ISY + Thermostat ... Fundamental Questions

[larryllix]

After my father died my mother didn't bother to maintain the humidifier on her furnace. Her 30 year old maple buffet side panel spilt from top to bottom with an 1/8" gap.

 

Her dining room table with full 1" maple top split almost down the middle from end to end with about a 3/8" gap. I could put a screwdriver blade down through it to the handle. In the summer, the gap closed completely and  then she sanded the top down, and refinished it with new stain and urethane finish. The next winter the gap split again to the same 3/8" gap.

 

Looking at the construction, they glued and screwed the top planks to another piece of hard maple, crosswise to the top lamination planks. That's a woodworking no-no. They should have had slide slots for screw fastening, or used a metal undersupport that doesn't swell or  contract.  Lasted 30 years though.

 

Without humidity added our homes here will drop to about 10-15% RH, especially if not lived in, with breathing, sweating, showers, and cooking moisture

[ScottAvery]

Wood furniture should last decades if not centuries, so destroying it in a few years of poor humidity control is quite a penalty to bear.

[Bumbershoot]

I agree -- low humidity results in mostly cosmetic issues, gaps in floors and drafty doors and windows.   

 

Friends moved from the Midwest to the West;  Three years after moving to the high desert (outdoor humidity generally in the range of 15-25% RH) their old wood furniture started to fail, mostly coming apart at glued joints.   It is difficult to keep cigars in good condition, gotta use a tupperdor.

 

So even at the crazy low < 25% levels, actual damage took years.

My humidifier runs a lot keeping the house humidity to 40% here in the high desert.  Itchy skin, dry eyes, dry cigars and desiccated fruits/veggies are problems, though I wouldn't trade 'em for the reverse.  This house is full of wood, and I haven't had any issues with any of it at current humidity levels (the house is less than 20 years old), though when remodeling a couple of years ago, the contractor let large pieces of wood (glulam beams, fireplace mantles, cabinets, etc.) acclimate in the house for at least a week before moving them into place. 

 

Automating the use of half a dozen exhaust fans in bathrooms and the laundry room (I use CAO wireless tags to get humidity data in these rooms) is helping to keep the humidity in the house fairly stable, though I don't know if driving humidity up with the humidifier, then driving it down in these rooms with the exhaust fans is really a smart practice.  I have no way to measure the long term cost/benefits of this.  It seems like it might be the right thing to do, though I don't really know.

 

One thing is for certain: installing quieter exhaust fans is my next HA upgrade...   

 

I moved to the high desert from the Puget Sound area when I retired, and I don't miss the battles with mold, moss and damp clothing at all.  I do miss the feel of soft, Puget Sound air on my skin and eyes.

[apostolakisl]

My humidifier runs a lot keeping the house humidity to 40% here in the high desert.  Itchy skin, dry eyes, dry cigars and desiccated fruits/veggies are problems, though I wouldn't trade 'em for the reverse.  This house is full of wood, and I haven't had any issues with any of it at current humidity levels (the house is less than 20 years old), though when remodeling a couple of years ago, the contractor let large pieces of wood (glulam beams, fireplace mantles, cabinets, etc.) acclimate in the house for at least a week before moving them into place. 

 

Automating the use of half a dozen exhaust fans in bathrooms and the laundry room (I use CAO wireless tags to get humidity data in these rooms) is helping to keep the humidity in the house fairly stable, though I don't know if driving humidity up with the humidifier, then driving it down in these rooms with the exhaust fans is really a smart practice.  I have no way to measure the long term cost/benefits of this.  It seems like it might be the right thing to do, though I don't really know.

 

One thing is for certain: installing quieter exhaust fans is my next HA upgrade... 

 

I moved to the high desert from the Puget Sound area when I retired, and I don't miss the battles with mold, moss and damp clothing at all.  I do miss the feel of soft, Puget Sound air on my skin and eyes.

