Curious if I’m overthinking my heating need for my basement renovation. 115′ perimeter, 50% above grade, all walls R15 closed cell, 7′ ceilings with new 4″ poured slab, 85sf of replacement R3 windows and a door. We run a 125k steam boiler with insulated pipes, that certainly throws off some heat. Call it 75 BTU/degree hour, with a 9F design temp, 4500 BTU/hr not including the boiler gains back of the napkin math? What about the slab loss? I can add a 7k mini split head on to my multi split compressor pretty easily, but even that seems overkill. The reality is we usually average around 30F in the winter months, so it’s probably half that the majority of the year. And I imagine we’ll keep the heat 60-65 and just bump it up nights and weekends /as needed.

Right now we’ve had multiple 100F days and it’s 68F and cool, with zero insulation and a couple leaky windows and a door. Can’t imagine there is any cooling load. And mini split heads don’t dehumidify well if they aren’t actively cooling.

Do I need to think about humidity? It’ll have a new vapor barrier under the slab. I’m almost thinking just throw heat strips in there with an in-wall dehumidifier instead of the mini split wall head. Any suggestions? Could I use an inwall dehumidifier like this? https://s3-assets.sylvane.com/media/documents/products/spec-sheet-ultra-aire-in-wall-dehumidifier-md33-r454b.pdf