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Combining Baseboard and Radiant Floor Heating

In my kitchen, the ceramic tile floor gets VERY cold near the yard door. I have tried my best to insulate around the door and at the bottom but the entire kitchen floor gets cold in that area anyway. My house has hot water baseboards throughout and since the floor is open to the basement below, I was wondering if it is possible to pull hot water from a nearby baseboard and run some tubing for radiant heat in the area. About 32 sq feet. Is this possible? Will I run into other problems combining the two systems such as improper water temperature?

Philadelphia, PA

Re: Combining Baseboard and Radiant Floor Heating


Yes, the modification you propose would probably work, given the small size of 35 sq.ft. of the kitchen---but first check out several things:

1) check out the boiler gauge when the system is putting out heat---there should be 180 degrees on the boiler gauge after the boiler has heated up for 10 minutes or so---often the controls in the aquastat are set back & the boiler is putting out much less than its normal heat--it's a simple adjustment to get hotter boiler water, which will mean more heat for the kitchen radiator or baseboard.

2) take a measurement of the length of the kitchen baseboard or radiator to see if the kichen baseboard is long enough to put out the heat that you need for the kitchen---also feel with your hand the kitchen convector when the system is running---you should not be able to hold your hand on the convector piping for more than a second or two if the rad/baseboard is putting out the heat it should be.

It's a simple matter to adjust the boiler hot water via the aquastat to get hotter water running thru the baseboard---since most kitchens are cramped for space, you may have only a couple feet of baseboard, which would only put out (580 btu/hr/foot) = 1200 btu/hr.

Next take the sq.ft. of the kitchen & multiply by a heat factor of 40---thus 32 sq.ft. X 40 = 1280 btu/hr (assuming 8' ceilings) needed to heat the small kitchen---if you can't add more baseboard due to cramped space, you can add a kickspace heater at the base of a cabinet & get an extra 2000 to 4000 btu/hr to heat the kitchen.

Kickspace heaters hook into the exising hot water heating lines & have a small footprint of 16" X 12" X 4" high & are thermostatically controlled--- I think the kitchen will feel lots warmer if you add more radiation, or raise the boiler water temp, or both.

I would recommend you look at the above options, before committing to sub-floor radiant lines---sub-floor radiant is more subtle in its heating performance characteristics & is more likely to yield 25-30 btu/hour per square foot of sub-floor radiant output: 30 (heat output) X 32 sq.ft.= 900-960 btu/hr for a 32 sq.ft. area.

For more info on this topic, Google "A Little Floor Warming Please", or "A Signature System" or "Underfloor Installation Offers A Retrofit Solution".

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