 

Yeah, I am not sure you want to vent out that hard to come by humidity.  Seems like it would be better to mix and move that humid air through the whole house.  Of course that would need to be monitored to ensure you aren't getting anything crazy out of whack.

[Bumbershoot]

Yeah, I am not sure you want to vent out that hard to come by humidity.  Seems like it would be better to mix and move that humid air through the whole house.  Of course that would need to be monitored to ensure you aren't getting anything crazy out of whack.

 

It is a bit of a trick.  I don't run the exhaust fans for long when the humidifier is running, and I do run the ceiling fans whenever the HVAC fan is running (for whatever purpose - heating/cooling/humidification).  The objective for the exhaust fans are to remove excess humidity from bathrooms and the laundry room, with the intent to reduce shower mold and dampness in the laundry.  This all works together (thanks, ISY), but I don't know if I'll live long enough to really know if it's worthwhile.

[larryllix]

It is a bit of a trick.  I don't run the exhaust fans for long when the humidifier is running, and I do run the ceiling fans whenever the HVAC fan is running (for whatever purpose - heating/cooling/humidification).  The objective for the exhaust fans are to remove excess humidity from bathrooms and the laundry room, with the intent to reduce shower mold and dampness in the laundry.  This all works together (thanks, ISY), but I don't know if I'll live long enough to really know if it's worthwhile.

I try to keep my humidity above 36% in the winter. This is almost impossible if my HRV runs more than a few minutes per day in this -15C degree weather.

If I have ISY manage it about as tight as I can get I only have to cart less than 3-4 gallons of water per day for my humidifier.

 

When I built my house many people commented if it was vapour sealed as tight as I have it I would never need a central humidifier, (so common here) on my furnace. I made the mistake of listening to them and now do not have enough room around my air-handler to add a humidifier. With an HRV removing new paint  and other household fumes for the last ten years, the vapour barrier being enough to keep in humidity is BS.

 

I have co-ordination programs in  ISY to maximise the efficiency by running ventilation, humidity and HRV simultaneously. MWaremans logging programs have helped me immensely to debug what I was doing, all inside the ISY spare memory space. These ISY programs have saved ma a lot of heating bill size as well as reduced my water hauling for the humidifier, and maximised home comfort.

 

 

I use ISY to compensate the thermostat when the outside home chill factor  is below a certain temperature factor, by adding in the square of the wind speed times a factor, to the difference between the average temperature outside (three sensors) and the setpoint inside. This adds 0.5C to the stat setpoint temporarily so that cold periods are not felt.

 

My window panes only condense slightly at below -16C. I don't adjust my humidity for my house structure. I have extreme  vapour barrier and insulation. The housing inspector told me I didn't need the vapour barrier with 2 inches of  foam on the outside, lap sealed. The double vapour barrier worries me somewhat but the wood was well dried and the outside seal isn't sealed on the top plate of the wood construction.

 

Yes. You can drive yourself crazy worrying about all the things you don't know about. Ignorance is bliss usually  

[apostolakisl]

It is a bit of a trick.  I don't run the exhaust fans for long when the humidifier is running, and I do run the ceiling fans whenever the HVAC fan is running (for whatever purpose - heating/cooling/humidification).  The objective for the exhaust fans are to remove excess humidity from bathrooms and the laundry room, with the intent to reduce shower mold and dampness in the laundry.  This all works together (thanks, ISY), but I don't know if I'll live long enough to really know if it's worthwhile.

If you wanted to get fancy you would "zone" your exhaust fan.  One zone would be the outside and the other zone would be your air intake plenum.  When conditions call for humidity, it would vent into the plenum.  When you turn on your bathroom fan, that would trigger your furnace fan as well.  That would mix the bathroom air with air from the rest of the house.

 

Now, that is probably way overkill. . . .but you could say you did it.

 

EDIT:  Oh and, don't do that for the toilet fan.

