Each part of a home needs to be designed so they work together as a "system." Here's a link to some climate-specific best practices to get you started in your research phase:

http://usgbcsouthfloridachapter.cloverpad.org/Resources/Documents/Homes%20Report%20Hot%20_%20Humid.pdf

In my experience, high-performance homes are less forgiving of design errors. I think you will be well served to include a HERS rater or similar consultant to work as a member of your design team. The investment will be paid back in improved energy efficiency, comfort, and longevity of the structure.

Best wishes for a successful project.

Good insulation especially attic area....minimum 2 stage condenser, var speed furnace (if nat gas is available; otherwise a variable speed air handler with a 2 stage min Heat Pump condenser). Since dehumidification is important to you, I would want dehumidify on demand feature. Brands would be high end Carrier and TRANE models.

TD

A properly sized and installed 18 SEER variable speed 2-stage heat pump would be a good solution. If you are going to be adding more insulation and improving windows, then I recommend a load calculation be done to determine the sizing. An over sized AC will do a poor job at controlling humidity. If the house is tight and the the HVAC is installed correctly then you should not have to spend money on a whole house dehumidifier.

Here's one set of options-

This is a complete system. The dehumidifier could be added to your build. Dehumidifier

Thanks, you've all given me a lot to consider and I appreciate the advice.

If this was a new build instead of a remodel, there are things we'd do that aren't feasible in this case. There's also a lack of qualified installers. I looked for a HERS rater and there are none in the area.

We'll likely need to include an addendum in our remodeling contract that specifies the exact HVAC equipment, and its placement, in order to not get the typical builder basic 14 SEER single stage system in the attic. Hence the need to become as well educated as possible in a short time.

We've learned from experience that an ERV is not a great answer in a humid climate when there are months in which there's no demand for cooling or heating. The shoulder seasons are long enough and wet enough to cause humidity problems. That's why we later installed a ventilating dehu in our current home. I like the Santa Fe products linked above.

It is very smart to include specific HVAC equipment and placement in your contract. General contractors are not knowledgeable about HVAC and try to spend the least amount of money on equipment and installers.

"There will be two to four months each year when there's no demand for heating or cooling, at least for most of the time, but there will be high humidity."

This is a situation that typically requires a dedicated dehumidifier. An air conditioner won't dehumidify because it will be too cool to run it effectively. Also be sure not to oversize the unit as that would impair dehumidification in the warmer months.

The guy in the video is a unicorn! We are doing the research for a project in a hot/humid area and it was close to impossible to find someone who was on the cutting edge of HVAC technology. We are willing to pay for the study and materials, but everyone just wants to do what they have done for the past 40 years.

We even contacted one of the companies that the guy in the video works with and offered to pay for long distance design services. The manager they assigned to us scheduled 2 calls and then blew us off at the time of the calls. We altered our plans to be home when it was convenient for him and he blew us of. We called up for a third time, and when we made a comment about him wasting our time, he told us to take our business someplace else!

Have you considered 12' high ceilings?

many HVAC experts do not understand dehumidify on demand...

Some posters on this thread don't understand the difference between a condenser and a compressor.

Should not need a whole house dehumidifier with humidify on demand thermostat and a variable speed 2-stage AC.

mike_home, would you please explain in simple terms. We thought the whole house ventilating dehumidifier would provide filtered fresh air at any time of year, even when the temperatures don't call for A/C, without increasing the indoor humidity the way an ERV can do. We need a way to provide fresh air (opening windows isn't an option much of the year between a multitude of pollens + humidity) but we also want to keep the humidity level at or below 45% which is not easy in our climate.

Virgil, not sure if you're serious or being facetious. FWIW, we have 11'+ ceilings in our current home (two main floor rooms have vaulted ceilings >18'.) I've never found that this house is any easier to air condition, much less dehumidify, than any previous home.

I did like your rhinos on the thread about a new front porch. My daughter-in-law would be delighted. Animal Kingdom Lodge is her favorite place to vacation.

tigerdunes

many HVAC experts do not understand dehumidify on demand...

How can you expect to find an expert when we're constantly told on this forum board and others... based on what someone thinks a job should cost --- shop for a better price. What ever that number is?

It's on this forum, it's on others. No, no, no we'll settle for the cheaper installer... we don't want a high priced contractor that actually knows what he's doing.

People, do the same thing to me. Throw me under the bus --- then you claim experts don't understand something... Define expert?

You choose with your wallet. You can't expect to find and expert that isn't getting paid. Can they call you Tiger? Sounds to me you just want to complain about something or demote someone when you yourself can't be bothered by doing it.

