How To Install Radiant Barrier Foil Insulation - FlatTop
Installation Method for HIGH PITCHED roofs.
The "FlatTop" method is the ideal radiant barrier installation method
for both high pitch-hard to reach attics and standard type attics. The
basic system creates a "false ceiling" that will act as flat surface
to hold radiant barrier foil across the top part of the attic. This makes
access within easy reach for even the tallest attics. You do not need
to create any ventilation and can essentially create a "room within the
attic" made of radiant barrier reflective foil. Combined with proper
attic ventilation, radiant heat will be reflected back towards the roof.
Ventilation from the soffits to the ridge (top area) will allow the heat
to be channeled out. Even on the hottest day, the space within the foil
cavity should be just a few degrees above outside temperature.
By creating the foil room inside
the attic the ducts and the insulation will be protected and significantly
reduce the amount of heat gain into the home.
Radiant Barrier FlatTop Method - Create a foil room with
attic ventilation running outside the envelope.
Finished attic using the radiant barrier flattop method.
Some form of grid must be made to support foil accross attic
span. This can be done with metal straps, nylon straps or long pieces of
wood.
This picture shows the strap accross the attic. The foil is pulled on
top of straps.
The best method to create the ceiling grid is to use metal
duct strapping. This is usually available from home improvement stores
or local air conditioning supply companies.
The straps can either be put over or under the foil on the slopes.
Use 1/4" hex screws to attach strapping on roof rafters.
A nut driver with a magnetic tip will hold the screws while you hold the
strap in place.
Use one screw to hold in place, then use a couple more screws
to "tighten" the straps. The metal straps can easily span 20-30
ft or more.
Close up picture of metal duct strapping holding up radiant
barrier foil insulation
Use high quality foil tape (UL181) to tape the foil to the straps. Have
a helper pull the foil tight across the top of the straps while taping.
This will give a "tight" appearance.
You can leave about 12-24 inches on the bottom of the foil to creat a
"skirt". This will create a channel for the air to flow around the foil
between the roof rafters to the top part of the attic where it will be
exhausted.
This picture shows the "skirt" on top of the insulation. The
RED line shows how the foil is folded back. This works well when you add
more insulation
after installing radiant barrier foil. The skirt acts as a "backstop" to
keep insulation from being blown into the soffits. You will loose the radiant
barrier qualities ONLY where you put additional insulation on TOP of the
foil.
Finished attic using the FlatTop method. Notice
there are no vents for attic air to flow through. Vents in the foil are
not needed if you have a clear pathway for air to flow from
the soffits to
the top
of
the
attic. Once the air is in the top of the attic it should be exhausted by
wind turbines, ridge vents, static vents or attic fans. You should NOT
MIX attic exhaust vent types. You want air to come in the bottom and out
the top. If you mix vents this is what can happen. Example: Combining wind
turbines and ridge vents. When the wind blows it will create a low pressure
for air to be pulled out of the wind turbines. Since the ridge vent is
closer than the soffit vents, it will pull air into the ridge vents (the
ridge vents will act as intake vents) and minimize cool air coming in the
bottom of the attic. All bathroom and kitchen vents should be vented past
the foil cavity and ideally out of the attic.
