Mix & Match radiators - bad idea?

Tremolux

Since all attempts to go "green" and "sustainable" have gone down in flames, we're left with an old brick building that can best be heated with the existing system: hot water.



The pipes are good, so we'll mate a very high-E boiler, and a high-E water heater, ( suggestions welcome ) to the existing connections, and add the valves needed to supply radiant heat to three 1st floor rooms.



When we received our first bids for replacing the broken cast-iron units, there was sticker-shock. Using steel panel radiators was just as expensive, and had lower BTU output for comparable sizes. So much for that idea.



We did some research online and connected with a distributor of Jaga radiators, a low-water unit from Europe. Using pdf charts of BTU output with 160 degree water, and a detailed heat-load for each room, we were able to find units that would fit the available spaces, and put out the required heat. Though we don't have an exact cost, due to shipping and questions of connection hardware, it looks like they would be less than half the cost of new cast-iron or flat-panel steel.



We thought we could get away with replacing only the broken units with Jaga's, and leave the existing cast-iron units in place ( with new valves only ) on the 2nd floor. Only two upstairs cast iron radiators were cracked due to cold.



One of the HVAC contractors who toured the building recently ( to plan the radiant floor sections ) told us that since it's a two story building, with three separate units ( 2 up, 1 down ) on a single water system, the low water units on the 1st floor would shut down the boiler before the 2nd floor cast-iron radiators could get warm enough.



If that's correct, is there any ( inexpensive ) way around it?



Should the radiators we use be "all or nothing?"



Are any other radiators available in the USA that are comparable to the Jaga's?



Here are some Jaga links:



<a href="http://www.jaga-usa.com/Low.aspx#Studies">http://www.jaga-usa.com/Low.aspx#Studies</a>



<a href="http://www.jaga-usa.com/ProductDetail.aspx?ID=1_2">http://www.jaga-usa.com/ProductDetail.aspx?ID=1_2</a>



<a href="http://www.jaga-usa.com/ProductDetail.aspx?ID=1_8">http://www.jaga-usa.com/ProductDetail.aspx?ID=1_8</a>





Thanks for your time & attention.