I don't claim to know it all, but I'm not going to sit here profess to say this or that and then don't actually do it myself.

I almost think it's more about wanting to complain when it doesn't work. The board is littered with systems just installed, not working.

You recommend Trane and Carrier, but if the price is too high we'll suggest you run to a more knowledgeable service provider that 'charges less'. Yeah those are the kinds of experts we want... ones who know so much they gladly take less money for their services.

You paint a rosy picture that doesn't exist like you think it does with Carrier or Trane for that matter. I just recently got a call from someone somewhere in Maryland. Recent Trane install not working. But as you know or should know by now this job is an in person sort of job. There's a lingo I speak then there's the lingo you speak. Nothing I can do over the phone. This is a local type of business thing. If I'm not there in person, much of what I say is not likely to help.

Just repaired one last night (Trane) on a home just over 5 years old. Keep recommending those Tranes and Carriers, I fix em all. If I can't fix em I replace them just like everything else.

I realize paying a higher price isn't a guarantee either... but no expert is going to exist in a field in which everything is Monday morning quarterbacked to death. Everything must be line item priced, we are not going to overpay or think we are over paying for something. But then we'll complain when there's no experts or HVAC experts that don't know dehumidify on demand? ha, ha, ha.

It's going to hit 100's here in Katy, Texas if not today sometime this next week. Feel like temps in the 105's to 110's. If your AC isn't working well at 90F it's only going to get worse from here.

I do believe you will need an expert. If you live in Katy, Texas maybe it's me. If not call Tiger. Oh wait I don't think he's accepting calls....

If there were competent installers in your area you wouldn't have a problem. When that's not an option you choose the next best. If you can't find an expert or afford one become the expert. You need to please just one client. If you want something done right do it yourself. You'll be surprised how much easier you are to please when you're the contractor.

Addressing the OP's problem is not as easy as finding the right installation contractor. The HVAC system and the various component parts need to designed and specified prior to installation. They need to be tested during commissioning to ensure the systems perform as designed. This is outside the expertise of many installers, and to be fair, outside the expertise of most architects, builders, and remodelers. Unfortunately, these important tasks are typically assigned to the low-bid installer.

While neither the design nor installation of HVAC systems are rocket science, I don't think it's a reasonable expectation for a homeowner to develop the requisite expertise in a short time frame from internet sources and YouTube videos. Fortunately, efforts like DOE's Building America project have developed climate-specific best practices for U.S. climate zones. While they won't make you an HVAC expert, they will equip you with the recommendations of some of the best professionals in the field. And they're free. I'm reposting the link I provided above to get you started:

http://usgbcsouthfloridachapter.cloverpad.org/Resources/Documents/Homes%20Report%20Hot%20_%20Humid.pdf

Should not need a whole house dehumidifier with humidify on demand thermostat and a variable speed 2-stage AC.

mike_home, would you please explain in simple terms

I have two Carrier Infinity 2-stage AC condensers paired with 3-stage furnaces. They are controlled with Carrier Infinity thermostats which have dehumidify on demand. Yesterday NJ had over 2 inches of rain fall in about a 5 hour period. This was after several days of upper 80s to low 90s temperature. Around 7 pm in the evening the outdoor temperature was 73 degrees with 100% humidity (as reported by my iPhone). Indoors it was 75 degrees and about 45% humidity. The house is two floors with a basement, about 37 years old and not very tight. In the mean time there were 6 people in the house and cooking every meal on a gas stove. The humidity control was done without a dehumidifier on a very cloudy day.

There are times when the humidity in the house spikes up. The AC will run in the cooling the dehumidify mode for long periods of time. In rare cases the temperature may drop a degree or two. But then again I usually set the thermostat to 78 degrees which I find comfortable at a 45% humidity level.

My point is invest the money in the best variable speed and multi-stage equipment first. If it properly sized and installed it should give adequate humidity control . The whole house dehumidifier should be the last resort. It should be the exception and not the rule.

"Should not need a whole house dehumidifier with humidify on demand thermostat and a variable speed 2-stage AC."

Well, in his situation - cooler, humid weather - that's the only way to dehumidify (unless you want to freeze and/or damage the equipment)..

Could you be a little more specific as to your general location? County and State would suffice. This could help with responses.

Not an expert, but I have renovated many homes and built two. I have lived and owned homes in Texas, Louisiana, Georgia and Virginia. Like everyone in the South, I have allergies. I've also lived in Utah, Illinois and New York, but they aren't in the South and HVAC answers would be different. Anyhow, I've lived pretty much everywhere.

