[MassHistPres] Calculations for energy saved by replacement windows

[slater at alum.rpi.edu]

Home Depot often comes in pretty low with basic vinyl replacement
windows -- and I've seen no-name contractor estimates in the $150 per
window range. I'm not sure if they were fake quotes to justify
replacement or what, but that's what we're faced with. $300 is almost
high-end for vinyl.

I think that if we're going to convince the public that replacement is
not the right thing to do, we're going to have to show them that the
cost savings is just not going to happen. The homeowners are being sold
purely on saving a lot of money in heating bills. I always ask "will you
guarantee those numbers to the homeowner", and of course, they never do.

In the formula I found, the infiltration number is the key -- if a
replacement window is compared to an original window and the
infiltration is the same, then 30 replacement windows at $300 apiece
equals a 61 year payback. I'm still not sure why the infiltration number
gets added to the U-Factor, and how they arrived at 1.0 for an "old"
window and 0.14 for an "new" window.

Subsequently, if expensive vinyl windows are the only way to get those
other ratings, then we can attack from another angle -- if it takes $600
to get a window that has a 0.34 U-factor with an infiltration rate of
0.14, then that puts the payback at 15 years even using the 1.0 and 0.14
infiltration rates. Problem is, if they can achieve the best ratings at
$150 per window (maybe by self-installing) then the payback rate drops
to 4 years.

If we can also show that the life span of a vinyl replacement window is
somewhere around 20-25 years, then we can also show people that the odds
of them seeing the payback is relatively small -- because after 20 or 25
years the vinyl windows will need to be replaced again. The only payback
is in years 21-25, then the cycle starts all over again. What are the
odds that someone will own their home only for between 21 and 25 years?
It's more likely that they will own it some other number, so they will
either be paying for the first or second set of replacements.

I think people will respond to us showing them actual numbers rather
than pointing to studies with a lot of scientific jargon in them.

Ralph Slate
Springfield, MA

<-----Original Message----->You were wondering about the payback
calculation,
>and why your numbers seemed to suggest such an early break-even point.
The only
>question I would raise with your argument is here:
> 
>>> I assumed that a vinyl replacement window costs $300 installed.
> 
>I've heard one (radio) advertisement in the Boston media market at that
price
>point. One. I don't know how this bottom-of-the-market window meets
your
>standard presumtions for efficiency. I can't say what installers are
getting in
>different parts of the state, but I thought (anecdotally--trying to get
>comparative figures from these guys reminds me of the deceptive scams
some
>automobile places were running 20 years ago) the going rate around here
was 2 or
>3 times that.
>
>
>-- 
>A. Michael Ruderman
>amruderman at gmail.com
>(781) 929-7847 
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