Walk into a west-facing apartment in a new tower in Tel Aviv on an August afternoon. The split AC unit is running at full capacity. The shutter is closed because the sun is direct into the apartment from 3pm onwards. The floor is hot underfoot because the polished concrete slab absorbed eight hours of solar radiation before the shutter came down. The electricity meter is spinning.
None of this is accidental. All of it was determined by decisions made at concept design stage — the window-to-wall ratio chosen for the western façade, the glazing solar heat gain coefficient selected (or not), the absence of shading devices from the design. These decisions were not made by mistake. They were made without anyone running the numbers.
What the Standard Requires
SI 5281 and SI 5282 together define Israel's energy and thermal performance framework for buildings. Since March 2022, SI 5282 compliance — demonstrated by an energy performance index (EPI) calculation — is mandatory for new construction, with most designs required to achieve at minimum Energy Level C.
The EPI calculation is a whole-building energy model accounting for building envelope, glazing area and orientation, shading, thermal mass, and HVAC system efficiency. Israel's climatic zones under SI 1045 run from Zone A (hot-arid Negev) through Zone E (cool Mediterranean highlands). Tel Aviv and the coastal plain sit in Zones B and C.
What Developers Miss
The western façade is Israel's thermal problem child. Israeli buyers consistently prefer western-facing apartments for sea views and sunset light. Developers respond with western façades that maximize glazing. The result is a systematic thermal design error embedded in the Israeli residential stock.
A west-facing apartment in Tel Aviv with a WWR of 55–65% and standard double glazing (SHGC ≈ 0.60) receives a peak solar heat gain of approximately 200–250 W/m² in the late afternoon hours of July and August — a cooling load that a standard 2.5 kW split AC unit cannot clear.
SHGC is not in the architectural specification. Ask the architect on most Israeli residential projects to specify the solar heat gain coefficient of the western glazing. In the majority of cases, the specification will read "double glazing, 4/12/4mm" — with no SHGC value. Low-SHGC glazing (SHGC ≈ 0.25–0.35) on the western façade reduces summer cooling load by 30–40% per façade.
Flat roofs with no solar reflectance treatment. A dark or untreated flat concrete roof absorbs 80–90% of incident solar radiation in summer. A cool roof coating (SRI ≥ 78) can reduce roof surface temperature by 20–30°C and reduce cooling load in the top-floor apartment by 15–25%.
Split AC loads and electricity bills. Concept-stage thermal improvements can reduce annual cooling energy consumption by 20–35% compared to a building designed to minimum code and no more.
What It Costs When Thermal Design Fails
An apartment that requires 30% more electricity for cooling than a thermally optimized equivalent costs its occupant approximately NIS 3,000–5,000 per year more in electricity. Over a 25-year building life, this is NIS 75,000–125,000 per unit — a value that an informed buyer will discount from the purchase price.
Most thermal performance failures in completed buildings cannot be meaningfully remediated. Replacing glazing on a completed multi-story tower costs NIS 800–1,500 per sqm of glazed area. Adding external shading devices typically requires a new building permit.
What Razore Does Differently
Razore Engineering runs full energy performance modeling under SI 5282 at concept stage — before the architectural form is fixed. WWR by orientation, glazing SHGC by façade, shading geometry, roof specification, and HVAC system type are all evaluated in parallel with the architectural massing study.
Razore's thermal simulation uses validated dynamic simulation software calibrated to Israeli climatic data for all five climatic zones. For pinui-binui and tama 38 projects, Razore performs explicit thermal bridge analysis.
Due Diligence Checklist: 5 Questions to Ask Any Developer
- Has an SI 5282 energy model been prepared at concept or schematic stage, and what EPI level does the design achieve? A Level C with no margin above minimum is a fragile compliance position.
- What is the solar heat gain coefficient (SHGC) specified for the western and southern glazing? Acceptable answers are specific numbers (e.g., "SHGC 0.28 on the west façade").
- Is there an external shading system, and is it included in the building permit drawings?
- What is the roof specification for the penthouse and top-floor units — is a cool roof coating included?
- For units adjacent to mechanical systems or in tama 38 structures: has a thermal bridge analysis been performed per SI 1045 requirements?
Questions about a specific project? Our team replies within 24 hours.
All data and figures in this article are for illustrative and educational purposes. Site-specific conditions vary. Consult a qualified licensed engineer for project-specific analysis. Engineering services by Razore Engineering & Consulting Ltd.