Research

Preliminary Results

Further information


Contact

Australian Research Council Linkage Project 140100375 Funds:


2014:  $30,535
2015:  $61,227
2016:  $30,692
Total: $122,454 


Strategic Research Priority:

Living in a changing environment


Strategic Research Priority Goal:  

Enable societal transformation to enhance sustainability and wellbeing


Field of Research (FOR):

120403 (70%), 080503 (30%)


Socio Economic Objective: (SEO):  

850704 (60%), 870503 (40%)


Keywords:

rammed earth; thermal performance; energy efficiency;


Delicious Digg Facebook Google Bookmarks Tumblr Twitter

Preliminary pageConstruction of the two houses was completed in September 2014.

Between this period and December, when the tenants arrived, we conducted several tests to see how the houses performed in an unoccupied condition.  Some example results for ten days in late spring are shown in the graphs below.  Data for wall surface and leaf temperatures and ceiling temperature were gathered using the commercial HOBO system.  Room temperature data was recorded using our in-house wireless sensors.  Over the course of this period the houses were exposed to temperatures between 7°C and 35°C with daily temperature swings of up to 18°C.

Comparing results for the monolithic and insulated houses makes the effect of including insulation readily apparent.  For the insulated house the outdoor wall surface and outer leaf temperatures are close to the outside air temperature whilst the indoor surface and inner leaf temperatures are close to the indoor air temperature.  The outer and inner wall leaves are isolated from each other.  For the monolithic house, there is a larger difference between the wall surface and leaf temperatures and the inside and outside air temperatures.  Temperatures on the surfaces and within the wall are also closer together showing that heat is able to pass through and be stored by them.

Thermal lag is the delay in peak outdoor and indoor temperatures and is due to high thermal mass walls absorbing, storing and releasing heat back into the house.  Therefore, longer thermal lags are generally found when more thermal mass is available. Although internal air temperatures changed little over this example period, thermal lags of between four to six hours were found for both houses.  The heat of the day was therefore offset to the early evening when outdoor temperatures were falling.  This makes it easier for the excess heat to dissipate, maintaining comfortable evening temperatures whilst recharging the rammed earth walls ready to absorb more heat the following day.

Although insulation is effective at separating the inner and outer parts of the walls, comparing results for the monolithic and insulated houses shows something quite unexpected.  There is no real difference between the room or ceiling temperatures in both houses. Both houses show a roughly steady internal temperature of around 20 to 25 degrees even when subjected to a sudden cold snap which occured on the 15 November 2014.  Although the temperatures in the walls dropped, this heat was successfully transferred in to the house so internal air temperatures remained largely unchanged.  Some questions therefore need to be asked about how these houses perform, specifically why the inclusion of insulation does not affect air temperatures inside the house.  A possible explanation might be that the non-rammed earth part of the houses’ envelopes around the kitchen, bathroom and the roof, are ultimately controlling internal temperature.  Another might be that thermal bridges in the insulated rammed earth walls where the insulation was not present, for example around windows, allowed heat to bypass the insulation entirely.  These questions are being investigated as part of the ongoing project.


Monolothic house (bedroom)

Graph Insulated RE house
Outside, inside and through-wall temperatures in the monolithic rammed earth house bedroom, prior to occupancy

Insuslated RE house (bedroom)

Graph Insulated RE house
Outside, inside and through-wall temperatures in the insulated rammed earth house bedroom, prior to occupancy