it can create a fire hazard.
Does faced insulation need to be covered?
To satisfy building codes, most faced insulation must be covered with half-inch-thick wallboard or other code-approved material to reduce the chances of its igniting during a fire. There is a type of faced insulation approved for exposed installations.
Related Question Answers
What side does vapor barrier go on insulation?
Vapor barriers are sheets of plastic or other material placed on one side of insulation sheets. This barrier is meant to keep moisture from getting to the insulation in the walls and ceilings, and it is required by building codes when insulating most houses. In any case, the vapor barrier must point to the warm side.Does foil insulation work?
This works well for most insulation materials, because conduction is the main way they prevent the movement of heat. Foil insulation works slightly differently, however. It means that foil insulation is going to have a higher U-value, but may well perform better than expected in the real world.Does foil bubble wrap insulation work?
(The bubble wrap layer is unnecessary, since it adds cost to the material without adding any useful thermal performance.) Since the main benefit from foil-faced bubble wrap is due to its radiant-barrier facing, the product is basically worthless unless it faces an air space.Does bubble foil insulation work?
The main one in the latter category is foil-faced bubble wrap sold as insulation. Foil-faced bubble wrap is a radiant barrier. It's not insulation. A radiant barrier reduces heat transfer by radiation and has two excellent applications in homes.What does the foil do on insulation boards?
Foil covering is claimed to add to the insulation value where the board faces onto an air gap. When the board is covered on both sides the foil adds no value. Almost all of the boards were perfectly fine for sticking in a roof.How do you install reflective foam insulation?
Installation Summary:- Install unfaced mass insulation between rafters ensuring a minimum of 1" ventilation space between the mass insulation and the underside of the roof decking.
- Unroll and staple reflective insulation to the under side of the rafters.
- Seal all seams with aluminum foil tape.