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Insulation, should I or shouldn't I?

Post in 'The Green Room' started by 4barrel, Nov 13, 2013.

  1. 4barrel

    4barrel New Member

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    I just had a energy audit on my house. The house does not have any wall insulation. It was built in the 1930's. I have insulated the attic, and had energy efficient windows installed. I read on the internet that it is not a good idea to have cellulose blown into the walls in houses that have this type of balloon construction. A good article on this is at bobyapp.com/blog/2009/06/myths-about-insulating-old-house-walls. The last thing I need is a situation in the future where I have to gut all the walls in the house due to mildew problems brought on by what this article says. What do you think?

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  2. semipro

    semipro Minister of Fire

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    Did they do a blower door test when they did the audit. If so how airtight is the house?
    In general, your resources are better spent addressing air leaks first rather than adding thermal insulation.
    When you insulated the attic did you seal all the leaks between the house and attic first?

    You probably ought to spend some time reading at buildingscience.com or greenbuildingadvisor.
    woodgeek likes this.
  3. woodgeek

    woodgeek Minister of Fire

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    can't answer the question unless we know your climate. Where are you?

    The info on your link is pretty outdated and not in line at all with current thinking. Only houses in the northernmost tier of the lower 48 (or points further north) can benefit from a 'vapor barrier'. All houses need airsealing. And if the house is airsealed, the insulation will not get wet or lead to 'paint failure'.

    My suggestions:
    1) If you haven't had an airsealing job done, do that first.
    2) No one in a 20th century house should over-humidify their house in the winter, they're not designed for that. I keep mine below 30-35%, and no problems.

    Historical fact....in the early 20th century, folks started to insulate wall cavities, and within a few decades did see major problems such as those in the article, paint failure, wet insulation, etc. The problem was **incorrectly** diagnosed at the time as due to water vapor diffusion through walls, and the cures at the time were to leave houses leaky on purpose (builders) and to install vapor barriers (code officials) up through the 70s and 80s. We now know the problem was water carried by air leaking into and flowing through the cavities (around plaster walls and vapor barriers) and could be alleviated by airsealing. Once the cavity is sealed, vapor diffusion (to both inside and outside) actually keeps the wall cavity dry. But thanks to that mistake back then, >50% of US housing stock is stupidly designed and/or built incorrectly.
    Last edited: Nov 14, 2013
    Floydian likes this.
  4. My Oslo heats my home

    My Oslo heats my home Minister of Fire

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    It can be done. I also have a balloon framed home, built in 1880. Only difference is that I have been doing renovations over the years and have taken into account the open framing and typically leaky house. My second floor is up to date with insulation, wiring etc. Since the balloon framing is typically open from basement to attic I had to consider fireblocking before we closed up the walls. The fireblocking also includes chaulking or spray in insulation to limit air getting into wall cavities. My home is now much tighter and I agree with woodgeek on the winter time humidity, keeping it low.
    Blow in will work, the spaces have to be air sealed to make it work to avoid moisture related issues.
    woodgeek likes this.
  5. 4barrel

    4barrel New Member

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    Woodgeek,I live In southern MA. No, the guy who did the audit did not do a blower door test. He said if I got insulation put in the insulation company would do that when they were doing the work to find all air sealing that was needed. I am paranoid about doing this. Funny though, if you go to cellulose.org, the website for the insulation, they tell you that a vapor barrier is not recommended for cellulose. Also, my house is vinyl sided, I don't if that is good or bad in this situation.
  6. woodgeek

    woodgeek Minister of Fire

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    vapor barrier does not equal airseal. Period. In the 70s people put up vapor barriers (poly/kraft paper) and didn't tape the seams so it leaked air. Stupid, moisture went around. Nowadays, you want to put up an airbarrier that has some vapor permeability, like tyvek that is carefully taped, or drywall that is mudded at the joints (and caulked to the framing). Very different animals. And vinyls siding is vented, so it can dry out underneath.

    In MA, contrary what any 80s-vintage builder would tell you, you do not need a vapor barrier for any type of insulation. In the winter, an insulated wall cavity can dry to the inside or outside by diffusion. You would only have (hypothetical) cavity condensation if you intentionally over humidified your house for very extended periods during very cold weather. If you look up actual rates of vapor diffusion through building materials like drywall, we are talking minute amounts of water. Actual humidified air flowing through unsealed cavities carries hundred or thousands of times as much water into there.

    Of course, densepack cellulose has both airsealing and fireblock properties. I would not rely on that however if I had open cavities...I would still seal any large openings before getting the cellulose done. In my 1960 house, all the rim joists/sills were drywalled (even the garage) without airsealing or insulation. I just had some pros denspak cellulose about 75% of it, maybe 100 linear feet, that was accessible. They only made 4 3" holes to patch, my floors there are not freezing anymore and my energy usage is way down. I was skeptical of the airsealing of cellulose, but now I'm a believer.

    If you are curious, as semipro said, do some reading at buildingscience.com or greenbuildingadvisor, and give bobvila.com a miss.
    Last edited: Nov 14, 2013
  7. altmartion

    altmartion Feeling the Heat

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    seal, seal, seal!! sealing your house should be done prior to insulating or at the same time. insulating is great, but if the house is extremely leaky than the insulation is not working at it's full capacity. make sure they dense pack. just blowing it in is short term. i just did this to my 100+ year old house and the difference is incredible. before it could be 20 deg outside and 70 inside and we always felt cold. now with the same conditions we could walk around the house in our skivvies. and the energy savings is huge. it stays cool in the summer as well. do you have a lot of cob webs?
  8. 4barrel

    4barrel New Member

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    I don't know what you mean by having cob webs. When insulated my attic, I sealed around the light fixtures, but not anywhere else. I did not know about this stuff a few years ago. Do insulation contractors do air sealing and insulating separately?
  9. altmartion

    altmartion Feeling the Heat

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    usually they offer both. cob webs look like spider webs but are basically dust and other particles.
  10. My Oslo heats my home

    My Oslo heats my home Minister of Fire

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    One of the worst offenders is electrical outlets, switches and such. In what would be considered old construction now, they were not sealed. It is now code that the electrical components that go through either side of a wall have a seal on them. Wire penetrating bay to bay or floor to floor must be sealed for both fireblocking and airtightness. New construction homes are so tight today that air makeup has to be introduced in order to displace stale air.
  11. maple1

    maple1 Minister of Fire

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    This stuff is very interesting.

    The one thing that the building inspector was most anal about over and above anything else 18 years ago when we built out house was vapour barrier. Every time he was there, he scoured all the seams on it, and reviewed the lettering on it. I remember the first time he came that we had it up, he told me I had to replace it because I put the wrong stuff up (too light). After looking at it again, he said sorry, that is the right stuff.

    Now, it seems like the better thing to do would be not to use any vapour barrier at all. Maybe even Tyvek on both sides of the studs? Amazing how thinking can change. It also seems that having the vapour barrier might also prevent adding foam insulation to the outside at some point in the future, as that might prevent outward drying of the wall cavity.

    Huh.
  12. My Oslo heats my home

    My Oslo heats my home Minister of Fire

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    liquid foam insulation, the ultimate vapor barrier and insulator in one. It does not need direct ventilation on roofs, can be directly applied, same in walls. Icynene is expensive but the ultimate

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