[Bumbershoot]

If you wanted to get fancy you would "zone" your exhaust fan.  One zone would be the outside and the other zone would be your air intake plenum.  When conditions call for humidity, it would vent into the plenum.  When you turn on your bathroom fan, that would trigger your furnace fan as well.  That would mix the bathroom air with air from the rest of the house.

 

Now, that is probably way overkill. . . .but you could say you did it.

 

EDIT:  Oh and, don't do that for the toilet fan.

 

Wow, interesting idea.  It wouldn't take too much to get the exhaust output into the intake plenum near the master bath.  I'm going to be doing some work to that area there in the foreseeable future, so I'll give it some thought.  Do you think this would make any measurable difference to air quality or energy use?  I tend to think not, as this is a fairly large house on one floor.  It wouldn't hurt, though.

 

Luckily, the toilet has it's own fan...

 

EDIT: The Mrs. occasionally uses fragrances in the master bath, which can happen most any time.  Hmmm, I'm not this is a good idea...

[apostolakisl]

Wow, interesting idea.  It wouldn't take too much to get the exhaust output into the intake plenum near the master bath.  I'm going to be doing some work to that area there in the foreseeable future, so I'll give it some thought.  Do you think this would make any measurable difference to air quality or energy use?  I tend to think not, as this is a fairly large house on one floor.  It wouldn't hurt, though.

 

Luckily, the toilet has it's own fan...

 

EDIT: The Mrs. occasionally uses fragrances in the master bath, which can happen most any time.  Hmmm, I'm not this is a good idea...

Making dry air humid consumes energy.  So, dumping warm humid air outside, sucking in cold dry air from outside to replace that air, then heating and humidifying that air is a waste of energy.  However, I'm not sure we are talking about enough warm humid air to make a difference you'll notice in your energy bill.  I guess it depends on your shower habits.

[larryllix]

Making dry air humid consumes energy.  So, dumping warm humid air outside, sucking in cold dry air from outside to replace that air, then heating and humidifying that air is a waste of energy.  However, I'm not sure we are talking about enough warm humid air to make a difference you'll notice in your energy bill.  I guess it depends on your shower habits.

The humidifier companies formerly promoted themselves by claiming you would save money on your heating bill due to  making you feel more comfortable at a lower temperature. I talked to a guy years back on Usenet groups that threatened legal action on a big HVAC company, and they stopped  advertising that.

[paulbates]

I'm not sure it saves anything, but addressing humidity is an equal factor in comfort to temperature. I've found that heat and humidity have lives of their own and need to be managed separately. I have my thermostats set to call for humidity and turn on the fan and the water (plumbed to hot) to the the humidifier so humidity runs when needed... sometimes it happens along with the heat cycle, sometimes not. It has been better inside in the winter since that happens. 

 

I also have the thermostats configured to run AC below set point by 1 degree to dehumidify in the summer when needed. That helps it feel better inside as well.

 

Paul

[Spenceteon]

Did I mention that I have to keep querying the SH wired thermostat to keep the humidity and temperature data up-to-date in my programs and variables?  Does anyone have that problem as well?  I set up a timed query and have each of my variable-setting programs query it as well.  I noticed that it hadn't updated in two days earlier today, so added the queries.  What would you say was optimal?  I have the timer set for an odd number (83 seconds), and the others run when the set switch is changed.

[apostolakisl]

Did I mention that I have to keep querying the SH wired thermostat to keep the humidity and temperature data up-to-date in my programs and variables?  Does anyone have that problem as well?  I set up a timed query and have each of my variable-setting programs query it as well.  I noticed that it hadn't updated in two days earlier today, so added the queries.  What would you say was optimal?  I have the timer set for an odd number (83 seconds), and the others run when the set switch is changed.

 

Mine update temp but will let it drift a bit before updating, hard to say exactly, but it is regularly off by more than a degree but never by more than 2.  The same is true for humidity, but humidity is constantly bouncing around so I get a rediculous number of humidity log entries.  

