I think air comes out faster with the slot design, something many may not find desirable. Just as an observation, the placement in the kitchen photo, just above the island, is a terrible idea.

Thanks. Can you elaborate why you think the placement is a bad idea? That isn't my house, so not like I'll be offended, but just curious why you think so. Thanks.

Probably blowing dust down onto your food/prep?

For sure not like the picture . We have mostly round diffusers for AC in the ceiling and only on the perimeter of the kitchen and the heat ones are not on the ceiling but near the floor and to be honest I never notice either .

I'm wondering why I don't see many implementations of these linear diffusers even in higher end homes where you'd think cosmetics are important.

There is nothing technical about this,it's simply a study in human nature. People accept rectangular covers as normal,therefore use them in homes of all price levels. A tiny segment of wealthy believe they are different in ways besides wealth and want to appear different. Appearing different ranges from wearing a larger hat than others,driving the only car in town a certain color or odd looking things in their house.

I'm not sure having folks think you are different is a compliment.

@acm , yes, that makes sense now about blowing dust onto prep area, thanks. We'll avoid that - I think that applies to either a conventional register or a slot diffuser.

@Patricia Colwell Consulting , that's interesting, I've not heard of different outputs for AC vs heat. I've only ever had a dual purpose register that outputs both heat and cold. It'll be a heat pump in the remodel, so it'll be the same case of dual purpose registers/diffusers.

We were just out looking at open houses and did see one that used linear diffusers throughout their house (ceiling).

Just seems to be a detail most people don't care about or pay attention to. I have read that they can lead to more directional air flow (vs diffuse), though if the air is directed more parallel to the ceiling vs shooting down, it would avoid strong air flow hitting just one particular area.

Great, thanks @wdccruise , we'll have to talk to the HVAC subcon and see if that'll be an issue. It's a nice-to-have for us, so if it ends up costing a lot extra, we probably don't do it. But if you're tearing down to the studs, you try to think of all the small things that'll be icing on the cake since you're spending so much to start with. . .

Linear slot diffusers are fairly common in commercial and office space construction, where ceilings are typically suspended or dropped. For residential applications, the size of linear slot diffusers in ceilings is limited by the spacing and orientation of ceiling joists. For installations perpendicular to ceiling joists, the size of a linear slot diffusers is limited to what fits between the joists (12" diffusers for joists installed 16" o.c.)

You don't see them frequently because they are a lot more expensive to install because you aren't putting a large grille over a smaller roughly cut hole where the duct comes out of the drywall.

There are options that are probably a little less expensive, because they are sized to fit over regular ductwork, but are still installed flush, mudded in with drywall compound

So, Charles Ross Homes, if you were lucky enough such that your desired diffuser positioning was parallel (vs perpendicular) to your ceiling joists, you'd have more freedom to select longer diffusers?

From your experience, is it a lot more expensive if a customer asks for this option?

Why would there be excessive dust blowing from your vents? It should be a closed system with plenty of use. Ducts should be placed for maximum efficiency.

@Eric, have you seen these ?

@Eric,

Yes, if the plan is to install linear slot diffusers parallel with the joists, you can choose longer diffusers. They are more expensive to purchase and install in part because they need plenums like the one in the photo wdccruise provided and they are more complicated and expensive to manufacture than simple, stamped diffusers.

@Daisy S, I would think the theory behind dust from the vents is that even with an air filter in the return, it’s an imperfect way of filtering the air that gets back into the system, so inevitably, dust will accumulate in the ducts. Probably little when new, but over time dust accumulatesmutates. That’s why there’s duct cleaning services.

When you turn on your HVAC system, some of that settled dust will come out of the vents. I think that’s the general idea for why you might not want vents above your food prep or cooking area.

@clt3, I went to that site and that looks like a great alternative to conventional metal registers if I need to stay with the standard form factor for cost reasons. Thank you. Do you have any personal experience with these - wondering if the air flow is as effective as a standard register?

Thanks again @Charles Ross Homes, that helps. Unsure at the moment about the direction of the joists, but I can pop my head in the attic later this week and find out.

Eric, my son used them for his bathroom ventilation. I cannot attest to the flow. They are a much sleeker look though.

Did some additional research on the Fittes/Aria vent covers - the main issue I can see is they have lower air flow. A 4” x 12” cover allows CFM’s in the range of 30-50 at typical residential air velocities compared to 100-160CFM for conventional vents and 95-195 for linear slot diffusers.

