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The trouble with fiberglass insulation

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  • The trouble with fiberglass insulation

    The owner had water running down their basement wall during a storm and asked me to look at it. The house is 2 x 6 construction built in 1998. The builder is very reputable and the house is built to code with no alterations, 100% above board.

    I traced the water problem to a failure of a waterproof boot on the electrical service mast. I did a temporary roof / flashing repair that dealt with the leak until spring when it can be re-roofed and then opener up the wall behind the service entrance from the inside.

    What I found inside the wall was sodden fiberglass holding water like a sponge. The air / vapour barrier and kept any evidence of a leak from the inside of the building but the OSB sheathing, the wood studs and the fiberglass were a mass of a variety of molds including the infamous toxic "black mold" which was thriving in the fiberglass.

    IMG_0299.jpg Wall cavity .... I can poke my finger through the rotten OSB. Fiberglass is fused to the OSB .... I'll scrape it off when it's fully dry. the OSB and the studs are covered with black mold.

    IMG_0300.jpgIMG_0301.jpg
    More wall cavity pics.

    IMG_0302.jpg Example of sodden, moldy insulation.

    This is why I always steer people toward Rozul insulation. Roxul is more expensive but mold doesn't grow on it and water drains freely from it. If it had been Roxul in the wall cavity instead of fiberglass the problem would have been noticed sooner because it doesn't hold water and the mold problem wouldn't have been nearly so bad because Roxul wouldn't have held the water there like a sponge for however many years the roof was leaking.

    Roxul also retains it's insulating value when wet, fiberglass is useless when wet.
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  • #2

    Re: The trouble with fiberglass insulation

    I think that was going to be a mess regardless of what was in there Doug. ! could be wrong and it really doesn't matter in this instance but, was Roxul available in 1989 and is the sheathing OSB or aspenite? It's probably the first OSB which was subsequently improved as I'm sure you are aware. Even so it would not have prevented that mess. I'd also be curious to find out what house wrap was used. That looks like the mess that happened in Vancouver because moisture could not escape the house wrap on the exterior and it sure as hell wasn't getting through the interior vapour barrier.
    "Do it Right!"

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    • #3

      Re: The trouble with fiberglass insulation

      Originally posted by Rusty View Post
      I think that was going to be a mess regardless of what was in there Doug. ! could be wrong and it really doesn't matter in this instance but, was Roxul available in 1989 and is the sheathing OSB or aspenite?
      Roxul wasn't available in 1989 but it was available in 1998 when the house was built.

      Aspenite was never approved as a sheathing material, it's OSB and the same OSB that exists today.

      Originally posted by Rusty View Post
      Even so it would not have prevented that mess.
      As I explained in the post fiberglass absorbs and holds water like a sponge, Roxul is free draining. Try putting a sample of both in a bucket of water then lift them out and see what happens. Fiberglass will soak up water like a sponge while Roxul will drain completely.

      Originally posted by Rusty View Post
      I'd also be curious to find out what house wrap was used.
      In this case it's irrelevant as the water entered the wall cavity through a leak in the roof. It's performance played no role and even if it did it's a red herring because the subject of this post is the properties of the fiberglass and it's role in the damage not the performance of the house wrap.

      Fiberglass is great cost effective insulation as long as you use it places where there is no risk of it getting wet. Once it's wet it's garbage ...... actually worse than garbage because it makes a bad situation worse by holding water and providing a great medium for mold to grow on.

      This is one of the problems of just meeting building code instead of using best practices. Provided everything is installed properly and every component of the building envelope is properly maintained you have a structure that performs but if something unexpected happens like a leak or if you don't maintain you property or if your siding guy or roofer was a little less dilligent than he should have been and took short cuts you have a rotten mess.

      This leak had been going on for years but it wasn't until the HO saw a puddle on the floor that it was discovered. This house was built to code by a reputable builder and with all the proper permits and inspections. Imagine how bad things can get if you don't follow the building codes and just use fiberglass and wood in situations where it's almost certain to get wet because you either don't know enough to control the movement of water through the building envelope or are just too cheap to do anything better.

