Picking the right cast iron radiator

I have chosen this style of radiator for my home and I'm trying to figure out the right one for each room.

Does any one know how to convert the displayed numbers into a BTU output?

Note for hot water, the above chart says "AVERAGE water temperature" - midway between supply water temp & return water temp - NOT "supply water temperature".

johnfrwhipple said:

I have chosen this style of radiator for my home and I'm trying to figure out the right one for each room.

Does any one know how to convert the displayed numbers into a BTU output?

Click to expand...

The heat loss across those rads would be entirely dependent on the system you have installed. IE the flow rates and working temps of the water.

One of the TV shows did a special on CI radiatiors & I picked out the ones I wanted
Turns out the company is in the UK & does not have a distributor in the US, & no plans for one
They were flooded with E-mails asking how to buy their product
They had no idea they were being featured on the TV show

I'll be buying some other ones in the US, maybe used

Calculating total BTU output for the radiators

Thanks for the information guys.

The chart is excellent - I can get a pretty good idea of the size now for each room and will leave the exact measurements for my engineer.

Happy New Years,

Again thanks for the help.


JW -

you can't go wrong over sizing a radiator either. the extra size means you can lower water temperatures.

Heat loss from building a window seat over standard baseboard heat

I have read online that just painting the radiators cause a decrease in heat output. This can be a blessing or a nightmare I'm sure.

If I had a standard baseboard heater with the copper pipe and fins (with cover) what do you think the percentage of heat loss would be if I built a window seat above the unit to conceal it. My ballpark guess is 30% do any of you HVAC specialist think this guess is way off?


JW -

Working on the BTU output for a 3 column radiator

Working off the Standing Radiator Heat Emission table above and the information from Burnham I came up with these calculations.

A 3 column cast iron radiator (as shown above) 32" tall x 4 3/4" deep x 25" wide totals 32 1/2 square feet. With a water temperature of 170 degrees Fahrenheit the chart show I get 150 BTU's per hour per square foot.

I have checked my math and this works out to the above unit producing 4875 BTU's per hour. This is fantastic as the standard base boards that are cheap and easy are only producing about 760 BTU's for the same foot print (2' linear feet).

I will send my specs to Burnham and they do all this calculating for me. I am trying to use as many of the cheap baseboards as possible and make up the missing heat with the column radiators.

If I have them painted white which I most surely do the heat output will be affected as I have read. Even if the painting drops this number by 10-20% the unit is still cranking out huge heat in a small area!


JW -

I recently repainted 3 CI radiators in our house
Possibly only the 2nd time they were painted - house from the 50's
Very little paint on them, a lot worn off
At the same time I turned the boiler Temp down ~20 degrees
Our house has always been warm since renovations/new windows & insulation

I'm sure it retains some heat, doubt I could tell
I do know it takes slightly longer for the house to heat up (due to lower temp)
And the heat will come on again sooner
But the Temp was too high IMO @190 - with a 2.5 year old in the house
Our boiler is oversized, & the kitchen radiator is huge as the stairs to 2nd floor are off the kitchen

Our 864 sq ft addition I am going to use CI radiators
I'd rather spend the extra $$ & have them instead of slant fins along a lot of the walls

Cast Iron radiators for looks

I agree they look great.

Since we made our decision to use them we see them every where now. TV, Books and movies.

Many of our design magazines that we flip through for ideas have them as well which we really didn't notice a few years back when we started collecting them.

Some awesome looking Rad's right here: Available in Canada and the US by Hudson Reed.

I have installed a few Runtal Radiators

Those Runtal style radiators work and look great - just not the look we are after.


I want the home to look when finished to have just been completed in the late 30's to early 50's. The amount of contemporary radiators out on the market blows my mind. You could almost start your whole home design around which radiators you want to use.


JW -

I have all old 6 tube CI radiators in my house. I found them at a local salvage yard. sandblasted, tested and re-fitted them, painted them to match the room colors, so some are beige, some are a light seafoam green, a couple are white, the one in the bathroom is dark tan. If I get them up to load and shoot them with my digi-temp, they all read the same.

Some just look like wall art...but cost a lot more