b'THE OFFICIAL NFBA MAGAZINEcontinued from page: 15problems associated with HVAC and plumbing systems, readwater condensing on an outside surface will simply run The Top Ten Corrosion Threats at www.corrosionpedia. off the structure or quickly evaporate, this is not the case com/2/2031/corrosion/top-10-corrosion-threats inside the building. Inside surfaces are seldom designed Appendix C of NFBA Metal Panel and Trim Installationto facilitate water drainage, and moisture evaporation Tolerances is titled Galvanic Corrosion and containsoccurs more slowly indoors because of lower air flow rates several recommendations for reducing corrosion throughand less direct sunlight. During warmer weather, indoor building design and component selection. For a goodcondensation enhances decay, corrosion, and mold growth.overview of the chemistry associated with corrosion, readersCondensation in animal confinement buildings is often are referred to an article by Mike Sondalini found at https:// reduced by installing faced fiberglass (Figure 7) or rigid accendoreliability.com/metal-corrosion-basics-controls board insulation directly under the roof cladding, or by RESEARCH & TECHNOLOGYspraying foam insulation against the underside of the Water Condensation and Deposition cladding.To function properly (and not cause more Condensation is the conversion of a vapor to a liquid.problems than they solve), these insulations must be properly Depositionistheconversionofavaportoasolid.installed and maintained.Insulations have the added effect Watervaporwillcondenseontoanysurfacethatisof reducing radiant heat gain during hot and sunny weather below the dew point temperature of the air, and waterand reducing heat loss during cold weather.Interior dripping vaporwillformfrostorhoarfrostonanysurfacedue to condensation can be reduced by adhering anti-drip thatisbelowthefrostpointtemperatureoftheair.liners to the underside of roof sheathing.These liners hold condensation until it can re-evaporate into interior air.Due to radiation related heat loss from exterior surfaces at night, most exterior surfaces will be covered with early morning dew and/or frost when the relative humidity of the air is high. Condensation and deposition moisture that does not immediately run off these surfaces, normally evaporates as the morning progresses and the surface warms. Condensation on exterior surfaces tends only to be problematic when drawn or forced into cracks and crevices by wind and/or negative pressure ventilation systems.Condensation and deposition tend to be most problematic on interior surfaces since many interior components are not designed to get wet or remain wet for an extended time. Some of the worst interior condensation and deposition FIGURE 7. INSTALLATION OF VINYL-FACED FIBERGLASS INSULATION conditions occur in uninsulated animal confinement facilitiesBETWEEN WOOD FRAMING AND CORRUGATED METAL ROOFING.that lack supplemental heat.During periods of extreme cold, operators often reduce building ventilation to curtail heat loss.Cold WeatherThis action invariably drives up interior relative humidity,Cold weather, particularly freezing weather in northern and the amount of water condensing and freezing on exteriorclimates, can have specific and pronounced effects on buildings, cladding (Figure 6).While decreasing ventilation mayincluding differential movement of building components and initially warmsystems due to frost heave, water infiltration due to ice dams animals, it hasalong building eaves, accumulation of moisture in building theoppositethermal envelopes, truss uplift, and disintegration of concrete.effect when it literally startsProblems caused by frost heave can be expensive to to rain in therepair depending on their location, cause, and impacts FIGURE 6. ICEfacility,and AND FROSTanimalsloseonthebuilding.Itsbesttoeliminatefrostheave ACCUMULATION ONproblems before they start through proper design and WOOD GIRTS ANDmuch of theconstruction of the building foundation, with proper EXTERIOR METALinsulatingattentiongiventofoundationinsulation,backfill WALL CLADDINGqualitiesof INSIDE A POORLYtheircoat. materials, and above and below grade water drainage.VENTILATED DAIRY FREESTALL BARN. W h e r e a sIce dams form on roofs covered with snow or ice when 16 / FRAME BUILDER - JAN2023'