One-Pipe Steam – Radiator Sizing and Removal During First-Floor Renovation

I don't think 15% oversized would be a problem and you can balance it out as conditions merit but I would err on the side of leaving rather than removing radiators since there is little benefit of reducing standing radiation if leaving the same assumedly working boiler. If a room is a bit warm slow down the radiator or add a TRV. Bathroom radiator would obviously go but why go through the trouble of swapping a 60 edr for 40 edr if you can just slow it down. If any drafts remain in the house they will end up at the floor of the sunken living room…

Kitchens are always hard. We want more cabinet and counter space and radiators are in the way. I would suggest electric radiant in the floor. Under what I might assume will be tile? Same goes for bathrooms.

@steamboilernovice , the way to determine how big a radiator is needed for a given room, is to perform a heat loss calculation on the room. When you know the room's heat loss at "design" (typically 70°F inside and 0°F outside, but this can vary depending on where you are) divide that by 240 to find the square feet of radiation. Then you can pick a radiator that will work.

There are several apps that can do the heat loss. You tell them what building materials are there, including insulation, window upgrades etc. and the program will run the numbers for you.

I don't recommend electric radiant floors in a "wet" room like a bathroom or kitchen. If water gets into the floor it will short out the radiant and can create a shock hazard.

Hydronic radiant, yes.

I've done only electric mats under tile in bathrooms. I think the key is whether you are doing it for comfort or for heat. I am doing it for comfort, not heat. The bathrooms in this case get for the most part enough heat from adjacent rooms. We turn it on in the evening in the winter so it's toasty on your feet brushing your teeth. On cold nights we often leave it on at a low setting to take the edge off on those nocturnal bathroom visits. Again, I would not want to depend on it for basic heat in a larger room, particularly a kitchen. Maybe a mat in front of the sink for when doing dishes…

You will need to consider the kitchen and the living room areas as one space — and it's not square feet of area, but total exterior wall area and windows that is of interest. I would treat the mudroom separately, despite the opening into the kitchen — but don't forget to include the exterior wall in the laundry area in the numbers! Opinions will probably vary on the bathroom. There is a fair amount of wall area there — but not that much effective floor area for the radiant (I estimate around 12 square feet) and am concerned that there may not be enough area to meet the BTUh requirement of the exterior wall As you note, however, getttng a steam radiator in there could be difficult! Run the numbers and see what really is happening. You might want to consider both electric radiant floor — and electric radiant in the ceiling.

If you want steam heat in the bathroom but don't have space for a radiator, you might consider the traditional New York City practice of running a vertical steam pipe in the corner with an air vent and cap at the top.

@steamboilernovice

After reading the above post I was going to also recommend a heat loss calculation room x room. I see you have done that so that is good.

Now the trick is to balance the radiation to their rooms heat loss. You going to need to make the radiation meet the rooms heat loss as close as you can Let's say all your radiation room x room = the heat loss + or - 10% or so you should be fine. If some rooms the radiation is say 50% over heat loss and other rooms match the heat loss you will have balancing issues.

Hope this makes sense. Good luck with your project.

Did you not see the part next to his name that said 27,898 posts?

Now it's up to you of course, but you might want to take his advice…

Well, you did ask for advice without offering to pay for it. Then of course, you got that advice, free of charge. The people who contributed on it have over 58,000 posts so far and counting. Whereas you have just 2.

Good luck.