Which way should ceiling registers point -- into or out of room?
OK, I'll admit, this seems like a really dumb question to me, but I'll explain why I need to ask.
We just built a new house and I found the HVAC contractor to be very good throughout the job. We have a multi-zone Carrier Infinity gas heat and air conditioning system for the basement and main floor, and a heat pump in the attic for the upper floor.
I noticed they were installing all of the ceiling registers so that the inside louvers (the things you pivot to open and close the register) would direct air toward the outside of the room, usually toward a window, but even in a large walk-in closet with no windows they pointed them to the outer wall. This means that if you open the louvers completely, the air goes straight down, but anything shy of completely opening them and it's pointing out of the room. You can't direct air toward the center of the room.
I asked the contractor about this because it seemed illogical to me and he said that's how they are supposed to go in, that they position registers above windows as windows are cold spots in the room, and the registers will keep those spots warm.
If I'd not found them to be very skilled and honest in their work up to that point, I'd have never believed this answer, but I reluctantly gave them the benefit of the doubt. I did have them reverse the one in the master closet which was pointing toward the wall, since there was no window to "keep warm".
The windows are all brand new, Low-E, double-pane Andersen windows, and the insulation package on the house is very thorough (1" of comfort foam for the entire envelope and then spray-in cellulose). As a result, we use the HVAC system only when it gets very hot or very cold out, and we're now using the heating for the first time. As I walk around, it just seems that the walls are staying a lot warmer than the room, and I wanted to see if anyone shared my contractor's opinion that the registers should point to the outside of the room.
contractor is blowing the air the way we have always done it, you want the air to "wash" the area where the load is such as outside walls and windows. you don't really want the air blowing into the room where you will feel it blowing on you.
just the way i was taught............
Well, good to know that he wasn't making it up because someone put them in wrong and he didn't want to turn them all around. Also means that if I want them the other way I will have to do it myself
The thing is, the walls seem to be getting a lot warmer than the air, and as a result in some zones it's constantly heating even though it's only set to 65 because the thermostat is on a wall far enough from the "warm walls" that the air there never gets warm.
From a capacity perspective I think we're fine, but it's a very open floorplan thus some of the spaces are on the large side. I think with the registers around the periphery and pointing outwards we may just never achieve enough warmth in the center of the room.
Are there any situations in which you would direct toward the center? Or is it always outward.
I think the idea is balance. The greater heating need is near the windows/walls, so that's why he directs the airflow there. Now if your rooms are really large I can see that not working well.
What kind of registers did you get? On my install, each vertical bar can be adjusted individually and I've adjusted it so that it directs the air in a more balanced pattern than what you're describing. Maybe you need something like that?
Edit: I went back and noticed that yours are ceiling registers where mine are wall registers. I think with ceiling registers you're dealing with the lesser of two evils as far as which direction. You definitely don't want it pointing toward the center of the house or the walls will be much colder as they'll go no heat. Like t527ed said, you need the air to wash over the room. It will always return back to the rest of the house (depending on where your returns are I suppose)
I don't think this post was too helpful, didn't notice you had ceiling registers when I first posted
T527ED is correct. You want to "wash the outside windows and walls" the air will than pass though the room as it is pulled back by the return.
You need to read ACCA's Manual T, which is for air distribution. This will explain that the "washing" described here is not the best way to design a system. But it's the way it has been done forever and most would be reluctant to change. You won't find one in a million HVAC contractors that have ever seen Manual T, let alone have a copy. They don't know about "throw" or "spread" and certainly don't spend any time designing a system. You could poll this board and very very few would have any idea what the acceptable air velocity at the wall contact should be. Air distribution is something we as an industry are not very good at doing.
While it is true that the throw should be towards the outside wall, most installers put them too close to the outside wall. The diffusers throw should be matched to the distance it is away from the wall. If it is closer, the high velocity can cause drafts, noise, poor mixing of room air, stratification, and streaking. If it is close to the outside wall and pointed inwards the the drop will most likely be in the occupied zone causing drafts. Ideally ceiling diffusers should be near the middle of the room.
Amen to everything you said.
Originally Posted by mbarson
Supply outlet location, register selection, and throw direction are dependent on a number of factors.
They have the registers directing the airflow in the correct direction, but having the supply outlets near the exterior walls, with an overhead duct system and large rooms, is likely not the best location, usually not even a "good" location. This is especially true for hot climates where cooling performance is the main concern.
There isn't enough opportunity for room air to be entrained in the supply air flow leaving the register before it hits the wall and spreads out. This can cause issues with hot and cold spots within the room because the air is not getting mixed around to even the temperatures out.
The velocity of the supply air when it hits the wall will also be to high. I don't know about you, but I find it very irritating when the curtains or blinds move when the HVAC system comes on...
Originally Posted by dcmcm5
It is so bad in my area, that I often have difficulty finding the registers I need in stock at any local supply houses. Everybody has been using the same cheep stamped face 3 way registers for so long, many people don't even know there are better options.
A big part of the problem is that most homeowners don't realize the value of having a properly designed air distribution system, and most home builders loose interest when they see the difference in cost between what it costs to do it right, and what they have always gotten.
The new home construction industry, and our industry in general, has been a race to the bottom for so long, that most don't know any different.
It's particularly frustrating to me because we actually did consider it worthwhile to invest in a high quality HVAC system, and some would say we even overinvested in insulation (I have a very long time horizon for living here). But our ceiling diffusers are mostly within 12 inches of the outside wall. In one case the diffuser in the basement ceiling is pointing outward not toward a wall but toward a staircase that leads down into the basement, so the room is cold but the stairs are the toastiest part of the house.
It sounds like this is effectively preventing the system from working, but I'm not very inclined to start tearing into the ceilings to install new ducts.
So what kind of registers would folks here recommend if I am going to experiment with at least turning them around and directing airflow back into the room?
Thanks all for the excellent advice thus far, I really appreciate it!
depending on the size of the registers you may be able to get fully adjustable grills to give you more control of what way the air is blowing. this way you could send some into the room and still have some of it hitting the walls and windows.
This should be a sticky for all home owners to think about before they start their HVAC projects.
Originally Posted by mark beiser
jbsjbs, it would be impossible to recommend a diffuser without seeing the application and knowing the cfm to the diffuser. If you have a long time line you may want to have the system installed correctly, its your comfort and system efficiency that will be short changed.
While I could be open to the idea of "fixing" it, I have to say that it seems even from this thread like there is little consensus in the field about what fixing it would look like. How does one even find a competent contractor if there are so many variables and little evidence of what is the right way to do it.
It's not really like my low voltage systems, where I can look at two pictures on the TV and know if one is better than the other. I'll spend enough on heating and cooling bills over my time here that of course I'd spend some money to have the system looked at, but the guy who did the install seemed as credible and knowledgeable as anyone I've worked with on HVAC issues, so I don't think I'd feel any more confident in the next person I hired to look at it, you know?