Should silver side of roof insulation go up or down?

Author: Elnora Reilly  |  Last update: Thursday, October 30, 2025

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.

Which way does silver insulation go?

No air space means no thermal value. The reflective side must be facing downwards when in roofs, upwards when installed underneath a floor and inwards when installed in walls.

Which side does the foil go on insulation?

Regardless of the method, the foil should be placed on the warm side of the room.

Which side of the roof insulation?

The fibre side is laid in contact with the ceiling. If you were creating a warm attic by insulating between rafters, then you would want little temperature difference between the inside insulation surface and the room. So the foil side should face the slates and the fibre side the attic space.

Should radiant barrier foil face up or down?

The shinier the foil, the better it will work--but the shiny side should be installed facing down toward the attic. Don't just lay radiant barrier material overtop floor insulation either, or it won't work. There should be an air gap on both sides--so attach it to the bottom of the roof rafters.

Warm roofs, the biggest mistake I see when doing a roof inspection.

Which way does the face on insulation go?

(The general rule for insulation is that the facing always goes toward the conditioned space.) The second layer of insulation should be unfaced so that moisture doesn't collect between the layers.

Which side of roof membrane goes up?

With most brands of membrane, the printed side will be facing outwards. However, always ensure to double-check any installation instructions provided by the manufacturer. Draping the breathable roof membrane instead of laying it taught ensures that the moisture does not run off quickly.

How to install foil faced insulation?

A Step-by-Step Guide How to Install Foil Faced Insulation Board
  1. Step 1: Measure the Area. ...
  2. Step 2: Cut the Insulation Board. ...
  3. Step 3: Apply Adhesive. ...
  4. Step 4: Install the Insulation Board. ...
  5. Step 5: Secure the Insulation Board. ...
  6. Step 6: Repeat for Additional Boards. ...
  7. Step 7: Clean Up. ...
  8. Step 8: Enjoy the Benefits.

Should attic insulation face up or down?

When installing fiberglass insulation in your home, be sure to put the paper or foil vapor barrier facing toward the heated and cooled living area of the home (down in attics, up under floors, in on walls) to prevent condensation from occurring.

Where do you put reflective foil insulation?

Where To Use Foil Insulation
  1. Pole barns that house animals.
  2. Workshops and garages.
  3. Storage units.
  4. Equipment sheds.
  5. Recreational vehicles like motorhomes or campervans.
  6. Transportation trucks.
  7. Cargo liners.
  8. Inside roof trusses or rafters.

Which way up does silver foil go?

Quite simply, it doesn't matter what side of aluminum folk you use. Either is acceptable. Since the exact same material makes up both sides, they will perform precisely the same way. The only difference is aesthetic.

Which way should the foil face?

Foil has a shiny side and a dull side because of how it is manufactured. Unless you are using foil that's labeled non-stick, which does have a non-stick side, it does not matter what side you use. Both the shiny and dull sides can be used the same way to cook, freeze, and store food.

Which direction does insulation go on a roof?

Start laying the insulation furthest away from the access hole then work your way back from the outside edges in. Install the insulation between the ceiling joists and butt pieces together at all joins.

Which way does the membrane go?

There are two sides to Thermafleece Breather Membrane, a black side and a grey side. On a wall: the black side faces outwards, the grey side faces towards the inside of the building. On a floor: the black side faces the ground. In a roof: the black side faces the sky.

What is the order of installation for a membrane roof?

Any residual from an old roof should either be removed or over boarded as this will adversely affect the performance of the EPDM rubber membrane.
  • Install Drip Batten. ...
  • Install Drip Edge Trim. ...
  • Chase out Wall Upstand. ...
  • Relax the Rubber Membrane. ...
  • Fold Membrane Halfway. ...
  • Apply Water Based Adhesive. ...
  • Sweep EPDM Membrane.

Does it matter which side of foil is shiny?

Either side of the foil can be used to place food on, unless you are using Bacofoil® The Non-Stick Kitchen Foil, then the food should be placed on the non shiny side side, as this is the side that is coated with a food safe silicon to stop food from sticking.

Does foil roof insulation work?

Foil roof insulation has excellent thermal properties. The reflective layers of the foil efficiently block radiant heat transfer, reducing the amount that enters or escapes the building through the roof.

Which way does foil board go?

Install the Foilboard® GREEN rigid insulation panel to the external face of the studwork, ensuring the anti-glare side is facing out, measure the area you require. Tape all penetrations, joints and gaps using the Foilboard® green PVC tape, ensuring the stop of cold / hot air transfer.

Does foil insulation need an air gap?

Foil insulation is particularly effective at reflecting radiant heat, which can be beneficial in both summer and winter. However, in order for it to work effectively, there needs to be an air gap between the foil layer and the surface it's installed on.

Which side of the insulation faces out?

The facing refers to the paper or foil side of insulation products. Always install the facing toward the heated or air-conditioned part of your home. This creates a vapor barrier that prevents moisture from passing through and getting trapped in the insulation.

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