uneven heat in my split level

8 years ago

last modified: 8 years ago

my house heats unevenly. we have a (brand new, very excellent) heat pump that uses our existing duct system. if I warm the lower rooms, the living room gets too hot.* I'm thinking of closing off vents in the living room, letting the heat from the lower rooms rise up. below is a diagram of my house as viewed from the side so you can see how it's set up.

the trouble is, I read that closing registers can be bad for circulation, wasting heat trapped in the closed off ducts. also that the change in pressure causes the heater to have to work harder. I think that advice might be only for people who are trying to entirely close off unused rooms -- I'm not. all doors are open most of the time. I just want to balance the heat.

one other thought is to schedule running the fan to circulate the heat instead? we're about to install Nest temperature sensors in the lower rooms so maybe I can get the nest to run the fan when it needs it.

thoughts?

*I do realize the lower floors are cooler due to crawl space and the basement only having one vent. we'll eventually get new insulation, but it won't be for a while.

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Comments (5)

Michael
8 years ago
For the bedrooms, this is just one option.

Jump Ducts
mike_home
8 years ago
Closing off one or two vents in a house is not going to cause damage to the blower. You can try closing the one of the vents in the living room and see how there is an improvement in balancing the temperature. Then you can try a second and so on.

If you have a 2-stage blower then having the Nest run the blower in low stage continuously may help. Be aware that will cause your electric bill to increase, but it may be worth it if you are more comfortable.
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Austin Air Companie
8 years ago
Your home design is such that heat makes it's way to the upper level and has no way out. So because heat rises the heat just builds and builds to the point of which you become uncomfortable.

The best way for these kinds of home designs would be a HVAC zoned system so that you can control each level individually.

Ideally each level should have a return air vent. In some situations this may not be feasible.

It's typically never a good idea to close vents at the registers. This varies, but more often that not it does little to any good and could cause more problems than it's worth.
fsq4cw
8 years ago
+1 - Austin Air!

SR
udarrell
8 years ago
Install dampers at main duct take-offs to help balance airflow...

Not only are Return-Air ducts grossly undersized but also
filter rack areas are also grossly undersized…

This is Extremely Important when Sizing filter rack areas…! Time
to start checking filter airflow fpm velocities...!

NCI is the National Comfort Institute, Inc.; they say to
verify the pressure drop for that filter at the design CFM & velocity and
compare it to the available static pressure of the system, the pressure drop
through residential systems should not exceed 20% of the fans rated static pressure.
A .5" Rated system x .20% is .1" of pressure-drop...

However; then they show the various WRONG steps in Sizing
filters for the CFM airflow & fpm velocity required; the problem is that
they use the listed total square footage of the filter and ‘never figure the
actual open area or AK ‘of the filter, which makes a huge difference in
selecting filter sizes for a particular required CFM & fpm velocity.

After much figuring I have found that the ‘open-air or AK’
of the low pressure drop filters is at around 0.645%. .Return-air filters are
not 100% open-air; for example RA grilles at 400-fpm velocity have a usual
pressure-drop of .03” while cheap filters have around a .08 or.1” pressure-drop
at 300-fpm velocity indicating many times more airflow resistance…!

A typical 16x25 or 20x20 is a total 400-sq.ins. x* .645% is
258-sq.ins open-air Ak / 144 is (525-CFM / 1.791666-Ak is 293-fpm velocity);
that’s only 350-CFM per ton on a 1.5-Ton
A/C…!

That’s how we have to size filters to come close to the
manual D requirement of 300-fpm velocity… Some say use 250-fpm, I kind
of like 280-fpm as being okay.