Fix hu­mid­ity, frost first, then take care of mould

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

QUES­TION: In June 2008, my boyfriend and I bought our first home. We did not get a home in­spec­tion due to the pres­sure of the hous­ing mar­ket and in­for­ma­tion that, if we did, we could lose out on the house. The house was built in 1977 and has an elec­tric forced-air fur­nace orig­i­nal to the house.

Ev­ery­thing was go­ing great for the first four months. Then I no­ticed on the ceil­ing cor­ners of the mas­ter bed­room, ad­ja­cent to the ex­te­rior wall, it was a lit­tle darker. I got on a lad­der and took a bet­ter look. It was fuzzy mould. I cleaned the mould and as I was do­ing so you could tell that there was a large area on the ceil­ing that had been re-stip­pled. My mother stated the mould could be due to high hu­mid­ity lev­els, yet our hu­mid­ity lev­els were be­tween 38 and 50 per cent. Then more mould ap­peared about a foot away from one cor­ner. We called the pre­vi­ous own­ers to see if they had this prob­lem and they said no.

My fa­ther went up into the at­tic to see if he could find the rea­son­ing and dis­cov­ered that we had Zono­lite in­su­la­tion. Later, we had it tested for con­fir­ma­tion and we found out that the pre­vi­ous own­ers knew about it. My fa­ther moved away some in­su­la­tion in one cor­ner to look at the vapour bar­rier and couldn’t find any­thing wrong, ex­cept some mois­ture be­tween the ceil­ing and vapour bar­rier. He un­blocked a few of the sof­fit vents to al­low more air flow.

We also dis­cov­ered that the new bath­room ex­haust fan the pre­vi­ous own­ers in­stalled was not in­su­lated cor­rectly, caus­ing all the ex­hausted air to ex­pel into the at­tic space. We’ve cor­rected that prob­lem, al­ready.

Af­ter the first clean­ing of the two ceil­ing cor­ners the mould did not come back, but in the other area came back over and over. I even re­moved the damp stip­ple, hop­ing that would dry out the area and fig­ured that this prob­lem had been oc­cur­ring for years. The area is cold to the touch and if you move a few inches away the ceil­ing isn’t cold. One day I no­ticed frost on the ceil­ing in that area, which would dis­ap­pear and reap­pear later. I also no­ticed the pantry ceil­ing cor­ner has con­den­sa­tion.

I’m in des­per­ate need for an an­swer to what is caus­ing this prob­lem and con­cerned about re­pair­ing it due to the fact that I have Zono­lite in­su­la­tion in the at­tic. Do you have any an­swers to the prob­lem?

Thanks, Rachael Hanischuk

AN­SWER: To of­fer an­swers to your prob­lem we will have to look at both of your is­sues — the mouldy ceil­ing and the dif­fi­culty with en­ter­ing and do­ing work in an at­tic in­su­lated with Zono­lite. Both are in­ter­twined due to the lo­ca­tion of the mois­ture and mould is­sues.

The first thing that must be dis­cussed is the root cause of the ceil­ing is­sue. You have cor­rectly made the as­sump­tion that ex­ces­sive mois­ture is the cul­prit for the mouldy ceil­ing. The dif­fi­cult thing to de­ter­mine is whether the mois­ture is com­ing from the liv­ing space or from an out­side source. In many cases, the an­swer is not clear-cut and the mois­ture is from both ar­eas.

You may have cor­rected the ma­jor­ity of the prob­lem by fix­ing the bath­room­fan duct­ing and open­ing up the sof­fit vents. That will take care of the ex­ces­sive mois­ture is­sues in the at­tic, but may not pre­vent re­oc­cur­rence of the mould.

Elec­tri­cally heated homes of­ten have a ten­dency to be dam­per than those with older gas fur­naces, due to the lack of a chim­ney, which is an ex­cel­lent method or re­mov­ing large quan­ti­ties of moist air from the home. Without a chim­ney, bath­room and kitchen ex­haust fans be­come more im­por­tant and may be needed more fre­quently and for longer pe­ri­ods of time.

A me­chan­i­cal ven­ti­la­tion sys­tem, such as a Heat Re­cov­ery Ven­ti­la­tor (HRV), may be in­stalled to fur­ther elim­i­nate ex­ces­sive mois­ture in the home. Once you have a han­dle on re­duc­ing the rel­a­tive hu­mid­ity in­side the home and at­tic, you can deal with the mouldy dry­wall is­sues.

If you had typ­i­cal in­su­la­tion in your at­tic, re­moval of the dam­aged dry­wall and re­place­ment would not be that dif­fi­cult. But if you have con­firmed by lab­o­ra­tory tests that the ver­mi­culite in­su­la­tion con­tains as­bestos, re­pairs may be con­sid­er­ably more dif­fi­cult. Cut­ting out and re­mov­ing the mouldy dry­wall may be the only way to pre­vent re­oc­cur­rence. Once the mould spores are em­bed­ded in the gyp­sum or pa­per of the dry­wall they may re­main dor­mant un­til the ma­te­rial be­comes suf­fi­ciently damp and then be­gin to grow again. This is why you are see­ing re­peated mould growth even af­ter you have cleaned the sur­face.

The only other op­tion is to clean the area thor­oughly and re­move the sur­face pa­per and some of the gyp­sum core of the dry­wall be­fore adding an­other layer of dry­wall over top. This will only be an op­tion if the mould has not com­pletely pen­e­trated the en­tire thick­ness of the ceil­ing sheath­ing or if the dry­wall is not too soft to cover up. If the mould is only on the sur­face, the pa­per layer may be re­moved, along with all the stip­ple, and the en­tire sur­face cov­ered with an­other layer of dry­wall.

To pre­vent new mould growth due to con­den­sa­tion, you may also be able to in­stall ad­di­tional in­su­la­tion over the prob­lem ar­eas near the ex­te­rior wall that will be re­sis­tant to mois­ture and air leak­age. If you don’t have to re­move the old dry­wall com­pletely, you may be able to pull away the ver­mi­culite from the area and in­stall rigid foam in­su­la­tion or fill any gaps with blown-in foam to seal the area. The dif­fi­culty might be to find con­trac­tors will­ing to work in an at­tic with this po­ten­tially haz­ardous ma­te­rial.

What­ever you do, tak­ing pre­cau­tions for breath­ing pro­tec­tion, in­clud­ing proper iso­la­tion and cleanup of the area, is crit­i­cal to pre­vent in­hal­ing haz­ardous as­bestos fi­bres present in some types of ver­mi­culite.

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