For the coin you are willing to invest, online forums is not the place to have system designed. Hire an engineer to design system and write a scope.

I’m not asking for a system design, those configurations have been proposed by the 3 HVAC contractors we consulted and the prices very standard for our area. It sounds like you consider them high but having ducts replaced alone is pricey and no we can’t afford to hire an engineer on top, and we do not want to waste money. I’m asking for experiences with these equipment types as I’ve never had a heat pump before, and asked some specific questions as a reality check vs what contractors are pitching as each had very different recommendations. If you don’t have an experience to share, feel free to scroll on by.

Are you referring to me? Please explain what I’m doing wrong, I’m not supposed to ask for help learning about this equipment here?

The two alternative HVAC systems proposed for your home are both variable speed. They may provide the required dehumidification without the need for a dedicated dehumidifier. I suggest the system be designed so that a dehumidifier could .be added in the future if your experience indicates you need it. I live in coastal Virginia. I found I needed to add a dehumidifier to the systems on each level of my home to provide dehumidification during "shoulder" seasons when there is little, if any, call for air conditioning. Mine were retrofit into the existing systems.

My concern with zoning your HVAC system is that you want to make a single, small room an individual zone. Albeit that it has some additional cooling load from the electronics, conditioning the room is going to require the system to operate at much lower capacity than it does when conditioning the rest of your home. The system may not have adequate turndown to do so. To determine if it does, you'll want to compare the calculated cooling load for the room with the cooling capacity of the system at the minimum compressor speed. Your contractor should be able to do this and show you the math.

Thank you! That was exactly my concern and wondering if the Mitsubishi dual ducted/mini split system would be better in that regard since the office would just be separate. We don’t love the idea of having to maintain a head, as far as cleaning it goes.

Alternately, if we didn’t zone it - and therefore wouldn’t need the “top of the line” systems, would adding the return and ensuring the ducts are properly sized generally overcome the additional heat load of a body and some electronics (we are not running servers in there, but have 2 computers and an amplifier for sound system, large laser printer etc)? If we don’t try zoning it’s more about the airflow balance so we’d work with the guy who focused more on the returns (same one that is heavily recommending the Evolution system) to ensure the airflow is much more balanced than it is now. Would the middle-priced options be as good at removing humidity as the variable speed ones.

If we add a whole house dehumidifier to one of the middle-priced options it will add about $5-6k to the price apparently, so bring it up close to the highest end options but perhaps that would be the best balance for removing humidity in all seasons?

Your heat pump should cool and dehumidify the air in your home. Using a dehumidifier for that purpose will increase the level of control, but at a significant increase in operating expense versus the heat pump.

You could indeed forgo the zoning if you size the duct work for the required air flow and install balancing dampers to fine tune the air flows to individual rooms. All bedrooms should have returns to maximize comfort.

Unless you have an adequate solar panel system on your house, or live in an area with low electricity prices because of having a municipal utility - like Palo Alto, Santa Clara, or Los Angeles, I would strongly advice against getting a heat pump system. In our area, gas heating is considerably less expensive to operate and since you have a furnace not even middle aged, I'd keep it and start from there by adding just AC. Our heating season demands are less than elsewhere and equipment normally lasts longer.

Something that has been glossed over and may need to be clarified is that there is nothing magic about a heat pump and dehumidification.

A heat pump has two modes - it has a cooling mode and it has a heating mode. When it's in cooling mode, it's exactly the same thing and works exactly the same way as a straight air conditioning system. Air is dehumidified with either running, the humidity (water vapor) in the air condenses to water as it passes by the cold coils and is drained away. That's why AC units drip. Think of the outside of an iced drink on a hot day - same thing.

A heat pump in heating mode does not dehumidify the air.

I live in coastal California and split my time between two homes - one in SoCal and one in NorCal. I think you've overstated the humidity concern. Unless you are uber sensitive to it. Yes, when we're having morning June gloom and it can be at times before and after June. It can be misty and damp. It's too cool to run A/C so you have no dehumidification option unless you get a separate unit. Few people bother with that, and many in coastal areas don't even have A/C.

Both of my places have AC. I use it occasionally on the hottest of days. The sun is strong and typical construction is lacking in adequate insulation. Small price to pay for our great weather.

Good luck.

It’s my understanding that a heat pump can only dehumidify when in cooling mode, is that not true of all systems? Our coastal climate means the most humid air is during cooler weather. Mornings can be foggy and chilly even in summer (56F and 95% + RH) rising to sunny drier afternoons. Then we go through a couple months (fire season…) when the fog disperses and we get hotter very dry weather, and then rainy season starts and we get highs of 55-65 with rain and humidity. So unlike climates where the summer is hot and humid, or winter is freezing and the RH is low, we have much more moisture when it’s not going to be running AC.

Currently, I find it too warm in the house to run a portable dehumidifier but we’ve been keeping windows closed and using our window AC unit on “dry mode” which works pretty well and cools instead of heating like the dehumidifier. But in winter we will not want to be cooling the air to dehumidify.

