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Heating Glass for High Value Interiors

Unlike art museums which are devoid of windows, high-end residential construction often has high glass to wall ratios. This is challenging in areas where there are are seasonal cold, damp and humid conditions.

Seasonally adjusted relative humidity set points (Figure 1) should be used to maintain acceptable conditions for artwork and high value collectables in residential interiors. For example; assume that a desired temperature control to be 72.5°F ± 2.5°F (22.5°C ± 1.4°C) would be ideal. Highly fenestrated residential window conditions present additional challenges to that maintenance. This is especially true with traditional multiple light aluminum and steel windows.

Architects and designers prefer the minimalistic profile of steel and Jansen has excellent high performance systems, however all multiple true divided lights can be, shall we say, "tricky" . How so?

Published u-values are deceptive because the values are measured at the center of the glass and ignore the two inch outer perimeter. If the values were measured at the edges of the glass, the performance plummets.

As a rule R-values on walls are high (the higher the better) and windows much lower and expressed in u-values. u-values are the inverse of R, so the lower the u-value the better. Heating glass creates u-value to near zero. This places the R value of IQ Radiant Glass windows on a par with the value of the walls.

This has a profound impact on thermal comfort at lower interior ambient temperatures and prevents condensation on window glass and metal frames.

Another advantage with heating class is its ability to adjust for changes in specific interior zones, thus augmenting a central system.

IQRG helps eliminate condensation. Since IQRG uses radiant heat, there is almost no convection. The concept behind central humidification is to maintain a nearly constant air condition: saturated air with a dew-point temperature just above that at the lowest acceptable space temperature and lowest acceptable relatively humidity, in our case 70°F (21.1°C) and 45% relative humidity,

For zones that are unoccupied with low cooling loads, the resulting space condition is the “Unoccupied” point in Figure 2.

In all cases, seasonal or by activity levels, individually monitored heating glass zones, controlled by the building management system will help maintain desired levels of temperature and humidity.

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