# Improvement of the Chimney Effect in Stack Ventilation
## 7 Conclusions  
Technical solutions strengthening the chimney draft consisting in the assembly of a rotary chimney cap (TYPE III) and the construction of the so-called solar chimney (TYPE II) werecompared with the experimental results carried out on a traditional chimney (TYPE I). The research shows that the rotary-type chimney increases the efficiency of gravity ventilation (for the assumptions \(\mathrm{T_{e}}>12\ ^{\circ}\mathrm{C}\) and \(\mathrm{V_{wind}}=2\)-\(5\ \mathrm{m/s}\)) compared to the chimney without the cap by an average of about 27%. On the other hand, for the maximum values, the chimney cowl improved the draft in the ventilation duct even by approx. \(\mathrm{ACH=0.40\ [1/h]}\). In the case of the solar chimney (for the assumptions of \(\mathrm{T_{e}}>12\ ^{\circ}\mathrm{C}\), \(\mathrm{V_{wind}}=0\)-\(2\ \mathrm{m/s}\) and \(\mathrm{I>100\ W/m^{2}}\)), the \(\mathrm{ACH}\) improvement by 16% is noticeable compared to the traditional chimney (for the same external climate conditions). However, in the case of maximum values, the solar chimney improves the draft in the ventilation duct by about \(\mathrm{ACH=0.36\ [1/h]}\). The conducted research has shown that for the average values obtained during unfavorable external climate conditions, the chimney cap works best, the \(\mathrm{ACH}\) value of which does not fall below 0.85 [1/h]. A necessary condition for the operation of the chimney cap is a slight wind blowing at a speed of not less than \(2\ \mathrm{m/s}\).  
Assuming that in the Polish (especially northern) climate zone, windy days are the most common days in the calendar year, it can be concluded that the chimney cap will be more effective throughout the year than the solar chimney.Guidelines for the design of gravity ventilation include:  
* Building location: on a hill, in a valley, etc.  
Figure 22: Comparison of thermal energy consumption for heating a building.  
* Shading/obstacles near the building.
* Considering air infiltration in the air balance of the apartment.
* Considering the opening of windows as an activity ensuring an increase in the intensity of gravity ventilation.
* Consideration of maintenance issues during designing gravity ventilation.  
Based on the assumed factors, two solutions to improve the ventilation air flow in buildings were assessed. The biggest differences in scores were noted for the cost and time of construction in favor of the chimney cap.  
Technically:  
* The chimney cowl is easier to install.
* The availability of technical solutions is greater in the case of the root.  
Economic:
* Due to the large number of companies involved in the production of chimney caps, the chimney cap is a cheaper solution to improve the chimney draft.  
The obtained results showed that the chimney cowl obtains the point advantage in terms of engaging the smallest possible resources, especially time and money.  
Based on the observations, no methods other than the chimney cap improving the efficiency of gravity ventilation were noticed. A chimney cap is a generally available product with its assembly, while solar chimneys have not been commercialized, which may affect the choice of the method.  
Conceptualization, R.A.-J., K.P. and M.N.; methodology, R.A.-J.; formal analysis, R.A.-J., K.P. and M.N.; investigation, R.A.-J., K.P. and M.N.; writing--original draft preparation, R.A.-J., K.P. and M.N.; supervision, K.P. and M.N. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
Data Availability StatementData are contained within the article.  
The authors declare no conflict of interest.