How many registers requierd

Originally Posted By: rmoewe
This post was automatically imported from our archived forum.

Can someone tell me the formula for determining the amount of registers required in a room.

Originally Posted By: dvalley
This post was automatically imported from our archived forum.

Richard,

One supply (preferably near the window area or outside wall) and one return.

If theres only one return register located in the main hallway of a home instead of in individual rooms, recommend that the lower part of doors to be cut back 1" in order to get sufficient circulation of house air to the individual rooms.

I do see two supply registers in larger rooms once in a while. As far as a formula![](upload://2ubpHK3yn8KBPErH5FUvdHPsrJn.gif), I check for sufficient heat at all registers

--
David Valley
MAB Member

Massachusetts Certified Home Inspections
http://www.masscertified.com

"Some cause happiness wherever they go; others, whenever they go."

Originally Posted By: rmoewe
This post was automatically imported from our archived forum.

David,

Thanks, there are 2 registers in the room, but I don’t think that it is enough. The room is 18’x 18’. They are also the last registers supplied, by the system. I don’t think that there is enough flow to the registers. I know this has to do with back pressure of the system. I just though there was a formula used for determining how many, and what size ducts would be sufficient. I am sure also depnds on how big the system is,too.

Originally Posted By: rsummers
This post was automatically imported from our archived forum.

Richard to really know how much air you need you first have to do a load calculation on the building to see what is required thats the only true way to determine it.

Originally Posted By: dvalley
This post was automatically imported from our archived forum.

of the run have a weaker temperature due to the long ductwork leading to that particular register.

I always make sure that this particular duct is insulated to help carry the heat to its full capacity until it reaches the last register. Also check the connection beneath from duct to register. This comes loose once in a while.

If the heat is still not sufficient for that particular room, other options may need to be considered. Separate zone, electric baseboard or a larger furnace.

--
David Valley
MAB Member

Massachusetts Certified Home Inspections
http://www.masscertified.com

"Some cause happiness wherever they go; others, whenever they go."

Originally Posted By: rmoewe
This post was automatically imported from our archived forum.

Thanks, for the answers. The problem is not with the heat, it is with the cooling. Hot air is lighter, so it will carry/move easier. The room is 18’x18’ and has 2 ducts. The supply lines are 8". I think that they need to be 10" supply, this will allow more air to travel through, and be less restrictive.

Load calculations are not an easy thing to do, I am a generalist. HVAC is one of my weak points, especially trying to do a load calculation!!!

Thanks, Rick

Originally Posted By: Blaine Wiley
This post was automatically imported from our archived forum.

As I read somewhere years ago, in general there should be one supply register for each 200 sq. feet of space. Since even that is beyond the scope of a HI, I just look for a supply register in each habitable room and make sure it has air flow.

In your case, document low air flow and refer to an HVAC contractor.