Why thermal insulation in the facade
The exterior wall is the most influential factor in a building energy balance. Up to 40 percent of winter heat loss and summer heat gain passes through exterior walls. Without proper insulation, an air conditioner works three times as hard to maintain interior temperature.
Exterior wall thermal insulation breaks this heat bridge. It creates a resistance layer preventing heat transfer between inside and outside. Result: the AC works less, electricity bills drop significantly, and the home becomes more comfortable.
How a rear ventilated facade with insulation works
A rear ventilated facade system consists of four layers, outside to inside: cladding panels (Alucobond), air gap, thermal insulation, and structural wall. The air gap between cladding and insulation is the magic.
Hot air rises from the gap creating a chimney effect that continuously removes heat. Cladding protects insulation from direct sun and moisture. The insulation itself does the thermal work. The interior wall remains at stable temperature year-round.
- Layer 1 (exterior): Alucobond panels, climate protection
- Layer 2: 40 to 80 mm air gap, moisture drainage + heat convection
- Layer 3: 80 to 120 mm thermal insulation, rock wool or polyurethane
- Layer 4: vapor membrane on interior wall
- Layer 5: the structural wall, protected beneath the entire system
Insulation types for ventilated facades
Rock wool is the professional standard. It is non-combustible, stable over time, and offers excellent thermal conductivity values. Typical 80 to 120 mm thickness gives R-3 to R-5 thermal resistance value. Rock wool also provides acoustic insulation, reducing external noise.
EPS (sprayed polystyrene) is a cheaper alternative but less recommended. It is combustible (even when fire-treated), less durable, and adds fire risk. We use mineral, non-combustible insulation in the cavity as standard. Polyurethane spray is an excellent acoustic and thermal alternative, but expensive and unsuitable for every system.
How much energy you actually save
Measurements in our projects show 25 to 35 percent savings in heating and cooling electricity costs after installing a rear ventilated facade with mineral insulation. In a typical 120 sqm home that consumed 8,000 NIS annually for electricity, savings are 2,000 to 2,800 NIS per year.
A large difference is also measured at peak load on cooling systems. An AC working at 90 percent capacity now works at 60 percent. This extends system life and reduces need for expensive upgrades. Savings accumulate beyond direct electricity bill.
ROI and payback period
The insulation adds a project-specific figure. On a building with 800 m² of facade and 24 apartments, that is an additional a project-specific figure. At a saving of an annual saving measured per building, the whole building saves a project-specific figure per year, and payback lands between two and four years. After that it is net saving across the remaining life of the facade.
Additional benefit that is harder to quantify in currency: buildings with a high energy rating sell better, and interest in that criterion is growing in the Israeli market.
What sets the price
We do not publish price bands, because the number changes from project to project. These are the factors that move it most:
- Facade geometry. The number of openings, corners and folds per m². A large flat elevation costs far less per m² than a detailed one.
- Substrate condition. On an existing building this is the hardest item to judge remotely, and the one that surprises people in cheap quotations.
- Access equipment. Standard scaffolding, a suspended platform or rope access. At height this is a significant line of its own.
- Panel grade and finish. Fire-retardant or mineral core, and a standard finish versus metallic, wood-effect or a custom RAL colour.
- Project size. A larger area lowers the cost per m² through repetition and installation efficiency.
A binding quotation follows a discovery call and a site visit, in writing and itemised line by line. Book a site visit.
Calculation assumptions: 800 m² of facade, 24 apartments, an annual electricity bill of 8,000 ILS per apartment, 2026 prices, undiscounted and with no assumed energy price inflation. Substitute your own apartment count and facade area and the method still holds. A building with fewer apartments per unit of facade area has a longer payback. Israeli thermal insulation standard 1045 is available from the Standards Institution of Israel.
Key takeaways
- Saving: 25 to 35 percent on heating and cooling, an annual saving measured per building.
- Added cost: a project-specific figure.
- Payback: two to four years, depending on apartment density per unit of facade.
- Mineral wool only inside the cavity. EPS voids system compliance.
- Acoustic bonus: 10 to 15 dB reduction in external noise.
Further reading: how a rear ventilated facade works, the 25-year comparison against render and stone, and cladding for residential buildings with thermal insulation.
Frequently asked questions
What percentage of electricity bill is saved?
On average 25 to 35 percent on heating and cooling costs. In homes consuming more energy (south-west facing facade, heavy AC use), savings can reach 40 percent. In already-efficient homes savings are less dramatic but still significant.
Does insulation suit every building type?
Yes, a rear ventilated facade with insulation suits any building type: residential, office, commercial. Adaptation in insulation thickness, type, and attachment system varies by existing structural wall. Proper design by a professional contractor is critical.
What is the difference between interior and exterior insulation?
Interior insulation reduces living space (shrinks apartments by 3 to 5 percent), does not handle structural thermal bridges, and creates condensation problems in walls. Exterior insulation solves all of these and performs thermally much better. It is the recommended professional standard.
Does this require engineering approval?
Yes, a rear ventilated facade system with insulation is part of the building envelope and requires engineering design. In new buildings the engineer plans this from the start. In an upgrade of an existing building, an engineer is needed to approve the addition and design the attachment connections. DAR GROUP always works with a structural engineer on every project.
