A commonly used procedure of calculation by (2) assigns to a transparent structure the same output value of a correction factor and total throughput screening of solar radiation on a monthly basis for the whole year. The question is to what extent this simplification is appropriate for low- energy and passive houses. The paper deals with a comparison between a nominal and detailed methods of calculating passive solar gains in situations of normal shading with normal structures and surrounding barriers, and their subsequent impact on the need for heating. The calculations have showed that even in extreme cases based on the presented examples (windows only on the Southern porch, windows just to the west with grills) for buildings with heat requirements of 15-20 kWh/m2.year, the precision of the calculations of passive solar gains are affected resulting on a higher demand for heating of up to 10%.

From the phase of architectural studies, the building process goes through steady changes. The expert "forecast" of the thermal behaviour of these buildings will almost always be hampered by the lack of input data. However, even in such cases there are ways to provide valuable information about future features of the project. The information doesn't need to be always accurate. For example, if we asked if the building will be low-energy, it would be enough to know, among other things, if the resulting heat needed for heating will not exceed a certain threshold. We are able to identify this already at the stage where we have a clear idea about, for example, the properties of windows or the exact shape of the building. In this case, it is appropriate to extend the standard calculation procedures to be able to describe not only one chosen object, but a number of variations that may occur depending on what the we know about the building at a given moment. This presents a method for design and estimation of thermal-technical properties of family houses with very low energy requirements. The method uses the creating of variants with the Monte Carlo simulation applied to the parametric model house (monthly calculation according to EN ISO 13790 and 730329 DESERT). The results show the influence of individual characteristics of the building on the heat balance and makes it possible to optimise the overall building.

Thermographic measurements and their subsequent diagnosis are a relatively quick method of non contact evaluation of buildings related to heating technology. Thermal images show complex temperature fields with optional colour scales and are thus very easy to understand even for a layman. The assessment and analysis of the temperature distribution allow the identification of places with elevated heat flow.