Sorry I can’t edit my previous comment. I’m just wondering if there is some way that the advanced systems are “creating” a dehumidification mode by cooling and then heating (like a true dehumidifier) or is it just changing fan speeds like the dry mode in the LG window AC. If it’s the latter I think we may still be unable to keep humidity controlled enough to meet our dust mite battle goals (RH under 50%).

Advanced & variable speed systems can manage humidity in a couple ways. Varying the compressor and blower speed to run longer and possibly lower the evaporator temperature slightly (avoiding freeze-up) to condense more moisture out of the airflow, and overcooling x°F (user preference). I doubt any systems aimed at the home market can heat/reheat the air as part of dehumidification. Specialty industrial systems can do that.

My parents' circa 2017 Lennox Elite variable speed compressor (100% to 40% in 10% steps as I understand) and variable speed blower with an iComfort S30 thermostat (with a humidity setpoint feature) has those functions. Dad understood all that initially. He lost understanding of the concepts as his dementia progressed and got upset that he'd set it at 75°F or 74°F and the room temp would get lower (overcooling was set at 2°F). I set overcooling at 0°F to settle his distress. He died three years ago but I haven't changed the overcooling as it maintains within a reasonable range of a 52% humidity setpoint*. Mom sometimes gets a bit distressed when it "runs all the time" but I can ease her concern by re-explaining the variable speed angle.

*It was initially set at 45% which led to the continual overcooling and dad's upset.

An air conditioner or heat pump will only strip moisture from the air when the indoor coil temperature is less than the dewpoint of the air passing over the coil (which is typically some combination of recycled indoor air and fresh air make up.) The same is true for a portable refrigeration-type dehumidifier. If you need to dry the air without refrigeration, you can install a desiccant-type system. Be prepared for high operating costs with either type of dehumidifier.

The Mitsubishi system proposed has a "dry mode" which provides enhanced dehumidification by reducing the fan speed to a low level like your window air conditioner. I suspect the Bryant system does, too, but check with the contractor to be sure.

Makeup air systems are extremely rare in the existing housing stock of coastal California. Windows are cracked open the better part of 12 months of the year, except when it's raining.

I'm a native and have never lived inland though I did move several hundred miles north from where I grew up as a young adult. I've honestly never heard anyone mentioning being uncomfortable or concerned about humidity during the few months, at most, of many days having foggy or overcast conditions. Heck, at such times, the weather can be in the high 50s to high 60s so it's cool. As you have described. The feeling of "mugginess" as is typical for summer conditions in most of the US, the part east of the Rockies, is rarely experienced or mentioned here.

Are you new to this area, tmnca?

The other thing I wanted to mention is that most people do just fine, and of course save money, with single speed equipment. I understand the capabilities that inverter or multispeed equipment can produce but honestly, they provide added comfort for conditions common in other parts of the country that we don't have.

I concur that ducted make-up air systems would be atypical in the majority of existing homes. That said, most residential HVAC systems operate at negative pressure (i.e., they are starved for air flow on the return side) and most existing homes are poorly sealed. Those conditions result in typical air infiltration (leakage) rates for homes of 1 to 2 air changes/hour versus 0.6 air changes/hour for a new, tightly constructed home. Infiltration is essentially a flow of unconditioned make-up air which needs to be considered when designing an HVAC system.

A lot of system leakage can come from gaps or leaks in old or poorly constructed ducts.

The California building code requires independent HERS testing and remediation when required for the installation of new or replacement HVAC equipment or ductwork. As I understand it, repairs are required only for ductwork that is accessible. Conscientious contractors include gap searches, duct sizing assessment, and needed changes and repairs as part of any project.

Not everyone in the HVAC business (or building contracting in general) does everything they should do and when they should do it. Because every HVAC installation is essentially a custom project, where the actual hardware is a component but the experience and knowledge of the pros doing the work greatly affect the end result, connecting with an expert HVAC pro is MUCH more important than what equipment is used for the project.

If this were my home, I'd make a simple cost effect upgrade. A dedicated whole house dehumidification system.

Your existing hvac is capable of heating and cooling. You can improve the ductwork for that.

Where do you live, dan1888?

Would your advice change to learn that what you're suggesting is all but unknown in the region being discussed? Do you think you're on to something that the pros here have overlooked?

Whole house dehumidification is nothing new, those pushing it are more in the camp of just selling another appliance in my experience.

That appliance is going to need maintenance, service, repair and replacement. A dehumidifier is typically going to have only a 5 yr. part warranty. So would I never recommend a dehumidifier? no.

As long as you understand fully the costs of such, like how much you run it -- your electric bill goes up not down. If the AC is off, the dehumidifier is on air coming out the vents to dehumidify is going to be in the 90F range (but dry air). If you have tall ceilings like maybe 10 -12Ft the differnence might be fine to you.

If your HVAC system is crammed into a closet or a tight attic? where are you going to put the dehumidifier? to also incorporate service, maintenance, repair and eventual replacement?

While AC's and or Heat pumps, of the generic variety offer some dehumidification they offer more over cooling to dehumidify and cycle off.

