Eng. Konstantinov, what are the main challenges in the design and construction of HVAC systems in high-rise residential buildings? Your question touches on two very large and significant topics in the field of HVAC systems.

High-rise buildings are a topic with increased difficulty in terms of the choice of systems, the type of heat/ cold carrier, locations for machine placement and many other factors. The concept of “high-rise building” is not yet well defined for the Bulgarian market. Buildings up to 100 meters high are one topic, and those over 100 and more are a topic of very high complexity. The designer of HVAC systems for buildings of both types must be very well theoretically prepared in terms of hydraulic sizing and selection of systems and elements.

Residential buildings are a topic that is present in our society with its complex issues regarding individuality, distribution, management, control, access to repairs of common areas and many others. High-rise buildings claim uniqueness with their architecture and this is an additional challenge for the HVAC specialist.

Combining the two topics into one makes the task even more complex. The choice of systems depends very much on the knowledge and experience of the designer and very well on being able to defend his decision based on calculations, analyses and defense of the criteria set for this decision.

How are the needs and expectations of investors and residents changing regarding air conditioning, ventilation and heating in this type of building?

As a rule, investors expect low investment and some quality, and residents - high quality at a low price. This seems an impossible task to solve. Nowadays, due to the high demand and supply on the market, high-quality developments have begun to appear, satisfying both parties.

The investor wants, respectfully to his clients, to offer a high-quality product with a proven origin, manufacturer, designer, supplier, contractor, and this to be a company that has proven on the market that it can take "full responsibility" for the functional parameters of the installation. The market value of a home is increasing, and it is also starting to become a main criterion in the investor's attitude in the after-sales period.

What are the most commonly used technologies at the moment? Is there a trend towards more sustainable or intelligent systems?

The latest technologies have very quickly found applications in such buildings worldwide. Meeting the criteria for individual management, energy consumption control, remote digital control, noise levels, preservation of facades, and others is accomplished magnificently with direct evaporation systems of the VRV type and similar. Great care must be taken when choosing the “responsible party,” because this is not air conditioning sales in the literal sense of the word.

What are the latest developments in the sector and what can we expect in the future - what will the building of the future look like in terms of HVAC and indoor climate?

The latest developments are already on the Bulgarian market. These are 5th generation VRV systems, operating on freon R32 and CO2. Developments aimed at environmental protection and increased energy efficiency. The building of the future in terms of HVAC systems will look in full harmony with all innovations in the field of digital management and control technologies, remote service monitoring, minimal controllable and individually manageable energy consumption. The quality of the living environment, purification and decontamination of indoor air will become increasingly serious criteria.

What role do the facade and structural elements play in the efficiency of HVAC systems?

A very relevant question. The facades and the selection of the structural elements of the buildings are the subject of activity of our colleagues, architects and design engineers. We, HVAC specialists, have an advisory voice based on checking the thermal parameters of the materials used and their behavior during operation in a certain configuration of the HVAC systems. The HVAC system designer must monitor the energy consumption of a building in great detail and based on modern software products during a one-year period of operation, using optimization variants of the machine part according to the manufacturer's characteristics. A good manufacturer, quality machines, but incorrectly selected for a given facade and building will lead to very poor results. I emphasize again - in such buildings, HVAC systems should not be approached as "air conditioner sales".

To what extent do modern HVAC systems enable full compliance and response to the requirements of modern standards such as LEED/BREEAM and ESG, to what extent are these options known and applied in Bulgaria?

These standards allow a building to be certified as a guarantee that it meets all the criteria set out in them. Some of these criteria concern HVAC systems. The design, the quality of the materials used, the method of production and transport to the site, the method and technologies used for installation, and many others are assessed. These options are not known in Bulgaria and are not taught in higher education institutions. We have adopted them and comply with them when approaching investors and their consultants from abroad. Specialized companies worldwide can monitor compliance with the requirements of these standards.

What are the trends in new construction in Bulgaria, especially in Sofia - what are the requirements of investors, the specifics of the systems applied, and the preferences of end customers and residents?

A new and constant trend is being noticed to increase the quality of the offered final product – housing. Criteria such as good location, good communication with the urban environment are starting to be leading. The design of the inter-building space, the services offered, the recreation areas – all these are factors that sell the housing and increase its price. The high-end market in Sofia implies the sale of a housing in a finished form and working installations. In the countryside, it is still sold as “plugs” – a nightmare that the newly moved-in residents will have a hard time getting rid of over the years.

Someone will constantly be finishing, breaking and installing. Direct evaporation systems, air-to-water heat pumps, combined with underfloor heating are widely available. It is gaining popularity for the system to have a built-in hot water boiler for domestic needs.

What are some good examples from your reference projects?

We are currently in the process of designing a high-rise residential building – over 120 meters high, in which we have implemented the most modern technologies and are fully subject to the above considerations. I assume that I will soon be able to present the development to the broad professional community – again unique for THERMOSIST and the European market.

Modern trends in HVAC systems - meeting the criteria for individual control,

Control over energy consumption, remote digital control, noise levels, preservation of facades, and more is accomplished magnificently with direct evaporation systems such as VRV and similar ones.

The latest developments in HVAC systems are already on the Bulgarian market - 5th generation VRV systems, operating on freon R32 and CO2.

The building of the future in terms of HVAC systems will look in full harmony with all innovations in the field of digital management and control technologies, remote service monitoring, minimal controllable and individually manageable energy consumption.

A new and constant trend is being noticed to increase the quality of the offered final product - housing.