New home build -- help on dehumidifiers, ERVs, etc!

Hi all! We're in central Ohio and are building a new home with a fairly high volume builder here. We just finished meeting with HVAC and I'm drowning a little bit in trying to figure out what options to select, so I'm hoping for guidance here!

Our house is 3200 sq ft (~900 of that is in a finished lower level). The HVAC team is proposing a 3.5 ton Daikin Fit heat pump and variable speed air handler. It looks like this unit isn't quite a good in low temps as a Mitsubishi Hyper, but it should still be enough for the central Ohio climate?

A couple of the options that I'm not sure about are as follows. We care a lot about indoor air quality.
Aprilaire 600M bypass humidifier
Aprilaire ERV
Aprilaire E100 dehumidifier

I haven't been able to discern what the difference is between these things (well, I understand the difference between a humidifier and a dehumidifier, but not which are required for the Ohio climate). I see people talk a lot about "ventilating dehumidifiers" here, but it seems like the E100 is not a ventilating dehumidifier? Should I go back to them and ask about options for a ventilating dehumidifier? Is the ERV a better idea than the humidifier?

We have a 250 sq ft "bonus room" above our garage (but it's accessed from inside the house, not from the garage). They quoted us $ for a 12000 BTU Carrier ductless mini split in this room. Is that a reasonable quote for this? How expensive will it generally be to add this after the fact instead of doing it during construction? I'm somewhat inclined to wait and see how the room fares without the mini split if it wouldn't be substantially difficult to add a mini split later.

Is there anything else I should be talking to them about adding? Like I said, we care about indoor air quality, and though I don't want to shell out tens of thousands of dollars I would like to make sure we start our home off with the most sensible HVAC setup!

Thanks so much for any replies, I know I'm asking a lot and am pretty clueless!

A humidifier and an ERV are basically in conflict, there should never be a need for both. A humidifier would go on a more leaky house, which have the tendency to dry out in the winter. An ERV on the other hand would go on a tighter house, which if anything would be more likely to have higher humidity in winter from internal sources, and need mechanical ventilation.

I would hope that your newly built house is tight enough to not need a humidifier... An ERV would have the potential for better ventilation, though you would really want it to have dedicated ducts rather than just tapped into the HVAC ducts (cheap). And by code you should have some sort of mechanical ventilation anyway, at a minimum bathroom exhaust fans that run constantly at a low speed - ERV is more of a "nice to have" than a necessity except for super tight passive houses or whatever.

Dehumidifier is IMO a necessity in new build houses down south, in your climate I'd say, again, it's more of a luxury or "nice to have". The main time it would be used is, say, a rainy days when it's sticky and humid, but not really hot enough to run the AC. Ventilation through both a dehumidifier and ERV would be redundant.

What I would be paying more attention to than these accessories is the main system and how well it's designed and installed. Was a load calculation done? Where is the ductwork going to go? The Daikin Fit output does drop off substantially down to 28K BTUs at 5 degrees outside - weather you will certainly get in your climate. Is that enough? Will there be electric backup heat?

I am curious about your concerns about "indoor air quality". There are several on this site that share your concerns. Most of the building/mechanical trades avoid the issue because of additional cost and complications.

The reality for me is that a significant percentage of the population is sensitive to these issues to the level that their lives will be longer and they will be more comfortable if we meet certain standards that eliminate the threats that that effect sensitive occupants health and comfort. This includes the indoor pollutants from building materials and occupants activity. "Indoor Air" is outside air with pollutants from the structure/occupants minus the oxygen, plus the CO2 from occupants.

Here is my list of issues.

Build a home that has the components that provide the control of outside air and moisture passing through structure necessary making control of interior environment possible. The control includes moisture and soil gases from the earth. The building industry has established a standard of building air leakage called "air change rate" measured by a blower door.
Hope your builder provides a measure air tightness. Few understand that a +20 mph wind is similar to a 50 Pascal blower test. Most experts suggest a fresh air change in the in 3-5 hours when the home is occupied. Outside air is 20.5% oxygen. People doing physical activity or if impaired need 19% O2 to allow their bodies function. Most suggest that a home should be .1-.2 natural air change at your local on the average winter condition. Understand colder temperatures increases the stack effect and typical 7 mph winds. Consider 20 mph is 20X more air change and calm winds and mild temperatures is less than an air change in 12 hours.

Hope I described your home.

Back to your post.

Air filtering of the recirculated air in your home should be merv 11 minimum, merv 13 if possible.

Your a/c should be setup to maintain <50%RH to control biologicals growth like mold, dust mites, and bacteria at the desired temperature in the home while occupied and receiving a fresh air change of +75^F dew point outside air is 3-4 hours. Any damp spots for +24 hour have risk of biologicals growing. The condensate pans should be pitched to drain without puddles in the corners.

During evenings and rainy days supplemental dehumidification will be required. Yes, a whole house dehumidifier with the fresh air ventilation option is simplest way to maintain during the evening hours and rainy days while the a/c does not run enough to remove the 3-5 lbs. of moisture per hour from the fresh air and occupants needed to maintain <50%rh.

Tell us how you got interested in this concept and Aprilaire as a provider of the equipment.

I personally am involved in the development of the Santa Fe Ultra line of ventilating dehumidifier for the last 34 years.

We seen big improvements in the health of enviromently sensitive people improving the homes indoor space of sensitively people's homes. Santa Fe Ultra/Broan/Trane lines of dehumidifier include the Merv 13 air filters high efficiency dehumidifiers.

Keep us posted on your progress and issues.

Regards Teddy Bear

Has a Manual J load calculation been performed for YOUR house? Production builders often do one load calc which is applied to every house in the development. Will a blower door test be performed before the drywall goes on so leaks can be sealed before it’s too late?
I also think that an ERV and a dehumidifier are redundant. I recommend a ventilating dehumidifier instead of an ERV.
I recommend using a mini split for the bonus room. Its load will differ from the rest of the house. Don’t bother ducting that room from the main system.
Is the HVAC team one hired by you or the builder? One hired by the builder will be looking out for them, not you.

Who is doing the HVAC work?
What builder?

Does their name start with an A and end in tron
Or start with an A and in a number?


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kdean1 said:

Has a Manual J load calculation been performed for YOUR house? Production builders often do one load calc which is applied to every house in the development. Will a blower door test be performed before the drywall goes on so leaks can be sealed before it’s too late?
I also think that an ERV and a dehumidifier are redundant. I recommend a ventilating dehumidifier instead of an ERV.
I recommend using a mini split for the bonus room. Its load will differ from the rest of the house. Don’t bother ducting that room from the main system.
Is the HVAC team one hired by you or the builder? One hired by the builder will be looking out for them, not you.

Click to expand...

I meet with a builder last January and I brought that up.
“We have already done that for all our models and they are very good”

4 months later I’m in a 1200 sqft ranch finished the month prior and it has a 80k furn and a 3 ton ac. I’m just thinking “yeah they are very good alright”…


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