HVAC recommendation

[John Lowder]

I am planning to retire to the NC coast. My new shop area will be attached to the side of my garage separated by a wall and door. I am concerned about the summer heat and humidity.
In my current dwelling, I have a Delta Dust Collector attached to my large shop tools and a Jet ceiling dust filtration unit. There can still be a significant amount of ambient dust in the air.
Our home plans are in the near completion stage. The contractor has suggested tying in to the central heat and air of the main house. I cannot see this working due to drawing-in and spreading dust throughout the house. I can't image my wife allowing this.
Would one of the ductless mini-split units be a better alternative or would there be a dust issue within the wall or ceiling mounted portion of the unit? I would appreciate any and all suggestions.

[Mike Heidrick]

A lot of the guys at the forums at garagejournal like the mini splits.

How does tying into to your house HVAC setup in a walled off shop spread dust in the house any more than any other system will?

[Ben Rivel]

No, definitely do not tie your houses main HVAC system into your shop. Yes a ductless mini-split is usually how people are doing it these days and IMO the best option out there currently. And definitely get yourself a better filter for your dust collector. Look into Wynn Environmental filters. Either way you should get something lower than 1 micron. Even better look at getting yourself a better dust collector, check out Oneida Air's offerings. You should not have "significant amounts of ambient dust in the air".

[John Goodin]

Having a vent/return in the garage that is attached to living space is a big code issue. Your contractor should know that is not allowed. Even if it goes to a walled off shop I doubt it would be allowed.

[Dick Strauss]

I agree with John...this is a big no-no according to code (with or without a return duct) because the fumes that might exist in the garage (CO from a motor, finish fumes, etc) may find their way into the main home space and cause explosions or death. Our house was built with a garage vent that I have sealed off to prevent issues. Our house was built in the 70s and I guess folks were more into fumes back then.

[Lee Schierer]

As others have stated, connecting your HVAC to a garage used for vehicles is a code violation.

However, if the space is is a garage converted into a workshop with no access for vehicles you can connect it to you house HVAC. My shop is a former two car garage that has had the garage door replaced by and outside wall. It is connected to my house HVAC. To prevent dust migration into the house, I built two filter housings on the cold air returns to hold standard air filters. I use a Merv 11 or higher filter and have had no issues with dust in the vents or the house other than what I track in on my feet or clothes if I forget to dust off. I do not do any finishing in my shop so the fumes do not get introduced to the house. All finishing is done in a detached building.

[John Lowder]

Thanks for all the input.
I'll probably go with the mini-split and look into better filtration.

[Charles Lent]

My shop is in a separate outbuilding with it's own heat pump HVAC because my last shop was in the basement of my former house, and even without a shop connection to the HVAC I was always getting complaints about sawdust getting into the house.
You will also want better humidity control in your shop than in your house. A separate 1/2 bath in the shop would also minimize your trips into the house to reduce the chances of bringing sawdust in on your clothes and shoes.

I also live in NC, but over near Charlotte. My shop isn't near the ocean, but it's within 100' of a lake and only about 4' above the water. Humidity control in my shop here is more important than temperature control, and I would suspect that your shop near the ocean will require the same. Insulate and vapor barrier your shop well as it's being built, and install it's own separate HVAC system with really good air filters. HVAC coils will plug up quickly without good filtration of the shop air. Ductless systems do not have good air filtration, so there will be problems keeping the coils clean.

Also, only open the shop doors to the outside for extended periods when the temperature outside is comfortable and the humidity is below 50%. Keeping the shop environment at a relatively stable temperature and humidity will minimize rust problems and keep your wood materials more stable. The heat pump in my shop is ON 24/7, but I turn it down in the Winter to about 55 deg when I'm not there and up to 80 deg in the Summer when I'm not there. In the hottest part of the Summer (95-105) my heat pump can barely keep up and runs almost constantly, but this provides better humidity control than a larger unit would.

I hope this helps in making your choices.

Charley

[Jim Becker]

I'd consider a mini-split for this for sure and in that geography, the "heat pump" nature of a mini-split will be pretty efficient.

[Alan Lightstone]

I use a mini-split in South Florida near the coast, as do several friends of mine. Works great, and is very efficient. Even more brutal weather in the summer than you will experience.

Most people like the Mitsubishi branded units. They call them electric ductless systems.