Heat rises, doesn't it?

[CARS]

OT a bit, but I need to talk about my house.

2 story, 40's, 28' square with an entry addition and 28' X 30' attached garage (had to throw that in).

The stairwell is open to the upstairs. Thermostat on main floor on interior wall (centered in the house for the most part). Furnace is 1 year old, high efficiency.

The problem we have had since we bought the place is that the upstairs is almost always 10 degrees cooler than the main level. With the open staircase I would think the opposite would be true. Even with all the room doors closed the thermometer on top of the staircase is 10 degrees cooler than the thermostat states.

One problem I see is that there are no returns on the second floor. If the room doors are closed, I can see air not flowing in as easily. But face it, it's an old house and I doubt it is totally tight.

The furnace may be new, but the rest of the duct system is not as efficient as it could be. I don't know if they really engineered systems back then. Pretty much happy to have forced air back then.

Any thoughts?

 

[TWX]

Hot air rises, but heat can radiate away very quickly through poorly-insulated walls.

 

[CARS]

Hot air rises, but heat can radiate away very quickly through poorly-insulated walls.

I forgot to add something about the walls.

When we insulated a couple years ago, they were un-able to do the walls.
It's a balloon framed house with lath and plaster walls. But, in the middle of the studs is another layer of lath and plaster! Seems that before there was triple pane windows they were experimenting with triple pane walls!

So, what I did was add 1/2" rigid foam to the outside, and taped all the seams before I installed the vinyl siding.

The blower door test guy was impressed how tight the house is for its age.

 

[Teken]

How does the heat get up to the 2nd floor? As you said there is no return for the air. But, if they ran heat ducts how is there no return air?

 

[CARS]

How does the heat get up to the 2nd floor? As you said there is no return for the air. But, if they ran heat ducts how is there no return air?

Well, I guess they chose not to run return ducts. As confusing as that is, I am confused that you are confused

 

[Falcon67]

No air return = no circulation. Our back bedroom in the old house was always warmer or cooler than the rest of the house. When we looked at upgrading the AC system, every company that came to bid said "Is this room different than the rest? You need a 12" return in this room to move the air." Room was 18x16 with the 30" wide door about 20' down the hall from the furnace return/filter .

 

[Teken]

Well, I guess they chose not to run return ducts. As confusing as that is, I am confused that you are confused

If I could make a humble suggestion . . . If you close one or two, or even divert a few of the vents on the main floor.

Please do let us know what you *feel* in terms of temps. Another suggestion on the cheap is to install a fan either on the main & top floor to draw the hot air up to the 2nd level.

 

[bczygan]

How are the registers set? Are the supply registers for the upper floor open?
Are there any dampers in the supply lines to the 2nd floor that are closed?
Filters in the supply lines clean?
A manual solution is to adjust and open/close registers and dampers to put heated air in the balance you want.
An automatic solution is to install electronic thermostatically controlled dampers for the supply ducts for upstairs and downstairs areas.

 

[Jackfre]

Check this out. It offers a possible solution.

http://tjernlund.com/airshare_ventilation.htm

 

[CARS]

A few years ago I tried to balance the system. I used a real scientific system of my daughters hair ribbons taped to the duct covers and adjust them till they were all "flying" at the same height (which wasn't much).

I thought about a ceiling fan above the open stairs, but that only helps the hallway if everyone has their door shut.

One of the big problems around here is that the HVAC guys who do work in my area are mostly "old guys" who just keep piecing these old systems back together. I am sure that if I went with a company from a larger city who builds new systems on a regular basis, they would tell me to tear it all out and start over. I agree with that to a point, but I really hate to open up all the interior walls.

The perfect solution in my mind is an separate attic system for the second level with ducts in the ceiling. But that doesn't sound cheap either.

 

[K13]

How is you ceiling insulation? That is where most of your heat loss is going to be. Like you said heat rises so it will go up in the room and if the ceiling is poorly insulated it will just keep on going.

 

[Falcon67]

The perfect solution in my mind is an separate attic system for the second level with ducts in the ceiling. But that doesn't sound cheap either.

That may well work - usually the cutover from one to dual systems is around 2500 sq/ft. If your current system is sized for the whole house, better to try and fix what's broke. If there is no ducting in the upstairs rooms, that will be a routing problem. If there are registers but only no return, you could maybe engineer a chase somewhere to route a duct back to your return plenum on the furnace. Depending on room layout and closets, that may require some real creativity. Our house in Houston was a two story with a big stairway from the entry up to the second, and all bedrooms up. The AC was in the attic with a return chase the went down the center of the house and stole part of the upstairs bath floor space where it headed down It also had an offset in it to miss the 1/2 bath on the first floor. A U.S. Home design hack. Ducts for the kitchen, laundry area came down through a chase in the master closet.

 

[CARS]

How is you ceiling insulation? That is where most of your heat loss is going to be. Like you said heat rises so it will go up in the room and if the ceiling is poorly insulated it will just keep on going.

