View Full Version : humidifier needed wih modulating furnace
09-15-2011, 01:42 AM
Considering a Luxaire Acclimate furnace ( modulating with VS motor) for my 1,000 sq ft. ranch - michigan climate.
Also asked contractor to price a new Humidifier , he said a humidifier wouldn't be required with this furnace?
My existing 20 yr old conventional furnace and humidifier sometime's struggle to keep the humidity up over 30% in the winter so it is a concern.
09-15-2011, 07:14 AM
That is a great furnace. I would be a bit worried about the contractor though.
First of all, did he perform a load calculation? You'll want that unit sized properly. Second, I can't imagine why he would not sell you a humidifier if you want one.
09-15-2011, 07:53 AM
My experience: After replacing a 20 yr old, oversized behemoth, with a smaller-sized modulating furnace (with outdoor combustion air) w/ vs blower, static shocks have been eliminated. Was considering a humidifier, but opted to wait and see.
09-15-2011, 08:07 AM
Do you really need a humidifier? It's about how high of %RH you want, the number of occupants, the amount of fresh air infiltrates through the home, and the dew point of the outside air.
MI winter outdoor dew point gets down to 0^F. Most windows will have condensation problems at 68^F, indoor temps, +35%RH, 35^F dew point, indoors. With 100 cfm of fresh air infiltration/ventilation, you need 2 lbs. of humidification per hour to maintain 35%RH. 4-5 occupants add a 2 lbs. of moisture per hour. No humidifier needed if occupied by 4-5 occupants 24/7 with 100 cfm air leakage.
You can figure out if you need a humidifier from this info. Most homes of typical size with a couple occupants with ideal fresh air to purge indoor pollutants will need a humidifier. If the same home does not need a humidifier or the windows condensate, the home is probably not getting enough fresh air to purge indoor pollutants and renew oxygen.
If the home is too dry with 2-4 lbs. per hour of humidification, the home is leaking excessively and should be air tighten.
There is an excellent iphone app to calculate the amount of moisture that needs to be humidified or dehumidified to raise/lower %RH. Search for Quest Calc. It is no charge.
09-16-2011, 01:41 PM
Thank You for the info - I am going to borrow a I-Phone and try and do some calculating.
I believe my house would be considered "loose" its brick but it has original ( 50's) single pane windows, moderate insulation with 3 occupants.
No issues with condensation in the winter but my house runs drier than I would like anyway.
The recommendation really took me by suprise also.
09-16-2011, 05:47 PM
What the contractor meant is that the new furnace draws it's air from outside, so it's not pulling in additional dry outside air. However, if it's still a very leaky home, you may still need supplemental humidification.
The home is pretty small however, so you might just wait and see what normal cooking and shower activities do.
09-16-2011, 06:10 PM
I would also be concerned with your contractor. He basically is telling you what you want in your home. If you have had a problem keeping humidity in the 35% range in the winter, then you already know that it's needed. Kinda bold of him to suggest you don't! Personally, I have a home that also is difficult to keep humidity up in, and enjoy our humidifier a lot. In fact could barely breath in winter without it. Look for a contractor truly interested in your comfort, not his opinion or biased. Our humidity problem really showed up when the kids left home and the showering slowed down!! We always ask about humidity needs and filtering when doing a home assessment!:.02:
09-16-2011, 06:18 PM
Dont wait to see if you need one. Get it now. Its cheaper to install it with the new furnace, than haveing it installed later (I dont care who the contractor is). Go with your gut on this one.
09-16-2011, 07:36 PM
Improve your homes envelope first, then see if you need a humidifier.
Ask you contracto to give you a price on installing the humidifier now, and what it will cost later. many will not increase the price if you nee it later.
09-16-2011, 07:50 PM
Furnaces with sealed combustion and make-up air do make a difference. If a furnace uses 100 cfm of outside air, the infiltration the dries out the home is reduced by 60-70 cfm. The home will have more moisture from the occupants. Why not wait and see how dry the home gets? When and if the home gets dry, check out how much moisture needs to be evaporated on the stove to get the moistue level you want.
This could tell you how big ofa humidifier you need.
Areas like the sill plate/rim joist are common areas of infiltration. A couple tubes of caulk may be all it takes.
Powered by vBulletin® Version 4.2.0 Copyright © 2013 vBulletin Solutions, Inc. All rights reserved.