Comfort and cost optimised air guiding concept for energy efficient housing

Ventilation systems for dwellings can be more efficient in terms of cost and energy, if the air guiding concept with cascade principle (overflow of air from sleeping rooms into living room). In this project, the planning principles had been developed and published in practice guidelines.

Short Description




Starting point/Motivation

The program aims at improving energy efficiency in residential areas while maintaining a very high comfort for the user. This can be achieved only with the installation of a ventilation system with heat recovery. The technology and device for this is already available. With a good design and realisation it is already possible to achieve acceptable results. However, this technology still incurs high costs and complexity in the systems which lead to sub-optimal solutions for the design and the realisation. This leads to a low user acceptance.

For this reason the first motivation of this project is to investigate concepts for ventilation which are as simple, cheap and energy efficient as possible ("low-tech") whilst maintaining high comfort for the users.

Contents and Objectives

Ventilation facilities with heat recovery can be more efficient, cheaper and demand less maintenance when the air guidance is designed according to the concept of directed air flow. This means, that the supply air can flow from the supply air rooms to the exhaust air room through the corridor and also through the living-room. This project investigates the effect of the air guidance on air quality, air humidity and the costs. A direct comparison of standard (with supply air in the living-room) and cascade (without supply air in the living-room) ventilation should show the advantages and the limits of cascade ventilation. In addition the issues of air-rating, floor-plan composition and noise insulation (related to the air flow openings) have been investigated and the results have been recorded on a website.


The influence of air guidance on air quality and air moisture could be quantified with numerical simulation methods. The multi-zone model has been validated with several measurements from former projects. A representative reference apartment for Austria has been modelled based on several statistical data. Thus, the influence of several input parameters (user behaviour, climate) could be analysed and eventually a direct comparison of the concept of air-guidance could be investigated.

Large-scale research of typical floor-plans has been carried out in order to classify them into several categories according to their topological properties. Every floor-plan category has been systematically simulated with the given multi-zone model in order to point out the possibility for cascade ventilation and / or its limits according to the topological properties of the floor-plan. It should be noted that computerised fluid dynamic (CFD) simulations were made to identify which arrangements of the air-flow opening could be critical for cascade ventilation.

Measurements have been taken in a "double-room" using several air-flow opening elements to investigate the airborne sound insulation and the air-flow capability.


The results of the project "Doppelnutzen" give necessary detailed information about the concept of cascade ventilation and systematic answers for design and realsation issues. It is possible to evaluate the adaptability of a given floor-plan to cascade ventilation. In addition, missing data on noise insulation and air flow capability in simple and low-cost air-flow openings have been collected.

The results of the project are the theoretical basis for the installation of cascade ventilation in several case-study buildings in the frame of the project "".

The results of the project are particularly interesting for designers, architects and residential building companies because the concept of cascade ventilation allows the design of highly efficient and low-cost ventilation systems. For this purpose, an online site and tool help them to access up the necessary information for specific cases in order to help them to design cascade ventilation correctly.

Prospects/Suggestions for future research

The results of this project have already been used within the frame of research project It should be noted that measurements will be made to validate the CFD simulation for critical cases concerning the arrangement of the air-flow openings in the living-room.

The concept of cascade ventilation will probably be installed in several case-study buildings. One of them is actually built by the project partner "Neue Heimat Tirol". The other is located in the region Vorarlberg and will be investigated within the research project "Klimagerechter Nachhaltiger Wohnbau (KliNaWo)".

Project Partners

Project management

University of Innsbruck, Unit Building Physics

  • Dr.-Ing. Rainer Pfluger

Cooperation Partner

University of Innsbruck, Unit Building Physics

  • DI Elisabeth Sibille, Mag. Gabriel Rojas-Kopeinig, DI Mattias Rothbacher, DI Harald Konrad Malzer

Project partner

Contact Address

University of Innsbruck, Unit Building Physics
Technikerstr. 13
A-6020 Innsbruck
Tel./Fax: +43 (512) 507 656 4