Am I being dumb ? - ICF floors, UFH and thermal bridging

[cliftonarms]

Almost all ICF suppliers have a concrete flooring beam product that attaches to the wall. All normally show UFH embedded in these floors.

 

Am I being a bit dumb in suggesting that this is a huge thermal bridge / dump of 30'C floor heat into the 10-15'C concrete wall core. And hence a big waste of floor heating energy into the wall core.

 

Am I missing something?

 

I'm looking to design in wet UFH floors for basement, ground and first floor, but dont see how ICF decks can be used on the ground and first floors without thermal bridging to the walls, ( basement will be insulated slab )

 

Someone please tell me I am being stupid !!!

Edited November 3, 2022 by cliftonarms
spelling

[Conor]

You put 50mm insulation on top of the deck, then UFH pipes, then 50mm liquid insulation.

 

As the ICF core is behind a fair bit of insulation, it's not a true cold bridge. E.g. on ours we have 175mm insulation on the outside and 75mm On the inside.

 

The deck you've shown above is a composite deck with structural screed. You wouldn't normally do that here (unless e.g. a garage) a standard prestressed 150mm plank system (typically 900mm wide and spans up to 5m) that fit tight together and only require a little grouting (you break the top of some of the hallow sections to bend in your wall bars). These leave a fush deck and no need for all the extra rebar and structural covering that detail shows. 

 

In the end, we used an insulated screed (TLA) over tha slabs rather than PIR boards as there was little cost difference and I didn't have the time to level everything out and lay 200m² of boards 

 

 

Edited November 4, 2022 by Conor

[Trw144]

Which ICF system did you use @Conor?

Did you add extra external insulation or was that a standard offering?

[Conor]

1 minute ago, Trw144 said:

Which ICF system did you use @Conor?

Did you add extra external insulation or was that a standard offering?

 

Amvic 300 blocks with an additional 100mm EPS on the outside. Was a lot of work but hopefully worth it!

 

(The plastic washers were later rebated in and covered with 25mm thick insulation discs before rasping and rendering)

[cliftonarms]

Excellent detailed answer @Conor and thanks for confirming I am not being dumb...

 

I especially like the insulated screed option.

Edited November 4, 2022 by cliftonarms

[Iceverge]

@Conor

 

The TLA is a very interesting concept.  

 

Would you recommend it? 

What is the surface of the screed like post pour, can it be trafficked OK or does it need protection?

Was it cost comparable to EPS boards?

 

I like the idea that ducting etc can easily be accommodated in there no cutting of boards or waste. 

 

 

[Conor]

16 hours ago, Iceverge said:

@Conor

 

The TLA is a very interesting concept.  

 

Would you recommend it? 

What is the surface of the screed like post pour, can it be trafficked OK or does it need protection?

Was it cost comparable to EPS boards?

 

I like the idea that ducting etc can easily be accommodated in there no cutting of boards or waste. 

 

 

 

For us, we had a few uneven slabs and quite a few steels protruding so laying sheets of PIR or EPS would have been a real pain. I factored in £800 of labour for two guys for two days levellimg and laying the boards. We were at a crunch time of the build with kitchen arrival immenent so dates were fixed and we didn't have the time outlrselves.

 

PIR was also through the roof at the time and hard to get, so the TLA worked out same price, if not cheaper 

 

You can walk on it in a couple of days after. It's a bit soft but fine for foot traffic. You wouldn't let a team of guys work on it all day tho. Or set a ladder on it. Same as insulation sheets really 

 

You need to get your polythene sheet and UFH pipes down within 3-5 days as the TLA becomes too hard to drive staples in. And they done tstick as well compared to PIR. We used mostly self adhesive clip rails anyway. But you still need to staple and will need a decent stapler and good hard, double barbed staples. Don't get the cheap ones off Amazon like I did!

Edited November 5, 2022 by Conor