New Arrival

[Jeremy Harris]

Are you set on beam and block for the ground floor?

 

The reason I ask is that a reinforced slab cast on to cheap EPS, directly onto a prepared sub-base can be pretty cheap, and you can just cable tie UFH pipes to the steel reinforcement before the slab is cast, then power float the slab to get a very smooth and flat floor.  No screed is necessary, so there's no lengthy drying out period.  You get a floor that works like a giant storage heater, and that can cool and heat the house (with the right pipe work) and the heat losses will be lower than a suspended floor for any given thickness of insulation, as the ground rarely drops below about 7 to 8 deg C in winter, whereas the air under a suspended floor will be close to outside air temperature, so could be sub-zero in winter.

 

 

Edited May 5, 2017 by JSHarris

[Nickfromwales]

1 hour ago, DNA said:

I clearly need to read up on what seems to be the dark arts of insulation. More urgently, I'm trying to make my mind up about tetris vs PIR slab insulation over my beam and block. I had already made my mind up on this but insulation pricing is causing a re-think.

 

Any experiences chaps? ....I'm working through a cost exercise right now.

Better to pay once for insulation, rather than pay forever the increasing energy bills. 

[DNA]

I'm just going through costs now Jeremy. I had originally planned for a ground slab but the ammount of fill needed means that its pretty much more expensive than block and beam. Not sure I like the using the groundslab for the underfloor heating though. Its a lot thicker than a screed and will be less responsive - I know the underfloor heating is meant to maintain an ambient temp but some responsiveness makes it much more user friendly.

 

I'm also not sure about heat losses as with insulation of top of the beams you essentially isolate the beams from the heated interior - so cold beams / hot screed kind of principle

 

[Jeremy Harris]

Our UFH in slab is brilliant, it both heats and cools and provides very good temperature regulation.  It's sat on 300mm of EPS, and the reinforced concrete slab is 100mm thick (not much thicker than some screeds), and the response time is fine, as it only needs to warm up a fraction to contribute a fair bit of heat into the house.

 

With beams, they can be a lot colder than the ground, though, as they are close to outside air temperature, so you need thicker insulation to keep the losses the same.

Edited May 5, 2017 by JSHarris

[Triassic]

I agree with Jeremy, UFH in the slab is far superior, to the extent that I'm doing it in my, soon to be installed, slab.

Edited May 5, 2017 by Triassic

[Simplysimon]

2 hours ago, DNA said:

I'm just going through costs now Jeremy. I had originally planned for a ground slab but the ammount of fill needed means that its pretty much more expensive than block and beam. Not sure I like the using the groundstab for the underfloor heating though. Its a lot thicker than a screed and will be less responsive - I know the underfloor heating is meant to maintain an ambient temp but some responsiveness makes it much more user friendly.

 

I'm also not sure about heat losses as with insulation of top of the beams you essentially issolate the beams from the heated interior - so cold beams / hot scren kind of principle

 

 

 

very similar story here, too much to dig out and fill so beam and block u value of 0.09 and ufh

engineer - underbuilding #2.pdf

Edited May 5, 2017 by Simplysimon
missed a zero

[DNA]

I think I need a beer now as this has caused me to really re-think!  I also just did a quick google on EPS and its circa £20 / 100mm sheet.

 

So i'm going to price up the following:

• Block and beam with options of concrete block or aircrete block and both with 110mm PIR and UFH in 60mm liquid screed;
• 100mm mesh re-enforced ground slab powerfloated with UFH on 300mm EPS on compacted type 1 MOT;
• Also going to have a look at Tetris with Block and beam and 75mm mesh re-enforced structural screed;

Any other options chaps in case I miss something

[ProDave]

There is always conventional strip foundations and an insulated timber floor, like we have.

 

Re insulation types and decrement delay.

 

We have a timber vaulted warm roof covered in 100mm wood fibre board, and then 200mm of Earthwoll between the rafters.  I have been working today right up in the top of the vaulted roof on the mezanine floor. The sun has been shining on it all day. It was not overheating up there at all, and my IR thermometer could not detect any difference in the internal temperature of the part of the roof compared to any other part of the structure. In fact the only solar gain I could detect was the considerable warming of the floor where the sun was shining on it through the windows.