 

I would prefer that it update the temp with even a .5 degree change and not so much with the humidity.

[larryllix]

Mine update temp but will let it drift a bit before updating, hard to say exactly, but it is regularly off by more than a degree but never by more than 2.  The same is true for humidity, but humidity is constantly bouncing around so I get a rediculous number of humidity log entries.  

 

I would prefer that it update the temp with even a .5 degree change and not so much with the humidity.

Exactly. If they would have forced a temperature update every 60 seconds (300 on batteries) it would act as a heartbeat and a more accurate update for the primary parameter wanted from any stat.

SmartiePants doesn't seem too versed in protocols. It's hard to believe they even designed Insteon. I doubt they did, or the mastermind left years ago.

[stusviews]

Did I mention that I have to keep querying the SH wired thermostat to keep the humidity and temperature data up-to-date in my programs and variables?  Does anyone have that problem as well?  I set up a timed query and have each of my variable-setting programs query it as well.  I noticed that it hadn't updated in two days earlier today, so added the queries.  What would you say was optimal?  I have the timer set for an odd number (83 seconds), and the others run when the set switch is changed.

 

It's certainly not optimal. I dislike anything that creates unnecessary traffic, most especially if a program is needed to fulfill a function that does not perform as it should. I had a KPL like that (since replaced) and did a similar correction procedure, something I wasn't happy with. But, you gotta do what you gotta do

[paulbates]

Did I mention that I have to keep querying the SH wired thermostat to keep the humidity and temperature data up-to-date in my programs and variables?  Does anyone have that problem as well?  I set up a timed query and have each of my variable-setting programs query it as well.  I noticed that it hadn't updated in two days earlier today, so added the queries.  What would you say was optimal?  I have the timer set for an odd number (83 seconds), and the others run when the set switch is changed.

The powerline / rf network can handle only one conversation at a time. If someone turns on a light linked by a scene, triggers a motion, etc... at the same time as that query, you may see as several second delayed response to that action. If the ISY happens to send a scene command in one program directly after the 83 second query runs, its likely some or all of the linked devices won't come on. Unlikely, but possible.

 

Its probably worth running it this way for a while, but if you start seeing the described problems, it will likely be a result of regular querying of the thermostat.

 

Paul

[ScottAvery]

This thread inspired me to complete the replacement of the whole house humidifier that was broken when we moved in.  I had been doing it in bits and pieces, but finally finished plumbing, power, and control wiring at about 1 AM.  up 4% by morning with heat going all night. (17 degrees this morning)

[Bumbershoot]

I'm not sure it saves anything, but addressing humidity is an equal factor in comfort to temperature. I've found that heat and humidity have lives of their own and need to be managed separately. I have my thermostats set to call for humidity and turn on the fan and the water (plumbed to hot) to the the humidifier so humidity runs when needed... sometimes it happens along with the heat cycle, sometimes not. It has been better inside in the winter since that happens. 

 

I also have the thermostats configured to run AC below set point by 1 degree to dehumidify in the summer when needed. That helps it feel better inside as well.

 

Paul

 

I have a Nest, and it manages the humidifier.  The only input I have into this is to enable the humidifier from their website/apps, set a desired humidity level and establish a "quiet time" when the humidifier won't run.  The humidifier will run during the heat/cool cycles or independently of them.

 

The Nest API doesn't expose the humidifier, so there's no independent ability to explicitly turn it on or off.  Additionally, the API only reports the humidity percentage in increments of five (though the values are shown in increments of one in their website/apps).  Through no fault of the Polyglot Nest node server, I cannot independently manage humidity levels, nor can I even use the reported humidity level effectively.

 

There has to be a reason for these API design decisions by Nest.  I don't know enough about HVAC systems to understand what damage misuse of the humidifier system can cause.  I very much expect this is an effort to limit corporate liability in the case that users burn out their HVAC systems and want to sue.

