Thread: What do you recommend for high rise humidification?

We run into high rise condos, particularly new construction, all the time without any separate means of humidification other than stand alone units provided by the owner or to-be buyer. In particular, is there any unit that can be installed in conjunction with modern hydronic fan coil units? It would be nice to respond a little more intelligently to clients when I'm addressing this.

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Generally, its complaints the other way around I've heard most often, i.e. too much humidity is of issue during the summer months with hydronic coil units using super-cooled water in summer months for air-cooling, esp. hi-rise. De-humidifying during the warmer months and a desire for "fresh air ventillation (HRVs, air-to-air, etc.) is what I heard complained most about in your area.

Rarely is dry air a concern in the heating months, as copious amounts of humidity are dumped and collected from normal living activities (such as respiration of living beings and plants)! Better sealed/inulated buildings tend to accumulate humidity as the heat and more humid air rises. As the coolest extreme days in the windy city hit - less is more otherwise there's complaints about sweaty windows!

Local to the unit remedies are usually the best alternative should the air be too "dry" during those 25-40 degrees periods.

So, suggest a decent hygrometer to monitor actual conditions as seasons change and develop game plan based on that info. Got it.

People often don't need to add moisture as much as they think, usually because they mis-understand humidity to begin with.

Residential hydronic fan coil units are not suited well for humidifiers. Typically the hot water temp to a FCU is at a much lower temperature than that of a gas or oil fired furnace so evaporating water to humidify is more difficult.

Atomizing type humidifiers are nice but require lots of cleaning or RODI water.

My opinion is that if you want to offer an intelligent response it would be "humidification with your type of HVAC system is not practical, use a stand alone unit."

Gents,

Just a follow up. I have had RH readings in the 12-20% range these past few weeks in mid and high rise fan coil or electric resistance baseboard heated units. I don't think we can just assume that these get enough humidity from normal day to day activities and therefore have been recommending stand alone units and the purchase of a reliable hygrometer. Recommended winter levels of 35-45% RH and try to keep below 50% RH in summer.

R.N.,

That sounds about right as you've had dramatic weather swings of late including frequent bouts with sub-zero and single digit temps accompanied by high winds quite often in the last few weeks, and deep freezes both before and after your recent blizzard and snowfalls before and since.

If the units are vacant (unoccupied - not actively being "lived in") those measurements might be dramatically higher otherwise (cooking activities, dishwashing, human respiration, showers, etc.). If not being "lived in", would suspect anything higher than 20% with such single (plus or minus) digit outside conditions would likely cause problems, esp high rise outside walls and windows and cause huge rebound problems when temperatures rise and fall (think condensation) and outside RH rises dramatically rises and falls. Absolute humidity and RH are not equal, avoiding saturation point/dew point and related moisture content problems is a concern. For example after the last weekend's thaw (and higher absolute humidity in outside air with warmer temperatures) and living activites - should the temperature suddenly dramatically drop - there could be much higher RH in the unit with just a hydronic coil air handler system.

Despite the presence of an air handler, hydronic heat is not "drying heat", and if water cooled not true A/C for the warmer months - not dehumidifying/conditioning either.

Do the units have heat recovery ventillators or similar system? What is the source of fresh air (to breathe!) and make-up air (even all electric units require - make-up air - exhaust fans, etc.).

New construction and finishing the unit as building can still be dumping MC. Once folks are actually living, breathing, bathing, cooking, cleaning, plants - pets respiring, in same the usual complaint is too much humidity - and uncomfortable clammy muggy environment in the summer and they're running dehumidification equipment and complaining of musty odors in closets, etc. and sweat on the ext. windows and walls in the winter when the temperatures return from zero or below to "normal winter temps"! Generally when it drops down to zero outdoors you don't want to be loading the inside heated air beyond 25% RH - so when you rebound to normal winter temps you can maintain 35-40% for comfort, and when temps dip to double digits negative outside you don't have condensation collections, icing up, in exhaust vents, shafts, ex. windows, soggy gyp board, walls, etc. from normal living activities.

Comparing hydrocoil air handler with electric resistance heat is apples and oranges!

I would not be recommending installing any humidifier in a high rise unit without the owner actually living there for a while, based on readings. I also wouldn't recommend it without the prospective owner talking with the association first.
I spend a fair amount of time in highrises. Generally, occupied units are not too dry. Vacant units tend to be drier. Sometimes I'll notice that a particular unit is very dry. I tend to think that's a product of location in the building.
I realize you want to serve the client but that is a can of worms I would not open. Highrises are tricky environments, introducing more humidity into a fairly controlled environment in a fairly uncontrolled manner could wreak havoc. You know the client isn't going to pay a smart guy to install it. They'll pay Joe cheapo and he'll throw in a General 800 because it's cheap and will fit into the ceiling crawl easy.
I did an inspection in a Helmut Jahn building with exposed concrete walls and ceilings. Talk about high humidity, it was sickening.

Originally Posted by H.G. Watson, Sr.

Despite the presence of an air handler, hydronic heat is not "drying heat", and if water cooled not true A/C for the warmer months - not dehumidifying/conditioning either.

Comparing hydrocoil air handler with electric resistance heat is apples and oranges!

