Triple Pane Krypton vs. Dbl Pane Argon "Is the $ worth it"

[mckelligan]

We were planning on replacing our windows in our 1986 colonial in New England with Harvey Tribute windows with high performance glass u rating .20 insead of the dbl pane argon gas U value .32. Most contractors are looking at us scratching there heads wondering why we want to spend he extra money. "To expensive," they say. One guy said "It would make more sense to him if we were building a brand new house with 2x6 walls." I guess they feel that the windows will be more insulated than the walls. Now we are starting to second guess ourselves. So I'm asking all the experts out there for help. Should we second guess ourselves and put in dbl pane argon gas or stick to are guns and spend the extra cash on triple pane krypton knowing we will be ahead in the end.

[advanced_energy]

most contractors know nothing about windows,hence his reluctance to recommend triple pane. i can guarantee that you will save money going with the tribute opposed to the clssic double pane. most energy is lost through windows certainly not through the walls. contractors are great at installation and building things but thats where it usually ends in the window business.your contractor needs to be educated. how he can assert that a u-factor of .20 will not insulate your home any better than a .32 is beyond me especially where you live., if you can afford triple,its certainly well worth the money.

[Windows on Washington]

In NE, triple pane would not be a waste of money.

Although "more" energy is lost through a window when compared to its surrounding wall assembly (given that it is insulated) that is not where most of the energy in the home is usually going.

[Oberon]

Maybe or maybe not - considering a reply early on a Monday morning...

Obviously there is no question that you want the most efficient window in the more efficient wall, and your contractor is correct when he told you that better window energy numbers do result in better performance in the more efficient wall.

However, that certainly does not mean that you want a less efficient window only because you have a 2x4 rather than 2x6 wall to start with. While a good U-.32 window, properly installed, will improve your overall comfort and the energy performance of your home versus the windows you have in place, a more efficient window will improve overall wall performance even more so - the question does the additional improvement justify the additional expense?

A good dual pane IG with the right LowE coating may very well meet all of your needs at (potentially substantially) less cost than higher performance triple. If you live in northern Maine or northern Minnesota, I would agree that the triple may well be worth the additional cost. But in Connecticut I would definitely consider the dual pane for the best overall value.

Consider that the U-.2 triples will meet 2015 energy star requirements - but does the rest of your home meet 2015 energy star requirements? Basically, meeting a future energy star level is a non-issue. You simply want the best performance for the dollars that you are planning to spend.

So, to add a few numbers:

Imagine a single wall in a home that is 100sqft (for simplicity). In this example we will assume that this wall has an overall R-value of 10 (typical 2x4 construction)including the effect of studs, outlets, etc (but not windows), and just say that this wall averages R-10 across its total surface.

If we add a 5’x 2’ (10sqft) window to this wall and this window has U factor of .32.

Wall = R10 or U.1
Window = U.32
Window = 10% of wall
Wall = 90sqft, window = 10 sqft, overall 100 sqft
Wall = 90 sqft x U.1 = 9
Window = 10 sqft x U.32 = 3.2
9 + 3.2 = 12.2/100sqft = U.122 or overall wall R value of 8.2.

Now if we change to a window with a U.20 –

Wall = R10 or U.1
Window = U.20
Window = 10% of wall
Wall = 90 sqft, window = 10 sqft, overall 100 sqft
Wall = 90 sqft x U.1 = 9
Window = 10 sqft x U.20 = 2.0
9 + 2.0 = 11/100sqft = U.11 or overall R value of 9.1.

So, changing from U.32 to U.20, in this example, results in an improvement of 63% in window performance, but it also results in an improvement of 11% in the entire wall structure – the higher the percentage of window sqft in the wall; the more the overall R-value improvement if using the lower U-factor window – in this example assuming 10% window coverage in the wall.

If your wall is 15% of the total wall area then the improvement to entire wall energy performance will be increased proportionally.

