ERV retrofit – main & 2nd story only?
Hello !
The house we bought 2 years ago was built in 1966 but it has had several updates done, bringing the ACH50 down to under a 4. The result is that the co2 can be quite high when windows are closed (winter or peak summer).
I was trying to figure out how to get an ERV added to the central hvac system but ran into a roadblock finding an intake and exhaust location on the exterior wall. One of the major problems is that the house’s main floor sits only slightly above grade, and one side of the house is completely against the attached garage, leaving only the other side for potential vent locations…. and of course that wall is full with other vents (3 bathroom, 1 kitchen, dryer, gas hot water heater vent, and gas meter).
I was thinking, could an ERV be installed in a main or 2nd floor closet with dedicated ductwork in the joist cavities? Has anyone successfully retrofitted in ERV into an older home? Would it be smart to try to exhaust one or more bath fans through the ERV instead of the current roof/wall vents?
Desperate to get some fresh air in the house without a big energy penalty.
Thanks!
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I did a retrofit of a 1800s home where we retrofitted a couple Panasonic Whispercomfort 60 ERVs into the existing joist bays. You can easily run the intake and exhaust ducts parallel to the joists to the exterior.
https://iaq.na.panasonic.com/erv/whispercomfort-60
Because this model doesn't have individual ducts, we put the units in the hallways near spaces that required fresh air... 2 in the bedroom spaces/halls, and 1 in the kitchen/living area. All this is assuming a normal door undercut for decent airflow between rooms.
Not to turn this into a Panasonic ad, but for bathrooms we used whispercomfort green exhaust fans which increase in CFM automatically when static pressure is detected in the home. https://iaq.na.panasonic.com/ventilation/fans/whispergreen-select-50-80-110-cfm-multi-speed
If you have the space in your partitions to run flexible ducting I see no reason why you couldn't achieve a similar solution with a ducted off the shelf ERV in a closet or something similar.
Side note, I was taught to avoid putting a ducted ERV in line with the HVAC system due to potential condensation issues within ducts especially in retrofits.
That's interesting, thank you for sharing.
Does that panasonic ERV extract stale air and deliver fresh air from the same place? How does this not create a short circuit loop? With no ducts going directly into bedrooms it doesn't seem like this would actually work. Did you measure before/after CO2 levels?
The unit looks pretty deep also, at 8 7/8". My house has 2x8 joists which are actually only 7.5" so this unit wouldn't fit in a joist bay, I'd have to build a deeper structure, in which case I'd probably be better off putting in a regular size ERV.
Re: the green exhaust fans, how would an increase in pressure be created? I thought houses normally run negative pressure?
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