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  1. #1
    Join Date
    Jun 2004
    Location
    St Louis, Mo for the past 25 years
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    7,332

    Default air sealing finished homes

    Another contractor and I were talking about energy upgrades and air sealing for people's homes. I am talking about a home folks live in, don't or aren't going to let you tear out walls so you can air seal around wires and plumbing stacks, and for some the basement is finished so you cannot seal from below. Looking at ways to try to help out folks while still making some money at it. So a couple of questions came up.

    One had to do with a recent article that I think Martin did on things that are not really all that great in regards to air sealing. One of his gripes was the caulking around door and window trim where trim meets the walls. I always thought it was a good idea in that if you keep the air movement from coming into the living area you would feel warmer, the air would feel warmer and some air exchange would stop. He seemed to feel otherwise. It may have been that he just felt it was not quite as good as it is thought to be. So it seems that may be out as something we could do.

    The other thing we discussed was sealing what we can whether in the attic or in the basement. Plugging any and all holes that we could and then being satisfied with that. The mold issue came up with the thought being if we seal in the attic but cannot seal in the basement we have a way for air to still get in the wall and not escape. So does it become like a balloon and the air just sits there and start to maybe cause problems or does it then become it's own little weather system in there. Air comes in the bottom hole is warm and moist, rises, cools down, sinks, looses humidity and then is replaced with more warm moist air.

    I guess the question is are we better to leave the house alone? Dick seems to always be talking about houses needing to breathe. Or do we seal what we can and think we have made improvements? And if the house is leaky and we fix one hole does the air just move to the unsealed areas and travel in with more force than before so you have done nothing.

  2. #2
    Join Date
    Jul 2004
    Location
    NOLA
    Posts
    4,018

    Default Re: air sealing finished homes

    Beezo, as you can see in other threads there is no one answer for all of the questions.
    Dick S lives in a very moderate climate and speaks from that perspective quite adamantly.
    Martin in Vermont has yet another perspective and those of us in the hot/humid yet another.

    Then of course there are those locations with both extremes.

    We get all twisted up in insulation, air sealing and renewables as well as green and whatever it is Dick is on about.

    I see this as a comfort, health and efficiency issue, the insulation and air sealing are simply means to an end, the end being comfort.......

    That said, it seems the first consideration is source control.

    Control the source of the contaminants, moisture, thermal transfer and pollutants and BAM, Bob's yer uncle.

    IMO, the discussion of open or closed cell SPF is off the track.

    In South Louisiana we need to heel the summer heat and constant outside moisture to the outside.

    So, air sealing the attic should be a benefit if you subscribe to the position that 40-60% of our conditioned air is lost through air leakage.


    Need more coffee,

  3. #3
    Join Date
    Oct 2006
    Location
    Greensboro, NC
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    1,514

    Default Re: air sealing finished homes

    I agree the attic would be a priority. I finished a bonus room this past fall and did all the air sealing I could from the info from GBA and on the forums.

    While working in the adjoining higher level attic of 2000 sq ft with 8" settled blown in - I was more aware of what to look for. There were pipe chases, can lights, bath exhaust, Romex holes - all while standing above, gave off quite a bit of heat flow. Especially a 2'x3' pipe chase - the air movement - moved the hair on my arm.

    A lot of these could be foamed in, some with Dow Blue Styro board, covers over can lights, duct boots sealed, etc.

    There's no question there's a comfort factor and energy savings.

    Now when I remodel, I air seal as much as I can.
    Steve

    "Get three coffins ready" - A Fistful of Dollars 1964

    http://youtu.be/KZ_7br_3y54

  4. #4
    Join Date
    Aug 2013
    Location
    KS
    Posts
    323

    Default Re: air sealing finished homes

    I’ve been thinking about this one too. I think you’d have to present a business case to clients to get them interested, showing a detailed bid or an average reduction in utility bills from air sealing and a return on their investment. Let’s not forget water intrusion in wall cavities that break down r-value. There is a lot of builds out the that have to info to tap into already and present.

