InsulMix Roof Screed and Wall Plaster: How Insulation Lowers AC Load

Cooling a building is mostly an argument with physics, and a thermal insulation roof screed is one of the quieter ways to win it. Reflective coatings stop sunlight from heating the surface, but some heat will always get through, particularly on thick RCC slabs that store energy all day and release it at night. That’s where insulation inside the roof build-up enters the picture. Panache Green’s InsulMix range works inside the structure itself, slowing heat at the layer where it would otherwise pass freely.

Why Insulation Matters Even With a Cool Coating

A roof gains heat in two ways: absorbed sunlight at the surface and conduction through the slab. Coatings tackle the first. Insulation tackles the second.

• Reflection cuts the energy entering the roof.
• Insulation reduces the rate at which remaining heat moves through it.
• Thermal mass stores heat that bleeds into the room after sunset.

On a thick concrete roof, the stored heat is a big reason bedrooms stay warm at 11 pm. Insulation reduces that store-and-release effect.

What InsulMix Roof Screed Is

InsulMix roof screed is a cement-based, pre-packed mortar. It contains sealed expanded clay, expanded microspheres and mineral additives instead of heavy aggregate, which gives it low density and low thermal conductivity. The published K value is around 0.087 W/mK for the roof screed, with a thermal resistance of about 0.287 m²K/W at a 25 mm thickness. A 50 kg bag covers roughly 15 sq ft at that thickness.
In short, a thermal insulation roof screed like this replaces the conventional sand-cement screed that is normally laid to slope on a terrace, so you are not adding a separate layer. You are changing what the existing layer does.

Where It Sits in a Roof Assembly

A typical RCC roof build-up with Panache Green’s CIS Roofing System looks like this, bottom to top:

1. RCC slab
2. Waterproofing (FAP or 2K system)
3. Insulating screed with slope
4. Protective layer (IPS or PCC)
5. Reflective Cool Tops coating

The reflective top coat handles solar radiation. The screed handles conduction. Together they bring the assembly’s U-value to roughly 0.39 W/m²K in Panache Green’s listed configuration.

Insulating Wall Plaster

Walls, particularly west-facing ones, take heavy afternoon sun. Insulating wall plaster such as InsulMix Wall Plaster uses a similar lightweight formulation to slow conduction through masonry. Panache Green lists thermal conductivity values from about 0.039 to 0.056 W/mK for the plaster range, and a wall assembly U-value of around 0.92 W/m²K with InsulWrap Wall Texture.
It’s applied like a normal plaster, which makes it practical for new construction and for renovation. Compared with fitting boards or panels, there are no joints or fixings to manage.

Choosing Between Options

There are several roof insulation materials on the market. A quick comparison:

• XPS or PU foam boards: very low conductivity, but they need protection and can have fire and moisture considerations.
• Bubble foil: reduces radiant heat but little conduction.
• Lightweight insulating screed: sits within the roof build-up, protected by the layers above.
• Reflective coatings: reduce heat gain but do not add resistance.

No single choice wins everywhere. For a large RCC roof, the screed plus reflective coating combination is robust. For lightweight metal sheds, reflection with ventilation is usually enough.

How This Translates Into AC Load

Cooling energy follows heat gain. If the roof and west wall pass less heat, the AC compressor runs shorter cycles. That’s the logic behind reducing AC electricity consumption, and why top-floor flats, school classrooms and hospital wards respond well. Panache Green has reported cooling energy savings of up to about 30% on suitable projects, with the actual figure depending on occupancy, glazing and equipment efficiency.
To measure it properly:

• Log kWh before and after at the sub-meter level.
• Record indoor temperature at fixed hours.
• Use a thermal camera on the ceiling.

Who Benefits Most

Top-floor apartments, school blocks, hospital wards and offices with RCC roofs see the clearest change, since they combine long occupied hours with heavy afternoon loads. Panache Green usually suggests starting with the roof, then adding wall plaster on west facades if budgets allow.

Practical Notes

• Screed thickness drives performance, so specify it clearly.
• Curing needs care, as with any cementitious product.
• Waterproofing must sit beneath the screed, not above.
• Keep drainage outlets clear.

Using thermal insulation roof screed correctly is mostly about detailing, rather than about the material alone.

FAQs

Does InsulMix roof screed replace waterproofing?

No. It’s a thermal layer. Waterproofing is a separate system in the assembly.

Can it be used on existing roofs?

Yes, during re-screeding or refurbishment, after assessing load and levels.

Is it heavy?

It is lighter than conventional sand-cement screed, which also helps structural load.

Does insulating wall plaster work on all walls?

It’s most useful on exposed east and west facades. Panache Green advises on locations.

How much will my AC bill fall?

It varies. Savings of up to about 30% have been reported on suitable projects.