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air conditioning ducting

8K views 45 replies 6 participants last post by  beenthere 
#1 ·
Installing central air and duct work in 1986 two story home, air handler in attic. Contractor says that it is not necessary to have ducts into each room on the fist floor but more importantly to have the correct amount of cool air sent to first floor. He wants to duct the air to first floor from stairwell--- the air return will allso be in the stairwell this does not make sense to me--every home I have been in with central ac has ducts into each room. Anybody set me strait??? thanks
 
#3 ·
Not sure what you mean by duct it through the stairwell.

But, the first floor doesn't require a duct to each room.

Got some, that the kitchen and dinig room have supplies. But not the living room. And or some other room that is near the stairwell.

Generally done in houses where space is a premiumn.

When possible to get to every room, it is better with a supply to each room.
 
#4 ·
I should have been clearer, the first floor room the contractor would not duct to is a bedroom as it has a closet and a door-- at present I use the room as a home office. As to the stairwell issue he would supply at one end and return from the other end of the well both at the ceiling. My concern is that in putting central ac into an existing home I do not create any future home inspection problems , and of course that the system function properly.
 
#5 ·
Using that room as an office, it muct have its own supply.
Even then, it will not be the same temp as the rest of the house.
Since the equipment(computer, printer, etc) will gernerate heat outside that of the other rooms normal heat gain.

A pump and dump stairwell, is not a good idea.
It will most likely leave you with a very cold and uncomfortable landing, with the rest of the first floor air stractifying.

Call other contractors.
 
#6 ·
ac ducting

I am curious about two other aspects of central air. If the return for the system (approx 14X30 for a 1400 sf home) is located on the ceiling of the second floor in stairwell what happens to bedrooms when the doors are closed- the bedrooms get supply but what about return. 2. Location of supply registers in ceilings how to determine? simply as far from retun as possible? Thanks
 
#7 ·
Depends.
How much undercut do the doors have.
If not much, then they will warm up when their doors are closed.
So may need to either increase teh undercut, or install transfer grilles/ducts.

As far as supply location in the ceiling.
A popsition that allows the air to either bath the outside walls, or to allow enough time for the room air and supply air to mix, before the supply air hits an object.
And not throw air directly at the return.
 
#8 ·
ac ducting

Thanks for the info--Comments on either Lennox or American standard equipment- Does 3 ton sound about right for 1400sf two story home built 1986 w/ full insulation attic, basement joists, walls and tripple pane glass Boston, mass area. curious as to the summer design temperature for Boston, Mass area thanks
 
#9 ·
My place was built right around 1956.
1650 sq ft. 2.5 tons. And I can maintain 72 when its 98 outside.
I have good shading, and crappy insulation. Good double pane windows.

So 3 tons sounds over sized to me.
You need a load cacl done.

You can do your own if you want.
Here is one that is easy to use.

http://hvaccomputer.com/talkref.asp
 
#10 ·
Yo, Murphy!


Three ton sounds heavy to me. Mass in more Northeast and I don't think your summer is a whole bunch longer and hotter than Mi.

I would have a manual J calculation done by a contractor to see how much cooling you need for sure. All that insulation in my area would call for a two tone ac.
 
#11 ·
ac ducting

Thanks for the input .. I have a couple of other questions.1. What size rectangular supply duct is needed for my 12 X 14 residential kitchen-- the duct would be round coming from the air handler in the attic to a round to rectangular 45 degree and rectangular 10W X ???D (can not go wider) stack inside a 2 X 4 wall thru a joist bay and out the kitchen ceiling. 2. the 2X4 wall is an interior partition- does the duct need insulation inside that wall? 3. other than the 45 degree at the top of the rectangular stack it is a straight drop to the kitchen ceiling - 91/2 feet--any problems with this set up like air flow noise, etc.....? 4. Any input on either Lennox or American Standard ac equipment quality would be appreciated. 5. . Same supply ducting set up as above-- but in joist bay would transition 90 degrees back to round then 6 feet horizontally to ceiling register- the room is a 11 X 11 home office. Home has full insulation and double pane windows with new storm windows. THANKS
 
#14 ·
I don't want to second guess your guy. Our methodology might be different.

There are all kinds of approaches that can be taken. Some of them may cause you to compromise due to limitations caused by home construction.

As far as brands keep in mind that the install quality is more important then the brand
 
#17 ·
Without knowing how much heat is needed, no way to say.
But, as hvaclover said, 2 supplies.
You can always close off the damper if 2 is more then needed.
But companies charge extra if they have to come back out to add one later. If you told them omly one.
 
#21 ·
ac ducting

In a former life I was in the contracting bus. -- most subs I ran into were bull**** artists-- don't pay the bills and would screw their mothers to make a buck. Thats the lessons I got after 20 yrs in the bus. I am spending $12,500 for this system and two ac contractors have given me two vastly difrent ducting stories. From my exper. the purchaser must beware and educate himself --not rely on a subs word -if you do your are asking for trouble.(like ceiling supply registers connected to nothing) If I can't get straight answers from these subs then screw em- I will keep my 12 grand and continue to use window ac's. I could go on for an hour with horror stories from my 20 yrs in the bus. Please note I said MOST subs not ALL subs, ALL would apply only to GC's ---- Been there done that and got a tee shirt.
 
#22 ·
That's the rub. You got two guys and they have diff approaches...just like I pointed out earlier.

I assume both guys are knowledgeable or you wouldn't be talking to them.

If you trust them then pick one you're most comfortable with.

Believe, micro managing the details and double checking info will just get you more confused.

