I'm getting ready to renovate a bathroom, and looking for advice on converting the heat in the room from baseboard to under floor radiant. The bathroom is small, only 5x8.

I'm happy with the performance of the heating system in the rest of the house, but would like to take the chill out of the bathroom tile floor in the winter months.

The house is a 900 sq foot single story ranch. All rooms are heated by baseboard convectors on a single zone. The boiler is a high efficiency modulating boiler w/ outdoor reset.

Initially, I thought about re-running the pex under the floor using the Uponor joist track system from below. However, the heating zone is plumbed with 5/8" hePEX, and the joist track seems to call for a max of 1/2" pex. Reducing the pipe diameter for the joist track, then increasing again to meet with the rest of the zone seems like a bad idea, though I'm no expert.

What about staple up systems? I imagine they transfer heat the subfloor less efficiently than with the aluminum plates, but that wouldn't reduce flow to rest of the house if I kept the same diameter pex.

A friend suggested using an electric mat under the tile floor, but I'm less inclined to go that route due to the high cost of electricity here in New England, especially where I already have the boiler.