Dear Sir / Madam,

Recently we instructed a registered BER assessor to carry out a provisional BER for a sample log house. He did a thorough job within the parameters of the test but we feel that the test does not take into consideration other factors relevant to log house construction. We scored very well and received a rating of B1 but we feel we should have scored higher because the method of calculating log walls ( U-valued at 1 w/m2k ) is inadequate. Our standard log wall is 140mm wide.

  We have been aware for some time of the limitations of the methods used in calculating U-values and feel this is now outmoded for a number of reasons. Firstly U-value tests are carried out in “steady state” conditions which are inconclusive in the real world - also they assume that the product is installed properly. The other fact is that they don’t take into account the Thermal Mass Benefits of materials like timber.  If a log building with a lower BER rating is more energy efficient than a building with a higher BER rating then the Thermal Mass Benefit of log must be taken into account. I live in a log house and I know from personal experience how energy efficient they are. I attach a document relating to research by The Log Homes Council (USA) and U.S. Dept of Energy. This report is based on research carried out for more than 20 years on the Thermal Mass Benefits of log buildings. Their report shows that log homes use equal or less heating energy as their timber frame insulated counterparts and that log mass is a significant benefit.  It is a very thorough and well researched document and should not be ignored by anyone in the business of energy efficient and sustainable homes.You will find the conclusions of these tests on pages 11 & 27 of the attached document.

It is also important to take into consideration the sustainability of the building materials used to achieve an energy efficient house. There is not much point in having a house that produces low CO2 if large amounts of CO2 are produced in the manufacture of its materials. Wood is carbon neutral; this means that the carbon dioxide emitted by manufacturing timber is equal to the carbon dioxide absorbed by growing trees and so the carbon cycle remains intact. Every cubic metre of wood used saves 2 tonnes of CO2 being emitted. It is interesting to note that timber and therefore log is considered one of the most sustainable building materials available and yet log buildings are being penalised by Planning Authorities and now SEI. The Log House Company feels that the rules are set in such a way so as to facilitate the unsustainable nature of the building industry.

Regards

Eamon Murray              

    

 

 

Filed under: Log Wall Construction & BER energy rating on September 5th, 2008