    The article below shows how the pro’s do it with little guess work. Blower door testing, smoke, infrared cameras, to determine where the high CFM (not ACH) is that makes the largest impacts. Couple that with humidity and thermal gages for moisture and heat loss cause and corrective action. For a small upfront investment in the proper equipment, not so bad learning curve, you can have a profitable business with a bright future solving 2012 IECC mandates too for existing and new construction. Ted S seems very knowledgeable and I am sure would offer some advice, especially for some $ :)

    An air tight lower utility bill home drops the HVAC load when it's time for an upgrade, or new, but in some cases not all a mechanical ventilation system might be needed as part of the clients upfront cost you present. ROIs in most cases are showing 3-5 years. That can also be financed easily through special loans (EEMs), lender qualifying utility bills and appraisals.

    http://www.energyconservatory.com/si...testingjlc.pdf
    Terry

  5. #5
    Join Date
    Jul 2006
    Location
    Portland, OR
    Posts
    2,396

    Default Re: air sealing finished homes

    In addition to attic . . .
    Seal dryer duct penetrations and install a decent damper
    Flue-top damper on any wood burning fireplaces, and glass doors
    Open and check pop-outs housing pre-fab gas fireplaces (they are often not insulated and/or air sealed)
    Install sock dampers, or other good backdraft damper, in range hood exhaust duct. Air seal duct penetration into conditioned space
    Replace/upgrade door weatherstripping - especially at thresholds
    Seal around any floor outlets above basement or crawl
    Seal around duct penetrations from basement or crawl

    Those were my biggies on a 1991 home I moved into. It is still nowhere near ACH-50 tight, but drafts are no longer felt

  6. #6
    Join Date
    Nov 2004
    Location
    Boston, MA
    Posts
    4,614

    Default Re: air sealing finished homes

    My recommendation would be to take a BPI (Building Performance Institute) course, specifically, the Building Analyst and Envelope classes.

    They will teach you what the WAP Weatherization Assistance Program has been doing successfully for nearly four decades. Make sure to find one with a well seasoned instructor (old guy).

    My company used to do some of this work, we performed blower door assisted air sealing. It is critical to run the door and use smoke sticks and the IR camera to really find the leakage points. You would be amazed and what you can do once you learn the techniques. Much can be done from air sealing at the attic floor, this pressure boundary can be diagnosed and fixed with verification from blower door diagnostics.

    What is important in this, and what you will learn in the BPI course, is that its not all about air sealing. The occupant ventilation must be considered, they will teach you how to evaluate that, then you must observe the attic ventilation in terms of ridge and soffit venting.

    The DOE's WAP has been doing this for so long, its one of life's mysteries why the I codes have been so slow in getting up to speed.
    I will never buy a Nissan Cargo Van.

  7. #7
    Join Date
    Nov 2007
    Location
    Dallas,PA
    Posts
    1,014

    Default Re: air sealing finished homes

    Beezo, I don't know what era housing you might be talking about in general but in my area there are a lot of houses built in the first half of the 20th century that had 1"x 10" or 1"x 12" diagonally applied sheathing.

    Great for structural integrity but if you think about it, the fact that all of those boards end up landing on the face of the sill and the top plate coupled with the fact that they were all laid up with a gap between them (and probably shrank additionally) creates a nice vertical channel which allows air currents to easily enter the wall assembly and to rise throughout the entire structure.

    Sealing these is probably best approached from the foundation/sheathing interface on the exterior of the building. Most typically I would use a foam gun and direct the tip into each of the open end gaps where the sheathing ends on the face of the sill. Might be a good idea to use some compressed air to blow the dirt out of these spaces first.

    At the top end it can be rather difficult to deal with depending on the construction of the individual structures. I have seen too many variations in actual construction to discuss the options I have used to seal the top ends.

    Another fairly common detail I have seen is that in many houses studs for partitions were nailed on jack to the face of a ceiling joist and there is then no top plate. These partitions create a direct chimney to the attic and even though attics may have been blown or batted at some later date the insulation is certainly not providing an acceptable air barrier.
    "ALS IK KAN" - Stickley

  8. #8
    Join Date
    Jun 2004
    Location
    Georgia
    Posts
    1,794

    Default Re: air sealing finished homes

    Quote Originally Posted by NW Architect View Post
    Flue-top damper on any wood burning fireplaces
    I've been looking for an approved stainless steel damper to fit UL 103HT double wall insulated chimney, but am not aware of any mfr who offers it, are you? Rather than placing the damper on top, it makes some sense to me to place it at the boundary between the conditioned and unconditioned space to keep unconditioned air from circulating within the flue. But again, I'm not aware of any mfr who offers this.

