When is a Cold Air Return required

This is probably a stupid question. I live on Lake Erie in ohio. Does every room require a cold air return? I have a 2 story colonial and am looking to remove a cold air return in one bedroom. The other 2
bedrooms both have cold air returns.
Thanks in advance. Clem
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Weeeelllll, yes and no about the stupid question part. It's most likely that the design of the heating system dictated the use of the two cold air returns. Forced air heating works by "pushing" cold air out of a room, and pulling in warmer air in its place. Removing a cold air return may well upset the design balance and cause that end/side of the house, whatever, to become cooler than the other. Certainly the bedroom would become less cozy.
I'd suggest you could "test" it, but ... furnaces require a certain amount of square footage to suck cold air from the rooms to work efficiently, and if your design isn't over-designed, you could fairly promptly burn out the fan motor by making it work too hard.
Now, you could probably -move- a cold air return within a room without too much loss of comfort, but even that depends on the layout of things.
Why do you want to remove a cold air return? Size of the return openings and furnace btu and fan motor size might allow someone to make a guestimate, but I sure can't. Oh, it's also related to the square footage of the hit air supplies, too. It's more complex than you probably think, but for the experienced it's really pretty simple.
Personally I wouldn't do it; get someone in to size up the situation who knows about such things first, preferable someone good, not just a neighbor who's "heard of" things.
HTH,
Pop

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On 22 Feb 2006 11:26:07 -0800, snipped-for-privacy@parker.com wrote:

If you don't have a cold air return, the room will fill up like a balloon, and eventually burst. Most likely the windows will blow out, and possibly the door. In extreme situations, the walls may be blown out also. If people walk by outside, you should erect some sort of barrier to catch the glass and other debris.

Remove NOPSAM to email me. Please let me know if you have posted also.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
A friend was told that with the high-pressure, small-i.d.-duct systems that you don't need room returns. Because ... you don't.
Simple physical fact- if you pump gases into a chamber, you will pressurize it until the net mass-flow-rate out equals the inflow rate. One result of the increased pressure could be flow to places you don't want- like through cracks to attic or past windows. Another result is decreased inflow rate- reduced room heating.
Simply put: to heat a ft^3 in a closed room, draw that air to the heat exchanger & then return it, heated.
Some older houses had louvered doors with served as part of the return; fully-skinned door creates problems there. In such a situation, I installed a "siamesed" return to 2 closed rooms. No more fungi in attic insulation.
J
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

There is only space for a certain amount of air in any room. If you want to put hot air in, you have to provide a way to get cold air out to make space. You can get a LITTLE bit of space from leaks, and more if you leave the door open, but if you're serious about heating the room, put in a cold air-return.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Do you have a return air grill in the hallway too ? For most rooms the common air return path is the door undercut - the spece under your door when the door is closed. I'll call an HVAC technician to check things and advice you.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

It's a design choice, One could have gone either way when designing the system. One per room allows for the doors to seal more tightly (no gaps at bottom) and allows for more zones (you may or may not have separate zones for each return). One might do this to prevent bedroom zone air from mixing with a large room or great space in a different zone etc.
You might be able to get away with sealing one return as long as they are indeed in common and you allow venting of the room with the sealed vent through or under the closed door (every door in the path back to the return and cannot cross another heating zone). This will likely result in an imbalance which may cause some rooms to be unevenly controlled. Some return ducts are greatly oversized (being made of wall cavities) but if yours are more carefully designed, you will starve the furnace of air making it less efficient and increasing air noise in the remaining returns.
Try taping it closed for now and see if you detect any important disadvantages.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
leave it there or relocate it. you will be reducing the heating efficiency and make summer central air conditioning more difficult. see lots of info at: http://www.buildingscience.com/resources/mechanical/default.htm
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.