It has an attic too, so when we blew the insulation in we just did the attic floor joists. Last winter was the first year of the insulation (any insulation). At the time we noticed a difference. Now this year (and it's not even cold yet), it feels like it did before we put that 8" (or so) of insulation. Edit: The attic is a cold zone. Very minimal sofit vents and 4 roof vents.

Maybe the best bang for the buck is to get rid of the "stuff" in the attic and roll out some pink stuff?

The attic entrance is in the master closet and I know that is a heat loss area because it is just a lid. But...

Back to one of the original statements is with all the room doors shut and an open staircase, heat doesn't get "trapped" in the upstairs hallway.

I will spend sometime this week on balancing dampeners and duct grills (almost all of the grills are adjustable).

Thanks for the advice and ideas everyone! If you think of anything I should try, let me know.

 

[rickairmedic]

Heres a little trick I give my homeowners with 2 story homes that dont wish to invest in a second system . Go to Home depots web site and type " equaliser " into their search box . This will bring up a register vent booster that sits on the registers upstairs and draws up to 8-% more air through those registers . These boosters plug into a standard wall outlet and have a built in thermostat that can be set to the same temperature as the main thermostat in the house . That way they only run when the heat or air are running .

The way to work your registers is to figure out where your furnace is in your basement . Then on the first floor almost completely close the registers closest to this location . The further from the furnace you get the more open you want your registers . I see this issue in almost every house I walk into " every register " in the entire house is wide open . The idea of almost closing off the closest ones and leaving the furthest wide open is it will allow the air to move further through the ducts . Most people dont realise the first four vents closest to the furnace get 80% of the airflow especially if they are wide open leaving 20% for the rest of the house .


Rick

 

[CARS]

Thanks for the tip Rick. I will see what I have going on right now (I bet they are all open too).

 

[Charles (in GA)]

The perfect solution in my mind is an separate attic system for the second level with ducts in the ceiling. But that doesn't sound cheap either.

That absolutely would be the best situation. You certainly do not have circulation now. I recall the old house my grandmother lived in, in west central MO had floor vents to let the warm air from the lower floor get to the rooms in the second floor. I think this house was built in the late 1860's or '70's. You need return vents from upstairs, or at least, vents in the doors into the rooms upstairs to allow air to return to the hallway and then downstairs. I leave all of my rooms open, rarely close a door, grew up that way, and I think that helps.

Experiment with leaving all the upstairs doors open for a week and see if that makes a difference. If it does, look at door vents or vents in the walls thru to the hall.

Charles

 

[Teken]

Rick,

Excellent tips as always . . .

 

[NUTTSGT]

Some interesting info in this thread.

 

[burleymike]

Sounds like your upper level is not getting heat much faster than it is loosing heat. Your lower level does not have a cold attic above it so it looses heat slower. Then you have the furnace closer to the lower level coupled with undersized, leaky duct work and inadequate returns.

If you only have 8" of insulation in your attic you need more. We had 10" of fiberglass and I just blew in 8" more. What a difference,the night after I did it I put 4 logs in the stove before I went to bed like usual.The next morning it was 71F in here instead of 66F like it used to be. Going to an R50 will only help things.

If bringing the insulation up to an R50 does not bring adequate resolution look at a mini split heat pump to agument upper level, if they will work in your climate. Otherwise you might need to look at all new duct work that is properly sized.

 

[Teken]

I would also suggest you tape all joints for the lines. That $5.00 worth of aluminum heat tape will pay for itself the first time you place your hands over the heat register!

I saw a 20% increase in air velocity from the farthest register in the house . . .

 

[CARS]

Thanks everyone for the great ideas. Especially Rick!

Taking his advice has already made a huge difference in evening out the two floors.

For some reason me and the wife always opened up the grills in the rooms that we use the most and idled down the less used rooms. By closing the main level grills, the upstairs was finally getting the heat it needed. I also told the kids to leave their doors open (of course the 14 yr old daughter didn't like the idea).

Once the upstairs was warmed up, I put a thermometer in each room and cracked open the main level grills to give the living spaces some heat. Within a couple hours and a few furnace cycles we had all the rooms at 65. (why 65? I am tight with my LP but the truth is even at 65, the boy is in shorts and a T and the girl is wearing a spaghetti strap tanks )

Short of a remodel, leaving the doors open a bit is going to have to do for circulation. Oddly, I did discover one return in the master bedroom (14'x20') under our bed. But with the master door shut, that one return is trying to do 1/2 of the 2nd level (master bed, closets, and small bath).

Thanks again for opening my eyes to a new way of looking at forced air!

 

[danski0224]

Your duct system is not matched to the "high efficiency" furnace.

During the blower door test, did they check each room for pressure differential or did they just test for leakage?

