10 posts / 0 new
Last post
oswald.1
uneven heating and cooling

Hello my problem is I have an old two story home buiult in 1905. It stays comfortable on main floor but the second floor is always 15 to 20 degrees hotter or colder than the main floor. I've been told that I need a variable speed blower on my furnace and a cold air return to the second floor. I only have one cold air return and it is in the dining room.

Re: uneven heating and cooling

Is it hotter in the summer and cooler in the winter? Do you only have one thermostat?

oswald.1
Re: uneven heating and cooling

yes it is hooter in the summer and cooler in the winter. we only have one thermostat.

Sten
Re: uneven heating and cooling

You should have a return on the second floor, that would be a place to start. Then try to balance your system using the dampers that are in the takeoffs on your main supply trunk. Less to the floor that's comfortable will force more to the one that's not. How's your insulation? If all that doesn't work then you may have to look into having your system zoned, then you need two stats not until. Another question is is it sized right?? The right BTU's and the correct sizing of the ductwork. Also, are you getting any air from the supplies upstairs.

motoguy128
Re: uneven heating and cooling

The good news is that you don;t have issues with heat rising in winter is seems, so the house must be reasonably air tight. The bad news is that you need more airflow upstairs. You'll need to add balancing dampers to the start of the branches if you have access to the ductwork.

Otherwise, adding a return upstairs will help a little, but you might need to install better quality supply registers. They aren't cheap, but a higher quality register will have a lot less restriction and will flow more air.

The second issue is that like the system in most homes, it's likely oversized. Short cycling will make temperature difference worse. You're better off undersized than oversized in most cases. Because a undersized system will simply fall behind a couple degrees for just a few hours a year. IT'st suprising how little heat you actually need.

I have a 3200sqft 1925 wood frame home in SE Iowa. Attic is well insulated and I have good storm windows and it's fairly tight in terms of air leaks. I only need a total of 75k BTU's to heat my home when it's -2F outside. A smaller 2400sqft early 1900 home with solid stone walls for example might only need a 45k BTU furnace with it's thermal mass. It effectively raises the design temp.

So, if you ready for a new system, or when you are, get it sized correctly using a proper load calculation. For now, change out the registers and make sure they are all open and in the warmest room downstairs, add a damper at the start of the branch or partly close the register.

bconvers9622
Re: uneven heating and cooling

It's difficult to balance hot air systems. I have a similar issue. I have a Coleman gas fired furnace, and the blower can't seem to deliver air pressure to some of the distant rooms. A variable speed blower seems like a good idea.

Sten
Re: uneven heating and cooling
bconvers9622 wrote:

It's difficult to balance hot air systems. I have a similar issue. I have a Coleman gas fired furnace, and the blower can't seem to deliver air pressure to some of the distant rooms. A variable speed blower seems like a good idea.

A variable speed blower will not help, balance the system , it's simple

Sten
Re: uneven heating and cooling
motoguy128 wrote:

The good news is that you don;t have issues with heat rising in winter is seems, so the house must be reasonably air tight. The bad news is that you need more airflow upstairs. You'll need to add balancing dampers to the start of the branches if you have access to the ductwork.

Otherwise, adding a return upstairs will help a little, but you might need to install better quality supply registers. They aren't cheap, but a higher quality register will have a lot less restriction and will flow more air.

The second issue is that like the system in most homes, it's likely oversized. Short cycling will make temperature difference worse. You're better off undersized than oversized in most cases. Because a undersized system will simply fall behind a couple degrees for just a few hours a year. IT'st suprising how little heat you actually need.

I have a 3200sqft 1925 wood frame home in SE Iowa. Attic is well insulated and I have good storm windows and it's fairly tight in terms of air leaks. I only need a total of 75k BTU's to heat my home when it's -2F outside. A smaller 2400sqft early 1900 home with solid stone walls for example might only need a 45k BTU furnace with it's thermal mass. It effectively raises the design temp.

So, if you ready for a new system, or when you are, get it sized correctly using a proper load calculation. For now, change out the registers and make sure they are all open and in the warmest room downstairs, add a damper at the start of the branch or partly close the register.

Dampers should be in the supply takeoffs, there made that way

motoguy128
Re: uneven heating and cooling
Sten wrote:

Dampers should be in the supply takeoffs, there made that way

Yes... of course... if you have access to the ductwork. Thats the best solution. IF not you can do some balancing at the registers, and can also balance a system by doing the opposite and reducing air flow restriction using better quality damper. Typical dampers are cheap stamped steel and don't have very good throw and are noisy at even moderate velocties. Better registers cost 5-8X more, but can flow much higher velocities, can easily mix air in even a large room with excellent flow. and flow much more air at the same static pressure. You can easily double airflow by using a slightly larger boot and grill size and good quality register.

The PO's in my house installed massively oversized furnaces. When I moved in some rooms were 5-7F warmer than other rooms. Now they are all within 1F and the noise at the registers has been nearly silenced. Based on my calculation, it has 120% more combined heating capacity than it needs and about 80% more cooling capacity.

Again, I was just giving an alternative to opening up walls.

bconvers9622
Re: uneven heating and cooling
Sten wrote:

A variable speed blower will not help, balance the system , it's simple

It's true, in some cases, however I found that in my system the humidifier caused somewhat of an obstacle the way it was installed. (going to re-install it....the installer just about closed up the plenum). However the variable speed blower was a great temporary fix for me.

TV Listings

Find TV listings for This Old House and Ask This Old House in your area.