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Community and Q&A

How long can the air tightness of construction be maintained?

Linee Baird | Posted in Energy Efficiency and Durability on

I’m fascinated by passive construction, however I have a nagging concern about it’s durability. I keep seeing “insulation last better than PV”. That’s great, but the insulation doesn’t matter once the air tightness is lost. Due to the the extreme air tightness built deep into the construction, how can simple things like caulking and other decomposing materials be replenished? After 30 years are you left without an airtight house and no heating/cooling system?

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Replies

  1. Nate G | | #1

    1. Nobody mainstream builds houses without heating or cooling systems, even Passivehaus builders, despite that being a stated goal.

    2. Why would caulk that's sheltered deep within a wall, safe from sunlight and water, decompose in 30 years?

    Durability is crucially important. I'm with you. But the problem isn't caulk in the wall. It's preventable major design errors like forgetting a WRB, reverse laps in window flashing, zero roof overhangs, basements with no water-management systems, exterior wood in sunny high-elevation climates, wood-framed buildings built in termite land, etc.

  2. Peter L | | #2

    Long term studies show that standard house caulks failed within 5-10 years of being installed. Silicone, latex, all of which failed with time. Modern technology has stepped up and today we have house tapes like SIGA which work 1000x better and testing shows that they will last the life of the building. Modern caulk has also stepped up and certain hybrid caulks show promise to last 50 years but time will tell.

    Wood frame homes will rack, twist, move, expand, contract, etc. That is the nature of the beast known as wood. It is organic and it moves with moisture, heat, cold and wind. You can't stop wood from moving but you can try and keep the gaps from letting in air and water. Hence the tapes and modern house wraps.

    ICF/concrete walls are really the time tested structures that resists air leaks because concrete doesn't move like wood does. If you visit Europe you will see that masonry buildings still standing hundreds, some thousands of years, those of course that weren't bombed during WWI & WWII.

    Long story short. Will a PH still be air tight 20-50-100 years from now as it was the day it was built? All depends on HOW it was built and what sealing methods they used. Silicone & latex caulk is so 1980's. If they used high-end tapes like SIGA then no doubt that when they test these buildings 50 years from now they will still be airtight. If they cut corners and used cheap sealing methods then most likely they will be somewhat leaky 50 years from now but still relatively air tight compared to homes built in the 1950's-2010's.

    In other words, built it right and tight and don't worry about it. We (those in our 40's+) will all be dead 50+ years from now so don't worry about it...

  3. GBA Editor
    Martin Holladay | | #3

    Linee,
    Your question comes up periodically on GBA. I will copy and paste the answer I provided the last time this question came up:

    I know of one study of air barrier longevity. A 2004 Canadian study by Gary Proskiw and Anil Parekh found little evidence of air-barrier deterioration after 14 years.

    I reported on the results of the study in the March 2005 issue of Energy Design Update:

    "A recent study by two Winnipeg engineers, Gary Proskiw and Anil Parekh, provides reason for optimism. In December 2004, Proskiw presented the study,“Airtightness Performance of Wood-Framed Houses Over a 14-Year Period,” at the Performance of Exterior Envelopes of Whole Buildings IX conference in Clearwater Beach, Florida.

    "Proskiw and Parekh compared blower-door results for 22 Winnipeg houses that have been extensively studied since they were built in the late 1980s. Blower-door tests were performed at all of the houses soon after completion. Follow-up testing was performed periodically on the houses, with the most recent blower-door tests performed in 2000.

    "The 22 wood-framed single-family stucco-clad houses were all built with careful attention to air sealing. The study divided the houses into two groups:
    • Nine of the houses had polyethylene air barriers, with poly seams sealed with [Tremco] acoustical sealant.
    • Thirteen of the houses were sealed with gaskets using the advanced drywall approach (ADA).

    "The houses, all completed during the late 1980s, were very tight, with original blower-door results averaging 1.14 ac/h @ 50 Pa. Measured again in 2000, the average airtightness of the 22 houses had deteriorated only slightly, to 1.45 ac/h @ 50 Pa — still below the stringent R-2000 standard of 1.50 ac/h @ 50 Pa.

    "Comparing the houses with polyethylene air barriers to those with ADA air barriers, Proskiw and Parekh noted that the houses with polyethylene air barriers showed slightly less deterioration in airtightness than the houses with ADA air barriers.

    "During the 2000 site visits, Proskiw and Parekh looked for leaks. They determined that most of the observable air leakage was occurring at accessible locations not directly associated with either the polyethylene or the ADA portions of the air barrier systems. Some of the leaks were at floor drains, around doors and windows, and at mechanical and electrical penetrations through the envelope. During his presentation in Florida, Proskiw described these leaks as “basically, just old weatherstripping,” noting that most of them could be easily remedied.

    "In their paper, Proskiw and Parekh conclude that there is no evidence to indicate that either polyethylene or ADA gaskets are unsuited for use as an air barrier material in residential wood-framed construction. As Proskiw pointed out in Florida, “No catastrophic failures were observed, so the durability of the polyethylene and ADA air barrier systems has been reasonably maintained over their 14-year monitoring period.”

    "These results were especially encouraging in light of the fact that 18 of the houses enrolled in the study suffered significant vibrations when an environmental cleanup project required the excavation and removal of contaminated soil from the homes’ back yards."

  4. D Dorsett | | #4

    IIRC Marc Rosenbaum recently blower-door tested some houses he built 30+ years ago where polyethylene sheeting was the primary air barrier, and found the tightness results to be the same as when they were new (within the measurement accuracy noise.) This bodes well for homes using smart vapor retarders as primary or secondary air barriers.

    Acoustic sealant caulks do not become brittle even after decades. Duct mastic also does well over temperature & humidity cycling for 50+ years.

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