Whether that flow rate is sufficient will depend on # of vents, room volume, and desired # of air changes, but thought I’d add that as a factor for anyone who happens on this thread.

Claims from linearslotdiffusers.com:

• 12" double-slot linear slot diffuser (3/4" slot width): 145 CFM
• 18" double-slot linear slot diffuser: 174 CFM
• 24" double-slot linear slot diffuser: 199 CFM
• 36" double-slot linear slot diffuser: 302 CFM (that's getting really long!)

Aside from the dust discussion, I wouldn’t want cold air blowing on my food.

We hve hot water hea tin our MCM ranch and so no regisrers and no dust. We do however need to have a different choice for cooling but I sure would not want that above my kitchen ever .

We retrofitted our homes existing standard size vents with slot diffusers for a modern look. We also used them in a a few rooms we remodeled with standard residential HVAC plenum boxes. The installations are straightforward enough that the homeowner can do it. We use a US based company that is reasonable and easy to work with. https://texasbuildmart.com/

@HU-53601241 We did end up going with linear slot diffusers everywhere in the house. Same product as you listed.

The airflow is fine and terms of quantity and direction, but the big demerit turned out to be noise. We had a two-zone HVAC system designed and when only one zone was on, the higher airflow rate coming out through half the vents made for a VERY noisy outcome. Unacceptably so, even with vent set to fully open.

When we contacted Texas Build Mart, they suggested we remove the inner piece that allows you to turn off a register or adjust level of airflow. We tried that, but once you remove the internal part, you can see right into the plenum and it's ugly (unacceptably so).

Our solution options were either:

a) turn on the other zone purposely when only one zone was active to reduce noise

b) disable the dampers of the air circulator so it was effectively a single zone system

We opted for the latter it's worked out fine. We don't really mind as our HVAC isn't on a ton anyway and I doubt we're spending a lot more by having a single zone versus two.

I think we still would have opted to do what we did, but it's something people should be aware of. Ours is a 4 ton heat pump with appropriate sized air handler for a 2350sq ft home, so I don't think it's oversized leading to higher than normal air flow when using a single zone. I think it's just an aspect of the linear slot diffuser design to consider.

"Ours is a 4 ton heat pump with appropriate sized air handler for a 2350sq ft home, so I don't think it's oversized leading to higher than normal air flow when using a single zone. " It sounds like you have a fixed-speed air handler supplying air to two independently controlled zones. If that's the case, the air handler is supplying the air flow rate intended for the entire home to a single zone when only one zone is calling for heating or cooling. That's a recipe for noise no matter what type of diffuser is installed.

It is a variable speed air handler, but it’s very possible that the installer didn’t configure it properly. Model # is Bryant FT4BNXC48L00

"it’s very possible that the installer didn’t configure it properly"

Page 11 of the installation manual shows that Jumper J4 should be removed for two-stage operation. Table 2 on Page 12 shows how the Printed-Circuit Board (figure 19) is to be configured for the Aux heat range and heat pump size. Descriptions follow on pages 13-14. The AC/HP CFM ADJUST (described on page 13) allows some control over the blower speed; if there was too much noise, you could try setting this option to "LO".

Assuming you knew the specs of the Aux heater and heat pump, you could check whether cables on the Printed-Circuit Board were set correctly.

I know the specs of the heat pump and there is no aux heat. They disabled the dampers to make the dual zone a single zone and now only 1 of our two Ecobees control the HVAC. They said that disabling the dampers and making it a single zone meant only one Ecobee could be active.

I would need to figure out how they disabled the dampers and second Ecobee so I could re-enable, and then set the jumpers per the manual and see if everything worked. That may be the tricky part.

Then need to know how to reverse everything in case I mess it up and need to go back to how it is now. 😃. Taking notes to document what I did is easy enough I guess, but not sure where to start in terms of re-enabling the dampers and second Ecobee.

"We had a two-zone HVAC system designed and when only one zone was on, the higher airflow rate coming out through half the vents made for a VERY noisy outcome."

Do you have a two-stage heat pump or a single-stage heat pump? See figures 12 and 13 of the installation manual for wiring. If it's two-stage and everything is wired and configured correctly, the HVAC may operate in stage one -- with slower blower speed -- most of the time. The result would be that the system won't be noisy most of the time even when you re-enable the dual-zone setup.

Before messing with the zones, I'd check that the Printed-Circuit board, stages, and thermostat wiring were all done correctly for single zone/one thermostat operation.