Comment by ungreased0675
1 day ago
An ERV with HEPA filter may be a better, less improvised option. Most systems can be adjusted for positive pressure, although the intent is balanced airflow.
1 day ago
An ERV with HEPA filter may be a better, less improvised option. Most systems can be adjusted for positive pressure, although the intent is balanced airflow.
If the airflow isn't balanced, there's little point to using an ERV. If half the air is escaping elsewhere, none of that heat is being recovered. You might as well delete the ERV and just use half the airflow, because that will get the same positive pressure for the same energy loss.
My recommendation was mostly for the practical, not functional benefits.
An ERV comes with installation instructions, has a warranty, was designed to run continuously, and an HVAC contractor can install it for you. 3D printing brackets and cutting holes in your own walls isn’t for everyone.
What if it's only 1% of air escaping
Then it's 100x oversized for the purpose of pressurizing the structure. ;)
ERVs are great for increasing air exchange (two-way flow), but unnecessary when pressurizing because that's one-way flow by definition.
If you already bought an ERV it makes sense to combine the functions, simply because you already bought the expensive ERV hardware. But if you weren't planning to install an ERV anyway, it doesn't make sense to install one just for this project, because it won't do anything to reduce the heating/cooling loss from this type of system.
The one-way component of flow is still 100% non-recuperated. If you install a cheap 100 CFM positive pressure system and it burns an extra $100, then setting your ERV to be unbalanced by 100 CFM will cost that same $100. Same leak rate, same heat loss, same cost!
This is one of those deceptive math problems where it seems like it should work, but really it works out "six of one and half-dozen of the other."
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