Browse Forums Heating, Cooling & Insulation Re: Insulating under slab, much benefit in this situation? 5Apr 11, 2018 11:40 pm We had a waffle slab (class M soil on a flat site), and the insulation was just laid as a flat base under the entire slab (with the waffle pods then placed on top). There's a photo of our insulation going down in this post on our build thread (second photo); you can see the slab edge insulation on the inside of the perimeter formwork. The base was levelled with standard concrete sub-base gravel; I imagine that you want it as level as possible to avoid gaps in the insulation (and to make sure the insulation evenly carries the load of the house to the ground across the entire slab base). There's other ways to do slab-edge insulation by attaching it later, but pouring the concrete directly against it avoids gaps and cavities. The insulation sheets are just placed at right-angles at the edges, and my understanding is that this is also what's done for insulating beams; also see page 6 of this brochure about Knauf ClimaFoam for angled profiles. Re: Insulating under slab, much benefit in this situation? 7Apr 12, 2018 8:55 pm I found this resource very useful when it gets to slab insulation and thermal breaks between external and internal slabs: https://www.laros.com.au/resources-solu ... -drawings/ They are offering some cool thermal break products too. Re: Insulating under slab, much benefit in this situation? 8Apr 12, 2018 9:09 pm Could you not just use the same insulation product between the slabs? Re: Insulating under slab, much benefit in this situation? 9Apr 14, 2018 4:46 pm Thanks for the Laros link, those diagrams are helpful and those thermal blocks could be part of the solution. - It would be using the same insulation product between the slabs, would just need to figure out how to keep the slabs structurally connected without too much messing around/increased cost. Re: Insulating under slab, much benefit in this situation? 10May 11, 2019 10:07 am Hi there Just wondering if you’ve moved in to your house yet and had a chance to feel the difference in the floor temp with the slab insulation? We are building in vic on a stifn raft slab and putting in 50mm under slab and around the perimeter. Would be good to get some real world feedback. Re: Insulating under slab, much benefit in this situation? 11May 11, 2019 5:38 pm Under slab insulation itself won't help much in regulating floor temp. The floor will be felt a couple of degrees warmer though, but surely not as warm as the inside walls (esp. tiles, so I would still advice to use warmer timber floors if it is a concern). Concrete slab has a thermal mass effect and the ground temperature is close to constant, so it will be smoothing out significant differences with the flywheel effect, so it will be always something average between the ground temperature and inside temperature. Insulation works better when there is a difference in temperatures (it slows down the effect), so in your scenario it will be working well towards preventing energy escape through the floor, so overall energy efficiency of your house will be high, but that won't necessarily be projected into the "warm" floors, just "slightly warmer". Re: Insulating under slab, much benefit in this situation? 12May 15, 2019 12:11 pm alexp79 Under slab insulation itself won't help much in regulating floor temp. The floor will be felt a couple of degrees warmer though, but surely not as warm as the inside walls (esp. tiles, so I would still advice to use warmer timber floors if it is a concern). Concrete slab has a thermal mass effect and the ground temperature is close to constant, so it will be smoothing out significant differences with the flywheel effect, so it will be always something average between the ground temperature and inside temperature. Insulation works better when there is a difference in temperatures (it slows down the effect), so in your scenario it will be working well towards preventing energy escape through the floor, so overall energy efficiency of your house will be high, but that won't necessarily be projected into the "warm" floors, just "slightly warmer". thanks for the reply, yes i'm across all that. I was interested to know if the insulation takes the chill off a tiled floor in winter You might be able to apply to divert the sewer at your expense. In NSW you would contact a Water services co-ordinator and they would give you advice as to whether or not… 1 16459 4 5285 To me, that's what it looks like: poor backfilling and/or compaction. The width is about 1000mm maybe. That conduit in the photo is for the NBN. The water is about… 4 8493 |