[etap]

My house has ceiling heights in the family room of 13',and the same in kitchen. It is all open,no inside walls. My dining room is 13' and the same in living room ,and foyer. I build this house about 5 years ago, and I have dual fuel system. I have 2380 sq ft. and I put a 5 ton system in,with a finish walkout basement. Every nite,I put the fan on continuous. I keep settings in winter at 69 and summer 78. My question is,I have all my returns low to the floor, and my supply air are floor registers. My question is, would it be more efficient to move the returns up high,or not worry with it.THX

 

[beenthere]

If your supplies have good throw, and you have ceiling fans.
I wouldn't worry about it.

 

[motoguy128]

You could spend a lot of money changing it and discover it won't make much difference.

You could leave one ceiling fan the area with high ceiling on low in reverse. It should help push some of the warm air down the walls without creating an uncomfortable draft.

 

[Brian GC]

There have been several threads about this that you could search under ‘return air’. You will find that viewpoints vary on the effectiveness of return location (high or low). But one thing is agreed upon – if air circulation is not sufficient enough to move all the air in a room as to significantly reduce temp stratification, a high return will work best for AC and a low return will work best for heating. A high return on an AC will continually draw/remove the hot air that collects on the ceiling. Conversely, a low return on a heater will continually remove the cold air that collects on the floor.

A few questions:
How does your system perform now?
Does the heater work more favorably than the AC?
Do the supply registers move all the air in the room?
Do you have ceiling fans?

If your heater works fine but your AC in lacking then I would suggest adding ceiling fans to circulate the hot air that collects on the ceiling in AC mode. Moving the returns high so the AC performs better and then relying on ceiling fans to push the hot stratified air down in heating mode is counterproductive IMO. Using fans in the summer, not winter, makes sense.

Since you seem willing to move the return, many here agree that the very best setup is a dual duct system. That is; having both high and low returns that can be changed by a lever… high return for AC and low return for heating.

Brian

 

[green jumper]

If your duct system is sized properly I would not worry about it. If its not sized properly then size it properly.

 

[motoguy128]

relying on ceiling fans to push the hot stratified air down in heating mode is counterproductive IMO. Using fans in the summer, not winter, makes sense.

I guess those crazy fan manufacturers have a reversing switch on them for no reason. "Counterproductive" is a little strong. Less effective, possibly, but running fans in the reverse direction will help. However, most builder grade fans don't have a remote control and the money probably wasn't spent to wire an additonal swithc ot change direction, so reversing the direction requires a 10' ladder. I will agree that running the fans in the forward direction would create a draft... and that would generally be counterproductive.

Don't expect to "feel" any improvement from using high returns. The thermostat is only 5' off the floor, so the HVAC controls the ar temp at that level. You don't feel what the air is doing 13' off the floor. It's wasted energy to heat that air so you may save a little energy, but since you're not 12' tall, you won't really notice much difference... especially if the lower celings in your home are isolated by a door or portal that will act as a weir to trap warm air on your 9' ceilings. You don't want the high ceilings to be a heat sink for the entire home. In that case it will feel cooler in the room with the high ceilings than other rooms further away with lower ceilings.

 

[Brian GC]

Motoguy,
Since this information was left out of your profile I hope you don’t mind me asking;what is your occupation, years in the industry, and what did you get your engineering degree in?

Brian

 

[jerrod6]

My 3 story house has ceilings of varying heights, and supplies from the floor in most rooms except one.
The first floor hallway has a low return near the floor and there is a high return 1 foot from the 14’ ceiling in the living room. The hallways on each floor have low returns, and each bedroom has a return in the wall about 1 foot from the ceiling.

The master bedroom has two returns one 1 foot from the 14 foot ceiling and another near the floor. I used to open and close these returns depending on the season but after nearly breaking my neck trying to get to the ceiling I decided to compromise. Now I leave both ceiling and floor returns partially open all year. Seems to work OK. Warm enough in the winter and sleeping under a light blanket in the summer.

