Why is the average thickness of thermal insulation increasing?

In the spirit of economy, sustainability of our buildings and, last but not least, environmental protection, the prescribed thermal engineering requirements are increasing year by year. In order to comply with these, we have to use increasingly thicker thermal insulations; from 2018, for example, 40% stricter regulations came into effect than the previous rules.

Energy review

The necessity of energy improvement of tempered buildings can be traced back to the spirit of Hungarian Standard 04.140/2-1979, which defined three conditions for a suitable building: 1. energy compliance (fulfillment of current requirements) 2. condition of preservation of structure (no condensation may occur anywhere) 3. thermal comfort (in tempered rooms intended for human occupancy, the temperature of the inner surface of the space-delimiting structures should not differ by more than ± 3oC from the air temperature of the room). The latter two must be practically treated as continuous needs even today, while energy compliance can only be achieved and maintained by increasing thermal insulation as regulations become stricter.

Some historical background is unavoidable because the vast majority of our current building stock was built when thermal insulation was not yet in the spotlight.

Before 1966

the criteria set out in the 1934 Construction Handbook were still the determining factors, the essence of which was that condensation should not occur anywhere. This was achieved at an external temperature of – 20°C and an internal temperature of + 20°C, with a relative humidity of 60%, with a k = 1.45 kcal/m²∙h∙°C for external walls at that time, or ~ 1.68 W/m²∙K in today’s units. They were practically not thermally insulated.

From 1966

The ME-30-65 TECHNICAL REGULATION, published in 1966. Thermal design of buildings and building structures

(Buildings in regular use) defined requirements in a way that is still considered modern today, depending on the structural mass*. For walls, k = 1.20 – 1.41 kcal/m²∙h∙°C, today’s U ~ 1.40 – 1.64 W/m²∙K, for ceilings, k = 0.90 – 1.05 kcal/m²∙h∙°C, today’s U ~ 1.05 – 1.22 W/m²∙K. In the case of a larger mass, a more permissive heat transfer value had to be followed, while in the case of a smaller mass, a stricter one had to be followed. (* Perhaps it is not without lesson that the mass definition at that time was in the range of 300-700 kg/m2 for both external walls and slabs. Most of our “modern” masonry and slabs today do not even reach 300 kg/m2 (!) which is unfavorable from a thermal inertia perspective. Low mass is particularly disadvantageous from a summer overheating perspective.) In the case of floors, in heated spaces, it could not cool below the dew point temperature.

0 i.e. zero on walls and floors, 1-2 cm XPS thermal insulation equivalent on a flat roof.

Minimum required insulation thicknesses over the years

*Note: for floors on the ground, the recommendation until 2006 was to only insulate the facade of the plinth or only the 1.00 m strip along the space-delimiting walls within the floor structure.

1991, the year of the first major change

A real “breakthrough” was brought by the Hungarian Standard 04.140/2-1979 (CONSTRUCTION SECTOR STANDARD. Thermal calculations of buildings and building envelope structures. Thermal sizing), which was valid from 1979 (and is still used in its methodology today), and most of all by its amendment in 1991.

From 1979, the external wall required k = 0.73 kcal/m²∙h∙°C (today’s U ~ 0.85 W/m²∙K), flat roofs and attics: k = 0.35 kcal/m²∙h∙°C (today’s U ~ 0.4 W/m²∙K), and in the case of floors, only the requirement for structural protection (no condensation) became a requirement.

1-2 cm on the wall, 0 cm in the floor, 5-6 cm on the flat roof XPS thermal insulation equivalent

From 1986 on the external wall: k ≤ 0.7 W/m²∙K (today’s U ~ 0.80 W/m²∙K), on the flat roof or attic ceiling: k ≤ 0.4 W/m²∙K (today’s U ~ 0.45 W/m²∙K) and on the floors: k ≤ 0.85 W/m²∙K, (today’s U ~ 1.0 W/m²∙K)

2-3 cm on the wall, 2-3 cm in the floor, 5-6 cm on the flat roof XPS thermal insulation equivalent.

Since 1992, no (new) requirement value has been defined for the heat transfer coefficient of a specific structure, but the average heat transfer coefficient requirement value for the entire building is determined based on the heated volume and cooling surface of the building. In the case of a continuously used building: k = 0.6+0.1∙(V/∑A) In the case of family houses, this is approximately k = 0.7-0.75 W/m²∙K, which also included, for example, much worse values ​​for windows and doors, so walls and ceilings had to achieve better values ​​than the average. The average value made it possible to offset the detrimental effect of a thermally weaker building structure by designing another structure with better technical performance.

3-5 cm on the wall, 2-4 cm on the floor, 8-10 cm on the flat roof is the equivalent of XPS thermal insulation.

2006 – update of Regulation ’91

With the 7/2006 TNM Decree, the minimum heat transfer coefficients were returned to the legislation and the average heat transfer coefficient requirement for the entire building was somewhat reduced.
The external wall had to meet U ≤ 0.45 W/m²∙K, the flat roof U ≤ 0.25 W/m²∙K, the attic ceiling U ≤ 0.30 W/m²∙K, and the floors U ≤ 0.85 W/m²∙K.
On the wall min. 6 cm, on the flat roof, attic ceiling min. 11-12 cm, on the floor min. 4 cm XPS thermal insulation equivalent.

Changes in minimum thermal insulation thicknesses over the years

2015 Energy Efficiency Directive

In order to meet the objectives set out in the EU Energy Efficiency Directive 2012/27/EU, energy regulations have been further tightened in several stages by Decrees 20/2014. (III. 7.) BM and 39/2015 (IX. 14.) MvM. Both pieces of legislation amend and supplement Decree 7/2006. (V. 24.) TNM on the determination of the energy performance of buildings in several stages, with several implementation dates.

Since its entry into force in 2015, Annex 5 of the Act first applied to new public buildings and subsidised investments, and from 1 January 2018, it has been mandatory for all new buildings to achieve the so-called cost-optimised level. This is the penultimate step of the current regulation.

From 2018:

external wall: U ≤ 0.24 W/m2K

flat roof, attic ceiling: U ≤ 0.17 W/m2K

floor: U ≤ 0.30 W/m2K

That is, on the wall at least 14 cm, on the floor 11-12 cm, on the flat roof, attic ceiling at least 20 cm XPS thermal insulation equivalent

2018 – 2020 is upon us

According to the 2012 EU directive, greenhouse gas emissions must be reduced by 20% by 2020. The last step is the introduction of the NZE (Nearly Zero Energy) building requirement, which will come into effect in 2021. The date is approaching, the effects of the measures taken are not yet very noticeable, and since compliance with the regulations can only be expected and held accountable for new buildings or buildings that have undergone complete, major renovation, the 20% energy savings projected on the entire building stock remain a dream for now.

From 2021, the minimum heat transfer requirements will not change, but the specific heat loss factors (qm / W/m2K/ ) will become stricter, depending on the A / V (cooling surface / heated volume) characteristic of the building, i.e. thermal insulation thicknesses may increase somewhat further.