# Amount of Baseboard Heat

• 07-29-2008, 05:07 PM
oldfords
Amount of Baseboard Heat
I need a little help on this one. I built a 'sun room' addition and will now add a new baseboard heat zone to my boiler. I went to slantfin.com and downloaded their heat loss calculator and it determined that I need 41 feet of the high output baseboard to adequately heat the room. The room is 28' x 16' with three outside walls. The ceiling height is 8' around the perimeter and goes to 12' in the center (vaulted). For the calculator I chose an average of 10'. The three outside walls are all Andersen permashield casement windows (it's almost all glass). Does this seem correct that I would need so much radiation, or could I have assumed something wrong in the calculator? Thanks.

Frank
• 07-30-2008, 12:08 AM
JacktheShack
Re: Amount of Baseboard Heat
Frank:

The Slant/Fin HLC is considered an excellent program & should provide an accurate picture of what you need---this of course, takes into consideration the additional factors which were not in your post, such as your location (cold area/very cold area), the large amount of glass present, the amount of insulation (if any) in the walls, the temperature of the boiler water as it courses thru the pipes in that room (anywhere from 150 degrees to 200 degrees), the gallons per minute being pumped thru the same pipes (could be anywhere from 1/2 gpm to 4 gpm), and the fact that 3 sides of the room are exposed to the exterior---all these factors will determine how many btu/hr are bleeding out of the room each hour & this same amount has to be made up by the baseboard output.

Another factor would be the ability of the boiler to provide adequate heat for the room if this is an addition.

Check the baseboard output ratings for both hi-output (800 btuh/ft @ 180 degrees) and standard BB (560 btuh/ft @ 180 deg.)---you should divide the total btu/hr heat-loss calc of the room from the Slant/Fin calc by the per foot output of both the hi-output & the standard BB to determine how many feet of BB you need.

If it's less expensive to cover all 3 walls with the std BB, go with that, rather than cover 2 walls with the hi-output---the 3-wall coverage would give you more even heat & may be a lot easier to install, depending on what access you have to the supply/return piping (risers) coming from & going to the boiler.

If you have diverter-tee piping or a 2-pipe system, you can add a TRV (thermostatic radiator valve) to the supply line ---or even a standard ball valve, to control some of the hot water going thru the piping---this will give you control over the amount of heat in the room.

If you want to cover just 2 walls with hi-output, the most attractive approach is usually to cover at least 2 of the walls fully with baseboard in order to present a neat appearance, which would total 44' in your case, again with a TRV or a ball valve.

If it is too warm with the extra footage of BB & you don't have a TRV or ball valve, you can always cover a portion of the finned convectors with heavy duty aluminum foil to reduce the room's heat output.

Since the foil will be behind the BB covers, it will be invisible.

Do not depend on HD/Lowe's to buy your baseboard---they have a very limited selection--you will get a better price & a much wider choice of styles at a local plumbing supply house.
• 07-30-2008, 07:01 AM
oldfords
Re: Amount of Baseboard Heat
Thank you for the quick reply. I most likely go with the high output baseboard, since I have that in my other zones, and since there is a door in one of the three outside walls, I will go with the two full walls. Any opinion whether Argo is better than Slant-Fin, or are they all the same? I have Argo in the rest of the house.

Frank
• 07-31-2008, 06:18 AM
JacktheShack
Re: Amount of Baseboard Heat
Frank:

I have no preference quality-wise between Argo & Slant/Fin---you perhaps stand a better chance of getting a design match for the earlier BB with Argo.