  9. #9
    Join Date
    Jun 2004
    Location
    St Louis, Mo for the past 25 years
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    Default Re: air sealing finished homes

    Calvert,
    I am mostly working on houses that are 80 to 100 years old. Some are brick 3 wye wall, some are frame with claps on the exteriors, sometimes stucco exteriors. One thing that almost all of them have in common is that they seldom have enough attic insulation. So my thought is before you come in a shoot it full of insulation it is the perfect time to get up there and seal as many penetrations as you can. Was in an attic 2 months ago and it had maybe 3 inches of insulation, some places completely bare. Wear a dust mask and take a broom and you could move all the insulation away from wires and pipe and figure out a way to seal them up.

    As far as using a blower door I get that as the best way to find leaks. But I do not have one, do not know of too many folks who want to pay for a test. I am thinking we know the most common areas of leaks, why not start there and repair them. Saves the cost of a test and helps but we do not know exactly how much it helps. Cash said something about telling folks how much they will save. The two or three blower door testers tell me they are very careful with putting any numbers out there since they don't know if the family sleeps with a window open year round, the kids never shut off lights or the TV or any other number of things. Sealing it up can help but how you gonna gaurantee it?

  10. #10
    Join Date
    Aug 2013
    Location
    KS
    Posts
    323

    Default Re: air sealing finished homes

    Quote Originally Posted by m beezo View Post
    The two or three blower door testers tell me they are very careful with putting any numbers out there since they don't know if the family sleeps with a window open year round, the kids never shut off lights or the TV or any other number of things. Sealing it up can help but how you gonna gaurantee it?
    Good question I dunno. I guess I'd present it without the variables or with a disclaimer that provided if everything is done to keep bills low by the occupants you can see an on average return of this.....no guarantees.

    But present a guessing game without the proper tools and knowledge will probably lead to a lack of confidence in the client to hire you. Altho I read the articles about common problems every house is different when it comes to air.

    From what I gather from that article crews go in and after a while based on utility bill they tracked a reduction can be fairly accurately predicted. Up front you may have to work cheap but in time when you get good it the word gets around like any other business.

    I read Martins latest blog on Furnance's and Ducks, how you can run shorted ducts to interior walls reducing load in air tight homes. Still working on understanding ductless minisplit heat pumps.
    Last edited by CASHCOW; 01-24-2014 at 12:44 PM.
    Terry

  11. #11
    Join Date
    Jul 2008
    Location
    Suburbia (Washington, DC area)
    Posts
    1,932

    Default Re: air sealing finished homes

    Beezo, you are definitely on the right track. A lot of attic air sealing can be done "visually"--without testing or special equipment--you just go up there, and seal up everything.

    One thing I'll put on the table is that you may not be aware of where air leaks really are. It's not just holes for wires--it's really every joint between two materials. Top plates leak on both sides, they need to be sealed. Balloon walls and furring strip channels leak very badly. Plumbing walls used to be padded out to fit cast-iron stacks, they were not capped off in the attic (in my house, I could see the basement floor from my attic).
    When I did a blower door test at my house, air was jetting out of the switches in my hallway walls in the middle of the house. I had no idea that air leaks happened at the tops of walls all throughout the attic.

    Another couple of points:
    --Every house has some 'odd' air leak in a place you might not have expected without using a door & camera to check it
    --If you are very good at air sealing, existing problems in a house can be exacerbated. The two main potential issues are combustion gasses including carbon monoxide, and humidity. BPI includes a lot of education and procedures to check combustion safety, and a verification that a home is either still 'leaky enough' for natural air changes to manage most pollutants, or that you know you need to include planned ventilation. That is, you use the blower door to verify how leaky the house is at the end, if it's below a certain level you put in a bath fan timer or HRV, some ventilation system.

    I second Ted's recommendation of BPI training. In 25 years in the trades I learned more in that one week than any other time, and the information I got there has allowed me to find and fix dozens of tricky problems I could not have otherwise.

    So, I agree that you could do attic air sealing without blower door and combustion safety testing, but it would be somewhat risky and in many cases would not be as effective.

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