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Does anyone have information on who manufactures windows with a high solar heat gain coefficient suitable for a solarium?

I live in northern Colorado and have been looking windows with a high solar heat gain coefficient (SHGC). I am not so sure how well high SHGC windows perform in climates where the sun is not visible from November to April, but in Colorado with about 6000 heating degree-days per year and nearly 300 days of sunshine, they can provide much of the house heat. I would like to say that I have found this discussion board very helpful in making decisions about what windows to purchase, and I would especially like to thank Jscott, Oberon, and Guy for their help.

In searching for windows with a high SHGC I have found that few window manufactures make windows with either a hard coat on the #3 surface or a soft coat on the #3 surface to provide a high solar heat gain. Of the manufacturers that I have contacted Milgard and Gienow use a hardcoat (Milgard uses PPG 500 and Gienow uses AFG). Pella appears to confine hardcoat windows to their Designer line; they are not available in the Impervia line.

Amerimax, Atrium, Simonton, and Jeld Wen do not offer a high SHGC product. Is, as some have suggested, the Energy star rating leading the extinction of high SHGC lowE windows?

There are numerous companies that make a high SHGC product. If you don't get Low E glass, your SHGC will be pretty high (in the neighborhood of .49 to .55). With a Low E coating (it seems that is your intention), hardcoats usually are around .39-.41 and softcoats around .32-.33, sometimes even lower. There is a nifty website that will SHOW you the performance stats - http://www.nfrc.org. When there, select the "certified products directory." It will show you the U value, spacer type, SHGC, # of glass layers, frame & sash type, Visible light transmission, condensation resistence, Low E type/emissitivity, etc. for hundreds of windows. Lots of good stuff. The only two I looked up there both had hardcoat Low E with high SHGC - Marvin and Pella, but I'm sure there are a lot more.

I tried to copy/paste a screen capture of one of their web pages to show the stats, but I must be doing something wrong (HTML is turned off on my profile, can not enable it - any suggestions to paste pictures?).

I don't come across too many requests for high SHGC. Consumers Reports magazine did a study several years back (a simulation) comparing Heat Mirror, Low E (softcoat)/Argon gas, and clear IG to determine which was most cost effective over a year period. They concluded that when factoring in not only heating costs but also cooling costs, the softcoat Low E performed the best, followed by Heat Mirror, and at the bottom of the group was clear IG. They stated that the savings from either of the 1st two products would eventually pay for themselves. However that was based on a northern climate (Madison, WI). Good news for people like Guy in those MN/WI climates.

tru_blu

I agree with you on all points, but I should have been clearer and more specific in my interest in a high SHGC product. Many manufacturers appear to offer clear, uncoated glass that provides a great SHGC at the expense of U value. What I am looking for is the best compromise between the two. The hardcoat products give up some SHGC in comparison to uncoated glass, but have a much better U value than uncoated glass. On the other hand, the U values for the softcoat products are better than the hardcoat, but the SHGC values are generally well below the .5 to .55 levels suggested for passive solar applications.

One of the best links that I have found for comparing U and SHGC values is found at: http://www.cardinalcorp.com/Tech/pdf/ig/IG05.pdf

Because this table shows values for products made by most of the glass manufacturers, the U and SHGC values for several products can be easily compared in one place.

I found the NFRC web site to be helpful in comparing products from different window manufacturers. However, this site shows only tested products, and is not necessarily reflective of the products that a manufacturer produces. For example, the NFRC products site lists a hardcoat product for Simonton, but when I called the company, it turns out that they no longer produce that product. I also found this to be true for Jeld-Wen, at least for their vinyl line.

My question should have been, “What window manufacturers produce a pyrolytic hardcoat product or a soft coat product, such as the Cardinal 178 on the #3 surface, that yield a SHGC approaching at least .5 and a U value of about .35 or less?â€Â￾

Colo:

When we first started with Simonton they offered glass packages that were tailored for specific regions (hard coat low-e for mostly heating and soft coat for mostly cooling) after reviewing the results of tests like the one Tru Blue stated it no longer made sense to continue this practice.

In your climate I would reach for the lowest U-factor available.

Bill
Uneeda Window of NJ

Bill,

Do you have the references for those studies? These results seem to be inconsistent with the energy ratings system that the Canadians use.

Also, a technology fact sheet entitled "Passive Solar Design", from the U.S. Department of Energy states, "Effective south-facing windows require a high Solar Heat Gain Coefficient (SHGC)â€â€￾usually 0.60 or higherâ€â€￾to maximize heat gain, a low U-factor (0.35 or less) to reduce conductive heat transfer..."

In my case, the solarium is a closable space where heat is collected during the day, but at night the sunspace is closed off from the remainder of the house. With double pane clear glass now in the solarium the nighttime temperatures commonly reach into the upper 40's while the temperature in the remainder of the house seldom goes below about 66 to 68 by morning. My heating bill for the last three weeks in December and the first week in January for a 2000 sq. ft. house was about $60 so this system using seems to be working. It would be unfortunate to change the windows and lose these advantages so I want to be sure of the windows that I select for the renovation.

