[nutshellml]

Evening all.. I'm getting conflicting info regarding my AC. I'm planning on adding Central Air / Heat (unit in my attic), I have a split level home with 5 bedrooms on the "top" level all off a long hallway. I have had some people say you need a return in every room (except bathrooms) to have a balanced system all within a degree of each other then some other AC guys have said, no, one large return in hallway is fine, even when the bedroom doors are shut you'll be good. THOUGHTS?

I know it's more work to run ducts to each room, hence maybe a little more expensive, but two reputable companies told me the opposite and i'm concerned.

 

[user_12345a]

Return in every room is better but where i am central returns are common.

You can get decent performance if there's a sufficient gap under the doors or jumpers, where a hole is cut in the interior wall and grills on both sides.

 

[Paul.le]

The system will work more sufficient with many small one comparing with one big one.

 

[nutshellml]

Return in every room is better but where i am central returns are common.

You can get decent performance if there's a sufficient gap under the doors or jumpers, where a hole is cut in the interior wall and grills on both sides.

Thanks, I definitely don't want to cut more holes or rely on the small gap at bottom of door. I'll push for returns in every room. I'm in NY/NJ area.

 

[Bud9051]

I'm not an HVAC pro (energy auditor) but lacking sufficient return causes the pressure in each room to increase, forcing conditioned air through the many leaks to the outside. That loss then has to be made up by outside air leaking back in anywhere it can. So, in addition to a poor balance for cooling room to room, you pay a price by cooling the great outdoors.

In addition, the absolute worst place (not my words) to locate an ac system is in an attic. The experts who made that statement are well aware that sometimes there is no option, but the statement adds merit to the advice to over insulate and air seal all of the mechanicals in that over heated space.

Best
Bud

 

[user_12345a]

In addition, the absolute worst place (not my words) to locate an ac system is in an attic. The experts who made that statement are well aware that sometimes there is no option, but the statement adds merit to the advice to over insulate and air seal all of the mechanicals in that over heated space.

Yes, any place but the attic.

I would get mini-splits before doing that.

If attic systems didn't exist before they would be against code now. Like oil burning blue smoke belching two stroke engines, they should be relegated to the dustbin of history.

People hang on to what was done in the past, keep on making the same mistakes because "it worked before".

 

[crabjoe]

Here's a decent video on why you want a return in every room.. ok, not in places like the bathroom, but generally you want all your rooms to have their own return.

 

[Paul.le]

Yes, any place but the attic. I would get mini-splits before doing that. If attic systems didn't exist before they would be against code now. Like oil burning blue smoke belching two stroke engines, they should be relegated to the dustbin of history. People hang on to what was done in the past, keep on making the same mistakes because "it worked before".

where the system can be placed is local code

 

[nutshellml]

@Bud9051 @user_12345a
Thanks for info, I wasn't aware of that. I have always been told/heard that best to have it in the attic and cold air vents coming down. It's very common around here to have them in the attic's. As for my house, I have a furnace in the basement feeding the entire house BUT it was just hot air and very dated, the ducts are too small to carry the AC and also this past winter the heat was not balanced. Any event, what I was planning to do is use my existing furance w/ a coiler on top for the main floor then add another unit in attic for "top" bedroom floor. If I could, I would maybe do splits, but it's 5 bedrooms and not sure that's the best way to proceed.

 

[Bud9051]

The mechanics of cooling from the top down are still good, it is just the blasted heat. Also, poorly insulated ducts carrying cold air in a hot and humid attic can cause condensation issues.

Not sure what your attic looks like, but an elevated walkway with plenty of insulation under it will allow you to access the unit for service and bury the rest of the attic and ducts in insulation.

Bud

 

[nutshellml]

Any idea on cost difference for say a 5 zone split system vs. traditional unit w/ ductwork?

 

[user_12345a]

Get some quotes, both will be costly.

Since you have a forced air system already it would be wise to see if it can be used for a/c.

It may actually be cheaper to run some new pipes up to the second floor, fix the issues than put in a separate attic system in.

depends on if basement is finished and if you're willing to put in bulkheads -> messy, expensive.

 

[beenthere]

How much of an undercut do the doors have?

A return in the hallway, and one in each bedroom would be best. But depending on under cut, may not be needed.

 

[user_12345a]

where the system can be placed is local code

just because u can doesn't mean it's a good idea.

 

[jlhaslip]

There needs to be at minimum a 5/8 inch gap under the door to meet code if there is no return in the bedroom. Alberta (Canada) code. I would think the US code would be similar, if not the same.