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Old 07-27-2014, 06:42 AM   #16
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Originally Posted by Energyrater View Post
You know that thermally we're talking about an area weighted R-value of 3.33 as opposed to the the 5.55.

But you're right on, it's all about the air leakage and operation.

The impact on total wall R-Value can be significant as the relationship is not linear.

If you view a 2x6 wall as an R-12 wall (R-19 but figuring on all the thermal bridging of the framing), the total wall to window ratio to be 70 - 30 (not uncommon to see more window than that in these houses that are full of windows), the data shakes out like such:

U-Factor 0.30 window yields a net total wall R-Value of 6.74

U-Factor 0.18 window yields a net total wall R-Value of 8.90

That is a 32% increase in average wall R-Value across the total. That is nothing to shake a stick at.

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Old 08-07-2014, 10:28 PM   #17
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Originally Posted by Energyrater
Air sealing in an older home will pay off. Insulating where there is little to none already will pay off, not so much when adding insulation where there already is plenty (see law of diminishing returns as mentioned above) Replacement windows won't pay off (especially triple pane) unless your current windows are single pane wooden windows with the panes broken. Done plenty of energy modeling to show that replacement windows will not payoff no matter what the manufacturers or salespeople try to say.
For me (especially as a landlord) the removal of lead encrusted windows may be of greater value in replacing the old wood windows with lead weights than the significant improvement in appearance, function, thermal performance, and eliminated maintenance. It is impossible to keep up on the maintenance of 50 peeling lead painted and dried out glazing compound windows!
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Old 08-08-2014, 07:55 AM   #18
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MaineLL, been there done that with the landlording thing.

I'll tell you what's hard to keep up with..... The repeated repair and destruction of your property by lowlifes.

Sorry for the hijack
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