I am renovating a 2nd floor 2100sf 1-story apartment in NYC. It is an older 6-story masonry structure with 9 windows in the unit (6 new tilt and turn aluminum units/ 3 double hung wood units). It is heated via radiators from a building wide steam boiler. We are installing a ceiling hung 5 ton Trane variable speed air handler and high efficiency 2-stage condenser for cooling only. System will run in the hotter June-Aug months primarily. Radiators run primarily Nov-March. And April-May, Sept-Oct typically no cooling or heat is needed. Dryer will exhaust and exhaust fans will be provided for two baths and kitchen.

I have just started to consider indoor air quality though. I have read up on this forum a little and wanted to inquire about indoor air quality measures best suited for this particular project and location.

It has been suggested in this forum that a simple Merv 11 filter with a ventilating dehumidifier could be a simple and effective setup. Wondering if a dehumidifier is necessary though in this climate as the only months with high humidity seem to be the months when the A/C unit would be running and dehumidifying the air. I have never tracked indoor humidity though so maybe just because one is typically comfortable in the fall and spring months without any dehumidifying action does not mean the air is under 50% RH where it should be. Any input would be appreciated.

Other whole house ventilation setups seem to be ERV, HRV or a simple system like the Aprilaire 8126.

Few specific questions -

Worried about noise from a dehumidifier since the only space to install the unit is above a dropped ceiling in the unit (drop ceiling is 2 layers gyp board). How quiet would this unit be in relation to the noise from a variable speed air handler? We hung the air handler with vibration isolators to avoid noise transfer to the apartment unit above. Seems like you need to do the same for the dehumidifiers.

If I get the dehumidifier I see that the ones from Ultra-Aire come with a Merv 11 filter. If I do not get the dehumidifier does a Merv 11 filter simply replace the 22x20x1” Trane air handler filter or do I need a separate filter box?

Would the system significantly benefit from a Lennox HC16 or IQAir Perfect 16 air cleaner? Or for that matter a UV purifier? Or is this a little overkill if I have proper whole house fresh air ventilation and a Merv 11 filter?

In a 40sf laundry room we are installing a gas dryer in a built in cabinet enclosure . Will provide 60sqin openings top and bottom of cabinet door per manufacturer but was not planning on installing a supply register to that room. I am just wondering if the user closes the door to the laundry room while the unit is running if there would be enough make up (and combustion) air to that room via a ½" undercut to the door. Or would a supply register used in conjunction with a whole house ventilation system be a much better idea?

We are also building a shower stall that will not have any pivoting openings in the frameless glass enclosure aside from the frameless glass door. I was thinking of installing an exhaust fan grille to the shower stall in addition to the bathroom so that moisture could be exhausted from the shower stall after use via an inline Fantech unit. Would construct that exhaust duct run in aluminum to avoid future corrosion issues. Wondering if anyone had any input on this setup. Wondering if they think this design could properly dry out the shower (via 30 minute or more fan timer) or would a pivoting opening (ie transom above the glass door) be necessary to dry the shower out after use.

Last – wondering about adding an evaporative or steam humidifier to the system for the winter months when the radiant heat seems to dry the indoor air out. I have heard that evaporative humidifiers do not seem to work near as well as steam humidifiers. On the other hand though wondering if a ventilating whole house system eliminates any need for a humidifier by supplying the apartment with fresh outdoor air with a higher humidity?

Thanks for any help.