I also have the world's best HVAC guy. He taught at Carrier's Southeastern training facility. He puts theory together with field practice. He's worked on and redesigned three systems for me at this point.

Because your home is not a new build, a lot of choices are eliminated for your application. Proper encapsulation of the attic spaces as an after thought will be difficult to do. With new construction, you biggest bang for your buck is passive insulation. In your case, it just depends on the scope of the renovation to determine their effectiveness.

Carrier is currently the best manufacturer of HVAC. In most of the South, if I had the choice, I would install a heat pump. The technology is amazing. The Infinity Units will heat successfully down to 26F. While you can back it up a basic air-conditioner with a gas furnace, unless there is one already onsite, I would simply go with all electric. Heat pumps are more expensive upfront, but save money through their operational costs. The Infinity line is the top of the line. If I were starting from scratch, I'd select the two stage variable speed units. Lots of controversy regarding spending the extra for 20 SEER versus 18 SEER and payback. Your contractor should have those figures. The mid unit is a really good choice, too. I just installed their base a/c unit as a replacement last week. I'm selling the house in five years and upgrading further wouldn't provide a reasonable payback. Thus, my choice.

My guy installed April Aire dehumidifiers on all 3 of my homes. Controlling humidity is the key to a healthy house envelope. This is where I spend my extra money.

Last, in my last three homes I have installed a GPS or Global Plasma Solutions unit. It acts as an air scrubber inside my systems to kill molds, dust mites and pathogens. It's generally found in commercial applications, but with my allergies it has been a huge success. Since I have installed these in my systems, my seasonal allergies are well controlled. Don't waste your money on ultra violet light systems. They aren't effective due to the volume of air that passes through the system. The GPS unit will do the trick. Most installers won't know what these are, but look it up on line and read about it. Global Plasma Solutions.

We bought our previous home with a roof leak and knowledge that there was some mold. We did the repairs and removed all of the moldy material. Still, we suspected that we would never get the mold out of the ventwork. My husband is sensitive to mold. After we installed the GPS and let it do it's work for a month, his reactions to mold disappeared. These gadgets work.

Last, encapsulate your basement or crawlspace. It's a good use of renovation dollars. Lots of homes in the South are not encapsulated. Do that and you will reduce a significant amount of humidity being introduced into your home. Reduce the humidity to below 45% and you make any mold inert. That's your goal.

This is my 2 cents from a homeowner and not a HVAC guy.

homechef59, thanks for the info on the GPS system. I will look into it.

The house we're buying is in N. AL. The TN Valley area can be tough on allergy sufferers. It's also prone to tornadoes. We're moving there because it's home to our first, and likely only, grandchild with whom we are both totally besotted.

Everywhere we've lived has been warm/hot and humid (FL, NC, LA, AL) so excess humidity is something we've always fought. We've dealt with mold before. There will be new batteries in our moisture meter and fresh respirator masks on hand in case they're needed to check things out.

I agree with you about encapsulating crawl spaces, but this house is on slab. At least we don't face that issue.

I'll look into Carrier and take a second look at Trane.

Charles Ross Homes, I will reread the link you gave when I'm less sleep deprived. It looks like it will be very helpful.

tl;dr

The quietest variable-speed AC you can buy.

One other thing. None of what you select will work if the system doesn't have adequate air flow design. That means an air return in every room. And, adequate air flow into the heat exchanger. Try to find an installer that gets excited about air flow. It's the most over looked element and makes a huge difference in performance. Try to find a contractor that uses sheet metal components where appropriate. While an entire system made of sheet metal boxes is cost prohibitive, if they use it in the appropriate places, chances are they will install a superior system. You will pay for it, but it will work as designed. I'm not a professional, just an end user who writes the checks. Air flow design is very important. Make them talk about it when you are in the design phase. Don't leave this to your general contractor. Insist on a conference with all three parties.

the location of supplies and returns are important. However OP is purchasing an existing home. Unfortunately central returns have become an acceptable feature. It’s a shortcut to homeowner and a savings to GC. They do work depending on placement, size and number depending on size and design of home. No doubt good airflow is important to comfort.

TD

Update: things just got simpler yet more challenging. The house will not be remodeled after all. We've decided to do a scrape and rebuild, and have found a great architect. No more concerns about fitting in an elevator since the new house will be one story. I am delighted.

We previously considered another house that would also require remodeling, and contacted the architect who designed it. Fortunately, as it turns out, it sold before we could make an offer. When I reached out to that architect about meeting to see the current property, he refused to wear a mask despite them being required in our area and regardless of our multiple risk factors. That made narrowing down our choices easier.

The advice y'all provided will be very helpful as we collaborate on this new house. Thanks again.