(repost from "building a home" forum)

So, even though I am super busy trying to beat winter and get a roof up, I know I have to be ready to get my heating system in place soon.

We are planning on using underfloor radiant heat with Al plates. We want to use a Munchkin Contender Boiler (or something similar) and have indirect domestic hot water.

My engineer that did my energy Calcs came up with a minimum load total of 68,439 BTU per hour. Using Slantfin, I came up with 50,000 BTU's per hour.

We use a woodstove to provide much of our heat. It is rated at 60,000 btu's per hour. We would like to set (and leave) the radiant and a low temp (just comfortable) and then use the wood heat to bring the warmth to where we want it.

I have talked to a few companies and I have received many different answers. They range from using 1/2" pex with no plates to 7/8" pex with plates. Many also quoted me with tankless water heaters, even though I asked to be quoted with Mod/con boiler and indirect DHW.

I am uncertain if my heat load calcs are correct (the seem high). It is a two story house with the master bed and bath in the loft. It has a large vaulted dining and living room. It is 2025 sqft, basically a 28'x44' building with about 2/3rds of second floor a loft. We have a whole bunch of large windows. I am using R21 in the walls, R38 in the ceiling, and R19 in the floor. The second floor will not be heated and I want to use a single zone.

I guess I am looking for some direction. I will be doing the majority of the work by myself. What would you do in my position?