Search found 12 matches

by ColoJ
Sat Jan 28, 2006 1:15 am
Forum: Ask Our Pro's a Question
Topic: Who still makes high solar heat gain windows?
Replies: 38
Views: 84612

The windows have been ordered from Milgard, hardcoat for the solarium south and east sides, softcoat for the rest. Thank you again for your help and encouragement. The research and the project have been interesting. To me, the insight that heat loss through windows is similar to parallel electrical ...
by ColoJ
Thu Jan 26, 2006 2:15 am
Forum: Ask Our Pro's a Question
Topic: Who still makes high solar heat gain windows?
Replies: 38
Views: 84612

Oberon, Thank you for the information about SHG and the insulating value of the windows. I agree with you, and I am betting that you are right. In fact, in the next few days I plan to buy the windows and test the hypothesis. If I am thinking about this right, clear glass will reflect about 16% of th...
by ColoJ
Sat Jan 21, 2006 1:33 am
Forum: Ask Our Pro's a Question
Topic: Who still makes high solar heat gain windows?
Replies: 38
Views: 84612

Will replacing my old clear double pane windows with more efficient windows give me too much of a good thing?

Thank you all for your input. Oberon, you are absolutely right in that I have no idea how much heat I am losing through the clear double pane windows. I have a nagging concern that by reducing the SHGC a little with replacement hardcoat windows, while improving the U value by a greater extent, that I could turn my plant friendly or at least plant tolerant solarium into a solar cooker; a kind of roach hotel where visible light enters and infrared doesn’t get out.

I haven’t kept detailed logs of inside and outside temperatures, but I can provide some data. Temperatures in the solarium approach freezing only at night when outside temperatures are below zero and even then only when a cold night follows an overcast day. To avoid damage to the houseplants on these nights, which are far more infrequent here than in Wisconsin and Minnesota, I crack two windows to permit air to move from the living space into the solarium. This is the only instance when heat is deliberately moved from the living space into the solarium. In January along the front range of northern Colorado, the average daily highs are about 43 and the lows are about 16 degrees F. Under these typical circumstances, the temperature in the solarium reaches a maximum of about 85 to 90 F between about 2:00 and 3:00 PM. Nighttime temperatures in the living quarters typically reach a minimum of about 62 to 65 F by morning. (I often turn on the gas forced air at this point to warm the living area to about 72 and avoid the “when I was a lad I struggled…â€Â￾ discussions with my teenage kids.) Temperatures in the solarium by dawn range between the upper 30s on cold nights to upper 40s and low 50s on warmer nights. On sunny days from late November through mid February, the solarium temperature warms to about 70 by about 9:30 AM. By opening doors and windows that separate the solarium from the living space, heat moves from the solarium to heat the living space by thermal siphon. The forced air furnace system has cold air returns in the solarium so that I can use the furnace blower without turning on the gas burner to move air from the solarium to the living area. The blower system works, but is not very efficient and needs to be improved, perhaps with a more efficient fan system. On a good day, I can get the temperature in the living area to reach the upper 70’s to low 80’s by late afternoon. At this point, the solarium is beginning to cool, and when equilibrium between the living area and the solarium is reached, the solarium is closed off from the living quarters. This all takes some attention, and works fairly well since my children arrive home from school at about 4:00, and when they are conscious of the world around them can close the solarium from the living area to maximize the heat gain. Thermostatic controls that control high efficiency fans to move air from the solarium to the living area would be a big help. (Any suggestions thermostatic control and air movement with fans would be appreciated).

Yesterday was overcast and the high temperature was in the mid 30s the solarium temperature yesterday eveing was in the low 50s.


As part of the renovation, about 650 sq ft of living space will be added to the existing 1900 square feet. There will be about 80 sq ft of south-facing glass added to the living area in the new addition that will provide some solar gain. No more glass area will be added to the solarium. The south-facing solarium glass will remain the same at about 270 sq ft. There are about 70 square feet of east- and west- facing windows in the solarium that are more heat sinks than sources since they are clear glass. I worry that by putting lowE on the west-facing windows and probably on the east-facing ones as well, I could also increase the heat retention in the solarium to intolerable levels. Is this a valid concern?

The discussion of the effects of thermal shades is also of interest to me. I don’t plan to use them in the solarium, but I plan to use them on the windows in the living area.

Please bear with me as I try to puzzle this through and tell me when I leave the tracks.

Windows lose heat via three routes, conduction, convection and radiation. I think that I understand the conduction. It is similar to electricity moving through a wire. The difference in temperature between inside and outside is the driving force, which for electricity is voltage; the movement of heat through the conducting medium (the frame, spacers, glass and gas between the glass) is equivalent to current; the ability of the window to resist this heat conduction is the resistance expressed as its reciprocal, U. (For electricity, V=IR or Vg=I where g=1/R; for heat flow TU=H where T is the temperature differential, U is the heat conductance, and H is the flow of heat per unit time). Adding cellular shades on the inside of a window provides an insulating barrier and lowers the U value so that the rate of heat movement from the warmer to the cooler region is slowed.

