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Certain building materials need to breath. Buildings built with green wood which has more moisture than ambient, and buildings with cast concrete will shed wate

Certain building materials need to breath. Buildings built with green wood which has more moisture than ambient, and buildings with cast concrete will shed water vapor for some time. If this can be managed, it is fine. Additionally, through all insulation there is an internal temperature gradient. If the there are discontinuities it is possible to get condensation when the temperature / dew point align just wrong. This can happen in in humid climates with inadequate insulation - especially fiberglass where moisture can easily penetrate the fiberglass to reach the colder outside walls. I agree, though. Air tightness and continuous insulation coupled with well-engineered ventilation is best.

throw0101a 6y ago
> Certain building materials need to breath. As explained in the linked video, they actually need to dry. This does not need to happen to the outside environment. IMHO, using the two terms (dry/breathe) interchangeably is causing confusion, as each has certain connotations in many people's minds. The person in that video lives in Austin, Texas, and when he builds or renovates structures he has a stand-alone, whole-house dehumidifier designed into the HVAC system (the client can of course reject the suggestion): * https://www.youtube.com/watch?v=OKJnP_6uxcg https://www.youtube.com/watch?v=OKJnP_6uxcg > If the there are discontinuities it is possible to get condensation when the temperature / dew point align just wrong. Which, as explained in the first link (BSI-001), is why you want external insulation (if possible); some portion of the insulation being continuous is code in many places nowadays. That way the condensation occurs on the outside of the water/vapour control layer. Joe Lstiburek: * https://www.youtube.com/watch?v=rkfAcWpOYAA&t=25m26s https://www.youtube.com/watch?v=rkfAcWpOYAA&t=25m26s This is harder to do with renovations, but is code in most places. In Ontario, Canada the code (IIRC) also specifics what minimum portion of the insulation that should be on the 'outside' of the vapour control layer: the colder the region the more has to be external, so that condensation happens on the outside of the structure. Having it 100% external is ideal, but would cause trade-offs in other aspects of the building, which may not be desirable. An example of such a structure: * During construction: https://www.youtube.com/watch?v=d8i-93ABo3I https://www.youtube.com/watch?v=d8i-93ABo3I * Finished: https://www.youtube.com/watch?v=hTwq-qUnr9I https://www.youtube.com/watch?v=hTwq-qUnr9I Sadly, last time I checked, there was still no mandatory air tightness test for new builds in Ontario.
- abakker 6y ago
  Here in Boulder County, new BuildSmart regulations will require new and renovated structures to pass a "Blower Door Test" Does Ontario not have any of those requirements for commercial or residential? Agree on the continuous insulation. Very hard to do for Renovations. Fortunately in Colorado, it is so dry that the vapor barrier is slightly less important than in places like new england.
  - throw0101a 6y ago
    > Does Ontario not have any of those requirements for commercial or residential? Last time I checked it no air leakage testing is mandated: * https://www.barriersciences.com/blog/potential-changes-ontario-building-code https://www.barriersciences.com/blog/potential-changes-ontar... * https://www.reminetwork.com/articles/canada-wavers-on-airtightness-testing/ https://www.reminetwork.com/articles/canada-wavers-on-airtig... I'm not in the industry, so only know about the rough outlines through casual interest.
MertsA 6y ago
>Additionally, through all insulation there is an internal temperature gradient. If the there are discontinuities it is possible to get condensation when the temperature / dew point align just wrong. Which is a good benefit of spray foam insulation. Your insulation is your air barrier and even if there was moisture in the pores of some open cell foam, it's not going to cause issues.
- poseva 6y ago
  Foam insulation has other problems, see for eg. thermal drift.

throw0101a 6y ago

> Certain building materials need to breath. As explained in the linked video, they actually need to dry. This does not need to happen to the outside environment. IMHO, using the two terms (dry/breathe) interchangeably is causing confusion, as each has certain connotations in many people's minds. The person in that video lives in Austin, Texas, and when he builds or renovates structures he has a stand-alone, whole-house dehumidifier designed into the HVAC system (the client can of course reject the suggestion): * https://www.youtube.com/watch?v=OKJnP_6uxcg https://www.youtube.com/watch?v=OKJnP_6uxcg > If the there are discontinuities it is possible to get condensation when the temperature / dew point align just wrong. Which, as explained in the first link (BSI-001), is why you want external insulation (if possible); some portion of the insulation being continuous is code in many places nowadays. That way the condensation occurs on the outside of the water/vapour control layer. Joe Lstiburek: * https://www.youtube.com/watch?v=rkfAcWpOYAA&t=25m26s https://www.youtube.com/watch?v=rkfAcWpOYAA&t=25m26s This is harder to do with renovations, but is code in most places. In Ontario, Canada the code (IIRC) also specifics what minimum portion of the insulation that should be on the 'outside' of the vapour control layer: the colder the region the more has to be external, so that condensation happens on the outside of the structure. Having it 100% external is ideal, but would cause trade-offs in other aspects of the building, which may not be desirable. An example of such a structure: * During construction: https://www.youtube.com/watch?v=d8i-93ABo3I https://www.youtube.com/watch?v=d8i-93ABo3I * Finished: https://www.youtube.com/watch?v=hTwq-qUnr9I https://www.youtube.com/watch?v=hTwq-qUnr9I Sadly, last time I checked, there was still no mandatory air tightness test for new builds in Ontario.

abakker 6y ago
Here in Boulder County, new BuildSmart regulations will require new and renovated structures to pass a "Blower Door Test" Does Ontario not have any of those requirements for commercial or residential? Agree on the continuous insulation. Very hard to do for Renovations. Fortunately in Colorado, it is so dry that the vapor barrier is slightly less important than in places like new england.
- throw0101a 6y ago
  > Does Ontario not have any of those requirements for commercial or residential? Last time I checked it no air leakage testing is mandated: * https://www.barriersciences.com/blog/potential-changes-ontario-building-code https://www.barriersciences.com/blog/potential-changes-ontar... * https://www.reminetwork.com/articles/canada-wavers-on-airtightness-testing/ https://www.reminetwork.com/articles/canada-wavers-on-airtig... I'm not in the industry, so only know about the rough outlines through casual interest.

MertsA 6y ago

>Additionally, through all insulation there is an internal temperature gradient. If the there are discontinuities it is possible to get condensation when the temperature / dew point align just wrong. Which is a good benefit of spray foam insulation. Your insulation is your air barrier and even if there was moisture in the pores of some open cell foam, it's not going to cause issues.

poseva 6y ago
Foam insulation has other problems, see for eg. thermal drift.