I agree with H.G. when he says that you should not try to maintain 35-40 % RH in the winter time. 68 degrees @ 40 %RH has a dew point temp of 44 degrees. You will definately find condensation occuring on the windows and possibily within the walls or structure of the unit. You should try to maintain less than 25% RH in the winter to prevent problems with mold or moisture.

I do not agree with H.G. when he says that hydronic heat is not drying or that hydronic heat is not as dry as electric. This is NOT TRUE. Neither electric or hydronic heat add moisture to the occupied area. Both raise dry bulb temperature only and 68 degree temp will have the same RH with either method of heating.

Also, a water cooled AC condensing unit will dehumidify the air the SAME as an air cooled condensing unit of the same capacity. The refrigerant temp at the expansion valve and the discharge air temp of the evaporator coil will be equal.

Originally Posted by Ken Amelin

I agree with H.G. when he says that you should not try to maintain 35-40 % RH in the winter time. 68 degrees @ 40 %RH has a dew point temp of 44 degrees. You will definately find condensation occuring on the windows and possibily within the walls or structure of the unit. You should try to maintain less than 25% RH in the winter to prevent problems with mold or moisture.

I do not agree with H.G. when he says that hydronic heat is not drying or that hydronic heat is not as dry as electric. This is NOT TRUE. Neither electric or hydronic heat add moisture to the occupied area. Both raise dry bulb temperature only and 68 degree temp will have the same RH with either method of heating.

Also, a water cooled AC condensing unit will dehumidify the air the SAME as an air cooled condensing unit of the same capacity. The refrigerant temp at the expansion valve and the discharge air temp of the evaporator coil will be equal.

Agree, well said. With minor exceptions. On DX AC the suction temp may tend to dehumidify the air a bit more due to a lower initial temp as the air enters the coil. Chilled water temperature may sometimes be modulated with the target being the leaving dry bulb and the flow varied to handle just the load imposed.

Originally Posted by Rod Butler

Agree, well said. With minor exceptions. On DX AC the suction temp may tend to dehumidify the air a bit more due to a lower initial temp as the air enters the coil. Chilled water temperature may sometimes be modulated with the target being the leaving dry bulb and the flow varied to handle just the load imposed.

I said air cooled and water cooled "condensiing units". Both of these type would have DX fan coil units. Chilled water units were not mentioned.

Also, a chilled water unit that has a coil selected with a sensible heat ratio of .80 +/- or similar to the dx coil will dehumidify the same.

To All,

Thanks for the enlightening discussion. There ARE too many variables to comment on a specific course of action and I will amend my report writing and leave it with the client verbally.

Hey Ken, dew point at 68F and 40% is 43F; you owe me a beer.

Originally Posted by Ross Neag

Hey Ken, dew point at 68F and 40% is 43F; you owe me a beer.

Ross,

Thanks for pointing that out to me. I use a Trane psychometric chart - missed it in interpolation.

When I'm in Chicago I'll look you up and buy you that beer!

Quoth HG: "Rarely is dry air a concern in the heating months, as copious amounts of humidity are dumped and collected from normal living activities (such as respiration of living beings and plants)! Better sealed/inulated buildings tend to accumulate humidity as the heat and more humid air rises. As the coolest extreme days in the windy city hit - less is more otherwise there's complaints about sweaty windows!"

How can you say that dry air is only rarely a concern? Upon what are you basing that statement? I inspected a high-rise in downtown Chicago the other day and the indoor RLH was 17%. Do you consider that healthy HG? Domicile Consulting (Me, Ross, and another guy) recommends that the clients install and monitor one or more digital thermo-hygrometers in their home (multiple units for larger homes) and that they maintain indoor RLH at 30% t0 50% This is consistent with US EPA guidelines. What standards are you referring to in your pontification?

How can you be so flippant and arbitrary in your response? I'm sure you're aware of the many deleterious effects of dry indoor air. Nose bleeds; increased risk for colds and influenza due to more 'hang time' for viruses, bacteria, etc.; dry skin, and worst of all...static cling!

What about art work, fine cabinetry, grand pianos, and other possessions that are adversely affected by low humidity and wide swings in humidity?

The risk of some sweating windows is small potatoes compared to the indoor air quality, health, and other considerations. Ross is talking about high-rises in his query. All the modern high-rises I've ever inspected have aluminum framed windows which will not be damaged by occasional condensation contact. When we see drywall or wood sill/stool at the base of these windows we recommend replacing those moisture sensitive materials with stone, Corian, or equivalent to prevent mold growth and damage.

Ross and I believe strongly that indoor relative humidity is an important component of indoor air quality and that IAQ is an important part of a home inspection. I don't think anyone will ever convince us otherwise...if someone does, it will be a serious student and thinker on the subject. Not someone who posts for the sake of posting. Good day!

Here's little program that you can install on your smartphone that will tell you if any surface in the home that you are inspecting is at or below the dewpoint.

Temperature, Dewpoint, and Relative Humidity Calculator

With a non-contact thermometer and a hygrometer you should be able to plug in those two variables (surface temperature and relative indoor humidity) and use the program to find areas of the home that are at risk for becoming a condensing surface.

Originally Posted by Dan Cullen

Here's little program that you can install on your smartphone that will tell you if any surface in the home that you are inspecting is at or below the dewpoint.

Temperature, Dewpoint, and Relative Humidity Calculator

.

Nice, thanks.