By way of comparison to a 2x6 wall (per your contractor)- which I am going to say is R-20 because the math is really easy (being lazy here - but it is close enough for this illustration):

So if we change to an R-20 wall we have:

Wall = R20 or U.05
Window = U.32
Window = 10% of wall
Wall = 90sqft, window = 10 sqft, overall 100 sqft
Wall = 90 sqft x U.05 = 4.5
Window = 10 sqft x U.32 = 3.2
4.5 + 3.2 = 7.7/100sqft = U.077 or overall wall R value of 13.

Now if we change to a window with a U-.20:

Wall = R20 or U.05
Window = U.20
Window = 10% of wall
Wall = 90 sqft, window = 10 sqft, overall 100 sqft
Wall = 90 sqft x U.05 = 4.5
Window = 10 sqft x U.20 = 2.0
4.5 + 2.0 = 6.5/100sqft = U.065 or overall R value of 15.4.

Or a potential 18.5% improvement to overall wall performance with the higher efficiency window in the higher efficiency wall (assuming I did all the math right..it is before breakfast on a monday morning...).



.

[FenEx]

Hmmmmmmm.... those calculations and the method look soooo familiar.

[Windows on Washington]

Straight out of the BPI handbook, or at least as I recall.

Oberron, I do not disagree in any capacity regarding the improvement of overall wall insulation value, however, my contention is that more energy is lost in the home via other pathways than just windows that can be addressed. The home should be looked at more comprehensively before saying "most" energy is being lost through XYZ.

[Oberon]

Fenex,

Well the short answer would probably be because I originally learned the formula from you - actually that would be the long answer too!

So ltns, what have you been up to and how is the energy rater thing going?

[Oberon]

Straight out of the BPI handbook, or at least as I recall.

Oberron, I do not disagree in any capacity regarding the improvement of overall wall insulation value, however, my contention is that more energy is lost in the home via other pathways than just windows that can be addressed. The home should be looked at more comprehensively before saying "most" energy is being lost through XYZ.

WoW,

I agree completely. I suspect that I did a poor job of presenting myself - again, it was before breakfast on a Monday morning.

I was trying to present several different ideas with the hope that the OP would ask more questions.

For example while resulting whole wall improvement comparison between the dual pane and the triple pane in this case is 11%, but the difference is between R-8.2 and R-9.1 - or an R-.9 difference.

What is the cost-value of that improvement to the homeowner?

Again, I wasn't attempting to draw conclusions, simply to (hopefully) offer something else to consider before making a final decision.

[Windows on Washington]

I know Oberon. I was just arguing my original point to clarify my stance regarding "advanced energy"'s post. Many homeowners get sucked into the information vortex presented by window replacement companies that they will save XYZ % and it is a complete manipulation of the truth by slickster salespeople.

[advanced_energy]

where i am located in the north east,i have no problem selling a triple pane of good quality. however,i sell a double pane with very good performance numbers and feel that suits my customers just fine. i offer the triple if they are determined to get one and never talk them out of it. if a customer wants something and i sell it,i give them what they want. a triple will result in better performance if the climate warrants it and its going up against a run og the mill duel pane with a u-factor of .32./ again the triple has got to be of sound quality.

[Window4U (IL)]

triple will result in better performance if the climate warrants it

True. There is only one place where it wouldn't result in better performance. That would a place where the weather is so perfect that there would be no heating and no air conditioning. Otherwise, triple will result in better performance.

[advanced_energy]

windows4u
the problem as i stated before,is that most people buy their windows at the behest of their contractor who nine times out of ten know nothing about windows. hence the typical response that triple pane is just a sales gimmick and most argon is lost anyway so why waste the money. funny story,i was at a home and coincidently(lol) her contractor conveniently stopped over and tried to ask me a few questions. well i just started asking him a few window questions and low and behold he got very quiet.i told him no offense but he was doing a disservice to his customer by talking about a subject he knew nothing about. he copped an attitue(tried to) and i just said i was sorry but there was no way i was going to just sit there and let some guy try and tell me 2 plus 2 does'nt equal 4.