The biggest change in performance occurred when I replaced the supply registers and grills. I changed from a design that spreads the air, to one that sends the air directly up into the room. This works great in the summer especially on the upper floors and I was surprised that it works just as well in the winter too. So I think good air movement helps.

 

[beenthere]

The biggest change in performance occurred when I replaced the supply registers and grills. I changed from a design that spreads the air, to one that sends the air directly up into the room. This works great in the summer especially on the upper floors and I was surprised that it works just as well in the winter too. So I think good air movement helps.

The mixing of the supply air and room air, makes a lot of difference.

 

[dash]

Reverse on ceiling fans is for winter use,blows air up,and washes the warmer ceiling air down the walls.

 

[Brian GC]

Reverse on ceiling fans is for winter use,blows air up,and washes the warmer ceiling air down the walls.

If that was true then using a ceiling fan in reverse in the summer would make you warmer…but we all clearly know that is not true. So how can the same ceiling fan warm you in the winter and cool you in the summer? The stratified ceiling air is warmer in the summer than in the winter, so by moving the warm air down (in forward or reverse) it should make things worse, but it doesn’t.

Whether a ceiling fan moves air in a room aggressively in forward or gently in reverse one thing remains true…moving air feels cooler. It is “counterproductive” to heat air and then blow it with a fan.

 

[beenthere]

It is “counterproductive” to heat air and then blow it with a fan.

Would it work better if they blew it with a blower instead of a fan. LOL


Since all force air heating systems, blow heated air.

 

[Shophound]

If that was true then using a ceiling fan in reverse in the summer would make you warmer…but we all clearly know that is not true. So how can the same ceiling fan warm you in the winter and cool you in the summer? The stratified ceiling air is warmer in the summer than in the winter, so by moving the warm air down (in forward or reverse) it should make things worse, but it doesn’t.

Whether a ceiling fan moves air in a room aggressively in forward or gently in reverse one thing remains true…moving air feels cooler. It is “counterproductive” to heat air and then blow it with a fan.

For a small to medium sized bedroom with a standard eight foot ceiling height, a ceiling fan in reverse, even on low speed, might cause some folks to feel a draft. Often the standard three speed switching on most ceiling fans can't slow the blades enough on low speed to keep the feeling of draftiness at bay. For these situations I would recommend a dimmer switch rated for ceiling fan use be installed. From there the occupant can set the blades to blow against the ceiling, but barely rotate, which would help disperse stratified air against the ceiling but not create an uncomfortable draft.

For vaulted ceiling rooms, a ceiling fan on reverse is also useful, perhaps with the low speed being sufficient. It's all about air speed and sufficient room between the air being stirred and where the occupants reside to assure the air is sufficiently mixed and slowed in velocity by the time it reaches the occupants.

A ceiling fan by itself has no "heating" or "cooling" capacity. It merely creates air movement, which affects heat transfer from the surface of human skin. Two things are always underway from your skin's surface...radiant heat loss and evaporation. In winter, dry indoor air elevates body cooling via evaporation/perspiration, so elevated air speeds aggravates these factors even more, leading to complaints of draftiness by many. In summer, stagnant air slows the body's ability to reject heat to its environment. Stirring the air dispels the film of air around the body that is warmed by the body's attempt to reject heat, enhancing heat transfer.

Human comfort is all about rate of heat transfer from the body to its environment. This is why four things in an indoor setting must be controlled with intelligence to create a well rounded sense of comfort...radiation, convection, conduction, and evaporation, translating to surface temperatures, air movement, surface temperatures again, and relative humidity. Us HVAC types tend to get a bit (understandably so...it is our business to move air) with the convection and perhaps the evaporation side of things, whereby the building science types trend toward the radiation and conduction ends. Time to merge all this together and approach the building as a system.

