Radiant flooring for a Minnesota house on a floating concrete slab

HeatingHelp

This discussion was created from comments split from: Most economical in floor heating.

CrystalM77

Hello! I live in Minnesota and just purchased a house that is a concrete slab. They didn’t note it was a floating slab which means it’s FREEZING. The house has no heat or cooling and I’m wanting to do in floor heating I have a combi boiler 180k BTU and pex. Now I’m trying to figure out how to lay the pex. I’m trying to keep it under $5k due to having only 1 income. How do I attach and what do I put under the pex for insulation? The house is 1100 sq ft I have 1000ft of pex. I want it to be a continuous run with 1 zone so I’m guessing I don’t need a manifold for the floor just the house water??? TIA 

hot_rod

A slab suspended above the grade somehow? Is that what you mean by floating?

If so the bottom and edges would need considerable insulation R-value if you intend to warm it.

But that is true regardless of the type of heating system.

Or are you thinking about an over pour with radiant? If so you need to consider the additional weight of an over pour.

WMno57

Hi @CrystalM77 Welcome to HeatinHelp. No heating or cooling currently? Assume the home was recently built? Building code and inspection may have required there to be foam insulation under the slab. If it wasn't built to code and inspected, then who knows?
How much ceiling height can you afford to lose? You need at least 4 inches of foam. Some other form of heating may make more sense if the slab is not already insulated.
@Erin Holohan Haskell could you split Crystal's case off to a new discussion please?

jumper

Depends on time frame. In long run solar powered "deep ground heat" will be most economical. Idea is that you can heat the ground during summer with solar thermal or year round with PV resistance. Eventually slab will always be warm. Decades ago when & where off peak electricity was almost free some industrial facilities used this technology. A company called Indeeco promoted it. Hopefully outside foundation was insulated.

I'm surprised that homes with solar heat plus radiant floors don't do it.

This method is opposite to EdTheHeaterMan's. And I truly mean no disrespect.

Erin Holohan Haskell

Welcome @CrystalM77! I've created a new discussion for you here so that your post doesn't get lost at the bottom of an older discussion.

Hot_water_fan

You want parallel loops. Probably 4, so you’ll need a manifold of some variety. You want loops because 1. Head loss of 1000 ft of pex is high and 2. Your floor will still be cold at the end of 1000ft, which is exactly the issue this is trying to solve. 

You want a closed system, so you won’t be connected to the house water at all except for the initial fill and possible make up water. 

You also need a heat loss. With 1000 sqft, you’re limited to about 20-30kbtu, if everything goes right. If that’s more than your heat loss, you’re good to go!

If budget is an issue, which it seems to be, you’ve picked a really expensive way to heat a house!