The cellular shades also help with convection because the cold glass and frame that have lost heat by conduction cool the adjacent air that then sinks along the window to cool the room air and create drafts. Cellular shades separate the air from the cooler surfaces and reduce convection.

All of this seems fine for me when considering standard clear glass windows. Where it begins to break down is with the concept of emittance and its effects on radiant heat loss. To me, emittance seems very close to mysterious emanationsjavascript:emoticon(':shock:')
Shocked. The way that I think of it, the LowE coatings, especially the hardcoats, are a kind of optical filter in that they pass shorter wavelength visible light, but reflect (or maybe absorb and reemit) longer wavelength infrared, which is heat. Visible light comes in and longer wavelength infrared is more or less trapped. The effect of a translucent cellular shade on this process seems complex to me, and I don’t see how to evaluate the effect of cellular shades on the radiant heat loss aspects of a window’s U value. I suppose that a reflective backing on the shade would reduce radiant heat loss, but I envision a positive feedback loop between the reflective backing and the E coating that could lead to heating the glass to damaging temperatures. The best backing would seem to permit both visible and infrared radiation to pass through the shade when going from outside to inside and reflect infrared radiation going from inside to outside. Although this would be good in winter, it would be opposite the desired effect in summer.

So, are cellular shades of much value when used with LowE hardcoat or softcoat windows?
by ColoJ
Thu Jan 19, 2006 2:24 am
Forum: Ask Our Pro's a Question
Topic: Who still makes high solar heat gain windows?
Replies: 38
Views: 84612

Bill, I wonder if the Simonton studies were based on differential placement of hardcoat and softcoat windows. That is, hard coat on south-facing windows with a good overhang that shades windows in summer but exposes them to sun in winter, and softcoat on the remainder of windows in the house. I can ...
by ColoJ
Wed Jan 18, 2006 12:40 am
Forum: Ask Our Pro's a Question
Topic: Who still makes high solar heat gain windows?
Replies: 38
Views: 84612

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 in...
by ColoJ
Tue Jan 17, 2006 2:44 am
Forum: Ask Our Pro's a Question
Topic: Who still makes high solar heat gain windows?
Replies: 38
Views: 84612

High SHGC windows

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.
by ColoJ
Mon Jan 16, 2006 5:21 pm
Forum: Ask Our Pro's a Question
Topic: Who still makes high solar heat gain windows?
Replies: 38
Views: 84612

High SHGC

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￾
by ColoJ
Mon Jan 16, 2006 12:25 am
Forum: Ask Our Pro's a Question
Topic: Who still makes high solar heat gain windows?
Replies: 38
Views: 84612

Who still makes high solar heat gain windows?

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 th...
by ColoJ
Tue Nov 29, 2005 12:04 am
Forum: Ask Our Pro's a Question
Topic: Vinyl or Fiberglass?
Replies: 5
Views: 7438

Thank you JScott. I am mostly confused by the difference in price that I have for the Milgard clasics and the Integrity fiberglass. (For the 36 inch by 79 inch picture windows for the solarium the Milgard bid was about $230/window compared to $570/window for the Integrity). I thought that the Infini...
by ColoJ
Sun Nov 27, 2005 1:07 pm
Forum: Ask Our Pro's a Question
Topic: Vinyl or Fiberglass?
Replies: 5
Views: 7438

Thank you JScott. The Marvin quote appears to be for the Integrity line since they show a pine interior. Maybe the Infinity line would have come closer to the Milgard bid. From what I could see on the web sites for Marvin Integrity and Infinity, the Infinity does not have a fixed window listed as an...
by ColoJ
Sun Nov 27, 2005 10:38 am
Forum: Ask Our Pro's a Question
Topic: Vinyl or Fiberglass?
Replies: 5
Views: 7438

I have quotes from Milgard for vinyl Classic for about $10,000, for Milgard fiberglass for about $26,000, and for Marvin Fiberglass for about $19,000. The Pella quote was about $13,000, but there are no awnings or casements with Pella in fiberglass, and it seems unlikely that I can get the LowE comb...
by ColoJ
Sat Nov 26, 2005 1:16 pm
Forum: Ask Our Pro's a Question
Topic: Vinyl or Fiberglass?
Replies: 5
Views: 7438

Vinyl or Fiberglass?

I live in Colorado at an altitude of about 5100 feet. We are planning a renovation with replacement of 20 year old Weathershield wood windows. The main issue is 17 south-facing windows in a solarium that provides much of heat for the house during the winter, and is well shaded by overhang in summer....