HVAC air exchange

[roger wiegand]

Our Aprilaire humidifier (ducted into the furnace) uses an evaporation pad that swaps out in under five minutes and costs about $20. We have a ton of solids in our water but still make it through most of a heating season on one pad. It flashes a light when it needs replacing. This is a no-drain unit, if you have a drain available a humidifier that flows some of the water over the pad and down the drain would last a lot longer, albeit at some cost in water.

[Jim Becker]

Despite living in an area with NO KNOWN LIMESTONE deposits, our water had calcium in it. Had to use distilled water in humidfier (ultrasonic.) Since adding a water softener (Fleck 5600,) i use tap water in humidfier. no white dust. Output from humidfier is piped directly into return duct, on a unit that has continious run fan, so it is distributed over whole house.

Our old property was literally on top of one of the only two exposed limestone structures in PA and I"m absolutely sure it was a factor, both with the humidifier challenges and our need to get an acid neutralizer to save the remaining copper pipes in the house. We have a softener here at the new place and the water here is very popular with a harmless, but smelly biologic that requires us to inject a dilute chlorine solution into the well. There's evidence that prior to the softener going in that there was some significant mineral issues. We only had the water tested for safety so exactly what is in it pre-softener, we don't know.

[John E. Hobart]

the absolute best system for whole house humidity control is either the April Aire or Honeywell Steam Humidifier .I worked in HVAC service and install for 20 years and saw most all types of systems
and either of those work the best, not cheap, around $1000 + but they will maintain 35-40% humidity in a 8000 sq. ft home. They are able to put up to 16 gallons of water in the air per day.

[Dave Fritz]

I'm confused. It's recommended winter inside humidity be between 35-40% humidity OR the highest level without causing condensation on your windows. I get condensation starting at about 28% humidity. Is that the max. I should expect then, or crank it up and deal with condensation? thanks again for all the excellent information.

[roger wiegand]

What you can reasonably achieve becomes a function of your inside temperature, your windows, your insulation, and your air sealing in the house. Maintaining something like 40% indoors at 75 degrees without condensation requires top quality windows that have been installed with all the recommended gap-filling foam in the framing around them. Many older houses can't get there, so it's a compromise. A little condensation on the windows won't hurt, puddles are bad, and condensation on the walls and such starts to get really bad, as there is probably even more condensation inside the walls, leading to mold growth. That can get very ugly.

Probably shooting for a little condensation in the corners of the windows is going to be about the best you can do.

You can go higher if you turn down the thermostat, another way to compromise.

[Kev Williams]

If you want more humidity than you may know what to do with, get a ventless propane heater or fireplace... in 2006 we spent the winter in a 36' fifth wheel trailer, and keeping it warm with the onboard propane furnace was costing over $40 a week in propane. So I bought a 22k btu ventless fireplace--
5erFireplace.jpg
The thing heated the place like gangbusters on about 1/3 the propane--
But OMG, the water would literally run down those cold, barely insulated walls!

As I understand it (and I'm not sure I really do ) - the humidity is a byproduct of (a) the release of water vapor naturally contained in (or with?) the propane itself as it burns, and (b) the water vapor released from the oxygen used during the burn... At least there weren't any calcium deposits! The wet walls and seat cushions go so bad we could only use the fireplace part time...

[Bill Dufour]

Kev burning anything with hydrogen in it will produce Hydrogen + Oxygen in the ratio of H2O. So burn any hydrocarbon and you get water + CO2. For propane the yield is about one pound of water is formed for every pound of propane burned.
California outlawed non vented heaters decades ago for causing too many suffocation deaths.. They still allow the propane job site torpedo heaters. I guess they figure the job site has good air leaks all over.
Bill D

[Tom Bender]

When we had our house built we specified a vapor barrier. At that time, 1985, the usual practice was to staple plastic to the studs prior to drywall. My builder objected because it made it hard to hit the studs with drywall fasteners. We insisted and he came up with a good option, foil backed drywall. The result is a very tight house that keeps the humidity in. Some days we have a little condensation on pretty good windows foamed in. No need for a humidifier. So my suggestion is to replace your drywall. Yeah, not helpful.

[Alan Lightstone]

50% RH indoors here today. Ah, sunny Florida where we've been hitting record temps every day.

I think the idea of an RO unit providing the water to the humidifier (and drinking) is great. I became quite the expert on these with the 1000 gallon fish tank in the last house. But you have to remember to rinse the RO membrane (adding a valve for that helps), as well as changing the carbon and filter cartridges (which was always a big pain), so adding this requires a lot of yearly maintenance too. An RO/DI unit would be better still, but for complex reasons it's said you shouldn't drink that. It's too pure. Isn't science fun.

Couldn't you use a Brita water pitcher filter (although it would probably get old pretty quick having to fill it that frequently)?

How about just making a still to provide the water?

And Jim, where did you get the MERV 16 filters from?

[Brian Elfert]

When we had our house built we specified a vapor barrier. At that time, 1985, the usual practice was to staple plastic to the studs prior to drywall. My builder objected because it made it hard to hit the studs with drywall fasteners. We insisted and he came up with a good option, foil backed drywall. The result is a very tight house that keeps the humidity in. Some days we have a little condensation on pretty good windows foamed in. No need for a humidifier. So my suggestion is to replace your drywall. Yeah, not helpful.

That seems strange. Plastic vapor barrier has been stapled to studs for years and is still done to this day here in Minnesota. My parent's house and mine were built in 1979 and they both plastic vapor barrier stapled to the studs.

[George Yetka]

Ive seen a lot of these whole house units eat the ductwork downstream. Read the directions for installation and do all the maintenance recommended. Humidification is still not very effective. I have installed 100's of steam humidifiers especially in hospitals and they often just get turned off after a year because of clogged dispersion tubes etc. The only areas that are maintained are OR's and Labs because they have state requirements. Clean steam is better but still has problems. some of the best humidifiers wont make it past 5 years. I dont know if its a lack of maintenance or what. After I install them they get a 1 year warranty like anything else. But I have removed or replaced many that we installed a few years later.

Best bet is a $100 room unit that you wont feel bad replacing in a couple years.

[Jim Becker]

The objection that "rockers" have to a poly (plastic) vapor barrier isn't about fasteners...there's zero impact on nails and/or screws from use of a poly vapor barrier. What it does affect, however, is using adhesives which is common when installing sheetrock in many situations. Since the wood or metal framing isn't exposed with a poly vapor barrier in place, adhesive cannot be used at all. I personally like using unfaced material and a poly vapor barrier because it further cuts down on air infiltration, but that's a subjective thing. It's also a bit more challenging to source unfaced fiberglass material, at least at the retail level so there's less DIY done with unfaced and a separate poly barrier. When I was in the insulation business for a bit back in the 1980s, I can think of only one builder we serviced that specified a poly vapor barrier and that was in a jurisdiction that for whatever reason, required it.