This biz is as much an art as it is science. But we would all go about the same job differently. That is the nature of the biz.

use your gut and pick one and trust him. You keep second guessing the guys work and you may want to fire him half way thru or he might walk off the job.
 
#23 ·
Here is what I would be doing if I were hired.

Vents in every room and put them up high on the wall or in the ceiling. Reason; to put the cold in the whole room and not just cool off some furniture. As hvaclover said, some rooms should get two vents for even distribution.

A return on every floor. Reason; to keep one floor from getting too much flow and another room from getting too little flow.

Vents to match the rooms. Reason; some rooms just get warmer than other like the south facing rooms or the kitchen. The worst is a south facing kitchen with lots of windows.

This is pretty standard in the business. If your guy is not putting vents in each room then ask why he isn't. I know of no other way to get air into a room without a vent of some sort. Even if the door is open there is a natural air pressure barrier that will keep the air from going into a room.

Keep in mind that wind makes tunnels in the air. It does not mix unless it is directed in many different directions. All my installs get vents that are at least 3 way so that the conditioned air mixes well with the existing air.

Velocity is another issue. Too little and it will just move air a few feet and not really mix it up. Too much and it feels like you are in a wind tunnel.

This is the key to an even temperature in the house.

Here is my temperature over the last 24 hours in every room except the bathroom and kitchen. The spikes is the heat coming on in the morning and that is it for the day. The temperature slowly drops off as the day progresses unless it is sunny in which case the south facing rooms heat up. But I have returns in there that pull that heat through the furnace as the fan cycles on during the day to keep the temperature normal. We keep it cool in our house as you can see and like it that way.
 

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#24 ·
good show Marvin an a perfect example of two people doing the job...but the diff is I would shy away from high wall registers as they don't work well in Northern and Northeastern climes. The air is hard to get from the ceiling to the floor(Due to it's tendency to raise) without very high velocity which creates noise. And there can also be the problem the air blowing so hard it would be an annoyance.

The biggest problem you have with high wall registers is unless the design is perfect it will be noisy and the stratification problems will cause a cold zone from the waist down.

Waist up it's warm....some times too warm.

High wall and ceiling registers are great for the Southwest and Western states where the emphasis is ac more than heat.

I have corrected many older homes at great expense to my customer here in Mi that had high wall and ceiling registers.

So as you can see two diff guys two diff methodolgies. Both guys good at the job.

Thanks for baring with me Marvin. I think you understand that was just an example for clarification to the HO and by no means a condemnation of your damn good abilities.
 
#25 ·
Good example of how different areas require different strategies. In the west high on the wall or ceiling is standard.

Returns are in the ceiling or high on the walls as are all the registers.

My vents aim down at the opposite corner of the room and don't just blow across the top.

In my experience the furniture blocks the flow of air on floor vents or low wall vents. Nothing like sitting at a desk in the middle of a heat wave and have cold legs while the room is 90 degrees.
 
#27 ·
2 stage is for "comfort", not for savings.

If you get additional savings because of it being 2 stage. Its from it being able to keep the indoor humidity lower, and being able to raise the indoor temp a degree or 2 higher because of the lower humidity, and still be just as comfortable.

They are worth the money, if you feel you comfort has value.

Get teeh VS blower if you get 2 stage.
They don't do as well removing humidity with a standard blower.
 
#28 ·
ac ducting

THANKS ---I am going with American Standard equip. The Allegiance 16 Ultra two stage 3 ton and the variable speed handler w/ Accu Clean 4TEE40. The home calls for 2.5 ton but no half ton in that 2 stage model. The contractor will start this Monday. Can't seem to find what cost vs value is on central air remodel--what % should I expect to get on home sale???? I live between Boston and Cape Cod. I believe that there is both a $300 federal tax credit and a $500 rebate from my electric co. Thanks to all who helped
 
#29 ·
Can't seem to find what cost vs value is on central air remodel--what % should I expect to get on home sale????
The return on high efficiency furnaces should be high. There are several points to consider.

Energy will do nothing but go up and anything to lower the costs is going to be a good selling point.

In fact I predict there will be a day when a high efficiency furnace will be the norm either by law or by code requirements.

Costs for good always goes up. Selling your home 10 years from now and having the high efficiency furnace in will look like a good investment to the purchasers even though you got it for less than half of the cost it will take to put it in 10 years from now.

There is a simple fact in home finances. Less money for things like interest, renovations, or energy costs mean more money for mortgage payments.

Air conditioning in moderate climates is not such a good investment. It is more for comfort and not a required item like it is in the SW. Most moisture situations can be handled by a dehumidifier. Still some people are just used to it and like having it there.

In the west side of the Cascades it is considered a luxury to have air. We rarely get long periods of hot days and it cools off nicely at night so demand is low for air. We are the only ones that have air in our neighborhood and that is only because I am in the HVAC business and got one that was damaged for a really good price.
 
#31 · (Edited)
Beg to differ.

national realty studies show that homes with major improvements of a high end and higher energy efficiency always sell more than homes with similar improvements but use lower end material or equipment of lesser efficiency.


What is going to to get a higher price: A improved bathroom with a plastic shower insert or one with a high end low water usage plumbing fixtures and custom tiled shower ?

The whole thing is about comfort and the appearance of value and low operating cost.

I think the same argument can be made for an attractively installed hvac
system with a 95% 2 stg VS furnace or ac with all the fixings, humd, air cleaner, nice plumb gas line, well crafted sheet metal. Any informed consumer would be willing to pay the extra.
 
#32 ·
It varies with the area.

If his area is one that A/C is almost a required luxurary.
It will help the value.

If A/C is something that is only needed a month or 2. Then it won't improve the value.

A high end furnace, means more here, then just a high end A/C does.
 
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