heating/cooling a basement


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Old 02-21-04, 02:01 PM
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heating/cooling a basement

ok, not sure if this should be here or in the basement thread, but here goes.

i live in chicago in a 2 story home with a full unfinished basement. the basement is fully below grade. there is a furnace and a/c unit for the first floor and another set for the second floor. i've noticed that in the summer, the basement remains cool, even on the hottest days. there are currently two registers in the basement for heating and cooling that are just cut into the main supply duct for the first floor system. usually in the summer i close them off since it's cool anyways, and during the winter i open them. still, during the winter it's too cool down there to be comfortable. my question is when i go and finish off the basement, i'm sure i'll be adding more registers, but how do i better equalize the heating and cooling betwen the basement and the first floor. it seems like during the winter i will always have either a too cool basement or a too warm first floor.
 
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Old 02-22-04, 06:46 AM
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If you onlyl got two vent now in the basement, it is not enough.. But once you get going on your basement, add more vent for each bedroom/office. and maybe a couple for the family room..

Then put a couple of returns in near the floor, that way it will draw up the cold air from the floor in the winter.

Once the basment is done, it will be the warmest room on the very cold winter night.

Is there A/C on the main floor furnace? In the summer just close off most of the vent.. I would suggest keeping one open to help keep the basement dry.
 
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Old 02-22-04, 08:47 AM
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For new runs in this basement room Id blank off the 2 what you have now. Cut take offs in the top of that duct for the first floor. have the pipe runs go to about 12" off the outside walls blowing down. You didnt say anything about a cold air return down there you do need one for sure. You could put it in the cold air drop. If you put any doors there cut off the bottoms so the air can get out of the rooms or set them higher off the floor. Now for summer dont close the registers all the way in summer down in the basement that way . You want them to help dehumidifi the air down there so the ducts dont sweat ED
 
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Old 02-23-04, 05:15 PM
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Lightbulb Temperature swings.

Another thing to consider is that if you want to have balanced temperatures between the first floor and basement you will need to have the basement insulated to the same level or greater than the first floor.
If you don't, as the furnace cycles to the stat on the first floor, the bsmt temp will drop too low before the furnace starts.
 
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Old 02-24-04, 07:06 AM
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thanks for the replies everyone...

another thought; in homes with basements, do builders typically oversize the furnace and a/c units knowing that someday the basement maybe finished living space? is there some sort of calculation i can do to find out if my current equipment can handle the extra loads of heating and cooling basically double the sq footage (it's a full basement).

also, Ed, you mentioned adding a cold air return to the cold air drop. does this mean just tapping off the main return duct for the first floor? and is there a rule of thumb for how many cold air returns i need? (one per room, one per supply vent, or one per so many sq ft of space)

thanks again
 
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Old 02-24-04, 11:24 AM
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When you ask about cold air returns . You have to look at a lot here. Like open stairs ??? Door on all the rooms???? Most of the time just one will work. If you think about the size of the unit it should do it. Most of the walls are in the ground and any heat you let out there in the basement will tend to warm the floors over head. So it not a big heat loss. With the AC this helps down there to dehumidifi the home and so the duct work dont sweat. ED
 
 

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