Control heat flow

Hi, I live in a three split level house, about 6 stairs separate the floors. This is our first year in this house and we are worried about a high heat bill in the winter. We have central heat and air with floor air vents. These vents have small switches that can open and close the air flow, yet it doesn't seal off completely all air flow. I work from home and am hoping we can direct the heat to the lower and middle levels during the day, while not heating the top level to save on costs. Is there any kind of cover we can buy to completely seal off air flow in the rooms not wanting heat? My husband thinks we can just put cloth on top of the vents but this seems like a fire hazard to me.
Any information would be helpful.
thanks-jennie
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The cloth would not be a fire hazard in most situations but still not a good plan.
A certain % of the vents can be closed with the "switch" with no problem. What % is the question. I would guess 20% of the total vents closed would be safe in most installations. That is just a guess. 30% maybe as a max.
HVAC systems need to move a certain amount of air over the coils or heat exchanger to avoid damaging the unit. Trust me on this one, the cost of a new unit is far more than you will spend on utilities.
Heat rises so what I would suggest for the first attempt is to close a few of the upstairs vents and fully open the ones in the lower level. How well this works is going to depend on where the thermostat is located and how much time you spend tweaking the system.
If you do not have really small children in the home a setback thermostat that turns the heat down 5-10 degrees at bedtime and then warms the house for morning can save you 10-15% on your bills. You can do this by hand, but you will never remember all the time.
When you start closing vents, the big thing to watch out for is the furnace turning off BEFORE the temperature is reached (cycling) this can indicate too little air flow causing the high temp safety to shut down the furnace because the heat exchanger has over-heated. This is a BAD thing. Do that too much and you will be buying a new furnace.
Colbyt
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There is the units operating temp at the heat exchanger, exceed it by blindly closing vents and you can exceed the limit shortining its life. You should measure the temp and learn about what you are doing. Attic insulation is rarely at optimum levels and you might save more than you will by shutting down rooms
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