Best U-Val Bang for the Buck (NO DRAMA)
Last Post 20 Sep 2014 08:37 PM by fun2drive. 67 Replies.
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ba_icfUser is Offline
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29 Mar 2014 10:21 PM
Posted By WestMichigan on 24 Mar 2014 01:52 PM
There isn't any data out yet, but Intus has a new line of vinyl windows. Anyone have any thoughts on their Arcade line? It is spec'd a little worse than the eforte, but it still seems pretty good according to their website. They are supposed to be getting NFRC data in April.

Lbear,

Why don't you complain that this guy looks like an Intus shill?  First post and only post, and telling people about some new windows.
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29 Mar 2014 10:28 PM
David Paulus, PhD, P.E., states:

Air leakage is measured by physical testing of a standard sized window. The test window is installed on a large wall. On one side, a vacuum is of 75 pascals (1.57 psf) is applied. This corresponds to approximately a 25 mph wind blowing perpendicularly to the window. Flow meters measure the rate of air leakage. This is divided by the total window area to get a reading (in the U.S) in cfm/ft2 to the nearest tenth (i.e., a test value of 0.17 would be given a rating of 0.2). The best possible rating by the NFRC is 0.1, as they will not round to 0. (AAMA records to 0.01)

Air infiltration becomes a greater percentage of total energy loss as the window's U-Factor becomes lower, because the energy loss through heat transfer is reduced. Low air infiltration is critical for a passive solar house, where energy loses must be kept to the absolute minimum. For these houses, casements or tilt & turn windows are the only proper choices.




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30 Mar 2014 06:48 PM
Posted By Lbear on 29 Mar 2014 10:10 PM
...snip...
I have yet to see double hung windows being used in a Passive House design. Why would you? There are better alternatives out there like casements and tilt and turn.

...snip...


In the above calculation that I presented, you can save about $8.96 annually by reducing the window infiltration from 0.3 to 0.05 cfm/ft^2/hr for a house with 836 ft^2 of windows. So assuming an average window size of 40" x 60", this would be 18 cents per window per year. If you reduce the infiltration rate to zero, the saving increase to 24 cents per window per year. Do you want the inconvenience of a window that swings into the living space, or out into walks and driveways to save that amount of money? There is also the consideration of mechanical worm gears for some of those windows or other mechanical devices with limited lifetimes. It is certainly an option to consider these better sealing window designs, but the buyer should be aware of that the cost savings might be minimal.

Berlin, Germany, capital of the country that originated Passiv Haus standards, is at a latitude of 52.5 deg., similar to Winnipeg, Calgary, and Saskatoon, all in Canada. Caution should be used when directly applying those guidelines to homes at very different latitudes. When German ancestors of those folks that came up with Passiv Haus standards moved to central Texas and established the King William area in San Antonio in the 1880's, they put double-hung windows (as well as large porches and shade trees) throughout their houses to deal with the Texas heat. See for example, King William link #1, King William link #2, King William link #3, and King William link #4.

With the advent of A/C, that window design would be less important in that climate today, but that type of window can be used in areas where cooling can be achieved naturally (without A/C), or during the shoulder seasons in warmer climates.

When we talk about sealing a house, we say to pay particular attention to areas low and high in the house to avoid the thermally driven leakage. Imagine the other way, of using tall windows that open at the bottom and the top to take advantage of that thermal drive to exhaust the hot air and pull in cooler air.
Lee Dodge,
<a href="http://www.ResidentialEnergyLaboratory.com">Residential Energy Laboratory,</a>
in a net-zero source energy modified production house
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07 Apr 2014 02:12 PM
••• similar to Winnipeg, Calgary, and Saskatoon•••
Comparing cities of maritime climates that seldom experience serious frost to the Canadian prairies which experience 40ºC of frost even if they are at similair latitudes is not really being responsible.

Double hung windows where often incorporated in cooling dominated climates. This is why they were invented. Open the top a few inches and the bottom a few inches and you get some circulation even if you don't have opposing windows. In my opinion this does not justify them in a heating dominated climate.

Interesting that your calc's show such a small return for proper windows. In Alberta, government certified energy auditors, all show even a small home with a saving of several 100 dollar a year by replacing windows.
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08 Apr 2014 12:23 AM
FBBP-

What I said was the following: "Berlin, Germany, capital of the country that originated Passiv Haus standards, is at a latitude of 52.5 deg., similar to Winnipeg, Calgary, and Saskatoon, all in Canada. Caution should be used when directly applying those guidelines to homes at very different latitudes."

