Floor construction with waterborne underfloor heating in basement

[AcidSleeper]

Hello.

I would like to add that I have tried reading and searching but haven't found exactly what applies to my situation.

Today, the floor construction looks as follows: slab, 150mm insulation (Gullfiber), 70mm joists attached to the wall structure, 22mm chipboard, vinyl flooring.

I'm going to convert the room from storage to a bathroom and will install water-based underfloor heating and wet room flooring.

How should my construction look?
I want to keep the same floor level (lower height works, but not higher)!

Thanks in advance!

 

[Tommor]

I think you should skip underfloor heating in the basement since you have so little insulation and don't want to build up in height. There is an underfloor heating system from LK along with a raised floor from Nivell.

But as mentioned, I don't think underfloor heating should be added in houses with little insulation, especially in basements, since there will be a lot of moisture migration with the risk of moisture damage...

 

[AcidSleeper]

I've seen several other threads with people installing underfloor heating in basements, and I also know several friends who have underfloor heating in basements. You should just be aware that you shouldn't turn off the heating in the summer!?

Back to my floor: The Nivell system and LK underfloor heating, does anyone have experience with this?

 

[Tommor]

yes it works but it's nothing to recommend unless you have at least 400mm insulation...
when you install with nivell, you also get an air gap between the concrete and insulation. then lk 16 slot board with reflection plate..
then you always have this that you can use ...
http://www.lksystems.se/sv/LK-Syste...ystem/Pa-barande-golv/LK-Sparskiva-XPS-30-50/

 

[AcidSleeper]

Oh, it seems not everyone recommends underfloor heating....

So how do you think I should construct my floor?
I don't want a cold floor!!!!!!!!

 

[ronolo]

It's perfectly fine to install underfloor heating in the basement. We have placed 100mm of foam insulation on the old uninsulated slab and poured a new 100mm slab with waterborne underfloor heating on top of that. It uses less than 6000kwh/year (geothermal heating) for 200sqm, of which the basement accounts for 1/3 of the area, so I don't think 400mm of foam insulation is a requirement. 30mm was LK's recommended minimum at the time, 2008.

 

[Tommor]

It's perfectly fine to install underfloor heating in the basement. We laid 100mm of insulation on the old uninsulated slab and on top of that poured a new 100mm slab with waterborne underfloor heating. It consumes under 6000kWh/year (geothermal energy) for 200sqm, of which 1/3 is the basement area, so I don't think 400mm of insulation is necessary. 30mm was LK's recommended minimum at the time, 2008.

and the recommended minimum is 200-300mm today... and that's the minimum...
now I wasn't specifically referring to economy, but construction techniques...
but to say that 100mm is enough as you say is just misleading OP, that's where you can talk about hidden faults when it's time to sell...

 

[Tommor]

30mm is, by the way, the overlay thickness on 16 pipes....

 

[gnuttisch]

You should know that there are many who form strong opinions based on what other opinion makers have written. It's like the blind leading the blind, so to speak.

What does your drainage look like today?
Plastic flooring is not recommended as it doesn't breathe; everything in a basement must be able to breathe.
Insulate as much as you can based on the building height; underfloor heating is for comfort. If you think you can spend a few extra bucks on heating, then do it.

 

[Fred vom Jupiter]

When I looked at the tables, I concluded that 7-8 cm of cellplast would be sufficient for my house. 30 cm is probably for a new slab above ground? 10 cm should suffice for a typical house with a basement.

 

[ronolo]

and the recommended minimum is 200-300mm as of today's date... and that is the minimum.. now it wasn't exactly the economy I was referring to, mind you, but construction techniques... but to say that 100mm is enough is just to mislead TS, there you can talk about a hidden fault when it's time to sell...

For new construction, yes. To disqualify everyone who is not building new, or tearing out the entire basement, from installing underfloor heating, I think is an incorrect recommendation based on personal experience. For example, 100mm works fine provided you have a surface layer that breathes. Properly executed drainage is probably recommended. The risk of reverse moisture migration increases the less insulation used.

A hidden fault in this case would mean that the seller has tried to hide something from the buyer. If you can't stand by your work and provide documentation of the work done at a potential sale, I don't think you should do it at all.

 

[Tommor]

If you believe that 10 cm insulation is sufficient, that's up to you, but I would never install underfloor heating under those conditions. But there is a difference between craftsmen and craftsmen...

 

[Tommor]

And basements are especially important to have good insulation to avoid the risk of moisture migration...

 

[gnuttisch]

If everything breathes and the walls are painted with silicate and one has good ventilation, no one still knows what the problem is with reverse moisture migration. Anyone who can prove they've had a problem with it? Haven't read about anyone who has had problems with it after a few years.

 

[anders07]

We have Nivell (with fan) and then LK EPS16 on top of it. We have a slab on ground, so we didn't dare to risk building any structure that might later have moisture problems. The slab was dry, and two out of three builders said Nivell was unnecessary, but with a slab on ground we preferred to be safe rather than sorry...

Isolating directly on the slab and casting over it seems to be a sensible option if you have the ceiling height for it. We only had a maximum of 140mm for the floor construction, so it was tight with Nivell, but it worked out...