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Radiant Attic Barriers    (Eligible for 30% Energy Tax Credit)
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Research done by the Florida Solar Energy Center (FSEC) shows an attic radiant barrier
can save 10% to 15% on the heating and cooling portion of electricity costs in a typical
Florida home. This would translate to annual savings of 3% to 6% on the entire electric
bill.

The installation of an attic barrier is relatively simple making it an ideal DIY project.
Basically you have two installation choices: Over the attic floor, or between the rafters
supporting the roof. Of the two, over the attic floor is the easiest. Simply roll out the
sheets, shiny side up, from one end of the attic to the other overlapping the sheets as
you go along.

No stapling is required because you want the reflective sheets to float freely above the
insulation allowing an air space underneath the barrier as well as above. If the barrier is
compressed against the underlying layer of insulation it will lose its effectiveness.

One concern frequently voiced with "over the attic floor" installations is dust
accumulating on the surface of the barrier and degrading its effectiveness over time.
But
some attics just aren't as dusty as others; it's really up to you.


In any case, take a minute to spend some quality time with your attic and have a look
around. You may have forgotten how much stuff is up there rendering an over the floor
installation ineffective as well as impractical.

If you decide to proceed with the over the floor application
make sure you purchase a
perforated barrier specially designed to allow moisture to pass through, and be careful
not to cover kitchen and bathroom vents or recessed lights.
Radiant attic barrier installation
Radiant attic barrier installation
When you install the barrier between, or along the rafters, the gable ends should also
be covered. If the attic roof extends over the garage, the Dept. of Energy recommends
extending the barrier by 8 feet over the garage to achieve the same effect as covering
the gable end. However, covering the gable ends is not necessary if the barrier is
installed over the attic floor.

Radiant barrier foil is not insulation per se and therefore has no inherent 'R' value rating.

Prices for radiant barriers vary by function and durability (tensile strength). Perforated
barriers, and high tensile strength barriers (80.4 lb/in) both sell for around $0.15 per
square foot. Standard strength barriers (14.1 lb/in) are slightly less at $0.12 per square
foot.

The cost an attic barrier can be further reduced with the new Energy Tax Credits. The
maximum credit is now 30% of the cost of the material up to $1,500. Installation is not
covered.
The second installation option is with
the reflective side facing down from
the rafters.

Diagram #1 illustrates between the
rafters. Diagram #2 illustrates rafter
to rafter horizontally across the attic.
  

Of the two, across the rafters would
obviously be easier to implement.

In either case make sure the shiny
surface is facing down towards the
attic floor.

Now you have to be asking yourself,
"How can the foil side work if it is
facing downwards?"

It may seem counterintuitive, but a
radiant barrier works just as well
with the reflective side facing toward
the roof or away from it.

This is because a radiant barrier not
only REFLECTS INFRARED ENERGY, it
also does not EMIT RADIANT HEAT.

These two qualities are known as
Reflectivity and Emissivity and work
together as one; not exclusive of
each other.
Diagram #1    Between the rafters vertical installation
Diagram #2    Rafter to rafter horizontal installation
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The attic radiant barrier was originally
designed as a means to reduce attic heat in
southern climates where air conditioning is
prevalent.

Lowering the temperature in your attic
suppresses heat gain on lower floors and in
turn reduces the cooling load on the air
conditioning system.

A reduction in the cooling load means the air
conditioner requires less energy to provide
the same amount of cooling; saving you
money.
Radiant Foil Attic Barrier