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      • #4

        Re: The trouble with fiberglass insulation

        Originally posted by dave_k View Post

        Fiberglass is great cost effective insulation as long as you use it places where there is no risk of it getting wet.
        Where would there ever be no risk of getting insulation wet if the building envelope was compromised? Just wondering.

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        • #5

          Re: The trouble with fiberglass insulation

          Originally posted by Kayak Jim View Post

          Where would there ever be no risk of getting insulation wet if the building envelope was compromised? Just wondering.
          This building meets the NBC and would work well over the entire economic life of the building provided it's kept dry.

          You run into problems with fiberglass when something goes wrong. in this case it appeared to be that the wind load on the electrical service wires cause the mast to flex and move working the waterproof boot loose which cause the roof to leak into the wall assembly.

          The problem isn't with using fiberglass insulation, which is great insulation and a great value. The problem is choosing fiberglass in situations where there is a good chance it will get wet like when insulating damp foundation walls or insulating with fiberglass then not detailing the air barrier properly.

          Just because it's an approved product that meets building code standards doesn't mean it's a good choice in every application. You have to use your head and think about the risks before choosing what products you use to build with. You also have to keep the maintenance up on your property ESPECIALLY if it's built to code minimums. You aren't protected from something like this even if it's passed and inspected by the city and your insurance won't pay out if maintenance has been neglected.

          This house also has roof and floor trusses and I haven't had a chance to look further than what was uncovered in the pictures. Again products that meet BC requirements and are excellent and economical building solutions but are vunerable to failure if a single component is damaged .... like in the case of rot caused by moisture.

          I don't have a problem with this type of construction. The only reason I posted this is to show what can happen if your use fiberglass in an common application that's been built to building codes and passed inspection. This house has electric heat, mechanical ventilation, a well drained site and a bone dry basement. It is about as risk free for this type of construction as you can get however things still went wrong.

          In light of this what are the odds of a fiberglass insulated wood stud wall staying dry and rot free in a damp leaky basement with forced air heat no mechanical ventilation. Would it be worth the extra $$$ to deal with water problem from the outside or build with metal studs and roxul or foam boardstock rather than risk having a foul rotting mess in your home?

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          • #6

            Re: The trouble with fiberglass insulation

            Originally posted by dave_k View Post

            Roxul wasn't available in 1989 but it was available in 1998 when the house was built.

            Aspenite was never approved as a sheathing material, it's OSB and the same OSB that exists today.



            As I explained in the post fiberglass absorbs and holds water like a sponge, Roxul is free draining. Try putting a sample of both in a bucket of water then lift them out and see what happens. Fiberglass will soak up water like a sponge while Roxul will drain completely.



            In this case it's irrelevant as the water entered the wall cavity through a leak in the roof. It's performance played no role and even if it did it's a red herring because the subject of this post is the properties of the fiberglass and it's role in the damage not the performance of the house wrap.

            Fiberglass is great cost effective insulation as long as you use it places where there is no risk of it getting wet. Once it's wet it's garbage ...... actually worse than garbage because it makes a bad situation worse by holding water and providing a great medium for mold to grow on.

            This is one of the problems of just meeting building code instead of using best practices. Provided everything is installed properly and every component of the building envelope is properly maintained you have a structure that performs but if something unexpected happens like a leak or if you don't maintain you property or if your siding guy or roofer was a little less dilligent than he should have been and took short cuts you have a rotten mess.

            This leak had been going on for years but it wasn't until the HO saw a puddle on the floor that it was discovered. This house was built to code by a reputable builder and with all the proper permits and inspections. Imagine how bad things can get if you don't follow the building codes and just use fiberglass and wood in situations where it's almost certain to get wet because you either don't know enough to control the movement of water through the building envelope or are just too cheap to do anything better.
            Sorry Doug for the typo on the date.

            I have to disagree with your aspenite comment but let's not worry about that it was a curiosity on my part as was the house wrap. Neither of which are pertinent as you point out.

            I have no disagreement with your fiberglass comments BTW.

            It is a shame it has to come to this but I'm fairly certain that you would agree the mast if installed properly should not move and cause this situation. I redid 3 services in the last couple of years and I guarantee non of them could flex and or move in any way, shape or form and storm collars installed correctly seal for decades. Once again it's a damn shame. I would probably blame a reroof contractor who did a lousy job.
            "Do it Right!"

