Will I need a dehumidifier in my SIP home? I am planning to install an ERV, but will that be enough in the shoulder seasons?

Lately here in south Louisiana for example, the temps have been getting up to the mid 70's, or maybe 80, but the air is really humid. The AC doesn't want to come on, so it's not removing any moisture. In a tight SIP house you would be cool enough, but would there be a moisture issue?

It was never an issue with any of the homes I built there, if the weather is nice enough to have your windows open the air will be moving thru even if humid, when it comes time to use the AC it will take any moisture in the air out

Don't count on the ERV being any appreciable value for moisture removal, but you won't need a dehimidifier

I talked to an HVAC guy today who actually looked at steel SIPS when building his own house (didn't eventually go with them though).

I told him the AC usually gets sized at about half of a traditional house. So, impressed, he says "oh so they get a thousand square feet per ton then?"

That feet per ton idea scared me a bit. He went on to say they do calculations, but their software only takes into account stick framed cavity walls with insulation.

Anyway I guess they install dehumidifiers when they've run into moisture problems in tight spray foamed houses. Of course the moisture could be from some other cause.

I plan to vent the stove and the bathrooms directly outside with their own dedicated vents.

Jelly,

Welcome back to the South.  Most of the HVAC people in my area use rules of thumbs instead of actual calculations.  I have heard many installers make similar statements. 

Jelly;

I have a local HVAC guru that will design for a fee, and will be sized correctly

Chris, I may ask you more about him later.

Alton, I know you were pitching in on a steel SIP project recently. Did they install an ERV? Dehumidifier?

Jelly,

We all are quite proud of the home in Florence that used AC Tech steel panels and Superior Walls.  Energy bills have been quite reasonable since they moved in.  I know they have geothermal, fresh air intake, humidifier, etc.  For more details, the owner would enjoy telling you about his home.  He used to participate on this forum.  Try him at g&jgarland at comcast dot net.

If all that seems to be too daunting, all you need to do is hire yourself a building contractor. A good contractor is licensed and insured, and can take care of all the aforementioned details for you in a professional manner, ensuring that everything is covered according to the highest standards.

~wolfehousebuildingmovers.com~

Bark,
I assume you are a licensed and insured contractor.
If so, you certainly have a high opinion of yourself and your fellow contractors. (And are very naive about the real world)
If you are not a contractor, somebody sold you a bill of goods about contractors.
Just as each individual human being is different, so are individual contractors.
While a great many are good, decent human beings, who do the very best job they can, others are not. And all are influenced by their own experiences and prejudices.
In short, while a good contractor is worth listening to, none are God. One cannot deliver perfect projects, with perfect results, even a majority of the time. If so, the world would not need so *^#* many lawyers.