Placing the PEX for radiant heating is relatively easy. What's not so easy is determining if this is a waste of money for you. It was for us. 1.)We live in the South, where the cooling season is longer than the heating season. Very little chance of payback unless you operate the system for longer periods. The smart boilers needed to accurately control a system in a temperate climate are pretty spendy and complicated and not very DIYable. 2.)We have wide temperature swings, sometimes daily, which magnifies the slowness of the "thermal mass pendulum." We see this just with our heated bathroom floors (separate system). It's going to be 42° tonight, so turning on the heated floors will feel good. You have to think about that a couple of hours in advance, because it takes that long to warm up. By the time they're warm, they're too warm for most of the timeframe except for that brief period that was 42°. The next day when the swing is back up to 60° and the floors are still 80°, the bathroom is too hot and needs a window opened for comfort. 3.) We insulated the new addition so well that a plain 110 volt 1500 w spaceheater can keep it 60° in the winter, and a 2 ton AC in the summer. If we'd put the money we spent on PEX towards additional insulation (we just used 2x6 construction with "standard" type insulation instead of the new high tech products) then the simple addition of the forced air furnace would have been more than sufficient for truly comfortable heating in the winter. For many people who have a long heating season and awkward spaces that forced air isn't comfortable for, radiant heating can work "miracles". For people in warmer climates, or in climates with great daily temperature fluctuations, a radiant system is very often not the best choice for either comfort or the pocketbook. Do your research well, and don't get caught up in the hype thinking it's a "must have". It isn't. And, it's sometimes even a drawback to comfort. We've never fired up the radiant in the addition. We've never needed to, even in 0° weather. And the bathrooms do work wonderfully well (imagine 6 cats lying on their backs in bliss!) but are also inefficient monetarily and for true comfort when confronted with wide temperature swings in a day. They are great when the temps say in the 40's and below for extended periods of time, but that't not how our winters here operate. It's 40 for a couple of days, then back up to 55°, then down to the high 20's, then 70° (must be Christmas day!) and then you have a 50° drop into the teens and on down to 0°. Radiant isn't very efficient or comfortable with weather like that.

A playroom? Perfect. How old are the children? I'd leave them up there and use them to accent the space for your little buckaroos. You wouldn't have to go overboard on a cowboy/cowgirl theme, just a few pieces would get the point across. It's easy to find vintage western stuff. there's some swell retro fabric on ebay or etsy for making a few pillows (or use different colored bandannas), and be sure to add a rocking horse if the children are under 7. *Not* one of those "crafty" wooden horses with rope mane and a flat seat that's about as much fun to play with as a board; a "real" Wonder horse on springs. Tacky? Perhaps, but no less so that all the gaudy colored, rounded edge, featureless plastic junk that you so often see piled up all over people's homes and yards. I also love Lindac's idea of a Gypsy Wagon, or hey, even Circus Wagon wheels. JMHO, but I think replacing them with some kind of generic pendant lighting would have all the appeal of a mausoleum, but then, growing up, my girls were known to frequently sneak a real, live pony into the house, so we probably take "play" a little more seriously than most folks... ;^)

R 13 isn't really great insulation. In addition, the Whisperkool unit isn't designed to vent to the outside. Cooling units are designed to operate within a general range of temperatures. So a fridge, an AC, and the Whisperkool unit are all designed to operate within their own unique parameters. An AC unit usually goes 25 degrees or so and expects the top temp to be somewhere in the 90s. So you get cooling down to the mid sixties or so. They don't get things quite as cold when the exterior temps are in the high 90s or 100s. A fridge is designed to cool down to the mid 30s or so, and to operate in an ambient temp of around 70. That's way past the condensation point, so you have really tight seals and super insulation. The Whisperkool is designed to cool down to about 55 or so from an ambient temp of around 70, not the 90s you may experience outside. It's not rocket science tho. If you want to get cooler, you need a larger evaporation coil and a more powerful condenser and you help the machine with tighter seals and better insulation. Thus, you can leave your door slightly ajar with a window AC unit and you'll still get fairly cool, but you wouldn't leave the fridge door slightly open. To your main question - the one degree fluctuation is not all that bad. Don't sweat it. To your larger question that you didn't ask - you're possibly overtaxing the Whisperkool unit. If it dies on you, you can replace it with a regular window AC unit. Just seriously oversize it, then tweak the thermostat - either replace / bypass it, or tape a resistor onto the probe so that it thinks the air is actually warmer than it is and it cools a bit more as a result. It's how I cool my wine cellar.

@msrose -- a fruit forward wine really can occur with any varietal or blend, but is often a style associated with certain types. But if you enjoyed the Gewurtztraminer, then you might like ones from the Alsace or from the PNW (e.g., Hogue, Chateau St. Michelle). There are also good Rieslings and Pinot Gris/Pinot Grigio from those areas. If you want something less sweet, you may want to try the Chateau St. Michelle Dry Riesling or an unoaked chardonnay/Pinot Grigio like those listed. If you find you still want a red and those other choices you tried aren't working for you, you might venture into a Zinfandel (Rancho Zabaco, budget Rosemblum slight step up). They can be fruit forward to the point of being jammy. Slightly OT, but I had read that much of the US red wine production was pushed to fruit-forward, bold wines by the palate of Robert Parker, an influential wine critic. He's the one who came up with those first 0 to 100 point ratings you see listed in advertisements, and now emulated by many publications. Thus the vintners let the fruit ripen longer on the vines, driving the sugars and resulting alcohol content up.