Over the years we have been slowly improving the performance of our hot water heating system, thanks to much advice obtained here. We have two other issues that still need addressed and the family is asking that I focus in on one of those before winter arrives.
We have a small 70's addition to our 1938 house, it is only 5x7, but contains a door and two windows. It is divided into two parts, a heavily used entry/exit and a bathroom. The whole area sticks out from the house and is over a crawl space. When the area was built out, those that be installed cast iron baseboard; a 2 foot section in the entry and a 2 foot section in the bathroom. The rest of the house has oversized CI radiators. The boiler usually only heats the system up to about 130 degrees until the stats are satisfied. On 5 degree design days last year I noticed the water temp getting up to ~137 degrees. The boiler is a two year old Slant/Fin and the run times are 35-60 minutes at a time, so there is no short cycling.
The bathroom and entry, as described above, are significantly colder than the rest of the house, and being somewhat isolated, don't get much natural airflow from the rest of the house. Fixing an electrical issue 2 years ago, we spray foamed the rafters in the ceiling and stuffed the walls of insulation. I hope to insulate the crawlspace in the future, but I think the sill of this addition was never sealed right, and until we put new siding on the house, that won't get fixed.
Slant/FIn's Heat Loss calculator is telling me that, even after insulating, I still need ~2300btu/hr for the space. The current cast iron baseboard, operating at 130-140 degrees, is only putting out a total ~1360btu/hr according to the specs I can find online.
I had two quotes for possible work to correct this, and I was wondering if anyone had some thoughts.
Quote 1: Install High-Output Slant/Fin Baseboard. The Multi-Pak 93 with the H-1 3/4" element, total of 5 1/2 feet of length in the two areas (3 feet in the bathroom where there is more room and 2 1/2 feet in the hallway.) They estimate this would put out 2100-2300 btu/hr.
Quote 2: Install two small panel radiators, one in the entry and one in the bath. The Buderus Model 21, 12" x 24" (970btu) for the bath and the entry would get a Buderus Model 21, 20" x 24" (~1400btu) . The estimated output total for the area was is ~2300btu/hr.
I have heard it is not a good idea to mix baseboard and cast iron radiators, but the installers for quote 1 said that because I have long run times on the boiler it would be okay. Would anyone have any thoughts or suggestions?