Perhaps this thread belongs under the plumbing category, but it is just as much about construction technology, so I'm posting my question here as well.
I have a house from -52 with an uninsulated slab on grade (no basement). On the ground floor, I am about to install underfloor heating in the relaxation room/sauna and laundry room.
My question is whether it might be worthwhile to demolish 25 sqm of flooring, remove a lot of crushed stone underneath, insulate with 20 cm, and then pour a new slab? The alternative is to lay about 10 cm of insulation on top and live with the energy loss. Of course, it's always best to have adequate insulation under the slab, but since I have a ceiling height of 2.40 and can thus lay at least 10 cm of foam insulation on top and then float the heating loops, isn't that a smarter solution economically? Can the energy loss that goes into the ground really compare to the costs of demolishing the concrete (which in some places is reinforced)? I have ground-source heating and thus fairly low costs today. Additionally, most of the living area is on the upper floor, so there's no need to constantly have high temperatures on the ground floor.
It would be interesting to hear if others have done this calculation. I can't quite see the profitability in demolishing the floor, at least not within a reasonable number of years. It's better technically, but in the end, the wallet decides. And I can fix a floor on top myself, unlike demolishing the floor.
I also have a former garage in the house that is now living space, where the ceiling height allows for even more insulation (15-20 cm). Are there any issues associated with laying so much insulation on top and then installing underfloor heating (apart from, of course, not placing any moisture-sensitive materials directly against the slab)? Because it's an enormous amount of work to demolish a heavily reinforced garage floor of 35 sqm...
/Andreas
I have a house from -52 with an uninsulated slab on grade (no basement). On the ground floor, I am about to install underfloor heating in the relaxation room/sauna and laundry room.
My question is whether it might be worthwhile to demolish 25 sqm of flooring, remove a lot of crushed stone underneath, insulate with 20 cm, and then pour a new slab? The alternative is to lay about 10 cm of insulation on top and live with the energy loss. Of course, it's always best to have adequate insulation under the slab, but since I have a ceiling height of 2.40 and can thus lay at least 10 cm of foam insulation on top and then float the heating loops, isn't that a smarter solution economically? Can the energy loss that goes into the ground really compare to the costs of demolishing the concrete (which in some places is reinforced)? I have ground-source heating and thus fairly low costs today. Additionally, most of the living area is on the upper floor, so there's no need to constantly have high temperatures on the ground floor.
It would be interesting to hear if others have done this calculation. I can't quite see the profitability in demolishing the floor, at least not within a reasonable number of years. It's better technically, but in the end, the wallet decides. And I can fix a floor on top myself, unlike demolishing the floor.
I also have a former garage in the house that is now living space, where the ceiling height allows for even more insulation (15-20 cm). Are there any issues associated with laying so much insulation on top and then installing underfloor heating (apart from, of course, not placing any moisture-sensitive materials directly against the slab)? Because it's an enormous amount of work to demolish a heavily reinforced garage floor of 35 sqm...
/Andreas
I calculated this before I broke up in the bathroom, the following applies if I'm not completely off...
Transferred power (W) = (Lambda value / thickness) * dT * A
Lambda for styrofoam is about 0.035 W/mK
Now you have to make some assumptions about the temperature of the slab and the warm floors. I assume the floor is 25C and the concrete slab is 5C. That gives a dT of 20C. Calculated per m^2 for 10cm styrofoam, it becomes (0.035/0.1)*20*1 = 7W/m^2. 7W/m^2 year-round totals 1533kWh per year for your 25m^2. If you assume that you pay for 1/3 of the energy you use with the help of geothermal heating, you would pay for about 500kWh per year to keep this warm. Assuming the same temperatures if you place the insulation under the floor, it would be half the effect due to double insulation. So you save about 250kWh per year by breaking up and insulating 20cm under the slab instead of 10cm on top. But I don't know if my assumptions about temperatures are reasonable?
I broke up anyway
Partly because I only had 220cm ceiling height, and partly because I needed new plumbing anyway throughout the bathroom. But it was "only" 12sqm...
Transferred power (W) = (Lambda value / thickness) * dT * A
Lambda for styrofoam is about 0.035 W/mK
Now you have to make some assumptions about the temperature of the slab and the warm floors. I assume the floor is 25C and the concrete slab is 5C. That gives a dT of 20C. Calculated per m^2 for 10cm styrofoam, it becomes (0.035/0.1)*20*1 = 7W/m^2. 7W/m^2 year-round totals 1533kWh per year for your 25m^2. If you assume that you pay for 1/3 of the energy you use with the help of geothermal heating, you would pay for about 500kWh per year to keep this warm. Assuming the same temperatures if you place the insulation under the floor, it would be half the effect due to double insulation. So you save about 250kWh per year by breaking up and insulating 20cm under the slab instead of 10cm on top. But I don't know if my assumptions about temperatures are reasonable?
I broke up anyway
Partly because I only had 220cm ceiling height, and partly because I needed new plumbing anyway throughout the bathroom. But it was "only" 12sqm...