 

Apparently, there are thermostats that allow independent control of the humidifier (mine is a Skuttle steam humidifier built into the HVAC ductwork).  Any recommendations as to a ergonomically/aesthetically pleasing thermostat (WAF) that can provide this functionality via the ISY?

 

Thanks in advance for your time.

[paulbates]

Its really a factor of how you can/want to manage it.

 

Why would you want to control humidity? Comfort and health for people and animals. Ideally it should be near the middle... 40% to 50%. It proven to me in the last 3 winters... we are healthier when keeping the humidity up above 34% when possible. Sounds simple? There are complications for maintaining that level, based on what type of building construction, windows and insulation/sealing- 

• Heating:
  •  =>40% can mean the humidifier will run around the clock (based on construction). That can use electricity and in my case hot water.. my pads are plumbed to hot. Humidity can collect in places like the attic, so actively venting it may be necessary
     
  • Window frosting. Again, depending on construction, windows will heavily frost when the temps drop... the windows can be damaged especially if they are wood. I have anderson wood framed windows sliding on plastic tracks. Newer window technology X pane, fiberglass, etc allow the level to be higher with less frosting. Humidity needs to be lowered as outdoor temps drop.
• Cooling
  • Our climate can be humid in the summer. Even if the temp is a setpoint, it "feels" uncomfortable > 60%.  There is an "overcooling" concept that will cause cooling to be called up to X degrees below setpoint to lower the humidity and make it "feel" comfortable. 
  • Dehumidifiers can be installed in the HVAC unit and called to lower humidity.
  • Fan cycling needs to be controlled... After a Cool cycle completes, the fan needs to not run for 10-15 minutes so the condenser drains. Otherwise, the fan will blow that moisture right back in the living spaces making it uncomfortable and starting the cycle all over again. I watched this happen on my systems

Options

1. Control with the thermostat. I have the Venstar Colorrtouch T7900.  The 9 digit (versus 8 ) means it has a humidistat and control features for configuring the status humidity behavior (both humidify and dehumidify)
   • A 24vac wire from the humidifier is pulled to the thermostat location
   • exposes to the API that humidity mode is running and what the humidity is
   • exposes set point fields via api for setting what you want the humidity to be
     • Just like the desired setpoint for heat may be different than for cool; the setpoint for dehumidify level may want to be different than humidify
     • The ISY (via nodelink) can establish humidify % / dehumidify %
   • I have a simple series of ISY programs that step humidity down based on outdoor temp to prevent frosting
   • My humidfy highest set point is 38%, but everybody including pets stops complaining / scratching=> 34%
   • I use the Venstar T7900's overcool feature to take the edge off in the summer. More cycles, less total runtime, better comfort. "Occupants" less frequently lower the temp on their own.
   • The advantage of this method is that, if the stat supports it, most of the control and contacting, etc, is handled by the stat.
2. Use your own humidistat and "roll your own" version of the above
   • Use zwave and/or tag humidistats. Place them around and average, etc
   • Use an iolinc to contact the humidifier and/or dehumidifier. (I think you need a relay that can read iolinc contact closure on one side and close 24vac on the other)
   • Also have your program turn on the HVAC fan at the same time if its a humidifier on your hvac system so that moist air is distributed into the living spaces
   • The advantage of this method is potentially better measurement as the stat may not catch all areas... again in my experience heat and humidity live different lives
3. Hybrid / additional
   • Support either of the above methods with local humidifiers / dehumidifiers. Have ISY programs turn on on/off modules in individual spaces by following when its being called for elsewhere

My goal was to make this 100% automated, and it is. There is no user control of humidity. I get pushover messages as the programs make changes so I can tweak... (eg its too dry doing it this way, or the windows are frosting if I do it that way). I do get comments when its really cold out and the humidity was lowered to <25%... but nothing to be done about that and I don't want the family manually turning it up.

 

Ease of use / what to do? 