 

[Brian GC]

For a small to medium sized bedroom with a standard eight foot ceiling height, a ceiling fan in reverse, even on low speed, might cause some folks to feel a draft. Often the standard three speed switching on most ceiling fans can't slow the blades enough on low speed to keep the feeling of draftiness at bay. For these situations I would recommend a dimmer switch rated for ceiling fan use be installed. From there the occupant can set the blades to blow against the ceiling, but barely rotate, which would help disperse stratified air against the ceiling but not create an uncomfortable draft.

If there is a problem of warm stratified air against the ceiling then it would be accompanied by cooler unwanted stratified air against the floor. If a fan was set so slow as to not move air in the occupied areas then the other half of the problem, cooler stratified floor air, would not be mitigated. Not that I want to go there, but the best draftless way to deal with it is with low mounted returns.

For vaulted ceiling rooms, a ceiling fan on reverse is also useful, perhaps with the low speed being sufficient. It's all about air speed and sufficient room between the air being stirred and where the occupants reside to assure the air is sufficiently mixed and slowed in velocity by the time it reaches the occupants.

Then it seems next to impossible to stir and mix unwanted low stratified cool air without causing an unwanted and cooling draft in the occupied area.

A ceiling fan by itself has no "heating" or "cooling" capacity. It merely creates air movement, which affects heat transfer from the surface of human skin. Two things are always underway from your skin's surface...radiant heat loss and evaporation. In winter, dry indoor air elevates body cooling via evaporation/perspiration, so elevated air speeds aggravates these factors even more, leading to complaints of draftiness by many. In summer, stagnant air slows the body's ability to reject heat to its environment. Stirring the air dispels the film of air around the body that is warmed by the body's attempt to reject heat, enhancing heat transfer.

True, moving air does not cool air temp but wind chill is real and calculable. Many variables would be used to determine wind chill factors. I would estimate that the very 5 degree rise that you are trying to achieve could be eliminated by wind chill factors.

Human comfort is all about rate of heat transfer from the body to its environment. This is why four things in an indoor setting must be controlled with intelligence to create a well rounded sense of comfort...radiation, convection, conduction, and evaporation, translating to surface temperatures, air movement, surface temperatures again, and relative humidity. Us HVAC types tend to get a bit (understandably so...it is our business to move air) with the convection and perhaps the evaporation side of things, whereby the building science types trend toward the radiation and conduction ends. Time to merge all this together and approach the building as a system.

Some of the smartest principles for heating are also the oldest…a fireplace. It creates no drafts, it allows the heat to gather on the ceiling while constantly removing the cold strata of air off the floor, it is quiet, it does not reheat your valuable heated air, temp transitions are without notice, and is both convective and radiant. But it has its own set of drawbacks.

Brian

 

[Brian GC]

Would it work better if they blew it with a blower instead of a fan. LOL


Since all force air heating systems, blow heated air.

I want to respect your status and respond to your posts but sometimes they amount to no more than forum heckling.

 

[beenthere]

I want to respect your status and respond to your posts but sometimes they amount to no more than forum heckling.

Well, sometimes they are no more then heckling.

Your post, has no validity to it.

Since once air movement stops, stratification begins.

So moving air with a fan, to maintain comfort, does make sense.

 

[beenthere]

Some of the smartest principles for heating are also the oldest…a fireplace. It creates no drafts, it allows the heat to gather on the ceiling while constantly removing the cold strata of air off the floor, it is quiet, it does not reheat your valuable heated air, temp transitions are without notice, and is both convective and radiant. But it has its own set of drawbacks.

Brian

A fireplace is one of the most inefficient ways to heat.

It draws in unconditioned outside air for combustion.
It does cause drafts across the floor.
The temp from one end of the room to the next can vary drastically.
Causes low RH problems.


I have a fireplace. I know how they work.

 

[Shophound]

If there is a problem of warm stratified air against the ceiling then it would be accompanied by cooler unwanted stratified air against the floor. If a fan was set so slow as to not move air in the occupied areas then the other half of the problem, cooler stratified floor air, would not be mitigated. Not that I want to go there, but the best draftless way to deal with it is with low mounted returns.

