Thermal insulation effects on the shutters

Shutters are also touted as an excellent means of additional thermal insulation. Blinds should help to save energy. Which heat-insulating effects a roller blind actually has in practice, therefore, is extensively examined in this article.

Calculation of the saving effect through shutters

There is no technically binding information as to how much the roller shutter can actually contribute to preventing heat loss at the window.

Experts assume values ​​of up to 40 percent sinking heat transfer with closed shutters as a guideline. This is not a binding statement, but at best an estimate.

It also does not state which assumptions are based on the estimate:

• for which period of time the shutter must be closed
• when the shutter is closed and
• from which U-value of the glazing surface is assumed
• In addition, the material and the insulation of the shutter is not specified in this estimate

Estimate is not reliable

It is safe to assume that this estimate is not reliable.

The differences in heat transfer between an optimally insulated shutter in a single-glazed single-pane window can certainly not be compared with the savings in uninsulated shutters in an optimally insulated passive house window.

Thus, this value is not powerful. In addition, another criterion in the calculation comes into consideration, which is always neglected here.

When the sun shines through the window into the room in summer or winter, the room heats up considerably. During the heating season, this effect can contribute to a significant heat gain within the room and thus to a reduction of the heating demand.

If, on the other hand, the shutter is closed, this heat radiation disappears, which provides additional heat in the room. This effect must be computationally necessarily taken into account.

Effect of the effect

The effect of solar radiation varies depending on the position of the windows. The strongest is in the south-facing windows.

Numerical values ​​at the passive house

Investigations on passive houses show that solar radiation on a sunny winter's day is about 20 times higher than the amount of heating energy lost through the window. In a passive house, the heat radiated in from the south is lost only after two or three days without sun. During this period, temperature gains at room temperature can be observed up to 4° C.

Values ​​at the usually insulated house

A sufficiently insulated, energy-efficient single-family house with energy-saving windows (U value 1.1) has significantly greater heat losses than a passive house. Nevertheless, one can still expect a high effect of solar radiation in such rooms here. Roughly estimated, 10 times more energy is added than is lost. Closing the shutters in the winter during the day, so certainly more disadvantageous than beneficial.

The gains in terms of low heat efficiency may therefore only be calculated during the nights.