Climatic tests on an enclosure for a wrought-iron gate

Protected in style

Relative humidity over time
© Fraunhofer IBP
Relative humidity over time (period 1 year).
Flottmann Gate in Herne
© Dratz & Dratz Architekten
Enclosure for the Flottmann Gate in Herne, Germany.

Scientists have conducted building physics tests to establish whether completely encasing a listed, wrought-iron Art Nouveau gate would eliminate conditions that accelerate corrosion. The gate is currently sheltered by a glass-roofed structure made of reinforced concrete, but is still subject to heavy weathering caused by rain driven into the structure by the wind. One proposed solution was to add glass walls at the front and sides; the aim of the study was to assess how effective this would be and to make recommendations for the best way to implement it in practice.

Taking the climatic conditions of the gate without such an enclosure as a baseline, the researchers examined the climatic impact that completely encasing the gate would have on its immediate environment. They performed their calculations using WUFI®-Plus, a tried-and-tested indoor climate model developed at Fraunhofer IBP. The following issues were considered: How do different air exchange rates affect the interior climate, and what are the ideal rates of air exchange? Particular attention was paid to relative humidity, temperature and the fluctuations in these values, with solar radiation and frost also being taken into account. The research team also examined the extent to which condensation formed on the glass panes and the gate itself. Given that condensation buildup is largely determined by the thermal transmittance of the glass used, additional calculations were made with a different U-value for the glass walls. Although the concrete showcase around the gate was built two years ago, the scientists still had to factor residual building moisture into their measurements as the protective structure had been almost fully exposed to weathering. The new plans do not include a heating system - only a slight amount of heat will be produced by five 35-watt lamps, which will illuminate the gate from the onset of dusk until midnight.

One important aspect the scientists had to consider is condensation, which can form both on the inside and outside of the structure, mainly on the glass panes and in areas where thermal bridges occur. Condensation would obstruct the view of the gate, and - much worse - could drip onto the it as well as leave condensation trails on the concrete.

Based on their findings, the scientists made the following recommendations:

  • Completely encasing the gate is a good idea, as an all-around enclosure would provide effective protection from driving rain.
  • However, a sufficient amount of air exchange is essential. After encasing the gate, residual building moisture must be removed by starting off with a higher rate of air exchange. This can be reduced once this initial phase is over, so adjustable vents are recommended.
  • Provided adequate air exchange is guaranteed by a suitable venting system, no additional ventilation measures are required.
  • In the event that increased amounts of condensation start forming on the inside surfaces of the enclosure, the rate of air exchange should be increased.

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Fraunhofer Center for Conservation and Energy Performance of Historic Buildings in Benediktbeuern


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Cultural Heritage Research at Fraunhofer IBP