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Papers by Gabriel Rojas
Duct routing often poses a great challenge when planning the installation of a mechanical ventila... more Duct routing often poses a great challenge when planning the installation of a mechanical ventilation system with heat recovery. This is particularly true for retrofits, where the necessary space for supply and exhaust ducts was originally not accounted for. This extended summary presents an alternative approach for duct routing avoiding ducts in the dwelling, while allowing the installation of a centralized MVHR unit and the implementation of a cascading airflow through the dwelling. The general advantages as well as some implementation details within a refurbishment case study are presented.
In an extensive simulation study using a multi-zone airflow and contaminant transport calculation... more In an extensive simulation study using a multi-zone airflow and contaminant transport calculation software (CONTAM) recommendations for the supply air rates for residential housing were derived as input for the revision of the Austrian standard ÖNORM H 6038 (2014). The floor plan, the occupancy and the contaminant and humidity sources are modelled to represent a typical Austrian housing situation. A humidity buffering model is also implemented. Based on common thresholds for CO2, relative humidity (r.h.) and TVOC the so-called relative threshold deviation is determined. It is used as a combined parameter to evaluate indoor air quality in terms bioeffluents, air humidity and pollutants arising from building and interior products. Additionally the potential mould risk due to high air humidity and low surface temperatures is calculated using the isopleth model. The results suggest a supply air flow into the bedroom of 20 m3/h per person for the chosen reference climate. It represents t...
This paper presents different ventilation solutions for the retrofit in existing school building ... more This paper presents different ventilation solutions for the retrofit in existing school building with a special focus on historic buildings. These building usually pose a major challenge for the integration of energy efficient ventilation systems, i.e. with heat recovery. For decentralized systems, the ductwork can be minimized by wall integrated heat recovery units, whereas for central systems, a horizontal air distribution in the attic combined with vertical ducts was found to be a possible solution for listed buildings. Former is problematic for aesthetic reasons due to visibility of the outer wall inlets, especially when no exterior insulation layer can be applied. A central unit with vertical ducts has the drawback of requiring many fire protection flaps, which are associated with high maintenance costs. Therefore a new ventilation system was designed and tested for a listed school building in Innsbruck (Austria), which is one of eight case study buildings within the EU-project...
Howcouldresidentialventilationlookin2020?Whatare the main design principles for both energy and c... more Howcouldresidentialventilationlookin2020?Whatare the main design principles for both energy and cost efficient ventilation systems with heat recovery? This paper investigates the potential and seeks to advise manufacturers and designersonhowtoenhancetheirproductsintermsofthermal and electrical efficiency as well as investment and maintenance costs.
Advances in Building Energy Research, 2015
This work analyses the measured indoor environmental data collected during long-term monitoring o... more This work analyses the measured indoor environmental data collected during long-term monitoring of a social housing project built to the Passive House (PH) standard. The indoor temperature, CO2 concentration and relative humidity levels were continuously logged in 18 of the 354 apartments. The volatile organic compound concentrations were also measured before the tenants moved in. Furthermore, a survey using questionnaires and interviews was performed to evaluate the occupants' satisfaction levels. For comparison, the indoor environment of six dwellings of a similarly constructed low-energy building, but without mechanical ventilation was also measured within this project. Within the Passive Housing, the average indoor temperature distribution during winter showed a surprisingly large difference compared to the low-energy housing and to other documented PH projects in Germany. Overheating during summer seemed to be an issue especially in the top-floor apartments. This re-emphasizes the need for proper shading solutions. The evaluation of the indoor air quality shows the need for controlled domestic ventilation for non-owner-occupied buildings. The combined assessment of measured data and survey results shows the importance of factoring in air humidity when defining ventilation rates. If no humidity-raising measures are applied, air exchange rates well below 0.5 h−1 can be recommended for locations with cold and dry climates. In general, the satisfaction level within the presented social housing complex built to the PH standard was very high.