 

 

[Simplysimon]

tetris - £40/m2  supply and delivered

[DNA]

I got a range of tetris prices last week ranging from something like £20 for 90mm (i think) through to 160mm at £28. - Insulation only though - no beams.

 

What's interesting about Jeremy's suggestion it the fact that I have got some big spans and on the margins of 150mm beams - another ground slab reason

[DNA]

Sorry Dave not a big fan of timber especially on the ground floor

[Simplysimon]

to be fair, to get u value i was looking at 160mm tetris with 75mm on top, that price was only for insulation!

[DNA]

Thought so Simon. Interesting floor srtucture on your plans though. Why did the engineer specify blinded hardcore beneath the beams as one of the benefits is avoiding the need for infill etc

[DNA]

Have you got any section details of your roof Dave as it sounds very effective. Not sure if I've the room to fit it in but it sounds a good solution

[Simplysimon]

bloody good question!, he went for slab first but massive spec and i said no.

[DNA]

Sounds familiar Simon and just about where I am right now - though haven't coughed up for the infil yet!

 

I've also got some as dug spoil from the reduced site area which I'd love to also just put back beneath the beams - its exactly where it came from and its just another cost to get rid of it.

[CC45]

Our spoil went back under the beams.  We put 225mm of pir on top of the B&B then 75 screed (could use less) with ufh in it.  Wecalso had to build up off the original ground so slab wasnt feasible.  It should be warm.

[PeterW]

3 hours ago, DNA said:

I also just did a quick google on EPS and its circa £20 / 100mm sheet.

 

Errrr... £10.65 from my BM..!

 

EPS is roughly 40% of the cost of PUR, and you need around 2.5 times as much. The benefit on PUR is less dig out, EPS makes for a better fully insulated slab 

[DNA]

That was pretty much my floor structure CC45 but I still like the groundslab approach which I've done before but on that job I laid PIR and UFH in a screed on top of the concrete. Its putting the UFH in the concrete slab as Jeremy suggested thats got me thinking now.

 

Which BM did you use Peter as I only took the first google price to start thinking about this. Anyone used Jablite 'Fillmaster' as well as its a single 300mm slab?

[Nickfromwales]

13 hours ago, DNA said:

Sorry Dave not a big fan of timber especially on the ground floor

Me neither. Only thing that your maybe not allowing for here, on this forum, is that most here are building airtight homes to near passive specification ( or better ) and the same logic does not apply. . 

Having a ventilated suspended timber floor, insulated to current BRegs ( so in a regular build ) is the devils handiwork IMO, and a suspended, ventilated B&B floor sitting at external air temp probably worse as it will keep the 'cold' for longer. . Why make a floor that is inherantly cold only to then have to over insulate it to keep it comfortable and economical to heat ?

@DNA. Might I suggest you spend an hour today reading Jeremy's ( @JSHarris )'s blog . I think you'll find a lot of what has been / is being discussed here in those pages, and the actual REAL life results. 

[Jeremy Harris]

The photos of our slab and UFH going down are in this entry: http://www.mayfly.eu/2013/10/part-sixteen-fun-and-games-in-the-mud/

[Nickfromwales]

Lol. I was going to link this entry bingo but you beat me to it.  

[DNA]

Thanks both. I'll take a look. I did look as Isolohr initially I just coudnt make the numbers add up.

[PeterW]

 

5 hours ago, DNA said:

That was pretty much my floor structure CC45 but I still like the groundslab approach which I've done before but on that job I laid PIR and UFH in a screed on top of the concrete. Its putting the UFH in the concrete slab as Jeremy suggested thats got me thinking now.

 

Which BM did you use Peter as I only took the first google price to start thinking about this. Anyone used Jablite 'Fillmaster' as well as its a single 300mm slab?

 

I use MKM but TP are the same. 

 

Fillmaster is not what you want - it's a commercial product for filling bridges and embankments ..!

 

depending on  where you are in the U.K. you can get it for £10 for 100mm and you just build up the layers - quick and easy

[Ferdinand]

If £10 (plus VAT?) is a TP price we should be able to beat that.

Is there a Seconds & Co for EPS?