New concept of a passive house - from design to realisation

Abstract

Papers presented to the 11th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 20-23 July 2015.

The article describes details of a new concept of the passive house. The passive house is a synonym for energy efficient house with energy demand for heating QH less than 15 kWh/m2·a and a primary energy demand QPE less than 120 kWh/m2·a. In climates where active cooling is needed, the space cooling energy demand QC roughly matches the heat demand requirements above, with a slight additional allowance for dehumidification. Another requirement is related to airtightness. Uncontrolled air leakage shall be less than 0,6 of heated volume per hour at increased and decreased pressure of 50 Pa. Thermal comfort must be met for all living areas during winter as well as in summer, with not more than 10 % of the hours in a given year over 25 °C. This concept at the beginning encountered energy efficiency only but had a few drawbacks in terms of user comfort and potentially even health aspects. Two main drawbacks were dry air in winter and unknown air quality in terms of CO2 which could resulted in bad air quality in spite of the mechanical ventilation system with heat recovery (MVHR). At the passive house conference in 2008 (Nürnberg, Germany) I presented my own passive house project, which introduced floor heating only instead of heating through the ventilation system [1]. Another improvement was implementation of the MVHR with rotary air-to-air enthalpy wheel which was developed many years ago but commercially available device with sufficient efficiency was offered shortly before my project started. This system prevented fast dehumidification of indoor air in winter. Based on the developed CO2 measurement unit in our laboratory the speed of ventilation in the heat recovery system was regulated in order to maintain fresh air under the limit 1000 ppm of CO2. After almost 4 years of living in the house and regular measurements of climate variables (temperature, relative humidity, CO2), analysis of energy invoices for 4 winter seasons (2011-2014) with calculated energy consumption proved the economic investment and energy efficiency with increased living comfort and assured healthy environment in terms of fresh air.