HVAC air exchange

[Dave Fritz]

We've had an air exchange added to our hot air furnace as well as an air cleaner that replaced a single 1 inch pleated filter. The TVOC and general air quality has improved considerably. At first the filters on the air exchanger were dirty after one month, now we're able to let them go much longer before replacing. It seems we had a lot of dirt in the duct work even though we'd paid to have the ducts cleaned. Now the concern is humidity. Our house has never gone above 25% humidity and regularly is at about 20%. We both have allergies and I have chronic sinusitis so those humidity levels aren't acceptable. I have a room humidifier in the shop that helps with static electricity and recently have been using that in our bedroom. It still only reaches 26%. I have a whole house humidifier on order from our HVAC company and plan on setting it at 35% during the winter unless we go below zero for too long. I'm wondering how you handle humidity in your home in the winter, esp. those living in the northern states?

[Michael Schuch]

I live in the high desert of Central Oregon. It is very dry here year round. I have a few of the evaporative humidifiers in the house as well as a big aquarium. The larger console evaporative humidifier can dump 10 gallons of water into the air in about a day and a half. I don't like the ultrasonic humidifiers at all. They leave a white dust everywhere if you do not use distilled water in them. With the evaporative humidifiers all the water deposits are left in the wick which has to be changed a few times a year.

We stopped using our very inefficient central HVAC since I installed mini-split heat pumps in the great room and 3 bedrooms.

[Jim Becker]

I hear you on the lack of humidity thing...here at our new place, it seems that the combo heat pump/oil heating dries the air significantly more than the natural gas units did at the old property, my an order of magnitude. My eyes are paying the price and Professor Dr. SWMBO's nasal passages are suffering, too.

For awhile, we did have a system mounted humidifier on one unit at the old property, but it got gummed up too much and often due to minerals in the water. I may need to consider one here before next heating season, however...

As to filtration, this house is the first time I've experienced MERV-16 filtration and it seems pretty darn effective relative to dust. Filters are expensive, however...I just bought two and even at discount they were about $160 for two.

[Dave Fritz]

I'm hoping by using softened water we'll eliminate some of the calcium build up. We have a contract with the HVAC company for maintenance so they'll have to change things out as needed. Getting old costs more as we have to hire more and more done, things we used to do ourselves. But then I haven't bought new clothes in ages. I like to shop at Goodwill or Agrace Thrift Store. Having parents talk about the depression as a child left it's mark. Paying someone to do chores is still cheaper than buying a condo or renting an apartment. We'll see how this works out.

[Myk Rian]

I keep the house at about 45RH. Any higher and my Wife complains the windows sweat.
Softened water doesn't help. You'll still get buildup on the element. Just change it once a year.

[John M Wilson]

I keep the house at about 45RH. Any higher and my Wife complains the windows sweat.
Softened water doesn't help. You'll still get buildup on the element. Just change it once a year.

We also have both upstairs & downstairs units set to (attempt to) 40% RH -- the thermostats even know to cycle into a very low fan speed (without heat) to push air past the humidifiers attached to the HVAC units when the humidity is low. I've tried several different kinds of central humidifiers over the 30+ years we've been here, trying to get around the totally excessive mineral build up from our municipal water. About 10 years ago, I installed Trion Herrmidifiers, which use a very stiff pleated pad, and the results are better than the previous set-ups. The unit purposely uses a little more water than will evaporate in order to wash the very mineral rich run off into the AC condensate lines, which drain outside. Like Myk said, I have to replace the elements each fall, but they're not very expensive.

If we get an extended cold snap (rare here in middle TN), I'll dial back the units a little to limit the condensation on the windows.

No problems with the white dust that the cool ultrasonic types seem to generate.

[Jim Becker]

I'm hoping by using softened water we'll eliminate some of the calcium build up. .

Yes, that's something we have here, too, so I'm hopeful that if we do add a humidifier, there will be little or no issue with buildup of "stuff".

[Lee Schierer]

Yes, that's something we have here, too, so I'm hopeful that if we do add a humidifier, there will be little or no issue with buildup of "stuff".

Only distilled water would leave your humidifier mineral free.

[Dave Fritz]

We also have both upstairs & downstairs units set to (attempt to) 40% RH -- the thermostats even know to cycle into a very low fan speed (without heat) to push air past the humidifiers attached to the HVAC units when the humidity is low. I've tried several different kinds of central humidifiers over the 30+ years we've been here, trying to get around the totally excessive mineral build up from our municipal water. About 10 years ago, I installed Trion Herrmidifiers, which use a very stiff pleated pad, and the results are better than the previous set-ups. The unit purposely uses a little more water than will evaporate in order to wash the very mineral rich run off into the AC condensate lines, which drain outside. Like Myk said, I have to replace the elements each fall, but they're not very expensive.

If we get an extended cold snap (rare here in middle TN), I'll dial back the units a little to limit the condensation on the windows.

No problems with the white dust that the cool ultrasonic types seem to generate.

When you say upstairs and downstairs I'm stumped on how you control the different zones. I've seen zone heating on this old house but it's usually with hot water heat. can you do that with forced air heat?

[Dave Fritz]

When you say upstairs and downstairs I'm stumped on how you control the different zones. I've seen zone heating on this old house but it's usually with hot water heat. can you do that with forced air heat?

We use water from our reverse osmosis system and haven't had that problem either with our small ultrasonic unit but can't with the whole house unit so we may have to change out the filters more frequently. BTW, thank you for all the information, I'm learning a lot.

[Grant Wilkinson]

Here in the great white north, I used the drum unit from this company

https://www.desertspringproducts.com/ds3200

Instead of a foam sleeve, it uses a plastic drum with ridges that capture the water. I installed one of their autoflush units. Every 48 hours, it flushes out the reservoir. Since installing that, I have had no mineral build up at all.

I don't work for them. :)

[Jim Becker]

Only distilled water would leave your humidifier mineral free.

True for sure. I'm just hoping that there's less stuff in the water here than at the old place.

[John M Wilson]

When you say upstairs and downstairs I'm stumped on how you control the different zones. I've seen zone heating on this old house but it's usually with hot water heat. can you do that with forced air heat?

Nothing that exotic: It's two separate forced air HVAC systems - one located in the attic to heat/cool the 2nd floor, one located in the crawl space to heat/cool the 1st floor. Each has its own thermostat. It seems to work best when I keep the thermostats within a degree of each other, as we have a large foyer area open to both floors, and if I offset them too much, then one unit or the other is doing all the work & the more distant rooms get either too hot or too cold.

[Dave Fritz]

Thanks, sounds simple enough. Some of the systems on this old house look pretty complicated but I'm sure they're well done.


Nothing that exotic: It's two separate forced air HVAC systems - one located in the attic to heat/cool the 2nd floor, one located in the crawl space to heat/cool the 1st floor. Each has its own thermostat. It seems to work best when I keep the thermostats within a degree of each other, as we have a large foyer area open to both floors, and if I offset them too much, then one unit or the other is doing all the work & the more distant rooms get either too hot or too cold.

[Bruce Wrenn]

True for sure. I'm just hoping that there's less stuff in the water here than at the old place.


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.

[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--
473997
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.