Use of solar energy increases every year. In Latvia, solar energy is used mainly by solar collectors. The main part of the solar collector is the absorber, but not less important is the covering material which protects the absorber from the cooling impact of the wind. This cover must be transparent for solar radiation, but opaque for thermal radiation of the absorber, which is at greater wavelengths. Therefore it is important to measure absorption spectra of possible covering materials at visible and infrared wavelength ranges. Absorption spectra have been measured for several materials: glass, polythene, Plexiglas, and cells Plexiglas. Absorption spectra for all these materials are measured in three ranges: ultraviolet – visible (UV – VIS): 250 – 1000 nm; near infrared (NIR): 700 – 110 nm; infrared (IR): 1200 – 8000 nm. UV-VIS spectra with the ‘Ocean Optics’ device HR-4000 have been measured, but NIR and IR – with ‘Bruker’ Furje spectrometer EQUINOX 55. Evaluation of absorption spectra showed that the most suitable material (from the considered) for covering of solar collectors is Plexiglas.

The dynamic of rapeseed oil oxidizing processes under the influence of light in brown glass, colourless glass, and colourless PET bottles during storage at 18+-2 deg C were investigated. The changes in A and E vitamins content in rapeseed oil packed in colourless PET packaging materials were determined after 4 months storage at 18+-2 deg C at daylight. The connection between different packaging materials' transparency and oxidizing of oil were observed.

Intensity of indoor/outdoor dialogue in the context of architectural history has rapidly evolved due to technological progress while the quality of environment expressed as harmony has proved to be of coincidental character. Reality reveals a pressing need to restore integrity, wholeness and harmony of environment, at the same time searching for a balance in the dialogue between interior and exterior space and a way to harmony in this complicated system. By analysing previous successful and unsuccessful examples in the architecture of publicly most sensitive objects in the re-established Latvia, one obtained a pyramid of subordinated guidelines to be used in architectural theory and practice in support of creating a harmonious architectural environment. The subject is of current importance not only among experts but in all levels of society: we all are users of this environment. In order to create a harmonious high-quality environment in the future, at first, one has to invest substantial resources in all levels of education; it will become a reflection of inner conflicts of a new concept of space, continue historical process of architectural development and introduce diverse approaches to harmonise indoor/outdoor space in a scientifically grounded way.

The article deals with the current situation in production of building materials and foreign trade in Latvia. Export and import of building materials are one of the most important factors influencing the production of building materials. The report analyses import and export development trends within two sections of the harmonized system: wood and articles of wood; the articles of stone, plaster, glassware and ceramics.