Building wall drying experiment to understand drying capacity of building walls

Objective 1: Find the natural air conditions inside a Hitex Diamond-clad building wall

The first objective was to find the natural RH and MC in building walls. Two walls were tested ith untreated timber framing: Hitex Diamond and Face-fixed Fibre cement. It was found that the Hitex Diamond RH in normal conditions was <55\% RH.

Objective 2: Can a Hitex Diamond-clad wall dry? How Fast?

The second objective was to answer: Can a wet wall dry? How long does it take? It was shown that the Hitex Diamond takes 20 days to dry below 18\% MC which equates to RH 70\% at which below this dangerous moulds can’t grow. The Fibre Cement wall system was still above 24\% MC after 20 days and the RH\% remained in the fungal growth range of >80\%.

Key Facts

1. Tests performed 2002-2003
2. Tests conducted by the University of Auckland Physics Department Atmospherics Group: Glen Manley, Karl Wette, Prof Geoff Austin. An Auckland City Council representative on the research committee.
3. Samples of the untreated timber framing of both walls were taken to Landcare research to find out if mould and fungi begin growing during wetted time.
4. A Fibrecement wall was tested alongside the Hitex Diamond-clad wall for comparison
5. It was found by Dr Nick Waipara that there was no fungal presence in Hitex Diamond wall, and 14 species were found in the Fibre Cement walls after just 30 days of wetting.
6. A number of Research Bulletins were created from the findings of this research and associated investigation and literature search and distributed to Council, Government and other Industry officials:
   • RB 301 Drying Wet Walls
   • RB 392 Wall Temps
   • RB 303 Drying Sole Plate
   • RB 304 Drying Wall Section
   • RB 305 Microclimate Wet Wall
   • RB 306 Interstitial Condensation
   • RB 307 Microbiological Examination
   • RB 308 Wood EMC