HVAC register placement

[jay156]

Hi, we're building an 800 sf in-law suite addition and the HVAC guy has the registers on the ceiling of each room. We're going to have an attic furnace. I thought it would be better to drop the registers to the baseboard of the walls, since the warm air would then rise. The general contractor though says that it's better to put them on the ceiling close to the exterior wall.

My question is which way will give us the warmer room? I'm also a little concerned about having them up high like that and constantly having air blowing in our faces. The cold air returns are up high on the walls right now, but I was thinking of moving those down low too, since the cooler air will sink, right?

Thanks.

 

[MintJulep]

Heat only, or heating and cooling?

Your contractor seems to be motivated to do what is easiest for him, not what is best for you.

 

[jay156]

Heating and air conditioning.

 

[MintJulep]

Diffusers on the ceiling work pretty good for cooling, but as you've already guessed, aren't optimal for heating.

Opposite for diffusers near the floor.

There are plenty of heat and cool installations with both configurations, and for the most part they all work alright all year.

 

[jay156]

He says the reason they put them on the ceiling was to get them close to the exterior walls. Putting them near the floor will mean they have to be on interior partition walls. Will that make a noticeable difference in the effectiveness of the heating or cooling?

 

[MintJulep]

It's all a compromise, at least part of the time.

It will probably be fine.

 

[jay156]

Okay, so if we put the registers low, would it be better then to put the cold air returns up higher on the wall? So the conditioned air doesn't get sucked right back in down low?

 

[KenRad]

jay156,

What MintJulep said is optimal; heat delivered near the floor, and cooling at the ceiling. But you only have one system, so you need to ask yourself the following:

1. In my part of the world, what will the unit be doing more often; heating or cooling?
2. If heating dominates, do I really want to spend the extra money and floor space to build a duct chase, to feed ductwork under the floor?
3. Am I overthinking an area that will only be used by my in-laws?

The best solution (depending on your location) might be to keep the attic unit cooling-only, with ceiling diffusers, and use baseboard electric for heat. This gives individual room control in heating, and simplifies the attic equipment. Comfort wise, it would be an improvement over ceiling-delivered hot air.

The return grille position is not too critical; it just needs to be far enough away from supply diffusers that air isn't short circuiting.

---KenRad

 

[cry22]

I had an old house where the vents were low with central Return far away. What happened is that those low vents are in such strategic locations (corner room), we could not install an "L" shape couch, A TV stand, or a large plant without blocking the vents.

So, before you locate your vents low, make sure you will get the heat, lay out your furniture so that vents will not be obstructed AND, as close to the window as possible.

I had to raise my vents (fortunaly they were inside the walls), any other way, the was not useable.