I know the answer - yes and no, it depends... I apologize in advance for the long post, but I want to get as much detail in here as I can.
I have an 1878 house that I bought in May 2013. The house is essentially a two story structure of 700 sqft per story, there is also an original one story kitchen addition of 400 sqft and a closed in porch of 150 sqft.
Shortly after I bought the home I did an energy audit which said that I needed to tighten up bypasses in the attics and spray foam the rim joist, which I plan to do. Currently we have one air exchange per hour, and we are in MN, so this leads to a lot of heating of the house in the winter. I imagine that if I seal most of the bypasses and add more attic insulation, this would improve the situation substantially.
The second story has been remodeled in the last 10 years and have wall insulation, the wall insulation in the downstairs is non-existent, except for in the porch, which is fully insulated. I also plan to add insulation in the attics to get to R-50, from current R-19. The floor is 1" subfloor and 3/4" pine on top.
I am hoping to do staple up radiant because I love warm floors (and my wife hates the baseboard heaters, which line the exterior walls in most rooms).
I have not done a load calculation, but here is some data that I have.
The house is heated with natural gas, and last winter, which was cold (lowest was -44 with wind chill),
had an average daily use of natural gas (both stories of the house) of a
little less than 10.5 therms/day in January and February. The main
floor is about 1100 square feet, so it gives me a little less than 40
btu/hr/sqft (not taking into account that part of the 11 therms that was used
for heating the 2nd floor (separate heating zone).
The boiler output is 83000 BTU/hr.
We have a total of 141 linear feet of baseboard heaters in the house --> 70000 btu @ 500 btu/linear foot.
The main floor comprises 48000 btu @ 500 btu/linear foot, which gives me about 43.5btu/hr/sqft for the main floor.
My wife would like to get rid of all baseboard heat, don't know if this is possible, could do one or two runtal wall radiators in strategic locations as the piping is available, but would prefer to have as few as possible.
Now, is staple up possible?
I heard from one company that I would need to add wall insulation before doing anything,
another specified 7/8 PEX ($2k), and
a third specified 1/2" PEX with extruded plates ($8k).
What do I need? Can I go with less heavy duty plates and save some money, or would it not get warm enough? Of the $8k, $3k was the heating plates.
Sorry for the long note, but I wanted to get as much info as possible crammed in.