Breathability is a confusing term in the building world. It refers to the ability of a structure to manage water vapour. In the UK if a house was built before 1940, is a single brick build and has suspended floors then it will be a breathable system. Important because if non breathable (non vapour open) materials are used on the walls/floors, then vapour can't flow and will condense causing mould and damage to the brick. Much better to refer to it as vapour open or vapour permeable then confusions like this won't happen

In building construction “breathing walls” means vapour and humidity metabolism through the building structure. Lots of people confuse it with building walls being not tight and letting outside air in.

@TheEmbrio

Жыл бұрын

True. Perhaps we should change that. Transpire, evaporate, wouod be better

Good discussion, Brandon. I might add that a small amount of outside pressurization air, filtered and tempered, would contribute to both air quality and humidity control. ASHRAE Standard 62.1-2019 offers guidelines to that end. They speak of 0.35 air changes per hour for residences. The downside is during the winter when you have to choose whether to heat it or not.

@levelupstrategies

2 жыл бұрын

Thanks for adding some tangible resources to the discussion, and reference to the ASHRAE Standard. Here's the link to the website if anyone wants to explore further. www.ashrae.org/about/news/2019/ashrae-releases-updated-versions-of-standard-62-1-and-62-2

@TheEmbrio

Жыл бұрын

I don’t think it’s ever a good idea to pressurize the home, humid hot air might create condensation as it leaks, creating humidity problems in the enveloppe. houses should be if not be at equilibrium, be vented by controled extraction. Air renewal is important, efficient humidity triggered fans exist, and heating cold but dry air is not so much compared to makntaining humid hot air at temperature.

Good information. Plasma TV? What year was this filmed?

@levelupstrategies

Жыл бұрын

Mark thats funny, and the video was filmed in 2022. Truth is that my wife and I don't watch TV, and the last TV I bought was plasma (about 10 years ago). - so when I'm free flowing in a dialogue - that's what came out.

Im in Winnipeg and my renovated house I believe is pretty air tight now, I also have 2" styrofoam on the exterior with 6 inches of rockwool inside the walls and the ploy vapour barrier. Just wondering about moisture getting trapped between exterior foam and interior poly.

@levelupstrategies

2 жыл бұрын

Tim, I originally hail from Winnipeg - so nice to meet you! You bring up a good, and also important point. The exact answer will depend on a calculation of the dew point in relation to the thermal gradient of your wall assembly. (there are engineers / software that does that). Speaking candidly about general principles, the issue will also be whether the 2" of styrofoam create another vapour barrier in the wall assembly. Some styrofoams do once they get to a certain thickness. If yours does, that will potentially pose an issue for you. I'll attach a link to a video that I have found very informative from one of the leading practitioners in this space. in the last couple of minutes an audience member asks a question similar to yours, and I believe Dr. Lstiburek's answer is to put a 1/16" air gap between the styrofoam and the exterior sheeting. (1h:37m.ish) kzread.info/dash/bejne/m3x2u9iqopXFmdI.html I hope this helps.

@grizzlyblear

Жыл бұрын

That’s exactly what I’ve been wondering about. We watch all these videos from the southern started talking about perfectly Air sealing the exterior when we have to deal with separating the WRB and VRB with the wall. Drying saturated lumber to the outside seems like a thought we need more of too. And what about spray foam trapping all that moisture? Great video, thanks

@markhoffman

Жыл бұрын

It will be fine.