Printed from at 01:09 PM, Jan 18 2017
Talk » Renovation » Discussing 'Extreme dry air.'

Extreme dry air.


Our apartment has incredibly dry air and I suspect it's the HVAC units (they're hotel-style PTAC units that both cool and heat). We already have two humidifiers going full blast and still wake up with parched throats. They're also a massive pain to clean each week.

The building management states that we cannot use anything other than PTAC units and not even another brand (!). What solution is there? I've heard there are add-on whole house humidifiers that latch onto these PTAC's.

Is it even legal for the mgmt co to restrict HVACs to a particular brand?

if you want, you maybe able to run a boiler. this will require piping throughout the house.

because of this reason, i ran all new pex lines and Pensotti radiators in the house i'm rebuilding adding on to. most hvac guys who came thought that i was crazy. my friends and family who have forced air, hate it, even with the humidifiers, electronic filters, etc.

No matter what you do, you've still got to haul water to the humidifier, even if it's added to the PTAC, unless you can somehow run a water line to the PTAC. Don't plan on being able to do that.

Fancier non-PTAC systems may already have a water line connected to the air handler, so they're all set.


My HVAC knowledge is minimal, but don't PTAC's already have a hot and cold water line running to them? My units have no opening to the outside of the building so I assume the waste cold or hot water gets carried away by the pipes. If that's the case, maybe adding an add-on humidifier to PTAC units is possible?

There're different PTACs. Some are completely self-contained, where you'd pay for the electricity to run them.

Some get their heat from building-supplied hot water or steam, and you pay only for the fan to draw air over the radiator and send it out into the room.

Some get their cold from building-supplied chilled water, and you pay for the fan to draw air over the coils and send it out into the room. The condensed moisture goes down a drain.

Some might supply only the heat, with the cooling coming from the equivalent of a through-wall AC.

Some buildings have both hot and cold supply/return pipes ("four-pipe" systems) so five in total including the drain. Most are two-pipe systems, with the building switching from hot to cold and back again with the seasons.

What they all have in common is that those pipes are sealed; you can't just tap into it to get water for your humidifier. E.g., hot water fed through up-risers to the stacks of PTACs, and the now-less-hot water circulating back in the down-risers to the boiler, where heat is added and the loop starts again.

In a four-pipe system where the heat is by steam, it's possible to tap into the steam for humidification if the whole system was designed for that. IIRC that's what Walker Tower seems to do.

You might want to look into something like this:

It and its ductwork could go into that space above your kitchen. Your sink pipe could be tapped into for the water (just like an icemaker) and the required overflow drain would be handy.

JWL, While I do not proclaim to be an expect in HVAC, it does not seem like heating unit is responsible for the parched throats as they typically do not do anything to humidity. Try turning off the heat so that your apt is cooler and you sweat less. Or check for some allergies (mold etc).

hows your air exchange rate? new air = more heat = dryyyyy
probably not something you can fix in an apt building.
humidify away!

No, 300_mercer. Heating -- by any means -- dries air out. Cooling by refrigeration dries air out.

Americans drink more water per capita than any other people. Americans are more dehydrated, on average, than any other people.

JWL2672, are you keeping your humidifiers watered 24/7, rather than just at night? Also, is it dry at the plant you work at?

Do you use neti-pot type squeeze-bottle saline rinses twice a day? Try that ... it's like having a personal humdifier in your sinus cavities all day and night. Just don't ever lean over or tilt your head, or you'll have an amusing stream of water come running out your nostrils.

>Americans drink more water per capita than any other people. Americans are more dehydrated, on average, than any other people.

And we get our water from France and Fiji!

And Poland

Yep, humidifiers going 24/7,

NWT, thanks for the PTAC knowledge. I've searched far and wide on the net and that was by far the most succint and comprehensive coverage on the types of units. I think ours is the 2 pipe system because we cannot use AC in the winter or heat in the summer.

We have no choice but to get up in the middle of the night to re-hydrate, which interrupts sleep and leaves us cranky in the morning.

Thanks for the suggestion on the Honeywell furnace humidifier. I'm going to bring it up with our Hvac technician.

Beware of the Honeywell. It could have its own problems. I removed it eventually after minerals build up from tap water.

Do you have plaster walls vs. drywall? Plaster walls will suck out all moisture.

The Honeywell humidifier linked above is designed for use with a forced air heating system. If you have PTAC units, you don't have forced air, and I'm not sure how you would fit a forced air heating system above a kitchen.

The Air-O-Swiss humidification systems, widely available in a range of models suitable for various configurations, are incredibly efficient at maintaining desired humididity levels without the burden of traditional humidifiers requiring weekly disinfection and wick replacement. This technology requires daily refilling with plain tap water and bi-monthly descaling, but truly make a world of difference in health and comfort for people, pets, and wood furniture.

The ghetto but effective sulution is large pot of water on top of the heater.

>The ghetto

watch your language

what is wrong with ghetto?

When we renovated, we installed a Nortec humidifier. Hard plumbed and connected to our central air ducting. Best change order I authorized. You can crank that baby up and you feel like you're in the butterfly pavilion in the AMNH. I highly recommend this to anyone thinking about it. No more waking up in the morning all dry and gross. We have centralized steam heat in our prewar co-op.

