Study On Critical State Of Condensation At Inner Surface Of Building Envelope

The indoor air temperature and humidity not only decide on the senses of human inits environment, can also affect the performance of the building envelope and indoorsanitary condition. When the indoor air temperature is low or humidity is high, it maycause condensation at surface of envelope. It affects not only the indoor appearance, butwill also affect the performance of enclosure structure, so that the heat preservationdecrease. At the same time, it also creates conditions for fungal growth at the surface ofthe envelope structure, and will cause further damage. Envelope condensationprevention is mainly from the reduction of indoor humidity or improve the indoortemperature. But the premise is to know what extent the indoor air temperature andhumidity to control, so that inner surface will not appear condensation phenomenon. Atthe same time, after adding insulation to envelope, there is no guidance to what rangewill indoor air can variation.Therefore, this paper aiming at envelope condensation problem, use couplingtransmission theory analysis and mechanism of condensation at inner surface of envelopto obtain state control equation of surface heat and moisture,. And paper use CHAMPSsoftware to simulate the air state of inner surface under coupling heat and moisturetransfer in envelope. Analysis of indoor air critical state of Changsha, Xi’an and Harbin,which is typical climate, when inner surface appear condensation, and using relativehumidity line simplifies the indoor air critical state. This paper provide basis forcontrolling state of temperature and humidity of indoor air to make the inner surface notcondensation.In this paper, it also study the critical state of the indoor air after optimization ofenclosure structure. Do the polyurethane foam insulation (PU foaming agent), at inside of structure with different thickness. Critical state of indoor relative humidity will bevalues. Then, we obtain critical state of indoor air when enclosure structure withdifferent thickness of insulation layer in Changsha, Xi’an and Harbin. Finally, accordingto the analysis of the critical state of indoor air when enclosure structure with differentthickness of insulation layer, we get the most optimum insulation thickness to controlcondensation at inner surface of envelope. Changsha adding20mm polyurethaneinsulation layer, Xi’an adding20mm polyurethane insulation layer and Harbin adding30mm insulating are the best.