Bath­room ex­haust fan crit­i­cal to main­tain­ing dry home

Winnipeg Free Press - Section G - - HOMES - ARI MARANTZ

QMy daugh­ter and her part­ner bought a River Heights bun­ga­low last Novem­ber. It has a bath­room that has a win­dow in the shower wall and no fan in the bath­room. The plan is to even­tu­ally use this as a guest bath­room and build a nice new bath­room down­stairs. How­ever, un­til money is saved and that hap­pens, I am won­der­ing if it is a good idea to pur­chase a dehumidifier and use it in the bath­room after show­er­ing to get rid of ex­cess mois­ture. They don’t have any mould or mildew on the ceil­ing but I am afraid that even­tu­ally there will be some. Also, they have cedar wall pan­elling in this bath­room and were told not to paint it as it ab­sorbs the mois­ture. I don’t know if a bath­room fan can be added. It would prob­a­bly be ex­pen­sive and would have to go through the at­tic and there could be as­bestos in­su­la­tion in there. What are your thoughts? Dawn Chap­pel­laz An­swer: Bath­room ven­ti­la­tion is crit­i­cal to main­tain­ing a dry in­te­rior home en­vi­ron­ment and pre­vent­ing mois­ture dam­age and mould growth. While the cur­rent older win­dow may be ad­e­quate, if used dili­gently, up­grad­ing to an ex­haust fan will ab­so­lutely be nec­es­sary in the fu­ture. As many peo­ple know, mois­ture is the No. 1 en­emy of all things home re­lated. In our in­te­rior house en­vi­ron­ment, the largest sources of mois­ture are nor­mally from the kitchen and bath­rooms. Get­ting that mois­ture to the ex­te­rior of the home, be­fore it can cause se­ri­ous prob­lems, is crit­i­cal to main­tain­ing healthy in­door air qual­ity. When your daugh­ter’s home was built, the older win­dow would likely have been ad­e­quate for bath­room ven­ti­la­tion, due to a large amount of air leak­age common with that age of home. The air leak­age through the old win­dows, doors, at­tic, and base­ment would have been enough to nat­u­rally al­low enough fresh air in­tru­sion to pre­vent most se­ri­ous mois­ture is­sues. Un­treated cedar is a good choice for this age of bath­room, as it is open-poured and does read­ily ab­sorb and re­lease mois­ture, but should not be in­stalled inside the shower en­clo­sure. If the bath­room win­dow is opened ev­ery time an oc­cu­pant takes a shower or bath, year-round, that would nor­mally be enough to al­low ex­cess wa­ter vapour in the air to exit the build­ing with­out sig­nif­i­cant con­den­sa­tion on the walls or ceil­ings in the home. If the kitchen win­dow is also left open on mod­er­ate to warm days, or when cook­ing, lit­tle ev­i­dence of mois­ture dam­age may be present in the home. Even to this day, this may still work rel­a­tively well if no ma­jor up­grades to air seal­ing have been done in the home. If the house still has a fur­nace and wa­ter heater which vent through the orig­i­nal chim­ney, and win­dows have not been up­graded to well-sealed mod­ern PVC units, there may still be a lot of air leak­age through the build­ing en­ve­lope. If at­tic or base­ment in­su­la­tion has not been sub­stan­tially up­graded, that will fur­ther al­low fresh air from out­side to leak into the in­te­rior en­vi­ron­ment. While this sig­nif­i­cant air in­tru­sion may not be good for the heat­ing bills, it may en­sure that the air inside the home dur­ing the heat­ing sea­son is suf­fi­ciently dry. The prob­lems may be­gin to oc­cur when your daugh­ter and part­ner be­gin to do ma­jor up­grades to the older home. Re­place­ment of an older fur­nace with a new high-ef­fi­ciency unit is of­ten the first item to cause higher in­door rel­a­tive hu­mid­ity (RH). This is caused by seal­ing the ex­ist­ing chim­ney. The old chim­ney may be a ma­jor source of ex­fil­tra­tion of moist air from the home, as the ex­haust prod­ucts from the fur­nace are di­luted by house air that goes up the chim­ney dur­ing the heat­ing cy­cle. Once this is closed off, all of that moist air stays inside the home. This up­grade is of­ten com­bined with a fur­ther tight­en­ing up of the build­ing en­ve­lope by re­place­ment of older win­dows and im­proved base­ment, wall and at­tic in­su­la­tion. All of th­ese im­prove­ments will not only be good for the en­vi­ron­ment and the wal­let, but they make the home more com­fort­able in the frigid win­ters. The down­side is that th­ese mod­i­fi­ca­tions will pre­vent much of the pre­vi­ous air leak­age, keep­ing the moist house air inside much longer. This will un­doubt­edly raise the RH in the home, pro­vid­ing an ideal en­vi­ron­ment for mould growth and mois­ture is­sues. To coun­ter­act the rise in RH inside the home as im­prove­ments are made, your daugh­ter and part­ner will have to make ac­com­mo­da­tions to get the hu­mid air out­side, while bring­ing in more fresh air for re­place­ment. The sim­plest way to achieve this goal is by use of me­chan­i­cal sys­tems to move air through the build­ing en­ve­lope. This is where the bath­room ex­haust fans comes in. Sim­ply open­ing the bath­room win­dow may no longer be ad­e­quate to ven­ti­late the bath­room, due to the larger amount of dis­solved wa­ter vapour in the house air. The win­dow may also freeze up quicker in the win­ter, pre­vent­ing good op­er­a­tion, for the same rea­son. That is why in­stal­la­tion of bath­room fans are so crit­i­cal when up­grades are made. The fans will work best in con­junc­tion with some form of fresh air in­take, which may be as sim­ple as an in­su­lated duct con­nected to the re­turn air plenum of the fur­nace, or as com­plex as a heat re­cov­ery ven­ti­la­tor. The level of up­grades to the build­ing en­ve­lope may dic­tate which method is most prac­ti­cal. In­stal­la­tion of a bath­room ex­haust fan will be crit­i­cal as fu­ture en­ergy ef­fi­ciency im­prove­ments are made to the home, but may not be that dif­fi­cult or costly. In­stal­la­tion in the bath­room ceil­ing, vent­ing through the at­tic, may be the most straight­for­ward ap­proach. If there are is­sues with as­bestos con­tain­ing in­su­la­tion, or dif­fi­cult ac­cess to the at­tic, fans which vent though ex­te­rior walls or the foun­da­tion will be an ac­cept­able al­ter­na­tive. Ari Marantz is the owner of Trained Eye Home In­spec­tion Ltd. and the past pres­i­dent of the Cana­dian As­so­ci­a­tion of Home & Prop­erty In­spec­tors — Man­i­toba (cahpi.mb.ca). Ques­tions can be emailed to the ad­dress be­low. Ari can be reached at 204-291-5358 or check out

his web­site at trained­eye.ca.

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