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  • Writer's pictureNidus Team


An energy efficient home

Over the last few years, energy performance has become a very important aspect in the equation of a building and is directly related to the operational cost of a building. An energy efficient home has lower monthly bills and maintenance costs and if we consider a period of 50 years, we can reach a value of 2-3 times higher than the initial cost of the building. According to the passive house standard - PassivHaus, the thermal performance of a building is determined by: air tightness, thermal bridges, building services to a lesser extent and, last but not least, the thermal envelope; this has a significant role in the energy exchange (heat) between the indoor and outdoor environments: the heat that is lost through the walls in Winter and the overheating in Summer. In this article we will only address the thermal envelope and leave the rest of the criteria for other future articles.

The thermal envelope of a building consists of: opaque surfaces (walls, roof, floor) and glazed surfaces (windows and/or doors). Each element of the envelope loses heat depending on its thermal resistance. The lower the thermal resistance, the greater the heat losses, and vice versa. Thereby, the thermal resistance of the envelope largely determines the building's heat loss and therefore, we aim for this value to be as high as possible, in order to increase the thermal performance and limit the heat losses.

In order to build an energy efficient house, the building materials and the way they are used in building the structure, finishes and thermo-system are very important.

Thermal performance comparison

We considered 2 wall configurations with the same area of ​​1 sqm: a timber frame wall filled with straw insulation (the Nidus Wall) and a conventional masonry wall, using the dedicated Ubakus software.

The Nidus Wall, timberframe filled with TERMOPAIE - blow in loose chopped straw
The Nidus Wall - timberframe filled with blow in loose chopped straw
The typical Masonry Wall - honeycomb brick insulated with EPS
The typical Masonry Wall - honeycomb brick insulated with EPS

In terms of thermal performance, the heat transfer coefficient U measures the amount of energy that is transferred through the wall, measured in W/m2*K and is the inverse of thermal resistance, R = 1/U m2*K/W. They are complementary values that measure the same thing - the heat transfer through a surface. The difference is in the nomenclature. In Romania, for example, we use the R value, as opposed to Germany where they use the U value. As reference points, the Romanian normative C107 / 2005 requires that the minimum thermal resistance of the outer walls to be R '= 1.51 m2*K/W (or U = 0.38 W/m2*K) and the PassivHaus standard requires U<0 , 15 W/m2*K (or R = 6.67 W/m2*K) ... the Romanian standards are a bit behind. Therefore, for the 2 wall configurations we have the following results:

NIDUS Wall: R = 11.1 m2*K/W or U = 0.090 W/m2* K;
Masonry Wall: R = 4.85 m2*K/W or U = 0.206 W/m2*K;

The NIDUS wall is 2.2 times more efficient than the masonry wall and also meets the passive house criteria for proper thermal insulation.

Comparing the same performance

To have the same degree of comparison, namely the same thermal resistance, we configured the masonry wall to reach the same thermal performance as the NIDUS Wall by increasing the insulation layer.

It takes an additional 280 mm of polystyrene (total 380 mm) to reach the same thermal resistance (R = 11.1 m2*K/W) and the total thickness of the wall reaches 730 mm, which is why this configuration is not feasible neither in size nor in investment.

In conclusion

From the thermal performance point of view, the NIDUS wall configuration is 2 times more efficient than the typical masonry wall for almost the same size, which translates directly into the energy consumption for heating/cooling and implicitly in the operating costs of the house. A better-insulated home has lower heat losses through the thermal envelope and we made sure that the NIDUS Homes are very well insulated with TERMOPAIE, an ecological and environmental friendly material.

If you want to learn more about the effects of buildings on the environment, we wrote an article about it: The environmental impact of buildings #analysis #comparison #thermalperformance #thermalresistance #termopaie #insulation #passivhaus #energyefficiency

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