Question for the HVAC experts - how to push more heat to third floor?

[Spidey]

Had ATCO come over to diagnose small leak under the furnace (93% efficiency unit) - turns out it was only a cracked condenser drain hose (whew!) I mentioned that our third floor bedroom is always a little colder than the rest of the house (furnace is on main level). ATCO tech said usually a second furnace is needed to fully heat 3 levels.

However, one of the bedrooms on the second floor is always a little too warm given that the furnace sits directly below it. We closed one of the registers in that room which helped knock down the higher temperature somewhat, but am wondering if there's anything more we can do for the colder bedroom upstairs without messing too much with air flow (eg. completely blocking one of the register vents in a couple of the warmer rooms?). We do have a space heater that we use in the upper bedroom, but curious about any HVAC ideas.

[Don K]

I’m assuming that you mean a 2storey home with a basement? Or is it a 2storey with a log and a basement (which would be 4 Floors.

If it’s just a 2storey with a basement under there is no issues with a single furnace (up to 2400 sq ft above grade) and the guy from ATCO is on crack... you can actually push 2800-3000 sq ft (above grade) off of one furnace if designed properly using a zoning system.

It’s hard to compensate for a poorly designed heating system but if your basement is undeveloped you can increase the size of the pipe come by off your main duct line and reduce just before it turns up and goes to the upper floors. This will increase volume and air flow as well. You may have to increase your fan speed. The registers can all be adjusted to properly ‘balance’ the heat in your home as well.

It might be worth calling someone to come have a look and make some modifications or adjustments to optimize what you are getting out of your furnace and ducting.

[Bassett]

We added an inline fan into the duct work. Helps get the heat up to the 3rd floor nicely.

[Spidey]

I’m assuming that you mean a 2storey home with a basement? Or is it a 2storey with a log and a basement (which would be 4 Floors.

If it’s just a 2storey with a basement under there is no issues with a single furnace (up to 2400 sq ft above grade) and the guy from ATCO is on crack... you can actually push 2800-3000 sq ft (above grade) off of one furnace if designed properly using a zoning system.

It’s hard to compensate for a poorly designed heating system but if your basement is undeveloped you can increase the size of the pipe come by off your main duct line and reduce just before it turns up and goes to the upper floors. This will increase volume and air flow as well. You may have to increase your fan speed. The registers can all be adjusted to properly ‘balance’ the heat in your home as well.

It might be worth calling someone to come have a look and make some modifications or adjustments to optimize what you are getting out of your furnace and ducting.


The house is on a slope and 2/3 of it ends up being 3 stories above grade. Thanks for the advice on duct sizing and fan speed. The furnace room is dedicated and undeveloped so this could be an option. When the plumber comes to replace the hose and reseat one of the PVC joints, I'll have them look at it. Good to know there's some options!

[Spidey]

We added an inline fan into the duct work. Helps get the heat up to the 3rd floor nicely.

Thanks for the tip! Did you do this during the build or after? If after, where did you locate the inline fan?

[dewalt18]

There's many options available to improve airflow, however since the space affected is likely above a fully finished area, most of them are less than desirable. An inline fan, or an inline duct heater (think toaster element) are both effective, and can be used in conjunction, however would require removal of drywall to expose ductwork and allow for running of electrical.

Quite often, a cold room is a result of no return air being drawn from the area. Basically this means that once the room fills up with air, no more can be added without some being removed (think trying to overfill a glass of water)

My first place to start on rooms like this is ensuring that there is adequate airflow both in and out of the space, and then moving on to more involved or more invasive measures

[CaberTosser]

As DeWalt noted, also check the return airs in addition to the supply air grilles. For instance you might notice that the supply air is wide open and accessible in the cooler room, but perhaps the return air grille has a piece of furniture or something blocking it. I have also gone to the extent of slightly reducing the return air in a room that is over-supplied when trying to increase airflow to a distant room.

Frequently bonus rooms over unheated garages can suffer greatly because 5 of their 6 sides are outside walls, contact someone such as myself to heat that pesky garage while making that bonus room (or master bedroom or whatever is above it) more comfortable and make the garage a good workshop option regardless of the weather.

[Bassett]

Thanks for the tip! Did you do this during the build or after? If after, where did you locate the inline fan?



Way after the build. In order to minimize ceiling and floor destruction I found an exposed duct in the garage (attached with a floor built on top) and added it there it pushes to the top floors nicely without dragging all the heat away from the other ducts.

[Spidey]

Thanks for the input everyone. The top floor bedroom is directly above the "warmer" bedroom. The heating airflow is definitely less than on the main and second floors, but covering a couple vents on the second floor bedrooms seems to have helped a bit. The cold air return is unobstructed.

And yes, Caber - I'm definitely with you. Our garage has in-floor heat which also supplies heat to our walk out rental suite. That's what sealed the deal for me when we bought the house. I love being able to work in my shop (I converted one of the bays of my garage) in short sleeves when it's -25 outside :)

[John d]

As noted all ready people under estimate the need of proper return air
And having the system balanced with proper tools