Finishing a 1982 Colorado Basement into an apartment

bryantroll

Hello,
Thought this might be a great place to ask, hopefully it is.
I am rehabbing a concrete dome house including a 1600 square foot basement. The basement and first floor have SolaRoll radiant floor heating but as I learned here, that system at 40 years old is on borrowed time so I am looking into a replacement.
Best I can tell, the basement slab is about 4” thick and is slab on grade with no insulation or vapor barrier. The foundation walls are concrete and look to have 2” rigid foam on the outside of the concrete. The space was finished with a pool table and wet bar, and one bedroom and a full bath, but I have gutted everything. From what I’ve read, a “finished” basement in the 80s was to a lower standard than would be ideal today so I am hoping to pick the best path available to me during the rehab now. 

To start, I am trying to decide on:
1) floor insulation/vapor barrier (if any),
2) wall finishing (frame/insulate/drywall, or just leave concrete walls?)
3) a heating system that makes the most sense
4) Flooring selection is another question.

I have about 7’ ceiling height so it’s not terrible but I don’t want to lose more than I have to by way of floor thickness. 
Does it make sense for me to measure the temp of the floor and the walls to see how much of a temp delta I need to overcome? I currently just have a couple electric space heaters in the place to keep things from freezing so air temps aren’t more than 48-50.
I have been considering multi zone mini splits for a heat and AC solution for both upstairs and downstairs but haven’t made any decisions yet. Winter temps are regularly around 15 F overnight with an occasional dip to 0 F or colder. 

Is this straightforward enough that I can make a plan with everyone’s help here and doing my own research, or do I need to get a GC involved who specifically has experience finishing basements?
Thanks for any input! 

Bryan 

Jamie Hall

The combination of that uninsulated slab and very limited overhead height is kind of a killer. I would suggest considering a very thin insulation on the slab and an equally thin finished floor, just to keep the floor from feeling cold (rugs or carpet will help). I wouldn't even try to heat the slab.

I would consider panel radiators and, possibly, some radiant in the overhead, if it can be installed without reducing the overhead height. I'd also insulate the walls -- with a vapour barrier -- as you may be able to lose the space.

You might be able to get away with minisplits, but be sure to size them adequately. If it were mine I'd use a small boiler and hot water heat.

hot_rod

How will you use the space? How nice do you want it to finish out? What is the budget?

If you are going to frame inside the concrete walls, radiant walls are fairly simple to build, pex tube and transfer plates. Typically a 3' high band around the wall will cover the load.

How old is the boiler? Is it original with the solaroll install?;

If you want inexpensive heat and cool a minisplits might be a better option.

bryantroll

I plan to finish the basement into a separate 2 bed, 2 bath apartment that I will live in for at least a few years while I use the main house as a rental. I hope to own the property long term so investing in a smart system now will hopefully benefit me for years to come. With that said, I have a lot of projects and a lot of expenses so I am looking to find a happy medium, best bang for the buck value play where I can.

Unfortunately the mini-therm boiler looks to be toast… it was turned off but not drained and subsequently froze and busted. We got it operational recently to test but it’s just pouring water out all around. I do like the idea of radiant panel heat but would it be cost efficient if I also need a new boiler? Opinions on a multi-zone hyper heat mini split system from Daiken, Fujitsu, or Mitsubishi? I’m surprised they’re not more popular in the US, unless I’m missing something. I hope to add solar within 3-5 years to offset some of my electricity costs. (Also considering a heat pump HWH).

For the floor, I was thinking a minimal thickness vapor barrier / insulation layer and then vinyl plank flooring to try and help avoid too cold of floors. Thoughts? The main floor will be tile but I’m afraid that tile in the basement slab on grade will be considerably colder and not the best move. Not sure how much improvement I’d get from thin insulation plus vinyl plank flooring.

As for the walls, not a problem to fir them out and insulate and drywall, it’s just an added cost. Is the 2” rigid foam outside of the concrete walls not sufficient? Good ROI to add insulation inside the concrete also? Oh right, vapor barrier here also is smart also. 

I’m pretty bummed about abandoning the old radiant in floor heating because I love warm floors, just doesn’t seem like this house is going to be the right fit for it.
The one possibility would be if I did underfloor radiant for the rental upstairs and then also utilized the same boiler for radiant panels downstairs. Seems like that could come at substantial extra budget that I likely won’t have though, especially for a rental. 

hot_rod

I think for a rental you would want AC capacity. That puts you into either a traditional ducted system, a hi velocity system Unico or SpacePak, or a multi head mini split.
Maybe consider a small electric radiant installation for the bathroom, and kitchen area. They can be installed in the thin set below a new tile job. Works in conjunction with a forced air system.

That gets you back into the radiant game without a complete boiler redo. A perk on the rental listing, “warm tile” floors.