Stop us­ing hu­mid­i­fier to im­prove home air qual­ity

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

QI have a hu­mid­i­fier in the fur­nace room with a dial switch 10-75 in my home in Ed­mon­ton. I be­lieve this is per­cent­age. It also has a switch from win­ter to sum­mer on it, which just opens the chan­nel in­side dif­fer­ently. I also have a heat re­cov­ery ven­ti­la­tor (HRV) unit, which I have set the de­hu­midi­s­tat to 40. On the main screen it says the rel­a­tive hu­mid­ity (RH) is 30. I set it on fan one and I have played around with the 20/40 or al­ways vent. Do th­ese in­ter­act with each other when one is set to high and the other is lower? Does the HRV set­tings af­fect the set­ting of the hu­mid­i­fier, and how does it af­fect the house? Does it also af­fect tem­per­a­tures in my house based on what my ther­mo­stat is do­ing? Is the HRV set up through the vents that also pro­vide us our heat? I’m ask­ing this last ques­tion be­cause we get cold air blow­ing from the vents of­ten when it’s still cold in my house. Is the cold air com­mon? I find this all very con­fus­ing — what to set things at and when, or how they all re­act to one an­other. Any ad­vice? Thanks, Scott Gill An­swer: You have come to the right place be­cause I al­ways have ad­vice for home­own­ers who are con­fused about sys­tems, me­chan­i­cal or oth­er­wise, in their homes. This time the ad­vice is painfully sim­ple. Shut off or dis­con­nect the hu­mid­i­fier and sim­ply use the con­trols for the HRV prop­erly as the win­ter weather changes. I re­ceive a dis­pro­por­tion­ate num­ber of in­quiries about HRV units, com­pared to al­most any other sys­tem in the home. The lack of knowl­edge about th­ese fairly sim­ple de­vices does sur­prise me, but not just be­cause they are gen­er­ally in­stalled in rel­a­tively new homes. I fre­quently ob­serve this ig­no­rance, which I at­tribute to a lack of in­for­ma­tion from builders or HVAC con­trac­tors in­stalling th­ese items. As with any newer sys­tem, home­own­ers should not just be handed a printed man­ual with lengthy in­struc­tions, but should have the sim­ple con­trols and main­te­nance phys­i­cally demon­strated, prior to use. A few min­utes of de­scrip­tion and op­er­a­tion would elim­i­nate this lack of un­der­stand­ing. Also, many HRV de­hu­midi­s­tat con­trols are not func­tion­ing when tested, but that ap­pears to be im­prov­ing con­sid­er­ably with the manda­tory in­stal­la­tion of HRVs in new homes in our area. An HRV is in­stalled in a new home to pro­vide two main func­tions. Firstly, the unit is de­signed to vent stale air from the home and re­place it with fresh out­side air. This ven­ti­la­tion func­tion is be­com­ing in­creas­ingly im­por­tant to re­move pol­lu­tants, CO2 and odours from our in­door en­vi­ron­ment as homes be­come more air­tight. The other func­tion of this me­chan­i­cal box, nor­mally lo­cated near the fur­nace, is to help reg­u­late the rel­a­tive hu­mid­ity in the home. This crit­i­cal func­tion is to pre­vent ex­cess mois­ture in the house air from caus­ing mould, rot and other nasty things from build­ing up in­side our liv­ing spa­ces. The way an HRV pro­vides both of its key func­tions is by turn­ing on at var­i­ous in­ter­vals de­pend­ing on how it is set. Many units have au­to­matic set­tings that will pro­vide a timed pe­riod of con­tin­u­ous ven­ti­la­tion, fol­lowed by a pe­riod of non-op­er­a­tion. To com­pli­cate this fur­ther, most newer units have mul­ti­ple fan speeds, which can be used to con­trol the amount of air moved in and out of the home. Also, the HRV can be man­u­ally turned on with timed switches lo­cated in bath­rooms, at least in new home in­stal­la­tions. This last func­tion is im­por­tant be­cause bath­rooms are nor­mally the largest source of wa­ter vapour in our homes, but can also help il­lus­trate my next point. The mis­un­der­stand­ing many home­own­ers have about proper HRV func­tion and pur­pose is par­tially due to a sys­tem typ­i­cally in­stalled in older, poorly sealed homes. A hu­mid­i­fier was of­ten in­stalled on the duct­ing near older fur­naces, due to the ex­treme dry­ing of the win­ter air in th­ese air-leaky build­ings. Be­cause so much cold air could pen­e­trate the build­ing en­clo­sures, re­plac­ing the heated air that es­caped through older chim­neys, walls, at­tics and win­dows, mois­ture con­trol and ven­ti­la­tion was not very im­por­tant. This al­lowed enough nat­u­ral ven­ti­la­tion, not only to negate the need for an HRV, but the large amount of out­side air in­fil­tra­tion made the in­door air too dry. To coun­ter­act this ef­fect, hu­mid­i­fiers were in­stalled that added mois­ture to the force air in the heat­ing sys­tem, rais­ing RH to com­fort­able lev­els. To sum­ma­rize th­ese points, and over­sim­plify the sit­u­a­tion in your home, you have one sys­tem in­stalled to re­move mois­ture from the air in the home, the HRV, and an­other one to add mois­ture to the air, the hu­mid­i­fier. Both of th­ese me­chan­i­cal boxes are sup­posed to be op­er­ated pri­mar­ily dur­ing the heat­ing sea­son, but have di­rectly op­pos­ing ob­jec­tives. Does this make any sense? The an­swer should be ob­vi­ous, and shut­ting down or re­mov­ing the hu­mid­i­fier will be your next course of ac­tion and solve part of your dilemma. Th­ese de­vices are an an­ti­quated throw­back to a time when air/ vapour bar­ri­ers and mod­ern ther­mal in­su­la­tion did not ex­ist. The fi­nal piece of the puz­zle is proper set­ting of the HRV con­trols. Yes, a prop­erly in­stalled HRV should en­gage the fur­nace fan when it comes on to help move the air through the fur­nace duct­ing, not just its own. This will al­low cool, room-tem­per­a­ture air to be felt at the reg­is­ters when on, but should not af­fect the over­all heat­ing func­tion of the fur­nace. Set­ting the HRV de­hu­midi­s­tat be­tween 25 and 35 per cent dur­ing a typ­i­cal Western Cana­dian win­ter should cause it to func­tion prop­erly, un­less the timed au­to­matic func­tion is set. This, com­bined with dis­con­tin­ued use of the hu­mid­i­fier, should yield com­fort­able and healthy in­door air, and help clear up any mis­un­der­stand­ing you have about the func­tion of th­ese two op­pos­ing sys­tems. 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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