Moisture barrier: it traps the humidity in places you potentially don't want to
Structural strength: yeahhhh... no
Longevity: not more than anything else, a pain in the ass to replace though
Improved air quality: The petrol derivate foam that leaves a god awful nasty smell for days/weeks and can offgas for years is good for air quality ? rock or better sheep wool is much better in that regard
In the end of the day people do whatever they want but I'd rather build smaller and spend more on rockwool than have extra space and nasty ass foam all around my house
Moisture barrier: it traps the humidity in places you potentially don't want to
This is more applicable to fiberglass. How does humidity somehow get past the foam while being kept there? I never see any evidence for these claims.
Structural strength: yeahhhh... no
Foam adds rigidity to wooden structures. This is actually very commonly brought up and noticed where houses creak far less on top of the sounds proofing. Saying "yeahh.. no" is not evidence of anything.
Longevity: not more than anything else, a pain in the ass to replace though
Definitely more than fiberglass, since fiberglass can sag and flatten over time.
offgas for years is good for air quality
This is not typical and happens when it is installed poorly.
> Moisture barrier: it traps the humidity in places you potentially don't want to
Definitely a risk with any type of improperly installed moisture barrier (like ZIP sheathing).
> Structural strength: yeahhhh... no
It would take me some time to find more formal studies, but there are a lot of videos on YouTube that demonstrate the addeded strength. Here's one: https://www.youtube.com/watch?v=4mMHJpSHKJM
> god awful nasty smell for days/weeks and can offgas for years is good for air quality ?
Everything I've read indicates that any offgassing/odor is gone in 24 hours or less.
> In the end of the day people do whatever they want
Agreed. To each their own. Closed cell spray foam also works well in conjunction with rockwool.
> It would take me some time to find more formal studies
No one will study the strength of insulation foam because it will never be authorised as a structural material.
> Everything I've read indicates that any offgassing/odor is gone in 24 hours or less.
Everything you read comes from manufacturers or bloggers/influencers paid by manufacturers. On construction forums you'll find plenty of people complaining of weird smells months/years down the line.
Again, people do whatever they want with their houses and health, personally I'm not touching this shit with a ten foot pole given the alternatives
I don't see the point of building tight, if you're going to have massive holes in the building, through which you force tons of air (which you should). Would you call a jar airtight if you never close the lid?
In multi-tenant dwellings, building tight can help keep people's smells to themselves. That's about it. Like if you have pressurized air in the hallway, keeping the common area fresh, if the apartment units are not built tight, smells can go from one to the other sideways, possibly forced by that very same pressure.
The main reason people build tight is to save on heating and cooling bills, or "save the planet". And mainly how that works is by not ventilating. Ventilating forces out all that hot or cool air that you paid for, so you have to heat or cool the replacement air.
> I don't see the point of building tight, if you're going to have massive holes in the building, through which you force tons of air (which you should). Would you call a jar airtight if you never close the lid?
I'm not quite sure why you're taking thing so literally about combining the two actions. I would call a jar airtight because the glass cannot be penetrated by air, nor can the lid and band.
You can then ventilate the airtight (proverbial) jar on your own terms: using filters and such to control the quality of the air that goes in/out.
The build tight is about the building enclosure; the ventilate right is about exchange stale/dirty interior air with cleaner exterior air in a controlled fashion.
A fully sealed building with zero ventilation would be horrible for people due to increased chemicals from people just breathing (CO2) or cooking. It is absolutely necessary to ventilate a building, but it can be done so to also reduce the incoming undesirable elements in the exterior air.
> Ventilating forces out all that hot or cool air that you paid for, so you have to heat or cool the replacement air.
Ventilating using HRV/ERVs takes the conditioned air and transfers some of its properties (temperature, moisture) to the incoming air to temper it. The incoming air is/can be also filtered to removed things like pollen, dust, wildfire smoke, etc.
> It's basically greed or ideology over health.
There are entire industry standards (ASHRAE 62.1 and 62.2) on the topic of good indoor air quality (IAQ) to make sure that 'just enough' stale air is removed (e.g., to reduce CO2 counts) while not 'over-ventilating' (increasing costs), and it is a topic of active academic research (especially post-COVID):
By not having a tight building envelope treated air can leak out, and untreated air can leak in, and depending on the size of the leaks (holes) you can even get bugs/creatures entering.
The whole point of buildings is to separate environments: inside versus outside. Leaking building compromise that separation reducing the control you have. And if you do not want to separate your interior and exterior environment live in a tent or under a tarp: plenty of ventilation, very little air-tightness.
Structural strength: yeahhhh... no
Longevity: not more than anything else, a pain in the ass to replace though
Improved air quality: The petrol derivate foam that leaves a god awful nasty smell for days/weeks and can offgas for years is good for air quality ? rock or better sheep wool is much better in that regard
In the end of the day people do whatever they want but I'd rather build smaller and spend more on rockwool than have extra space and nasty ass foam all around my house