Rats, I meant to post the link:
We have the unit under the "residential" tab.

This may be a partial solution at best, but how about getting an oil-filled heater and turning down the PTAC units?


Contrary to what alanhart said, I do not think that all heating dries the air out. We also have PTACs and they would dry the air out terribly. We have been using oil heaters for two winters now, leaving the PTACs on the lowest setting, and no more dry air! No more parched throats at night (and there is an oil heater right by the bed!) and no more really dry skin. They are not expensive (ours were $60 each), require no maintenance, and lower our heating costs as they can be used to heat more efficiently due to their portability. For us, it also made more sense to get rid of the dry-air source by turning the PTAC down than to try to counteract it with a humidifier. The downsides are they are not attractive and don't help if you have dry air in the summer (we don't).

Really, my solution works and is the cheapest and easiest way. Its actually free.

And it's a microbial incubator.

Comment removed.

is that your excuse?

Comment removed.

Thanks for all the great recommendations. I did a google search for "ptac" and "humidifier" and this conversation is 5th on the list so hopefully others with my problem can benefit from the recommendations.

I'm going to look into that Nortec humidifier. Sounds like the best option in an apt without central air or a furnace.

Have you tried jason10006's recommendation of a pot of water atop the heater? I'd certainly give that a shot before going down the road of specialized equipment that produces 140 degree F water as a waste product and requires a dedicated electrical circuit.

"And it's a microbial incubator."

Not if you change the pan every day, an wash periodically, which you have to do with a humidifier anyway.

Jason, do you change your pan every day and wash periodically?

I tried the pot of water and it did not work. PTAC units do not get hot enough, or at least mine doesn't, to speed up the water evaporation to the point it helps with the dry air.

Comment removed.

^^8am on Thursday, April 4, blather blather yammer peas and carrots peas and carrots lorem ipsum^^

Hey, Crazy Riccardo, how have things been for you? C0lumbia C0unty and Jim Hores miss you.

This conversation has done nothing to correctly answer the question, and has only gone further down the path of leading people to believe that certain heaters strip water out of the air.

Without going into great detail, here’s a quick summary of the science driving this:
There are 2 basic measurements of moisture in the air.
1. Relative Humidity (commonly used for most hygrometers, how much water is in the air as a percentage of how much it can hold without raining)
2. Atmospheric Dew Point Temperature (the word temperature is usually left off, uses atmospheric pressure as a reference point; also called absolute humidity, absolute moisture content)
• A third similar, but more complicated measurement is dew point (at different pressures, used by weather men to tell when it will rain or produce dew)

Let’s focus on the first 2. The relative humidity changes with temperature. Atmospheric dew point does NOT. Relative Humidity can be converted to atmospheric dew point, but only as calculated from the current pressure and temperature.

Addressing the issue raised:
The comment from “300_mercer” was the only one that was on target, but it appears that he was ignored. As a general rule, heaters only affect relative humidity. This is because they raise the temperature of the air (simple but a very key point that has been missed thus far). If you find a heater that does not raise the temperature of the air, it would will give you the most comfortable relative humidity, but would then not qualify as being a heater…I digress.

2 things would have to be true of a heater for it to have any marginal effect on absolute humidity.
- It has to pull air from outside the area (outdoors or another part of the building)
- The area the new air is coming from has to be at a lower absolute humidity

The only heating systems that would generally qualify for this would be:
A) A combustion system (oil, coal, gas, wood, etc...) which takes suction indoors (very common, fireplace, furnace etc…)
B) An HVAC system that takes suction outside (UNCOMMON for most houses due to it being much more efficient to heat air that’s already warm).

If you DON’T currently run a HUMIDIFIER, then it is safe to assume that the absolute humidity indoors is IDENTICAL to outdoors (REGARDLESS of your heat source). Raising the temperature in your home will make it feel drier (lowering the relative humidity), but does not affect the absolute humidity (dew point).

The only common household appliance which strips water from the air is a DEHUMIDIFIER (hence the name). Coincidentally, a dehumidifier also heats your house, but only marginally (and unintentionally, since they are usually only important in the summer, when indoor relative humidity is high).

TO CONCLUDE, heating the air does NOT remove moisture, but it DOES make it FEEL drier (by lowering RELATIVE humidity). The absolute moisture content of the air in your house is primarily determined by the outside temperature. This will always be lower in the winter time. When you raise the temperature of that air, the relative humidity goes down significantly (hotter temps make it feel drier). All heat sources are identical in this nature. If you choose to run a HUMIDIFIER, it will be LESS EFFECTIVE at changing the relative humidity in your home if you are constantly pulling dry outside air into your house through your heating system. Look around outside your house. If you see a chimney, AND NO external suction point for your combustion system, then you are pulling cold, dry outside air through the cracks of the house any time the furnace is running (thereby lowering the value the effectiveness of your indoor humidifier).

IF after reading this thoroughly, you feel that it is incorrect, don’t worry. You are one of the majority of people that misunderstands this simple, yet elusive concept. 90% of the “answers” I found on some famous “answer” websites were incorrect.


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