• To be candid, the Venstar colortouches are pretty technical looking. There is a "simple thermostat" mode but it supersedes the scheduling feature. So no. My wife has been using the Venstar app for the last few years for temp adjustments, or taps the up or down button on the stat and that does. Again, no manual humidity adjustments, all automated
   
• You could keep the nest and use option 2 above for ultimate fine grained control. If you did, I would configure the nest to not control humidity and control all on your own so you know what's what.
   
• There's the upper model ecobee which is popular and controls humidity on its own... but that's as much as I know. Larry or io_guy could chime in on it vs Venstar.

I know this was a lot, but after chipping away at it for a few years, its all related and what you choose to install needs to cover all of the areas

 

Paul

[larryllix]

I find a similar situation as Paul with the humidty figures. I constantly hear people say their humidity is about 50-60%. I think in a calibrated world this is way-off-centre.

 

I try to keep my humidity between 36% and 44%, set on my ecobee3 and ecobee4. My humidifier could run 100% of the time and I would never be able to keep it over 40% using about 10-15 gallons of water per day. If my humidity approaches 40% my windows would be raining and running water onto the floors in the winter. Double pane with low-E coatings and argon gas filled.

 

I have no wired humidifier but use ISY to interrogate my ecobee4 for it's  setpoints, and current humidity. Then I run my floor humidifier co-ordinated with air-handler fan cycles. This is also co-ordinated with my HRV ventilations system. They all get pulses of long or short run time based on the requirements of the setpoints. 

 

The HRV ventilator cycle length is based on whether the humidity or dryness outside will benefit the house interior and also if the temperature outside will benefit the inside air temperature. This means that when the stat does a setback and the air outside will give free cooling, it get it. If the stat brings the setpoint up in the morning and the air temperature will benefit the inside temperature it will get it from outside via the HRV.

 

All these cycles are based on ISY's knowledge of the house temperature and humidity from my ecobee4. This worked just as well with my Venstar T7800 stat previously, also.

[Bumbershoot]

Its really a factor of how you can/want to manage it.

 

Why would you want to control humidity? Comfort and health for people and animals. Ideally it should be near the middle... 40% to 50%. It proven to me in the last 3 winters... we are healthier when keeping the humidity up above 34% when possible. Sounds simple? There are complications for maintaining that level, based on what type of building construction, windows and insulation/sealing- 

• Heating:
  •  =>40% can mean the humidifier will run around the clock (based on construction). That can use electricity and in my case hot water.. my pads are plumbed to hot. Humidity can collect in places like the attic, so actively venting it may be necessary

     

  • Window frosting. Again, depending on construction, windows will heavily frost when the temps drop... the windows can be damaged especially if they are wood. I have anderson wood framed windows sliding on plastic tracks. Newer window technology X pane, fiberglass, etc allow the level to be higher with less frosting. Humidity needs to be lowered as outdoor temps drop.
• Cooling
  • Our climate can be humid in the summer. Even if the temp is a setpoint, it "feels" uncomfortable > 60%.  There is an "overcooling" concept that will cause cooling to be called up to X degrees below setpoint to lower the humidity and make it "feel" comfortable. 
  • Dehumidifiers can be installed in the HVAC unit and called to lower humidity.
  • Fan cycling needs to be controlled... After a Cool cycle completes, the fan needs to not run for 10-15 minutes so the condenser drains. Otherwise, the fan will blow that moisture right back in the living spaces making it uncomfortable and starting the cycle all over again. I watched this happen on my systems

