By adding insulation of the proper thickness to the system, not only are you saving energy by preventing heat gains throughout the system, but also raising the surface temperature above the dew point (Figure 3). Keeping the surface temperature above the dew point, 72☏ in this case, is of the utmost importance in preventing condensation from occurring. This is obviously not an acceptable condition within a space, but what can be done to prevent this from happening? Preventing Condensation: Use Insulation! The water vapor molecules in the 80☏ air will condense into a liquid as the surface temperature (Ts) of 40☏ is far below the dew point of 72☏. Take for example the following 40☏ chilled water pipe in a hot, humid space.

With surface temperatures far below the average indoor dew point, these systems can quickly perspire and create an apparent indoor rain. Condensation: It’s Raining Indoorsīelow-ambient systems, such as chilled water, refrigeration, and cool air duct systems, are highly susceptible to the formation of condensation on their surfaces. Thus, maintaining the surfaces of below-ambient systems above the dew point temperature is paramount to controlling the formation of condensation.

If a surface is below this dew point temperature, the air around it will cool and the water vapor will condense into a liquid. For instance, at 68☏ and 70% relative humidity, the dew point is 58☏ while at that same temperature but 30% relative humidity, the dew point is a crisp 35☏. The higher the relative humidity, the closer the dew point will be to the temperature of the air conversely, the lower the relative humidity, the cooler the dew point temperature is. The Dew Point is the temperature at which this water vapor being held in the air condenses into a liquid. Phoenix, Arizona, is next on the list of arid major cities with a relative humidity of 40% with most major cities averaging around 70%. For instance in Las Vegas, Nevada, the most arid of the major cities in the United States, the average relative humidity is 30%, meaning that, on average, only 30% of the maximum amount of water vapor at that temperature is being held in the air. The amount of moisture in the air can be measured by the relative humidity, or the percentage of water vapor in the air compared to the maximum amount of water vapor that that temperature air could hold. 1 This means that water vapor is always going to be present in the air around your systems and will condense into a liquid with the right conditions. For this reason, in addition to moisture protection according to DIN 4108-3 (in German), a drying reserve in accordance with DIN 68800-2 (in German) is required, which should also allow harmless drying of unintentionally penetrated moisture.All air on earth contains at least a little bit of moisture in the form of water vapor because of the earth’s atmosphere and climate. Moisture protection in wood structures is particularly important. If the water vapor accumulates on a cold layer, condensation is likely to occur. Because the outer, colder layers can only contain very little water vapor, it must be ensured that the water vapor escapes as easily as possible from the outside. This is why water vapor diffuses through the component from the inside to the outside. In winter the warm room air contains more moisture than the cold outside air. At this point, the following simplification is sufficient: The article Wasserdampfdiffusion und feuchte Wände (in German) explains how moisture and mold can occur. Therefore, the U-value calculator examines your insulation for potential moisture problems. Moist and moldy walls are the nightmare of many builders. More detailed information can be found on the left-hand side of the screen using the buttons U-value, humidity, heat, etc.įor commercial usage, calculations are made according to DIN EN ISO 6946 (U value), DIN 4108-3 (moisture protection) and DIN 68800-2 (drying reserve).

The main results are displayed at the bottom of the screen. To insert wooden beams into an insulation layer.

Exterior wall dew point calculator