Whole house dehumidifier vs. variable speed HVAC

[Not that Bob 739]

I live in a valley where fog and humidity lingers frequently. I often have condensation on the outside of the windows from the spouse jacking the AC to frigid over night, but that's another subject. I am constantly fighting humidity and "musty smell" so I run room dehumidifiers which do okay but not great and are a pain. It's time to replace the HVAC and I've asked several installers about a separate whole house dehumidifier. They all say a variable speed HVAC will do the job. I still think I would like the option of running a separate whole house dehumidifier when it's humid but the air temp doesn't justify turning on the HVAC. Thoughts please. 

[immamac 43713]

Get both. 

[FORTY NINE TO ZERO 2645]

2 hours ago, Not that Bob said:

I live in a valley where fog and humidity lingers frequently. I often have condensation on the outside of the windows from the spouse jacking the AC to frigid over night, but that's another subject. I am constantly fighting humidity and "musty smell" so I run room dehumidifiers which do okay but not great and are a pain. It's time to replace the HVAC and I've asked several installers about a separate whole house dehumidifier. They all say a variable speed HVAC will do the job. I still think I would like the option of running a separate whole house dehumidifier when it's humid but the air temp doesn't justify turning on the HVAC. Thoughts please. 

Are you me?  I’m in Galveston and debating the same issue. 
ac guy is saying two stage with vfd air handlers with humidity control will do the job.  The house was built in 1880s with like 40 single pane windows and shitty insulation so the seer rating doesn’t matter to me.   Number one is cooling. Number two is humidity control.  He is saying that a vfd Compessor won’t help much since my house wil leak cold air like a sieve. 
 

ive also heard that having a dehumidifier indoors will just pull more humidity into the walls from the outside. So don’t want that to happen either.   Anyone know how true that is?

Edited October 22, 2021 by Xian

[Nivek 17081]

I put in a variable speed HVAC (trane) about 3-4 years ago as our old unit was dying and our humidity was high.
Problem solved. Plus it is quiet.

All in all I am happy with it.

[Jkwellborn 6897]

Your unit is cooling the house quicker than it can get the humidity out. If you get a smaller one, it’s gonna run longer.

[texhorn 351]

We built a few years back and did the whole home spray foam thing. AC is single
speed but the house has a single speed 4 ton for 2900 sqft and does a terrific job at controlling humidity and keeping the house cool. We undersized it a little so it would run longer and control humidity. I will say a Texas winter can be a bit challenging when the humidity is high out but it’s not hot enough to run the AC long enough to pull the humidity down. I didn’t do a dehumidifier but I wish I did. Go with both of you can. whole home dehumidifier to supplement your AC and keep the humidity down on the cooler humid days

[Nivek 17081]

Also the Trane Variable speed does have an option on it to set the humidity.  There are limits to how effective it is, but it can be tweaked a little.

[Not that Bob 739]

1 minute ago, Nivek said:

Also the Trane Variable speed does have an option on it to set the humidity.  There are limits to how effective it is, but it can be tweaked a little.

The quiet part got my attention. 

[VirginiaLonghorn 4827]

I know you asked the time, but here’s the watch I built …

I live in a 4 season climate with summers akin to Houston, but with cold winters that have periods of both dry and damp.  Our house is ~2800 square feet, split level, wooden frame built in 1969.

In 2010 we replaced our HVAC with a Trane XL20i.  It is variable speed and programmable for temp and humidity.  Quiet is an understatement.

However, its efficiency was tested by our 50 year old structure that’s not the most air tight despite replacement doors and windows.

In 2016, we added an Aprilaire whole house dehumidifier for the summer and an Aprilaire whole house humidifier for winter.  They work great as a team with the Trane and, I think, help achieve/maintain comfort without taxing the main system to do all of the work.

Worth looking into …

 

[Nivek 17081]

3 hours ago, Not that Bob said:

The quiet part got my attention. 

It really is noticeable now how little noise it contributes.  The older one was dying and very loud on its way out, so I thought that colored my perspective,  but the new one makes less noise than my neighbors does, when I am standing next to mine.   One thing I noticed was that all of the screws for the outside unit have a little sound dampening on each one.    I will say that it came with its own Nexia thermostat and it can be hooked up to Alexa and what not, but I largely don't give a shit about that.     And the idea of having my kids fiddle fuck with the AC would drive me sane.  

[Jkwellborn 6897]

Trane units were the most quiet 30 years ago too.