In-slab heating is an effective energy-saving option for large areas because it allows the slab to be used for heat storage. However, don’t make the mistake of thinking that a heated slab will store heat for long without proper insulation underneath. We know that insulation is a big factor if you want to improve the efficiency of your home, whether you keep it heated or you don’t.
Importantly, if you are going through the trouble of heating your home with in-slab heating, you want to make sure you’re not unintentionally losing that heat.
Now, variables like soil conditions, ground temperatures, ground water, floor cover and distance from the slab to the surface of the ground can affect heat loss. To understand the importance of insulation under a heated slab, continue reading.
Lower Installation Costs Might Mean Higher Utility Costs
Try not to get swindled into a reduced construction cost that follows a lack of insulation installation. You’ll end up paying it off in utility bills in the long run as you lose heat and have to use more energy to heat your home.
Insulation Keeps the Heat Moving Upwards
A heated slab that only has contact with the ground below it is as the mercy of that ground’s temperature changes. Installing insulation under the slabs will reduce temperature swings in the heated space and respond much quicker to changes you make in thermostat settings. Insulation stops the radiant heat from moving down into the soil. It keeps the heat, or rather increases the heat that radiates upward into your home.
Best Slab Performance
If you truly want to achieve the best-heated slab performance, you need to invest in insulation. It is important, however, that you insulate appropriately. Make sure the insulation is waterproof and thick enough and is extended deep enough and wide enough to be useful and not allow heat loss.
This is because there are two areas where heat can be lost from the slab. Not only can you lose heat from a downward heat flow from the slab, but you can also lose it from the perimeters. The shortest distance from the slab to the outside is at the perimeter, which is the band of earth, concrete, block, etc. that is around the edge of the slab. Extending insulation not only downwards, but also beyond the borders of the perimeter will help ensure that you don’t lose heat from any of these sources.
If you are concerned about the perimeter heat loss, or if you are installing this in-slab heating in a basement area, you should consider slab edge insulation.
Simply ensure (during installation) that you leave a thermal break between the slab and any direct path to the outside. This is because contact between the edge insulation and a foundation of wall that isn’t insulated can cause the heat to travel up the wall to the outside, similar to a chimney drafting.