The key to indoor air quality is a trickle of filtered fresh air to purge indoor air pollutants that accumulate and renew oxygen while the home is occupied. Maintaining <50%RH avoids problems with mold, dust mites, and bacteria that grow in damp spots with a ductable whole house dehumidifiers like the Santa Fe, Broan, Trane, etc. with filtered, fresh air during calm winds and +55^F outdoor dew points. This will keep the all of the internal space <50%RH with fresh air, healthy and comfortable.

I would suggest a whole house dehumidifier located in the basement with a 6" fresh air inlet from outside combined with an 8" return the main floor to the whole house dehumidifier. If the basement is open style, the dehumidifier supply could be open to the entire basement. With a dampered fresh air duct and the main floor return and supply to the basement operating the dehumidifier 24/7, a steady flow of fresh air is mixed with the house air is filtered by a Merv 13 air filter circulated throughout the home via the basement door under cut or open vent between floors. A big benefit is the basement is now dry and fresh and will provide a minimum of a ton of free cooling via the recirculated air to the entire home for the summer.

During the winter, a little fresh dry air added to the home along with the increase in natural infiltration will keep the windows from sweating. I use this concept in my WI home. I need very little cooling during the summer months and keep my windows close most of the year. I use a Santa Fe Ultra 70H on a 2,100 sq.ft. home.

Back to the original question, an HRV will add fresh air and moisture. This will make your home more moist when the outdoor dew points are +50^F. During the winter there is a heat recovery benefit. If the fresh air needs are high, there may be enough of a benefit to make the additional investment in the HRV and whole house dehumidifier.

Keep us posted.

Regards Teddy Bear

 

No, 4” ducts are too small. They may have been from an older high velocity furnace system.

It is possible install a dehumidifier without ducts but it won’t provide its full performance.

You can guess at what might make conditions better in your home, or you could hire someone with home performance qualifications to actually diagnose the problem and offer some suggestions to target the problems.
Most homes will benefit from a dehumidifier. Cheap units work but are not serviceable when they fail. Good units from Santa Fe, Brian, or Aprilaire have higher capacity and longer life span.

 

Is this something that's feasible for 4" ducting, and also no pre existing HVAC system?

 

I don't care for ERV/HRV because they don't address humidity in the house. Every house I have tested is normally under a negative pressure which causes infiltration. I recommend a dehumidifier and the add-on duct and damper from outside to make it a ventilating dehumidifier. Doing so can reduce negative pressure or even achieve a slight positive pressure.