Options

1. Control with the thermostat. I have the Venstar Colorrtouch T7900.  The 9 digit (versus 8 ) means it has a humidistat and control features for configuring the status humidity behavior (both humidify and dehumidify)
   • A 24vac wire from the humidifier is pulled to the thermostat location
   • exposes to the API that humidity mode is running and what the humidity is
   • exposes set point fields via api for setting what you want the humidity to be
     • Just like the desired setpoint for heat may be different than for cool; the setpoint for dehumidify level may want to be different than humidify
     • The ISY (via nodelink) can establish humidify % / dehumidify %
   • I have a simple series of ISY programs that step humidity down based on outdoor temp to prevent frosting
   • My humidfy highest set point is 38%, but everybody including pets stops complaining / scratching=> 34%
   • I use the Venstar T7900's overcool feature to take the edge off in the summer. More cycles, less total runtime, better comfort. "Occupants" less frequently lower the temp on their own.
   • The advantage of this method is that, if the stat supports it, most of the control and contacting, etc, is handled by the stat.
2. Use your own humidistat and "roll your own" version of the above
   • Use zwave and/or tag humidistats. Place them around and average, etc
   • Use an iolinc to contact the humidifier and/or dehumidifier. (I think you need a relay that can read iolinc contact closure on one side and close 24vac on the other)
   • Also have your program turn on the HVAC fan at the same time if its a humidifier on your hvac system so that moist air is distributed into the living spaces
   • The advantage of this method is potentially better measurement as the stat may not catch all areas... again in my experience heat and humidity live different lives
3. Hybrid / additional
   • Support either of the above methods with local humidifiers / dehumidifiers. Have ISY programs turn on on/off modules in individual spaces by following when its being called for elsewhere

My goal was to make this 100% automated, and it is. There is no user control of humidity. I get pushover messages as the programs make changes so I can tweak... (eg its too dry doing it this way, or the windows are frosting if I do it that way). I do get comments when its really cold out and the humidity was lowered to <25%... but nothing to be done about that and I don't want the family manually turning it up.

 

Ease of use / what to do? 

• To be candid, the Venstar colortouches are pretty technical looking. There is a "simple thermostat" mode but it supersedes the scheduling feature. So no. My wife has been using the Venstar app for the last few years for temp adjustments, or taps the up or down button on the stat and that does. Again, no manual humidity adjustments, all automated

   

• You could keep the nest and use option 2 above for ultimate fine grained control. If you did, I would configure the nest to not control humidity and control all on your own so you know what's what.

   

• There's the upper model ecobee which is popular and controls humidity on its own... but that's as much as I know. Larry or io_guy could chime in on it vs Venstar.

I know this was a lot, but after chipping away at it for a few years, its all related and what you choose to install needs to cover all of the areas

 

Paul

 

I appreciate the work and thought you put into this.  I've emailed your post to myself so it won't get lost in the avalanche of information that this forum presents.

 

On first thought, I'm inclined to consider option 2 that you suggest.  That way, I might keep the Nest, which has a good WAF.  I'll take a look at the Venstar T7900.  I'm using a few sensors to measure humidity in various parts of the house, and I'd like to manage it using the ISY, which the Nest won't let me do. 

 

The relative humidity in this part of the world tends to be low, dropping into single digits during summer afternoons.  The situation get a bit more complicated in the shoulder seasons here, as the HVAC has to alternate between heating and cooling (cool nights with warm days).  It all goes completely bust in the summer when we throw the doors open and windows and let the outside in.  We have no need for a dehumidifier at all, so the problem is simplified by that.

 

This is going to take more thought.  I probably ought to place a few more sensors around the house, study the problem and make a conclusion in the fall (that'll give me a winter, summer and shoulder season to collect data).  I also should watch the Nest closer, and it does present data to Polyglot help distinguish between fan modes.

 

Thanks for all the thought and work you've put into this, and that you're willing to share it; it makes this forum a good place.

[paulbates]

YW. We have long periods in the spring and summer where temps and humidity are mild. The house came with dampers into the attic and a gable fan. I replaced the flimsy dampers with Tamco 9000s (silicone seals - every edge, foam core blades) and a Belimo actuator when we re-insulated the house. Keypad keys can turn that on and off... dampers open and fan goes on.

 

We use that a lot, and all of the humidity and fan cycling automation "goes to sleep" if key doors are open, the dampers are open and the fan is on. Keeps it comfortable with lower costs.

 

Paul