103 Series Brick Apartment — Heat Loss Through 510mm Brick Walls

The 103 series is one of the most recognizable apartment building types in Latvia. Built from the early 1970s through the late 1980s, these 5-story brick buildings are found across Riga — in Kengarags, Jugla, Bolderaja, Ziepniekkalns, Teika, Purvciems — as well as in Liepaja, Daugavpils, Valmiera, and other Latvian cities.

Unlike the 602 series panel buildings, the 103 series uses load-bearing brick walls (510mm thick) with reinforced concrete floor slabs. Depending on the construction period, the walls are made of silicate brick or hollow clay brick. The thick walls give an impression of solidity, but their thermal performance still falls far short of modern standards.

Sources: nopo.lv, cityreal.lv

Thermal performance of a typical 103 apartment

Let's estimate the thermal characteristics of a typical 2-room apartment (~55 m²) in a 103 series building, using the calculation method from EN ISO 6946:

Note: U-values are estimated using R = d/λ + surface resistances (EN ISO 6946). Silicate brick masonry λ ≈ 0.87 W/(m·K) per SP 50.13330 (high humidity conditions). Hollow clay brick λ ≈ 0.62 W/(m·K) per BS EN 12524. Cement render λ ≈ 0.5 W/(m·K) per BS EN 12524. Actual values depend on brick type, mortar condition, and moisture content.

How does this compare to the standard?

Every element of a typical 103 series building exceeds the maximum permitted U-value set by LBN 002-19:

• Walls: ~0.9–1.2 vs 0.23 required — 4–5× worse than the standard (depending on brick type)
• Floor: ~2.7 vs 0.20 required — ~14× worse
• Windows: ~2.8 vs 1.10 required — ~2.5× worse

103 vs 602: which is warmer?

A common question among Latvian apartment buyers. The 103 series walls (U ≈ 1.2) perform noticeably better than 602 series panels (U ≈ 1.6) — the 510mm brick thickness compensates for the higher thermal conductivity of silicate brick vs claydite concrete. However, both are still 5–7× worse than the modern LBN 002-19 requirement of 0.23.

The 103 series also has an advantage in airtightness — brick walls with mortar joints are generally less prone to air infiltration than aging panel joints. However, the 5-story height (vs 9 for 602) means less wind exposure on upper floors.

What are the known problems?

Despite being perceived as more solid than panel buildings, 103 series buildings have their own thermal weak points:

• Mortar degradation in brick joints after 50+ years, creating cold bridges and moisture paths
• Cold corners and mold at wall-floor junctions due to thermal bridges
• No insulation in the original design — the 510mm brick was considered sufficient in the 1960s
• Flat roof with minimal insulation, causing significant heat loss for top-floor apartments
• Uninsulated basement ceiling affecting ground-floor apartments

What can be done?

The good news: brick buildings are generally easier and cheaper to insulate than panel buildings. The brick substrate works well with external insulation systems:

• External wall insulation (ETICS system) — 150mm mineral wool or EPS brings walls close to LBN 002-19. Brick substrate provides excellent adhesion for the system
• Window replacement— modern triple-glazed windows (U ≈ 0.8) exceed the standard requirement
• Roof insulation — adding 200mm insulation above the flat roof is one of the most cost-effective improvements
• Basement ceiling insulation — relatively low-cost improvement that reduces ground-floor heat loss significantly

How much does this cost you?

For a typical mid-floor 103 series apartment in Rīga (~55 m²), we can estimate the annual heating cost through walls and windows alone, using Q = A × ΔT × t / R with Rīga climate data (ΔT = 19.9°C, heating season 4,608 hours):

Renovation scenario: 150mm mineral wool on walls + triple-glazed windows (U ≈ 0.8). Mid-floor apartment — walls and windows only. Ground and top floor apartments lose significantly more through uninsulated floor/roof.

Potential savings: ~€430 per year on heating through the building envelope alone. For a ground-floor or top-floor apartment, the savings can exceed €1,000/year.

Get a detailed report for your apartment

Data in this article is based on publicly available information about 103 series buildings from nopo.lv and cityreal.lv, and calculations using EN ISO 6946 methodology. Material thermal conductivity values are from BS EN 12524. Heating cost estimates use the average Latvian heating tariff of €0.08/kWh and Rīga climate data per LBN 003-19. All values are estimates — actual thermal performance depends on building condition, moisture content, and renovation history. This article is for informational purposes only.