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            • Thread Continues Below...

            • #7

              Re: The trouble with fiberglass insulation

              Originally posted by Rusty View Post

              I have to disagree with your aspenite comment
              Aspenite was the trade name of MacMillan Bloedel waferboard. The difference between waferboard and OSB is OSB conforms to a CSA standard and meets BC requirements. Waferboard looks just like OSB but is different in composition and isn't rated for use as sheathing. People often use the terms Aspenite, waferboard and OSB interchangably ..... just like they use plexiglass when they mean acrylic. Mac Blo may have labelled their OSB with the trade name Aspenite or the industry in your market may have just continued to call OSB Aspenite. When someone building a house says "go get me a sheet of Aspenite. I know what he's talking about and I'll come back with OSB however when discussing BC issues and the question comes up as whether we're talking about apsenite or OSB the difference is important.

              Originally posted by Rusty View Post
              It is a shame it has to come to this but I'm fairly certain that you would agree the mast if installed properly should not move and cause this situation. I redid 3 services in the last couple of years and I guarantee non of them could flex and or move in any way, shape or form and storm collars installed correctly seal for decades. Once again it's a damn shame. I would probably blame a reroof contractor who did a lousy job.
              This could have been an ICF structure and the leak would have happened just the same however it could have leaked for decades and done little more than strengthened the concrete.

              As I've stated a couple of times now the issue is the role fiberglass insulation played in making a bad situation worse. This was an extreme case with water pouring down into the wall cavity for years but you can get similar results with a house with high levels of insulation and poorly detailed air / vapour barrier or from water condensing on a cold concrete foundation wall. Mold need food and water to live. Paper (drywall) wood and OSB provide the food and soaked fiberglass holds the water in place which is the ideal conditions for mold to thrive.

              How the water gets into a wall cavity isn't the issue however if you don't understand building science and build accordingly it can become an issue very quickly. This is why choosing the right materials for the application and designing assemblies that work well as a system is so important.

              I built eight houses with exactly this type of wall assembly between 1993 - 96. They all got through the warrantee period without problems, the people were happy and as far as I know they still are. Pricing was very competitive during that time and there was only about $10k profit in each house and no one pays for details they can't see.

              When I built my own place, I changed a few details which didn't really cost more than a $3-4k on a 2500SF house. I kept the OSB but used roxul simply because I knew despite the price difference I would sleep better with Roxul in the walls. I also ice and water shielded the entire roof, detailed the penetrations with blueskin and spent a week detailing the air/vapour barrier. I also made sure there was zero cellulose in the basement ( retainer t's, foamboard and paperless dw). Minor details however the basement did flood one time and the only damage was to door and baseboards (Roppe rubber floor) so it paid off.

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              • #8

                Re: The trouble with fiberglass insulation

                Not disputing it, but I always find it odd that fibreglass insulation which is spun glass fibres retains moisture and thus loses insulation properties when wet, while wet rockwool which is spun molten mineral rock doesn't. I assume the glass fibre themselves are not porous and both insulations work at least in part by trapping air. I read that rockwool manufacturing introduces a small part of oil which helps give it it's hydrophilic property but wonder why they couldn't come up with a way to make fibreglass hydrophilic?

                Given the points raised by Dave, it's a wonder that fibreglass insulation is still allowed by the building code when there is an alternative. Yes you can keep it dry if you do everything right but if a small mistake can lead to a serious problem then why take the chance? I'm not a builder so I may be mistaken but the same argument could be made for ordinary drywall behind shower tiles. If you do everything right you can keep it dry but one small mistake and you have a big problem. I'll duck now while the missiles start firing.

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                • #9

                  Re: The trouble with fiberglass insulation

                  I think I agreed with your fibreglass comments in post #6 when I said; " I have no disagreement with your fiberglass comments BTW."

                  Without the leak it would be in great shape and still doing it's job wouldn't it ? Sorta like the broken window doesn't leak unless it rains.

                  We've both been doing this for a long time and I admit if I had a crystal ball I would have used some of todays better products but unfortunately they didn't exist at the time. However, the wind has not been seen that could have blown over some of the solid brick houses of the 40's and 50's. It's all relative isn't it?
                  "Do it Right!"

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