In your situation i would go with a window with maximum solar gain and get blind that have Low-E if such a blind exist. I was told by Sunrise Window com. that the blinds in there windows have a Low-E coating on them but i do not know if this is true. Maybe someone here does and will post if this is so and where to get these blinds. (just lower the blindes at night). If blinds like this do not exist, i would still go with a window with maximum solar gain under your circumstances.

Unfortunately, you are correct that a higher SHGC will provide a higher U-factor. Along the lines of Researcher's post, you may want to consider insulated blinds that can be closed at night. You may also wish to continue your research of passive solar direct gain systems. You can increase it's effectiveness by increasing the thermal mass materials in the space. Dark ceramic/masonry tile (no carpet), large clay pots for plants, and other heavy heat absorbing materials will store heat for later release. The key is storing more heat than you lose.

FenEx, have you ever heard of blinds with a Low- E coating on then?

No Researcher, I have not.

Low emissivity coatings are effective in glass coatings, as they are part of an insulating system. Unless they are an integral part of the same, they have NO insulating value. Radiant barriers are ONLY effective when combined with an air/gas space. Sunrise handed you a bag of @%$#.

Pella's between-glass blinds I think are still available with a Low E coating. For years they had white and Low E (which was a gold color). However, last year they changed to 10 colors, and the Low E gold-colored blind was relabelled as "Golden." I'm not sure if that means it still has a Low E coating on it or not.

I think {i hope} you are joking. the colors of blinds available for some windows and doors is white and ALABASTER. i dont know if it possible to produce a glass that is high soar heat gain. i think that is called clear glass. you dont spray or bake anything on to the glass to gain solar heat do you?i have never heard of this. would like to know more if someone has correct info. a magnifying glass is the only thing that could add artificial solar heat gain i think????

A clear no low-e, low-iron (no green tint when looking sideways at the glass) insulated glass is the best I know of for promoting solar gain.

I would rather compromise and have something like Ultra-U or triple low-e glazing.
The solar heat gain might not be as great, but at least you would retain some of the gain you do receive.

Since the best U values are reached with about 0.5-inch gap in argon and a little less in Krypton (I think that I learned that on this site), what is the effect of putting the shade in the IGU, especially if the shade is a conducting medium in the middle of an insulating gap?

I agree that putting insulating shades on the windows will help. We use these now on our north- and east-facing windows, and they are a big help in making the house more comfortable and retaining heat at night. Is it the case that the U values of the window and the insulating shade will add linearly? Since these are resistances in series, I think that this should be the case. If a cellular shade has an R value of 3.5 (U= .29) and the window itself is U=.33 (R= 3) does that really give an effective U of .15 (R=6.5)?

As for the question of solar mass, the solarium has an 8-foot by 28 foot by 4-inch concrete slab as solar mass. It would have been better to have included a masonry wall as described on the original drawings, but when the house was built in 1986, the wall was not included. Nevertheless, the solarium seems to act as buffer from cold in the winter and heat in the summer since it is a space where temperatures are allowed to fluctuate in a volume that is separate from the major living quarters of the house. It seems to me that triple glazing or ultra lowE would keep the solarium warmer at night, but that it would yield far less heat in the daytime that can be transferred to the living area by thermal siphon or fans.

It is true that the greatest solar heat gain will be from single pane clear glass, which also provides the worst U value. My understanding of the coatings, both the sputtered soft coat and the pyrolytic hard coat is that they increase the insulating value of the window by reflecting long wavelength radiation back into the living space far more effectively than clear glass. This combined with the improved insulating capacity of the argon or krypton decreases the U value. Judging from the tables from Cardinal glass, pyrolytic hard coats give a SHGC that is closer to clear glass than the soft coat. Although the U values for the hardcoat products are not as low as the softcoat, they are far better than clear glass. In the end it is a trade off. The question seems to be whether, or under what conditions, the trade off becomes beneficial when winter heating and summer cooling conditions are taken into consideration.

All of this begs the original question of what window manufacturers still produce a pyrolytic hard coat product.

I checked a few websites - the only manufacturer with a hardcoat Low E that I could find was Pella. The NFRC had mentioned Marvin, but Marvin's own website didn't mention it. I would think that it may be available from Marvin and others as a a special order. Pella is a unique case. They use a Low E2 softcoat on insulating glass, like many others. However, in their Designer Series, with includes an interior removable glazing panel, the hardcoat is available on the single-pane windows. So if you select "Designer Series double glazed" (single glass + glazing panel) you will get the hard coat (because you can touch it), and if you select "Designer Series triple glazed" (insulating glass + glazing panel) you will receive the Low E2 softcoat (because it's between the insulating glass). Designer series is the segment of Pella that also allows for between-glass blinds. Anyone know of other windows that offer a hard coat Low E out there?

Sorry about that. I missed your original question.
Being in Colorado, either you or your contractor should contact Norandex. They are the biggest supplier out there for Simonton. They have both soft coat and hard coat available in the windows.