use magnetic vent covers or not?

[gbig2]

I have a propane furnance, forced air. Two rooms are not used. Is it ok to block both the supply and return vents with magnetic vent covers in those rooms? It should reduce my heating costs correct? Thanks

[Gunnery Sergeant Hartman]

DO NOT USE THOSE!!!

It will cost you more money!

Your system is designed to move a certain amount of air and if you cut that flow down, the equipment will be working harder.
The fan will push the same amount against a greater static pressure and overwork the fan and overheat the exchanger.

[curry]

He's right. You could cause an irrepairable over heat.

[Midwest]

I believe these devices fall under snake oil energy saving sales tactics. These things will not save you and will in fact possibly cause damage as stated by others, costing you.

[craig1]

it really depends on your system. if you have the minimum number of vents required, then covering anything could cause damage. on the other hand, if you have many more vents than the minimum, you could cover some with no ill effects. you could have a contractor look at your system and see if it is ok for you to cover a few vents.