Ground source ductless (mini split) heat pump

[timselectric]

No one said anything about adding return air from the garage, EVER, so quit mentioning it.

If you put a supply in the garage, from a system that gets its return from the house. The wall, attic, and door between the two is the garage return.

 

[Odom1957]

If you put a supply in the garage, from a system that gets its return from the house. The wall, attic, and door between the two is the garage return.

Incorrect. A garage should be sealed from the conditioned space of a house to be up to code. If it is not, then that should be fixed before you do any other upgrades to a house.

Also, a fresh air intake (makeup air) should be added to the evaporator in order keep from getting negative pressure inside the house if you do this.

The air going into the garage has to go somewhere, and normally it is vented outside into a soffit.

The problem is not with the potential of return air getting into the house though. It is the inefficiencies of losing conditioned air to the outside. This is why no one wants to add a vent in their garage.

The proper way to condition a garage is to add an evaporator in the space, and tie it to the existing outside condenser system, just like a multi-split does.

 

[Zwy]

No one said anything about adding return air from the garage, EVER, so quit mentioning it. There is nothing in any code I am aware of that prohibits a supply duct from being placed in a garage. There is specific prohibitions for return ducts only.

Any duct ran into the garage would create positive pressure. That creates a problem where infiltration around doors and even sill plates enters the house from the garage. This is why a supply duct is not to be run into a garage.

Most codes written concerning garages now require a negative pressure ventilation system for a garage. This is a move in the right direction. As house envelopes have become tighter and tighter, any exhaust emissions in an attached garage can enter a house. Over the years, countless stories have been told about mysterious illness in a family that was caused by positive pressure in a garage and the exhaust making its way into the residence. Many times it is a mother that starts the car, takes the children to school, then returns home and works from home. Even if the garage door is open the entire time, it will still have positive pressure once the door is closed with a warm vehicle parked inside.

My shop building is pretty tight. Infloor radiant heat. One door is 26 feet wide by 16 feet tall. In cold weather after opening the door and closing it, a whistling sound can be heard around walk thru doors and if strong enough an inswing door can be hard to open. The cold air that entered is being suddenly heated and expands. This is what creates the positive pressure. The same thing occurs with an attached garage, heated or not as there is a temperature differential.

To the OP, a better way to install horizontal ground loops is to make circles with the pipe so that it overlaps itself by 1/3 or so each loop. This gives you a much better thermal area for the given horizontal space. You can even stack loops on top of each other, filling a foot or so of soil between layers. You just need to stay below the frost line. Deeper isn't better in this case, as the ground will be the same temp.

 

[justinm001]

Most garages are insulated and shouldn't be vented with soffit like an attic is. Pumping air from the house into the garage creates a positive pressure in the garage and negative pressure in the house. The airs going to make its way back to the house, maybe not all but some.

But to OP if he's using as an office then it's considered conditioned space

 

[timselectric]

The proper way to condition a garage is to add an evaporator in the space, and tie it to the existing outside condenser system, just like a multi-split does.

Exactly
Keep them separate. No air exchange between the two. And preferably a positive air pressure on the house side of the door.

 

[justinm001]

Exactly
Keep them separate. No air exchange between the two. And preferably a positive air pressure on the house side of the door.

How can you create positive pressure in a house? Bathrooms have ceiling vents that suck air out. I always wondered why houses aren't more like cars where their AC some pulls air from outside, filters, conditions, and then bring inside. This way leaks vent air instead of bring unfiltered air inside the house

 

[timselectric]

How can you create positive pressure in a house? Bathrooms have ceiling vents that suck air out. I always wondered why houses aren't more like cars where their AC some pulls air from outside, filters, conditions, and then bring inside. This way leaks vent air instead of bring unfiltered air inside the house

You've got it.
Bring in more than than you exhaust.

 

[Checkthisout]

You're not allowed to have duct openings in the garage dingus. Fire and smoke can pass through the duct into the house.

This may or may not apply but energy codes would require that the garage space be properly insulated including the door. Unless your house building permit shows that then no Bueno.

Even being hacky, I personally wouldn't do it because you're just going to carry fumes into the living space. It won't kill you but car exhaust isn't pleasant, especially in winter. Grinding fumes, welding fumes etc.

A mini split is like $800.00. Any adult male should have that much cash on hand to dedicate to the task of heating and cooling the garage. If you don't just quit and give up.

 

[Rusty959]

Sounds like what I need to do is buy a cheap mini split that does not have pre-charged lines, replace the outdoor heat exchanger with a plate heat exchanger, charge it up, run the other side with my geothermal loop and see if it works.

 

[Checkthisout]

Rusty, I already answered your comment, but I'll explain it again.

No one is stupid enough to add a return duct from their garage to the rest of the house, but there is nothing in the code preventing the AC in the garage from being part of the main house AC.

You can add a duct, with no return air.

 

[Checkthisout]

Sounds like what I need to do is buy a cheap mini split that does not have pre-charged lines, replace the outdoor heat exchanger with a plate heat exchanger, charge it up, run the other side with my geothermal loop and see if it works.

If it's just for cooling just run water over the condenser from your well.

 

[740GLE]

up to 11 feet deep, I did all the digging with a bobcat E50.
Dont need a trench box if you never get in the trench. We assembled the slinky above ground, tied it up using paracord and lowered it in the trench with the excavator bucket and a couple people who could pull the line tight from a bit away from the trench.

I just saw that ladder in the trench. Stay safe.

 

[justinm001]

This may or may not apply but energy codes would require that the garage space be properly insulated including the door. Unless your house building permit shows that then no Bueno.

Every attached garage should be insulated including the door.

 

[740GLE]

Every attached garage should be insulated including the door.

You’d be amazed at what new construction, even in the Northeast, gets away with.

Our garage walls have no insulation but is dug into the hillside with insulated doors, never have I seen it drop less than 50f

 

[timselectric]

My attached garage was only insulated in the parts of the walls and ceiling that separated it from the house. Nothing in the exterior walls or ceiling section.
I insulated it, when I converted it to living space.

 

[Checkthisout]

0

Every attached garage should be insulated including the door.

My post was a response to the person saying an HVAC vent in the garage that is tied to the house ducting wasn't against code.

It's clearly against code.

And now its against most energy codes to even heat/cool the space period unless you have proper insulation which then means you would need a building permit proving as such.

It was just to point out the silliness in someone asserting that an hvac vent in the garage that is part of the house hvac isn't against code.

 

[MentalNomad]

Based on the photo in the OP, they have a detached garage.