I am planning to replace some old (late 1800s) single pane windows with
vinyl inserts. I'm interested in getting some additional information;
regardless of brand, what are the key factors I should look at when making
my selection? What is an acceptable warranty duration?
Also, looking at the preliminary information I've collected, it appears
that I'll get substantial benefits to energy efficiency with the double
pane, but only a marginal increase above that for the argon filled. Is it
worth the extra money? Are any of the glass coating options worth looking
at, or are they just sales tactics to up the price?
After installation, should I put the old storm windows back up as an extra
layer- if so, how much additional thermal insulation are they likely to
If your existing wood windows are structurally sound, consider instead
retrofitting them with modern weatherstripping and double pane glass.
For example, in the Northeast there is a service offered by the people
at bi-glass.com (no affiliation).
Just like someone els said, If you current wood windows are still in
good structural condition you should concider installing weather
stripping or energy efficiemt jamb liners instead of new inserts. The
thing that the double window manufacturers dont want to tell you, ( I
have gotten some very frank answeres from them) Is that the actuall
energy loss through the glass its self is very minimal. Double panes
only make a few point increase inefficiency. The biggest part of
energy loss in old windows is Air infiltration around the sashes. Also
wood windows are much more effencient than vinal. Wood is much better
insulator than vinal. As well as if you keep the original wood sashes
than you dont change the look of the house. The windows are the eyes
of your house, they have a great deal to do with the over all look of
the house. Also the tripple track storm windows are junk, they do
nothing to eliminate air infiltration, all they do is keep weather off
the wood windows and help them last longer. You should go with a good
positive sealing single pane storm and that will fix all air
infiltration issues. If you have any questions check out my website.
www.fairviewglass.com, send me email if you have any questions. Hope
this helps you
To the whole house perhaps but..
" The U value of single clear glass is 5.4
With ordinary double glazing this is improved to 2.6
With Low-E glass the U value is reduced to 1.8
If argon gas is used to fill the air gap, the U value will reduce to 1.6 "
Smaller the U value the better. (U value is similar to R value in the USA)
so that's a factor of 3 ish reduction in loss through the glass itself.
The biggest part of
If you seal up all the air gaps around your windows make sure the house has
sufficient other sources of ventilation or you will have condensation
I agree that fenestration is always considered a major loss or gain in any
Here are the U values I pulled from ASHRAE Handbook of Fundamentals (older
version, they may have changed slightly, but are the U.S. equivalents - your
site presented metric values).
(The values are for vertical glass on the exterior)
Single glass 1.10 1.04
insulated glass- 0.1875" spacing 0.62 0.65
0.25' 0.58 0.61
0.5" 0.49 0.56
w/low emittance coating (0.6) 0.43 0.51
w/storm windows (1"-4" space) 0.50 0.50
As shown, glass is a poor insulator and a great deal of heat is lost or
gained through glazing. For illustration purposes, a storm window has an
equivalent R value of R-2 per sq.ft. Compare that with a ceiling with an R
of 30 or higher or a wall cavity of R-19 (per sq.ft.).
So comparing std. insulating glass of .58 with one which as an emittance
coating of .43, assume 100 sq.ft. of glazing - 100 x .58 = 58 UA vs. 43 UA.
Assume a temperature differential of 70 def. F the std. insul glass will
loose 4060 Btu per hour vs. the low emittance at 3010 Btu per hour. That's
a different of 1000 Btu's per hour. Averaged over a heating season of 8,000
heating degree days and you quickly see that the better windows will pay for
themselves in a few years (faster in colder climates).
That I'm afraid is complete nonsense. Glazing is always the biggest loss in
any conditioned structure (normally) followed by doors and foundations.
Walls and ceilings have a large exposed surface area, but now are required
to have copious amounts of insulation (esp. in the new chapter 11 of the
2006 IRC) that their losses (on a sq.ft. basis) are actually quite small by
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