A room can be more connected to the outdoors through ductwork or building flaws. It does not take much of a pressure difference to move huge amounts of air from an area of high pressure to low pressure. These differences are measured in Pascals, not inches of water column or PSI.

With balloon framing and a warm first floor, you enhance something called the stack effect. Warm air is rising, but not where you want it to.

Closing the registers on the first floor and directing the warmth upstairs can simpy be masking the problem due to reduced stack effect.

Humidity/moisture moves just like heat: from more humid to less, in an attempt to reach equilibrium. Humidity can drive air movement.

Closing registers can also increase duct static pressure which: reduces fan airflow, reduces efficiency and shortens equipment life. Increased static pressure within the ductwork will increase electric bills and shorten the life of a variable speed blower motor.

 

[bczygan]

Very good!
A forced air system is just that, air that is forced through duct work at pressure. You have discovered how to manipulate the flows to get heat where you want it.
A lot of buildings, especially small ones, instead of having return air duct work use grilles and undercutting. Especially in small homes, this is true. Undercutting is where the bottom of the entry door to a room is cut 3/4" up from floor level. Hot air rises, but comparatively colder air descends and will flow under the door and into hallways and stairwells. When people install wall to wall carpet over hardwood floors they sometimes forget to undercut the doors further up to accommodate this and the gap gets blocked and the return air reduced or eliminated. As mentioned above you can install grilles in the walls of rooms to allow air flow. You can also install grilles in doors. These solutions will allow the daughter to keep her door closed as she desires. It will allow you to also keep your sons doors closed, which may be something you desire! Keep these grills low for return air so they pass the cooler air that is near the floor. Some small homes will have a return air duct and grill in the hall to pull the air collected there. Two story homes may have a simple grille between the second floor floor and the ceiling in the first floor to allow cooler air to descend.
Another thing to consider is the leakage you have upstairs. Small things add up to large differences. Things like insulating electrical receptacles and light switches, weight pockets for double hung windows, shim spaces around windows and doors. Weatherstripping doors and windows makes a huge difference. Caulking windows and windowpanes also makes a big difference. As mentioned above, loss through even very small openings in the building envelope, at pressure, results in big losses over time. And this is heated and conditioned air which is then replaced by unheated air from outside.

 

[CARS]

During the blower door test, did they check each room for pressure differential or did they just test for leakage?

No. Not that I am aware of. I think it was just for whole house leakage.

 

[danski0224]

No. Not that I am aware of. I think it was just for whole house leakage.

Well, that's fine if you want to establish the tightness of your house, and as long as you can breathe indoors, it isn't too tight.

Testing ducts can follow the same misguided path- the ducts can be sealed and test good, but have very poor airflow characteristics.

I would suspect that there is more to your problem than just poor ductwork.

On another forum, someone had problems maintaining humidity in the home. The cause of the problem was determined to be an open but abandoned 4" hole from a dryer duct that was open to the living space and the attic. The pressure differential between the two planes was enough to literally dry out the house, as more unconditioned and dry air was brought in from outdoors to replace what was vented to the attic.

Your simple blower door test did nothing to point out ways to solve any problems. All it did was establish that you have XXXX CFM of leakage at 50 Pa, not where the leakage was from.

The attached image is from my own house. I fired up the blower door, the infrared camera and got out the smoke pen.

The picture is a return duct opening in the ceiling. My return duct is in the attic. With the blower door running, attic air is being pulled into the return ducting. This was verified with the smoke pen as a smoke exiting the return ducting with the blower door fan on. So in the winter, conditioned house air is leaving through the ductwork. This happens 24/7, and flow increases as the temperature differential increases.

All of the exterior electrical outlets had a breeze, too.

 

[Stuart in MN]

It's a balloon framed house with lath and plaster walls. But, in the middle of the studs is another layer of lath and plaster! Seems that before there was triple pane windows they were experimenting with triple pane walls!

My house (built in 1913) has the same construction - a second layer of lath and plaster in the middle of the studs. I believe it was call back plastering.

I haven't tried it, but I've seen an interesting gadget for old houses with an open stairwell: it's basically a cloth tube with a fan at the top, hung in the stairwell to pull warm air from the first floor up to the second floor. It looks simple enough to build. You put it in the corner of the stairwell so it's not in the way, and since it's made of cloth it will simply push out of the way if you do bump into it.

A guy on another forum built one and put in his house, and reported it did a good job of equalizing temperatures. It also helped circulate air conditioned air in the summer.

 

[fromnwmt]

We had a similar issue i cut a register in the floor of the second floor then added a door fan they are triangle shaped to fit in the corner of a doorway (yes you can still close door if necessary) for a clean look I was using a large box fan angled up the stairs worked great but always tripping over it....

 

[BadgerBoilerMN]

Easy on the old guys. There are smart guys and dumb guys. Try to find a smart guy and ask him about zone dampers and Honeywell wireless thermostats. I use them at home and at the office.