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What are the best methods for humidifying a residential home with Forced Hot Air? If price is no object, do steam humidification systems perform markedly better than cheaper evaporation based systems?
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What are the best methods for centrally humidifying a residential home with FHA? Do steam systems work well? Are they worth the significant premium over evaporation based systems?
*I see very few of the stean type, so can't comment on them.Best reasonably priced seems to be the evaporative drip type: with the metal mesh palte that the water drips down and the drain for anything htat makes it to the bottom.The inexpensive drum types have to be cleaned frequntly (monthly?) and can get fairly disgusting fairly quickly. I wouldn't put on in my house now that I've looked at hundreds of them as a home inspector. Stuff (mold, bacteria, etc) can grow in there and then get aepolsoled and sprayed around the house. (Think of an evaporative as a potential biological weapon terrorist lyurking in your ductwork!)Current thinking tends towards weatherstripping and weatherization instead of humidifiers. Keep air exchanges down so the moisture naturally introduced by daily living stays aroun d longer and you might not need a humidifier (and you'll save on heating costs.)BTW, furnaces do not dry the air in a house. They take dry cold air (that finds its way in from outside) and make it warm dry air.
*May I ask where you live and ehy you want a humidifier?-Rob
*I've used a little ultrasonic steam unit in the baby's room and it worked fine and wasn't gross like the rotating sponge/fan units. And in a small area worked okay. But for a typical whole house, you're looking at 10 or more gallons a day to bring the humidity up to the desired 50% range. So a system that tops itself off is nice so you are not hauling water all day. And that would seem to dictate an add-on to your existing forced air system. Or at least tying into its ductwork.Getting the RH% up to 50% will stop the static shocks, chapped lips and the cooling effect of really dry 70F air. But you'll see condensation on single pane windows in more weather conditions. And if any inside air leaks in the building envelope, it will condense and/or freeze there - causing mold, rot, and apparent spring-time roof leaks. So if you electrical boxes, lighting fixtures, attic door, etc. are not well sealed, consider the big pictures before throwing a lot more moisture into the (temporarily) indoor air. Posting your city and state would allow us to comment on your particular climate. My own house works very well at 50F and at -40F. It wouldn't work well in Miami or Phoenix. -David
*Thanks for the input to date. Our residence is in Boston, where winters can get dry.
*Tosh,The best humidifiers I've seen for residential use is the Aprilaire computer-equiped powered humidifier. It has a program in it's little brain that will adjust the humidity level based on outside air temperature to conform to ASHRAE recommendations (between 40 and 60% relative humidity).Steam humidifiers are not available, as far as I know, in sizes that would be compatible with a normal residence. Maintenance would be a pain, and cost is always an object.The powered humidifier used a fan to recirculate supply air through the unit and not derate your furnace. By-pass type humidifiers take air from the supply plenum, pass it through a drum and dump it into the return. This causes a loss in efficiency and air flow to the house.
*Thanks for the advice re Aprilaire. I'll look into them.
*In Boston, if considering a humidification system addition to the central air, I'd consider adding a dehumidifier also. So the bath towels don't mildew on the towel rack in the summer. -David
*I'm guessing you have a "newer" house since your in Boston w/ FHA.Don't bring the humidy above 40%, IMHO.Weather strip first, then see if you need a humidifier. (Get a pressure door test. It'll pay for itself very quickly with fuel savings.)
*"Don't bring the humidy above 40%, IMHO." Just curious, what is that based on, Bob?"Current thinking tends towards weatherstripping and weatherization instead of humidifiers. Keep air exchanges down so the moisture naturally introduced by daily living stays aroun d longer and you might not need a humidifier (and you'll save on heating costs.)" You've just described here, the precuser to "sick building syndrome" and one of the major causes for poor indoor air quality.
*Tosh et al. The last time a poster asked about whole house humidification, all hell let loose. Fred Lugano was one respondent involved.Rob Susz asked why you wanted to add humidify, and Tim suggested one ask why humidification is necessary. Any house that has to have humidity added is "broken" : the house is either leaky or excessively ventilated. Suggest you consider tightening up the house first. And based on the degree of tightening, you may find adding huidity unnecessary. GeneL.
*What I was trying to point out, that if a house (or any occupied structure) is not provided with fresh air and exhaust, the people inside will suffer. The fact is that a "tight" house will experience an inleakage/outleakage rate of 1/2 air change per hour. In a 2500 sf house with 8 ft ceilings, that equates to 150 cfm. In most parts of the country, that means extremely dry air in winter and humid air in the summer. A properly sized central AC system will dehumidify in the summer. So what to do in the winter? Humidify. Extremely low humidity is as bad as extremely high humidity. The acceptable range for relative humidity is from 30 to 60% and target should be 40 - 60, year 'round. In winter, as outside air temps fall, the lower end of the scale is more comfortable. In summer, the AC probably won't get you below 50% without subcooling the house (and causing other problems).If you seal up a house so well that no moisture has to be added to be in the comfortable range, you will have air quality problems related to CO2, products of combustion, dander, off gassing of all sorts of items, VOCs from cleaners, etc... the list is very long.
