Musty smell in a house? The prob­lem could be un­der the prop­erty

The Observer (Sarnia) - - HOMES - JEANNE HUBER

Q: We are try­ing to fig­ure out the next step in deal­ing with a musty odour in our 1928 brick row­house. It was orig­i­nally built as a cor­ner store and does not have a full cel­lar. The odour is most dis­tinct in the liv­ing room. When we pur­chased the house, the in­spec­tor thought the smell was from the wet earth un­der the liv­ing room, drawn in by the de­hu­mid­i­fier. We moved the de­hu­mid­i­fier to the cel­lar and be­gan us­ing it only when it rains ex­ten­sively, but that did not re­duce the smell. We’ve also tried air­ing out the house, scrub­bing sur­faces and us­ing odour-elim­i­na­tor prod­ucts. Noth­ing has worked.

Friends have sug­gested in­stalling a vapour bar­rier un­der the hard­wood floor­ing in the liv­ing room, but that would be ex­pen­sive and dif­fi­cult be­cause the crawl space un­der­neath is not re­ally ac­ces­si­ble. Would ce­ramic tile or cork tiles pro­vide a vapour bar­rier?

A: The so­lu­tion is prob­a­bly to “en­cap­su­late” the crawl space – a treat­ment that in­cludes seal­ing the dirt floor and out­side edges of the space and then pro­vid­ing a way to keep the air tem­per­a­ture and hu­mid­ity level there sim­i­lar to what is in your liv­ing space. There is no way to elim­i­nate the mildew prob­lem by in­stalling dif­fer­ent floor­ing be­cause the prob­lems are rooted in what is go­ing on within the crawl space.

Builders used to think that the way to avoid musty smells in and over a crawl space was to pro­vide plenty of ven­ti­la­tion un­der the house. To keep a house warm, they in­su­lated the floor from un­der­neath, of­ten with a vapour bar­rier in­tended to block mois­ture in the crawl space from get­ting into the house.

The think­ing has al­most com­pletely changed. Hav­ing ex­te­rior vents in a crawl space ac­tu­ally al­lows warm, hu­mid air to flow in dur­ing the sum­mer. When air in the liv­ing space is cooled by air con­di­tion­ing, that mois­ture con­denses on the un­der­side of the cold floor­ing, and mildew grows, es­pe­cially when there is a mois­ture bar­rier to keep the con­den­sa­tion from evap­o­rat­ing. In the win­ter, the op­po­site hap­pens, with the same ef­fect.

The so­lu­tion is to elim­i­nate the con­di­tions that al­low con­den­sa­tion.

Ac­cess into crawl spa­ces of­ten is pretty tight, but don’t as­sume there is no way to retro­fit your crawl space. The pic­ture you sent shows what is prob­a­bly just a foun­da­tion vent, and there is prob­a­bly an ac­tual ac­cess door some­where else, said Chris McLaugh­lin, a sales man­ager at JES, a com­pany based in Vir­ginia Beach that does crawl space en­cap­su­la­tion.

“Some­times there is a door in a closet and some­one has put car­pet over it, so you don’t even know,” he said. If there re­ally is no open­ing, his com­pany can cut one in, ei­ther on the out­side (with a steel lin­tel to sup­port the bricks over the open­ing, in a case such as yours) or in an outof-the-way place such as a closet, which would then be out­fit­ted with a trap door. Call at least two com­pa­nies that spe­cial­ize in crawl space en­cap­su­la­tion and ask for an on-site eval­u­a­tion and rec­om­men­da­tion, with an es­ti­mate of costs.

Mo­hammed El- Ghoul, owner of Home En­ergy Sav­ing So­lu­tions in Rockville, Mary­land, said en­cap­su­lat­ing a crawl space al­most al­ways elim­i­nates musty smells. The ex­cep­tion, he said, is when there is “bulk wa­ter” flow­ing into the space. So the first step in fix­ing your prob­lem is to make sure there is no ob­vi­ous source of wa­ter, for ex­am­ple from gutters that dump next to the foun­da­tion or sprin­klers that splash against the walls.

Then a com­pany such as El-Ghoul’s will send a crew to clean up any de­bris in the crawl space. This in­cludes re­mov­ing any in­su­la­tion with a mois­ture bar­rier in­stalled on the un­der­side of the floor­ing. In­su­la­tion with­out a mois­ture bar­rier can be left in place as long as it isn’t moldy or fall­ing down in places.

Once the space is clean, the crew spreads a mois­ture bar­rier, such as thick six-mil­lime­tre plas­tic, across the dirt floor. They also in­stall a mois­ture bar­rier up the walls and seal all seams. Fresh in­su­la­tion goes against the walls, over the mois­ture bar­rier. The fi­nal steps in­volve clos­ing off out­side vents and adding a vent or a reg­is­ter for the heat­ing and air-con­di­tion­ing sys­tem. This makes the crawl space, in ef­fect, part of the heated and air-con­di­tioned space of your house. Some­times, El-Ghoul said, a de­hu­mid­i­fier in the crawl space sub­sti­tutes for a heat­ing and air­con­di­tion­ing reg­is­ter.

This work isn’t cheap, but in ad­di­tion to solv­ing the odour is­sue, it should re­duce drafts. And by keep­ing the floor fram­ing drier, it also may help pre­serve your house, be­cause pests such as some kinds of pow­der­post bee­tles are more likely to in­fest moist wood.

El-Ghoul es­ti­mated that for a typ­i­cal Wash­ing­ton row­house, the bill of­ten comes to $1,700 or $1,800. But for com­pli­cated sit­u­a­tions, in­clud­ing ones with ex­ten­sive mildew that needs to be cleaned up, it could go into the thou­sands.

McLaugh­lin said the min­i­mum cost is more likely to be around $4,000 to $5,000, which would in­clude a more ro­bust de­hu­mid­i­fier than ones typ­i­cally sold to home­own­ers, and the elec­tri­cal work needed to run it. The up­per limit could be tens of thou­sands of dol­lars if the floor struc­ture is rot­ted and needs to be re­placed, he said.

Retrofitting a row­house is usu­ally sim­i­lar to work­ing on a de­tached house, El-Ghoul said, be­cause the crew treats the neigh­bour’s crawl space as if it is an ex­te­rior wall. But rarely, row­houses have shared crawl spa­ces. That presents ad­di­tional is­sues – and cost.

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