Duct routing often poses a great challenge when planning the installation of a mechanical ventila... more Duct routing often poses a great challenge when planning the installation of a mechanical ventilation system with heat recovery. This is particularly true for retrofits, where the necessary space for supply and exhaust ducts was originally not accounted for. This extended summary presents an alternative approach for duct routing avoiding ducts in the dwelling, while allowing the installation of a centralized MVHR unit and the implementation of a cascading airflow through the dwelling. The general advantages as well as some implementation details within a refurbishment case study are presented.
In an extensive simulation study using a multi-zone airflow and contaminant transport calculation... more In an extensive simulation study using a multi-zone airflow and contaminant transport calculation software (CONTAM) recommendations for the supply air rates for residential housing were derived as input for the revision of the Austrian standard ÖNORM H 6038 (2014). The floor plan, the occupancy and the contaminant and humidity sources are modelled to represent a typical Austrian housing situation. A humidity buffering model is also implemented. Based on common thresholds for CO2, relative humidity (r.h.) and TVOC the so-called relative threshold deviation is determined. It is used as a combined parameter to evaluate indoor air quality in terms bioeffluents, air humidity and pollutants arising from building and interior products. Additionally the potential mould risk due to high air humidity and low surface temperatures is calculated using the isopleth model. The results suggest a supply air flow into the bedroom of 20 m3/h per person for the chosen reference climate. It represents t...
This paper presents different ventilation solutions for the retrofit in existing school building ... more This paper presents different ventilation solutions for the retrofit in existing school building with a special focus on historic buildings. These building usually pose a major challenge for the integration of energy efficient ventilation systems, i.e. with heat recovery. For decentralized systems, the ductwork can be minimized by wall integrated heat recovery units, whereas for central systems, a horizontal air distribution in the attic combined with vertical ducts was found to be a possible solution for listed buildings. Former is problematic for aesthetic reasons due to visibility of the outer wall inlets, especially when no exterior insulation layer can be applied. A central unit with vertical ducts has the drawback of requiring many fire protection flaps, which are associated with high maintenance costs. Therefore a new ventilation system was designed and tested for a listed school building in Innsbruck (Austria), which is one of eight case study buildings within the EU-project...
Howcouldresidentialventilationlookin2020?Whatare the main design principles for both energy and c... more Howcouldresidentialventilationlookin2020?Whatare the main design principles for both energy and cost efficient ventilation systems with heat recovery? This paper investigates the potential and seeks to advise manufacturers and designersonhowtoenhancetheirproductsintermsofthermal and electrical efficiency as well as investment and maintenance costs.
Advances in Building Energy Research, 2015
This work analyses the measured indoor environmental data collected during long-term monitoring o... more This work analyses the measured indoor environmental data collected during long-term monitoring of a social housing project built to the Passive House (PH) standard. The indoor temperature, CO2 concentration and relative humidity levels were continuously logged in 18 of the 354 apartments. The volatile organic compound concentrations were also measured before the tenants moved in. Furthermore, a survey using questionnaires and interviews was performed to evaluate the occupants' satisfaction levels. For comparison, the indoor environment of six dwellings of a similarly constructed low-energy building, but without mechanical ventilation was also measured within this project. Within the Passive Housing, the average indoor temperature distribution during winter showed a surprisingly large difference compared to the low-energy housing and to other documented PH projects in Germany. Overheating during summer seemed to be an issue especially in the top-floor apartments. This re-emphasizes the need for proper shading solutions. The evaluation of the indoor air quality shows the need for controlled domestic ventilation for non-owner-occupied buildings. The combined assessment of measured data and survey results shows the importance of factoring in air humidity when defining ventilation rates. If no humidity-raising measures are applied, air exchange rates well below 0.5 h−1 can be recommended for locations with cold and dry climates. In general, the satisfaction level within the presented social housing complex built to the PH standard was very high.