2 speed AC's and or Heat pumps, fractionally more dehumidification but typically guarded with over cool function where the AC or heat pump in AC mode will be allowed to over cool to user selected range of 0 to maybe 5F less than set point. (certain scenarios people complain of too cold for the sake of trying to dehumidify)

Carrier / Bryant variety of of Inverter tech: The infinity models have 5 speeds to choose from so this is a step up from 2 speed. If the units speed of compressor is running in 20% / 40% it's run time is going to be longer, the longer the unit runs the more dehumidification can take place. It's still an air conditioner (not a dehumidifier) -- a better function of dehumidification with money saving in operational costs... but equipment costs / repair costs will be higher especially because it's Carrier. (other major names same difference more or less as they will require proprietary controls things of that nature)

Bosch: BOVA 2.0 (they make other models too but the focus here is premium equipment, not equipment trying to masquerade as premium equipment) It's an inverter, doesn't require proprietary controls, it's controlled via temperature on a thermostat. The function of how it runs provides better dehumidification than (in my opinion) any other option that I know of.

1% steps up an down. The compressor modulates essentially in 1,000 BTU's steps. Starts up around the 17,000 BTU mark and then ramps up and down from there via algorithm in the outdoor condenser control board. The only con currently with the Bosch 2.0 is they chose R454b for the newer unit. So this option may have more unexpected costs in the future up to and including replacement for a different unit with a cheaper refrigerant.

I have the Bosch BOVA 1.0 at my own house in Katy, Texas. Installed in Oct. 2019 sitting here this morning with 41% RH in my home office. Electric bill this past month was about $103.00

I feel that Bosch Bova 1.0 at the time is pretty good for not wanting to waste money. (But the Bosch is premium equipment, comes with premium price tag to install it.)

For me if things are getting a bit sticky I just adjust temperature 2 degrees lower, under most dehumidification scenarios here. Simple and to the point. No proprietary garbage here except for out in the machine's control board.

"If the AC is off, the dehumidifier is on air coming out the vents to dehumidify is going to be in the 90F range (but dry air). If you have tall ceilings like maybe 10 -12Ft the differnence might be fine to you." The air temperature at the supply grills depends on how the dehumidifier is integrated with the HVAC system. Mine is designed to run in tandem with the air handler which distributes the conditioned air throughout my home. The temperature at the supply grills is nowhere near 90F. Ceiling height doesn't affect the discharge temperature from the dehumidifier nor does it affect the indoor comfort level.

More about dealing with humidity.

and why your correctly sized hvac by itself can be in need of assistance. Which means you can save a lot of unnecessary expense by not buying another hvac system. Contact Santa Fe or a similar dehumidifier company to get the contact info for the sales rep for your region. He can give you the number and name of a contractor competent to solve your issue. He'll know who the good guys are.

I guess Dan has confirmed his limited knowledge of the area being discussed.

40% RH in my office this morning in a very humid climate.

I have no dehumidifier, or ERV.

I have a zoned HVAC system with Bosch Inverter outdoor condenser.

Why spend money on another system if you don't need to?

(The $$$ question, I know you're going to spend it on something though.)

But I want to spend more money, and more money and more. Ok, go ahead then.

Ray,

The video compares two alternatives for providing fresh air ventilation in homes in different climate zones: dehumidifiers (the subset of those with the ability to bring in outside air) and energy-recovery ventilators (ERVs.) The introduction of fresh air (i.e., ventilation) is important for indoor air quality and occupant health--more so as homes are built progressively "tighter," which means less outdoor air infiltration.

A whole-house ventilation system is required by the International Residential Code (M1505.4) which I'm guessing you're not familiar with since you won't work in areas that require codes and/or inspections of your work.

The "V" in HVAC stands for "ventilation" which in my experience, most contractors advertising themselves to be HVAC contractors know little if anything about.

Charles,

I don't work in new construction Charles.

New construction vs old construction?

New construction = tighter requires ventilation. Old construction = drafty

Regardless if I lived in an area that required permits or not doesn't change much the type of home I am called to service. Does it? Older areas of construction all have varied levels of problems.

Builder problems: #ButFirst >> the builder is not coming back to old construction. If they do what they say may be something along these lines---

"You've come this far, we might as well tear the house down to the foundation and start over." -- the first video Dan posted is exactly what that builder did several years ago trying to fix an older AUSTIN, Tx home on a "budget".

Even working in an area that requires a permit, that is for new equipment not performing a repair Charles. Most of what I do involves repairing. Not saying I don't replace equipment sometimes, but most of the time it's repairs.

Some events along that way involve repairs to fresh air systems, maybe in the realm of 10% of homes I am called to.

Probably around 1% chance for me to run into an ERV around here. ONE PERCENT and I'm being very generous here with that figure.

Today I'm at 42% RH in my home office. My home was built around 1978.

SO?

Charles may go back to making claims about mold growing without humidity condensing into liquid form. Good luck seeing it. -- You're not going to see the ventilation either.

We will just call these ghosts in the machine. You'll get to see those ghosts when we tear your house down to the foundation and start over. Yes, you'll need to pull build permits for that -- even in my area. LOL