I did not say that Berlin has the same weather as Saskatoon, but I specifically said that folks should be cautious about using standards developed for Berlin and applying them to locations in the U.S. that are far south of Berlin. Since we are talking about window ventilation, let us compare temperatures in July for Berlin, Saskatoon, and middle America, say St. Louis. Using Weatherspark to compare July maximums for daily high and low temperatures for the three cities:
Berlin 59F 78F
Saskatoon 56F 77F
St. Louis 69F 89F

So if we are choosing windows for mid-America, like St. Louis, or further south, the summertime temperatures in Berlin are much closer to the summertime temperatures in Saskatoon than they are to those in St. Louis. Now in modern times, air conditioners are often used where they can be afforded in the type of heat found in St. Louis in the hottest parts of the year, and other cooling dominated climates. In some heating dominated climates like where I live, the expense of air conditioning can be completely avoided with good window ventilation. Double-hung windows are an excellent way to obtain good summer ventilation, but there are others.

You have not provided any reference for your comment about "saving of several 100 dollar a year by replacing windows." If the windows in question are old and leaking badly, such a savings is certainly possible. If the windows are replaced by any type of new windows with a leakage of 0.3 cfm/hr/sq ft, which is the maximum leakage specification for all new windows, then choosing a window with much lower leakage than that spec does not appear to save much additional energy or money. I am open to reconsidering the matter if you have calculations that show a different result than what I have presented.

Interestingly, the average cloud cover in Berlin varies from 80% in the summer to 90% in the winter (from Weatherspark), which makes passive solar heating less practical in Berlin than in many locations in the U.S. and Canada. This is a prime reason for the overemphasis on U-value compared to solar heat gain coefficient in Passiv Haus standards. If you live in an area where the sun shines and where passive solar gain is an advantage in reducing heating energy, then consider high solar gain windows, even at the expense of U-values. (In this area, Canadian standards that support high solar gain windows appear better than U.S. standards.)
Lee Dodge,
<a href="http://www.ResidentialEnergyLaboratory.com">Residential Energy Laboratory,</a>
in a net-zero source energy modified production house
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08 Apr 2014 01:52 AM
Lee - I would be very careful about using weatherspark for comparative purposes unless you have means of verifying their results. After all they claim June is Calgary's deepest snow on the ground month. Weather sparks Berlin data cannot be used for any purpose as it only averages back to 2006. Further you are comparing average maximums not maximums. We would expect the prairie provinces to have higher deviations from average then would a maritime climate. I know from personal experience that the prairies can have many 90 to 100º temps but they are offset by days that don't exceed 60º so really average temps are not as important as actual highs.

As I said, I agree with you that d.h. are good for ventilation. That is why they were invented.

Your calc's for base on "day of test" results. That is new, perfect condition seals. The down side to any sliding seal is that they wear down quickly, so even if they made the .3 cutoff on test day, they no longer do after a few ventilation cycles. This is a bit more important in a heating dominated climate then in Texas.

I would certainly agree that solar heat is very site specific so window selection should be done base on your site and the sites orientation, not what some book says.
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08 Apr 2014 11:41 AM
'Your calc's for base on "day of test" results. That is new, perfect condition seals. The down side to any sliding seal is that they wear down quickly, so even if they made the .3 cutoff on test day, they no longer do after a few ventilation cycles."

This would be very interesting to see such test results. Do you have a reference to such a study for modern technology window designs?
Lee Dodge,
<a href="http://www.ResidentialEnergyLaboratory.com">Residential Energy Laboratory,</a>
in a net-zero source energy modified production house
fun2driveUser is Offline
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20 Sep 2014 08:37 PM
KB
This thread is back from the dead as I am curious to what you selected for windows and doors. I would assume by now you have them done and installed.

My requirement for impact glass has be looking at a few more new names you provided like Sunrise (purchased by VPI this summer and I don't know anything about VPI either).

You mentioned Inline and I also saw one of the forum posters used CoMetal as did Eugenepan.
I hope to build a matrix as well but only those that incorporate impact glass as their product line for those of us that have to use it.

Looking forward to an update and thanks for all the leg work on researching various manufacturers...
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