How to Install a Whole-House Humidifier | Ask This Old House

Ask This Old House plumbing and heating expert Richard Trethewey shows an efficient, low-maintenance way to humidify the air. (See steps below.)

Richard visits Charlotte, NC to install a whole-house humidifier. A whole-house humidifier should be installed by a professional HVAC contractor.

Steps for How to Install a Whole-House Humidifier:
1. Disconnect the flexible supply ducts from the sides of the heat pump.
2. Remove the existing main trunk from the top of the heat pump.
3. Build a new sheet metal trunk.
4. Cut three 4-inch-diameter holes into the top of the new main trunk.
5. Over each hole fasten a take-off fitting with balancing damper.
6. Mount a louvered sheet metal elbow to the top of the heat pump, then attach the new main trunk to the elbow.
7. Attach one 12-inch-diameter take-off fitting onto the side of the main trunk. Fasten a second fitting to the bottom of the trunk.
8. Cut a 2 1/2-inch hole in the back of the trunk, then insert the humidifier wand. Secure the wand to the trunk with sheet metal screws.
9. Run a new copper cold-water supply line from the water heater to the humidifier.
10. Connect a drain line from the humidifier to the existing drainpipe on the heat pump.
11. Have a licensed electrician run a new 220-volt circuit to the humidifier.
12. Control the humidifier with a humidistat set to approximately 35 or 40 percent.

About Ask This Old House TV:
Homeowners have a virtual truckload of questions for us on smaller projects, and we're ready to answer. Ask This Old House solves the steady stream of home improvement problems faced by our viewers—and we make house calls! Ask This Old House features some familiar faces from This Old House, including Kevin O'Connor, general contractor Tom Silva, plumbing and heating expert Richard Trethewey, and landscape contractor Roger Cook.

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How to Install a Whole-House Humidifier | Ask This Old House

[murphyrichard]

Good show! Been watching with my dad since I was a kid

[nix]

Nice big clean attic with water nearby. Now do a typical installation, you know, tiny attic/crawlspace, no power, no water, cobwebs, dead mice, leaky toilet drain, etc, etc, etc.

[deankay]

Richard Trethewey is my hero! He has 40 some seasons with this old house and his son is following in his footsteps in the technology side of HVAC by exploring every type of reduced emissions electrical supply, co-ops that build a central supply being wind, ground, reduced electrical frequency (Less than 60hz) smart thermostats, GEO fencing and pushing proper building techniques like his father “If you insulate, you must ventilate”. In a house built in the 80’s, I have insulated the attic, the walls outside with R-14 EIFS to reduce utilities. It works! I wish I knew of certain products and had systems they use today “IF” properly installed.
Buying a house built 10, 20 or 40 years ago, I would know more than the average home inspector. But they get paid. Pull up, park and look at the roof. How many vents that are not for attic but piping. Say three, yet inside there are 4 bathrooms and hood over the cooktop range. Isn’t that 5. Is most smelly air vented into the attic or outside. Call the city permits office and ask about recent or permit history. It’s on computer! Home ad says new lights, 800 sq ft addition, new pool or hot tub, finished basement, 240 Vac in garage. No permits! Wait, stop. Old wood 1980’s windows. Many use body filler, fill rotted wood, sand, paint and caulking. What R-Value is in the attic, are the vents in the eves? Does the inspector check outlets for GFCI, or Arc-Fault? No! Fire them.

[BoredT-Rex]

This guy has such a smooth confident voice

[michaelmorris]

I have this humidifier. It works. This unit is for houses thay are 4000 sq ft or more. It adds a noticeable increase to your electric bill. Annually you must replace the steam generator about 80 dollars plus you need to change the scale filter on the waterline about 25 dollars. I have a guitar collection that requires a certain humidity to keep the instrument stable and playable. to me the cost of operation is justified. I do recommend other types of humidifiers for homes less than 4000 sq ft.

[fox]

I feel bad for whoever has to replace that water heater

[UndefinedBailiwick]

That attic is pretty convenient to get into, however it would be a real pain replacing that water heater.

[Blobjonblob]

I'd also tape the joints no harm in doing so.

[FlyEaglesFly]

Dampers are to be install horizontal to airflow not vertical. This will help keep air balanced better as the thin part of the metal is in the air not the round part like a paddle in water. Secondly they should have sealed the duct with sealant and let dry. Lastly..if you have ductboard or soundlined duct..DO NOT INSTALL a humidifier.. it will cause mold!

[Bremend]

The water heater is in the attic? RIP the guy that has to change that out every 10 years

[lesfogerson]

To guys make great videos that informative and fun to watch. Thank you.

[jrchicago]

What’s the trade off... cost of electricity to heat to steam, or the cost of water running off in a cool humidifier just prior to heating in the return? Seems with 220v needed for steam the cost of energy would surpass the run off costs of water. What I don’t understand is why run off cool humidifiers don’t reuse the run off water recirculated in water supply loop as a second supply. The lift required takes energy, but is it far lower than running these steam units. Perhaps the steam unit is needed on heat pump applications. It would help to clarify this.

[free]

How come you don't insulate the sheet metal plenum?

[rafalciemski]

Do you only use this type of humidifier in winter? I live in Nevada
where air is dry all year around and temperature in summer reaches 110
F. Can i use it all year around?

[PaintingPowerLLC]

if it is a heat pump, why they did not cover high pressure line with insulation? Where is the axillary pan condensation discharge pipe?

[josephnorcalusa]

helpful information, thank you for sharing !!

[neolightproductions]

I need something like this. I bought a cabinet kind that just blows a fan through a filter. Doesn’t seem to be helping at all. I like that this one looks like a warm mist one. I believe those work better than the pass through a filter kind.

[carolgiesler]

I just had the canister replaced in my Carrier Humidifier System. I turned the power back on~ How long will it take for the system to be completely restarted?

[erickvillazana]

the humidifier can help feel my house warm on winter cuz is cold the heater is on is hard to the heat pump stops and the aux heat turn on to helps

[GD]

Very nice system! Will be installing it soon.