Field studies to investigate Impact of increasing R-value of building envelope on winter indoor relative humidity of Auckland houses

Abstract

PURPOSE / CONTEXT The study investigates relationships of winter indoor relative humidity and R-value of building envelope of the Auckland houses.

METHODOLOGY / APPROACH Field study of indoor micro climatic conditions. Air temperatures and relative humidity adjacent to floors and ceilings of different indoor spaces of the two houses with different R-value in their envelopes and shaded outdoor spaces were continuously measured and recorded at 15 minute intervals, 24 hours a day, by Lascar EL-USB-2 USB Humidity Data Logger during the winter months.

RESULTS The study identifies the differences of winter indoor relative humidity of Auckland houses with different insulation and glazing in their envelopes and the major problems of building thermal design of local house with lightweight timber frame construction.

KEY FINDINGS / IMPLICATIONS Increasing R-value in building envelope of Auckland houses in accordance with the requirements from NZS 4218:1996 to NZS 4218:2009 can significantly in- crease 19.6% of winter time when indoor relative humidity are 40% and 60%. Maintaining indoor relative humidity between 40% and 60% can minimize the indirect health effects.

ORIGINALITY Quantitative relationships between R-value in building envelope and winter indoor relative humidity, and the identified thermal design problems of local houses with lightweight timber frame construction can be good references for improving indoor health conditions of the future Auckland housing development.