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Solar sunshades in Buenos Aires Argentina  (C) Daniel FriedmanLow-E Solar Shades for Controlling Sunlight, Heat Gain, Heat Loss on buildings

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Low-E Solar Shades:

This article discusses the effectiveness of Pella's Low-E Type E solar sun shades for passive solar heating in buildings.

Avoiding unwanted night-time heat loss through windows. Effect of night-time insulation on day-time passive solar gain. Solar Age Magazine Articles on Renewable Energy, Energy Savings, Construction Practices.



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Effectiveness of Pella Windows with Type-E Slim Shades for Passive Solar Heating in buildings

Our page top photograph shows an older but very effective solution to solar sunshading installed on an apartment building Buenos Aires, Argentina. (These solar shades are not a Pella product).

These hinged solar screens can be latched and opened or shut as a hinged-vertical sunscreen (photo left side) or as an awning-type sunscreen (photo right side). As we show below, this system also permits individual sections of the louvered screen to be open or shut from indoors.

The question-and-answer article below paraphrases, quotes-from, updates, and comments an original article from Solar Age Magazine and written by Steven Bliss.

What is the effectiveness of Type-E Solar Slimshades?

Question:

Please evaluate the effectiveness of Pella windows with Type-E Slimshades for passive solar heating. - Jim Chambers, Sunbuilders, Inc., Ft. Wayne IN

Answer:

With the solar shades closed, Pella gives the window an R-value of R-4.35.

This window R-value compares favorably with double-glazing at R-2 and triple glazed windows at R-3.

Although this is lower than the R-values claimed for many night insulation systems, there is no problem with loose edge seals - often a weak point with movable insulation. As with any night insulation over windows, the shade must be used to be effective.

Slimshades have the advantage of being easy to operate.

How about the blocking of solar gain, not just night time heat loss where solar shades are used?

Even when fully open, the low-e solar shades intercept and reflect some sunlight that you are trying to capture for passive solar heating (passive solar gain) in the building. And unfortunately, no one seemed to know (in the 1980's) just what the shading effect is.

Glenn Chafee, director of R&D at Pella Windows said in a 1985 interview that there are so many variables involved that the company had not tried to measure the shading.

Several other research centers around the U.S. echoed this view, though one expert ventured an estimate of 50-percent reduction.

This reduction would make the solar transmission of windows equipped with these shades roughly equal to that of low-e double glazing.

Between-the-glass shades offer convenient night insulation and summer shading, but so far, an unknown amount of shading.

The question-and-answer article about the use of solar shades or solar blinds and blocking unwanted heat gain from sunlight in buildings, quotes-from, updates, and comments an original article from Solar Age Magazine and written by Steven Bliss.

The link to the original Q&A article in PDF form immediately below is preceded by an expanded/updated online version of this article.

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