*Tim,That 40-% figure is from doing a lot of home inspections in NW Ohio (which is similar to the Boston area, weatherwise; not quite as biting a cold because of no salt in the air ) and findiong that often, during the winter when the humidistats are set much above 40 there are also various signs of condensation.Your point on IAQ is well taken. From various seminars I've taken, it seems that pre-70's "non-tight" homes can take a lot of weatherization before the IAQ issue gets going, but this is, I'm sure, open to discussion.
*There is a fine line between keeping the humidity level high enough for comfort and low enough to prevent windows sweating. More humid air takes more energy to heat. 40% RH is a good number, well within the "optimum zone", the lower end being 30% rh.Historically, we have done some really stupid things in the name of energy conservation. The self-induced problems caused by well meaning but ignorant maintenance that I've seen in schools, churches, hospitals and residences would boggle your mind.I agree whole heartedly that a leaky house should be sealed up before making other modifications. But something that I see as a chronic problem, more so in residences than in other occupied buildings, is the failure to realize that the heater/furnace/air conditioner, exhaust fans, flues, vents, etc.. are all parts of a ventilation system.
*Barkeep,Give that man another of whatever he's having. Such wisdom should be rewarded
*Let's look at the historical data for Boston, January 2001http://205.156.54.206/cgi-bin/box/clm2.plMost of your month was above freezing! No depoint data, but my brother has lived between Roxbury and Marlboro for the past 7 years. I know your weather tends to be damp in the winter (at least as compared to Rochester.)You can tighten up the house enough to prevent the drying, and still be within safe ventilation limits per ASHRAE.-Rob
*Tim. I concur with your last paragraph.One can have a very tight house and not suffer from the problems you listed. Rob concurs. One must know what one is doing. GeneL
*Something of note, since buildings were really leaky, (i.e. prior to the the energy crisis of the 70's) to current practice of having relatively well sealed and insulated buildings and bringing in outside air to maintain IAQ, the heating and cooling loads are about the same. In the interim when buildings were tight but not well ventilated, loads decreased, but so did IAQ.As far as Tosh's original question goes, I recommend a power humidifier mounted on the supply plenum with a computer controlled humidstat (sensing humidity in the return plenum) that will provide feedback and control to the unit to maintain the level of humidity in the house as desired. It will accommodate a leaky house when OA is very dry and will also limit output when there is little or no need.Humidification in residences is optional and depends on the owners preference.
*Are humidification systems appropriate within a high-velocity (mini-duct) forced air system? We live in MN and have VERY dry winters. We typically set up a few steam humidifiers around the house, but they are a pain to maintain.While whole-house humidification sounds like a great idea, I would be concerned about pumping damp air through my house's duct system and promoting mildew/mold in it and/or the actual humidification unit.
*Has it occured to anyone with a winter-dry house to get a blower door test?Tim - I have tested many 1800's era homes that were tighter than some new energy star homes! The problem started when we switched to drywall from plaster.-Rob
*Rob:"I have tested many 1800's era homes that were tighter than some new energy star homes! The problem started when we switched to drywall from plaster."Wow! In the areas I'v done most of my work in (MA, PA, OH) old houses tend to leak like sieves around windows, receptacles and along the floor/wall intersection. That's without doing blower door tests, though.Where abouts are you located?I'd be very interested in your experiences with this.
*I don't know what constitutes an "Energy Star" house, but your point is well taken. Residenses run the gamut of construction techniques and quality and as some bright fellow on this thread said previously you gotta seal it up before you spend too much effort on modifying the HVAC system.As far as Darrell's questions go, I don't have any experience with the mini-duct systems, but the principles of humidification remain unchanged. If you "pump damp air" into the system in an uncontrolled manner there will be problems. A properly operating humidifier will not create mildew or mold in your ducts. As far as the unit goes, some are more maintenance intensive than others, the powered units are less likely to "mung" up than the bypass type, but some regular maintenance is required.
*Bob, I am in Rochester, NY.It seems local practice here in many houses was to lath and plaster all of the ceilings and exterior walls at one time, then build and plaster the interior walls.By plastering the entire exterior shell they were making less work for themselves, but they were also making airtight assemblies.Now factor in very few or no electric boxes cut through the wall and it gets easier to see how this is possible.Granted, not all old houses are like this, but many are.-Rob
*Rob,Interesting. How about where the interior walls met the floors?Thinking about regional differences today; imagine the regional differences 100 years ago -- or come to think of it, it's amazing there aren't more!
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What are the best methods for humidifying a residential home with Forced Hot Air? If price is no object, do steam humidification systems perform markedly better than cheaper evaporation based systems?