Green Means
Windows that Perform
By Shannon Scott
Nothing beats a room with a
view… unless it’s a room with two different views, through responsibly manufactured,
insulated, heat reflective windows.
When building or
remodeling, selecting
windows will be one of the most important, energy saving and esthetically
pleasing decisions you make. High performance windows help keep interiors
warmer in winter and cooler in summer. There’s
no longer any reason to limit the amount of glass because of excessive heat
loss or gain. So enjoy the views!
The best windows are low
thermal emissivity (Low-E) coated, gas-filled, multi-paned, made with solid
framing materials. Look for Sustainable Forest Initiative (SFI) or Forest
Stewardship Council (FSC) labels, which mean wood was sustainably grown and
harvested.
Window design and placement is referred to as fenestration.
National Fenestration Rating Council (NFRC) stickers on windows verify
performance factors. Some better makes and models are Sierra Pacific,
Anderson Eagle, and Marvin Integrity.
Sierra Pacific, SFI certified windows are available from Franklin
Lumber. These windows are made here in the west, which minimizes the
negative environmental impacts of long-distance distribution, the number one
contributor to green house gasses.
National Fenestration Rating Council Performance
Factors
U-factor measures how well a product prevents heat from escaping.
Ratings generally fall between 0.20 and 1.20. The lower the U-factor, the
greater a window’s resistance to heat flow and the better its insulating value.
U-factors are dependent upon the type and placement of the Low-E
coating. Some placements reflect heat into a room to prevent heat loss,
while others reflect it out to keep interiors cooler.
Solar heat gain coefficient (SHGC) measures how well a product blocks the
sun’s heat. The SHGC is the fraction of incident solar radiation admitted
through a window, both directly transmitted and absorbed and subsequently released
inward. SHCG is expressed as a number between 0 and 1. The lower a
window’s solar heat gain coefficient, the less solar heat it transmits.
The SHGC is also dependent upon Low-E coating, type, and placement.
Leadership in Environmental and Energy Design (LEED) gives credits for
U-factors and SHGCs of .35 or less. The smaller the number the better the
LEED rating.
Visible transmittance (Vt) is an optical property that indicates the
amount of visible light transmitted into a room. Vt is expressed as a number
between 0 and 1. The higher the Vt, the more light available.
Condensation Resistance (CR) measures how well a window resists the
formation of condensation. CR is expressed as a number between 1 and 100. A
higher number indicates better resistance to condensation. Quality
windows are dry, year round.
Designs
Casement windows have cranks or knobs that turn
to open the windows along a vertical plain. This design captures and
directs air flow better than other window styles. Don’t believe the myth
about this style not holding up in strong winds. Quality windows hold up.
Double-hung windows slide up or down, and often
tilt in at an angle to form a horizontal plain. Some manufactures make at
least one of the two pains easily removable for cleaning. This style doesn’t direct air flow in, but is
good for areas with limited space to open or close.
Awning windows are similar to double-hung
except there is only one pane and often only one opening option. An
awning window will usually hinge at the top and swing out.
Fixed, picture, or plate glass windows are windows that don’t open.
Fixed windows are cheaper because there’s no operational hardware.
These can save you money in areas where you already have air flow, or emergency
exit windows. To save money and expand views, combine fixed and opening
styles. Bedrooms must have egress (exit)
windows in case of fire, but you can certainly combine an egress with a fixed
to maximize a tranquil bedroom view.
Gliders or sliders are the cheapest models
available and there’s a reason for it. Tracks quickly and easily become
dirt filled which makes operation less smooth. They do not open out
either vertically or horizontally to capture air flow guiding it into rooms.
Air flow must be fairly direct in to the windows. These work well for
interior pass through windows, or if space to open is extremely limited.
Non-toxic windows
Avoid vinyl clad
windows. Vinyl releases toxins (off-gasses) urea-formaldehyde a
carcinogen, and phthalates found in PVC (poly-vinyl chloride). Phthalates
are carcinogens, can interfere with normal fetal or child development, can harm
reproductive health, and are allergens.
Placement
Windows on at least two sides of every
room allow light to enter at different times of the day and change the way a
room looks and feels. Residents are offered views in more than one
direction and better ventilation. Plenty of glass reduces the need for
artificial lighting, which further saves energy costs, and lifts spirits by
making a home brighter.
Window heights should be proportionate
to room size, and offer views out when standing and sitting. Sills heights approximately
2 ft. above the floor are usually good. Sill heights above 2 ft.
can limit views when seated. Floor to ceiling windows are grand as
long as sills are high enough above exterior grade so that snow loads don’t
pile up against glass.
If privacy from neighbors is a concern,
don’t reduce glass. Instead, strategically place trees and shrubs to
block unwanted gazes.
When installing windows,
caulk well with a low or non-VOC caulk. Caulking well disallows drafts,
creating a tighter building envelop for greater energy efficiency.
Glass connects us with the outdoors and helps us feel
better when we’re inside. Everyone
enjoys gazing at fall’s orange sunsets, winter’s swirling snows, or summer’s
Red Tailed hawks. Quality windows are
not cheap, so budget for them. Knowing a
home is more energy efficient and less toxic affords peace of mind, so install
great windows and enjoy the views.
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