One factor overlooked here...tolerance levels for air movement before one declares their environment to be "drafty". If air is set in motion by a reversed ceiling fan near the ceiling, it will affect the air movement in the entire room. The fan is forcing the overheated air to fall, which will displace the cooler air near the floor at the same time the warmer air is mixing with the cooler air, causing it to warm up and rise. Repeat cycle ad nauseum.

The velocity in the lower regions is the focus. Spin that fan too quickly, the air in the room mixes well, but the velocity may be objectionable from occupants. Slow the blades down, the air mixes more slowly, the occupants may not object.

Then it seems next to impossible to stir and mix unwanted low stratified cool air without causing an unwanted and cooling draft in the occupied area.

Not really. Especially if humidity is controlled well. In fact, a tight house will likely feel less "chilly" from the onset, so the fan on reverse may or may not be sought after. With that said, the trend is to build "great rooms" with giraffe-head height ceilings, which even with tight construction will present thermal challenges to the occupants. Maybe we should rethink interior space articulation, in that mile high ceilings ain't so great after all. Personally I find lower ceilings to give a room a more sheltering feel, and less of an exposed one.

True, moving air does not cool air temp but wind chill is real and calculable. Many variables would be used to determine wind chill factors. I would estimate that the very 5 degree rise that you are trying to achieve could be eliminated by wind chill factors.

ASHRAE's comfort index is more applicable in this scenario, since we're dealing with an indoor environment vs. an outdoor one.

Some of the smartest principles for heating are also the oldest…a fireplace. It creates no drafts, it allows the heat to gather on the ceiling while constantly removing the cold strata of air off the floor, it is quiet, it does not reheat your valuable heated air, temp transitions are without notice, and is both convective and radiant. But it has its own set of drawbacks.

Fireplaces are especially troublesome in tight construction if no provision for outdoor combustion air is made. They're not great in loose construction either, since they most often draw from the interior space, not from a dedicated outdoor air source. They can also be a hazard if not tended and maintained properly. I love an open, crackling fire like anyone may, but I never use my own fireplace, for it lacks provision to draw air from outdoors. Until that modification is made, the fireplace is a handsome architectural element, but little more.

 

[udarrell]

Comfort Levels of Individual Occupants Can Vary

In real cold climates, homes built with open architecture from first floor to to second floor ceiling are a nightmare to heat.

In the summer, if upper floor areas can be closed off, you can let the heat stratify to the ceiling area. Winter is a different story!

I like 8 foot ceilings & closed off stairwells.

As shophound stated, "human comfort is a touchy situation." Sometimes the difference in the inhabitants can mean, with a specific condition, that some are very happy & others are very unhappy.

I never had that complaint brought up to me, but am sure many have had to deal with it.

 

[Brian GC]

I was not proposing that people use fireplaces to heat their houses. I was simply listing desirable characteristics of a fireplace that modern-day forced air units rarely share with them. Fireplaces have many drawbacks, but so do the multitude of poorly installed forced air heaters that are being routinely installed daily.

A fireplace is one of the most inefficient ways to heat.

Efficiency is only important if wood costs are high. I probably pay a lot at $125 for a pallet of walnut in December and it’s lasting me through March. It heats my 1,500 sqft downstairs so that my downstairs heater rarely comes on. Crunching those numbers tells me it’s not that inefficient.

It draws in unconditioned outside air for combustion. It does cause drafts across the floor.

The cfms are so low that I doubt you could back up the claims of draftiness. Mine has dedicated intakes but for those that do not I doubt it would draw more outside air than a rangehood, bath fan, water heater, or cloths dryer - and we all seem to tolerate those during the winter. And if outside air did leak in, it would reduce the overall performance of the fireplace, but not nearly ruin it.

The temp from one end of the room to the next can vary drastically.

That is true, but as stated, different areas of the house remain consistent in temp.

Causes low RH problems.

Since drawing outside air is so significant then how could in-taking damp (high RH) nighttime air cause lower humidity indoors?

I have a fireplace. I know how they work.

I use my fireplace…I know how mine works.