Q.
What is an R-value?
A.
Manufacturers usually represent the energy efficiency of windows
in terms of their R-values (you may also see U-values reported).
R stands for the resistance to heat flow. If a window or patio
door has a high R-value, it will lose less heated (or cooled air)
than one with a lower R-value. Usually, window R-values range
from 0.9 to 3.0 but exceptions do exist. The U.S. Department of
Energy’s ENERGY STAR® program, as well as other organizations
interested in window/fenestration quality issues use R and U values
to report results.
Q. What is a U-value?
A.
U values are a measure of the conductance of heat, that is, how
a material draws heat in. For example, in your search for the
best window you might compare the U-values of fiber glass frames
versus aluminum frames for conductivity. If a window’s U-value
is low, it will lose less heat than one with a higher U (conductivity)
value.
Q. What factors can affect the R-value of a window?
A. The
(1) type of glazing material, (2) the number of layers of glass,
(3) the size of the air space between the layers of glass, and
(4) the thermal resistance (R-value) or conductivity (U-value)
of the frame and of the spacer materials. You will want windows
and doors with thermally improved spacers that can intercept and
absorb the heat that may have been conducted by the spacer material.
COMFORT LINE FIBERFRAME Windows & Doors have thermally improved
spacers. In addition, the tightness of the (5) installation can
affect an R-value. Choosing an experienced, recommended installer
who works to a manufacturers installation recommendations is very
important.
Q. What is Low-E glass?
A.
Low-emissivity — low-E — glass has a special surface
coating to reduce heat transfer back through the window. These
coatings can reflect from 40% to 70% of the heat that is normally
transmitted through clear glass but still allow the full amount
of light to pass through. The view is neither tinted to a perceptive
degree nor is it distorted. Low-E coatings are not the same as
reflective film applications.
Q. What are “layers” of glass in a window or door?
A. Standard
single-pane glass is one layer of glass. This is what has been
used traditionally in homes for hundreds of years. However, it
has very little insulating value — approximately R-1. Windows
over the last two decades have encouraged replacing the use of
single-pane windows with double or triple glazing to increase
the window’s ability to resist heat flow (produces higher
R-values).
Q. What are air spaces?
A. Standard
single-pane glass is one layer of glass and therefore does not
create an air space except inside your home. Double glazing produces
an air space between each of the panes of glass. That air space
can be “just air” or can be filled with argon or krypton
gas to improve resistance to heat flow since inert gases transfer
less heat than air. The width of the air space between each pane
is important because air space affects resistance. The space considered
most effective between each pane of glass is usually between 1/2”
and 5/8”.
Q. Why fiber glass for the frame of windows and doors?
A. Inner
Stability:
Fiber glass exhibits the least amount of expansion and contraction
of any fenestration framing material. When there is expansion
and contraction, fiber glass is most like its component glass
glazing and, therefore, expands and contracts similarly.
Dimensional Stability: Fiber glass parts hold their forms
and shapes under sever mechanical and environmental stresses.
Test Results: Exceptional test results for fiber glass
performance in the areas of water leakage, air leakage, wind load
and forced entry.
Durability: Fiber glass is practically impervious to harsh
atmospheric conditions and can’t corrode. Complete
Performance: Fiber glass frames incorporate the best characteristics
of all other materials and offers more in important areas of stability,
energy conservation and maintenance over the long term.
Q. What is the process like that produces fiber glass for windows
and doors?
A. The
process is called pultrusion. This
process produces continuous strands of strong glass fiber rovings
and glass fiber mats impregnated with resin. This material
is drawn through a heated steel die that thermally sets the shape
of the finished stock. The end product is a thermoset fiber glass.
Very high strengths are possible due the high glass concentration
and orientation of glass fiber rovings and mats parallel and perpendicular
to the length of the material being drawn through the thermoset
die. High concentrations created in proprietary ComfortLine formulas
produce high grades of the end fiber glass product. In the thermoset
process heat is used to cause a chemical reaction that binds and
bonds all of the material into a set shape to form the finished
window lineal or other part. Once the materials are cured in this
way they cannot be reformed; hence,the process is irreversible.
The result is a very strong material impervious to almost all
exterior elemental materials that might attack it.
