While you are under the floor, check the possibility of insulating adding a vapor barrier.

And definitely caulk around all the doors and windows and anywhere pipes or wires pass through the walls ... it makes a huge difference in comfort.

Good advice lazygardens! We have a lot to do in that regard, it's a little overwhelming. We've been putting off tearing the basement ceiling down because of the work (stucco on wire) and the mess and expense (abatement). We updated the electrical before we moved in 5 years ago, but now have plumbing and HVAC to do. For my sanity we did the kitchen and enlarged the family bath. Now it's time to do the not so fun but oh so necessary stuff. Our yard is bordered on the side by the alley in a very dusty part of the country so I am looking forward to getting rid of the forced air. Having the honed AB in the kitchen reminds me everyday what's being pushed through our home.

Oh, how I wish in-floor heating were affordable 8 years ago when I started actually using my kitchen.

My house has the heat retention of a sieve.
I don't have many options, so I picked up several toe-kick Braun low-voltage heaters. They have thermostat control, so it can be governed.

I'm not saying this is a good solution for you, when you have in-floor heating as an option, but I thought I'd offer.

Just wish the installer person had actually hooked these up when he was here ... in ... MAY. I have 4, but so far and just plain freezing.

"My house has the heat retention of a sieve."
HeeHee.
I'd guffaw, but a little too close to home. We have always planned on the in floor, under floor I should say, heat but it was put on the back burner. Like I said, we live in dust central with pets and any help in the cleaning department makes the cleaning person (MOI) more pleasant to be around! I think I had those Braun in a previous house and they actually worked pretty well.