Floor Insulation

TripMeUp

Registered User
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Hey all,


I know there is already a lot of info around on this but it is hard to collate and then make sense of (for me anyways!!)
On a new self- build, with regard to floor insulation, I will have UFH downstairs and so have decided to put 125mm insulation on the Ground Floor, then the UFH pipes and then the screed of say 65mm. I read somewhere here that it is best to put this 125mm down in layers with joints staggered, so how would 125mm be best broke down into layers? i.e. in 2 or 3 separate layers?
Someone mentioned to me that I should prevent heat loss into the walls and foundation by putting 50mm insulation in around the wall perimeters also. How does this work?
Does this go in standing up vertically along the walls of each room to a height of 125mm with the horizontal layers pushed tight up against it, so that after the screed is poured, the screed covers over the horizontal insulation and the top of this vertically standing insulation?
Am trying to save expenses, so am I right in saying that this is something I could do myself? Once floor slab is level and cleared completely, could I do as outlined above, making sure everything is put in tightly and then let the Plumber in to do UFH?

Upstairs, I will have a concrete slab floor with room heating by Radiators? Firstly, do I need to wrap the slab in anything to seal from below? For floor insulation here, I presume that you would not need 125mm here though? What would the recommended be to achieve a good level of insulation or given it is Rads , do I need any at all? Do I also need to do the vertical insulation here if the rooms are made up of timber studding?
Thanks for any help,
 
Two layers of insulation would be fine, you should be able to get 75mm and 50mm. We usually use 25mm kingspan strips for the perimeter insulation These are 150mm and stand vertcally against the walls, flush with the finished floor level. You can use the floor insulation to wedge these in place, however a few dabs of gripfill is advisable to keep them in place as they can float when pouring the screed and its much easier to make sure they'll stay put beforehand rather than trying to fix them during the pour. Also, if they do move and stand proud of the floor, it makes powerfloating awkward. 65mm of a screed is a bit skimpy IMO, for UFH screeds, we normally lay 80-85mm.
 
Hi Baldyman, (feels rude typing that!!)

Thanks for the info, very useful

Any ideas about upstairs? Also, in terms of the floor perimeter insulation for downstairs, should I still put this in if their has been perimeter insulation fitted in behind the radon barrier?

thanks again
 
I'm only knowledgeable on the groundworks side of things, so I won't claim to know anything about the first floor - maybe one of the plumbers on here can help you there.

I don't understand why the perimeter insulation would have been fitted before the radon barrier but if neither can I see a problem with it. It should be fine, there would be no need for another board there IMO. Just to confirm, you fitted the perimeter insulation, then laid the radon barrier, turned it up the insulation board and then over the block and down into the cavity?Am I correct in this assumption? If so, it sounds ok to me, drive on with the floor insulation. Hope you remembered the radon sump and outlet pipe!
 
Hi again,

"I don't understand why the perimeter insulation would have been fitted before the radon barrier but if neither can I see a problem with it. It should be fine, there would be no need for another board there IMO. Just to confirm, you fitted the perimeter insulation, then laid the radon barrier, turned it up the insulation board and then over the block and down into the cavity?Am I correct in this assumption? If so, it sounds ok to me, drive on with the floor insulation. Hope you remembered the radon sump and outlet pipe!"

The above is exactly what was done, including remembering the sump and outlet pipe!!
But of course this is only around the external walls so should I not proceed with doing this around each room's internal walls when laying the floor insulation??
Just to let you know the order of things so far, we let plumber put his piping in for various things and then poured the subfloor slab..we will then put the floor insulation down, then the UFH and then the screed...so what do you think, will the perimeter insulation in each room help or be required????

thanks
 
The perimeter insulation on the internal walls is a relatively new fad, I've only done it on one house in the last 12 months. IMHO its a bit OTT, but it's not a major expense, especially if you can do it yourself so, for the sake of it, you might as well put it in.If you don't you'll only be wondering if your bills would have been lower.
 
We were advised to put in the perimeter insulation as well by our heating company. There reasoning was to do with thermal bridging where the heat would hit the cold external wall and try to heat that up as well which takes heat from the floor. As baldyman27 said it's not a major expense so will be worth it in the long run.
 
Cheers for the help guys....
Sounds relatively cheap and straightforward so will go at it myself....

If anyone has any ideas on the upstairs slab and floors, please let me know....

thanks again
 
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