A　comprehensive　numerical　study　of　the　equivalent　thermal　conductivity　of　a　multi-holed　clay　brick　with　the　size　of　240　x　115　x　90　(in　mm)　has　been　conducted,　and　50　kinds　of　combination　of　holes　and　arrangements　are　examined.　The　indoor-outdoor　temperature　difference　varies　from　50　degrees　C　to　20　degrees　C.　The　effects　of　following　factors　are　studied　in　details:　the　hole　surface　radiation,　the　width-wise　and　length-wise　hole　numbers,　and　the　indoor-outdoor　temperature　difference.　The　major　findings　are　as　follows:　(1)　the　radiation　between　hole　surfaces　has　some　effect　on　the　equivalent　thermal　conductivity,　thus　it　should　be　taken　into　account;　(2)　the　hole　number　and　arrangement　affect　the　thermal　conductivity　in　a　rather　complicated　manner.　Analysis　shows　that　depending　on　the　relative　importance　of　natural　convection,　surface　radiation　and　heat　conduction　through　the　clay　solid,　the　thermal　conductivity　may　decrease　with　the　hole　number　or　increase　with　the　hole　number　and　(3)　among　the　50　kinds　of　combination,　the　optimum　configuration　is　found　which　has　five　length-wise　holes,　four　width-wise　holes　and　all　the　holes　are　from　bottom　to　top　in　the　depth　direction　of　a　brick.　Its　equivalent　thermal　conductivity　is　0.419　W/(m　K),　which　is　only　53.1%　of　solid　clay　of　which　it　is　made,　showing　great　energy-saving　possibility　if　it　is　adopted　in　the　construction　of　building　wall.　Detailed　discussion　of　the　simulated　results　is　conducted　and　flow　field　and　temperature　distributions　are　also　provided　for　some　typical　configurations.　(c)　2008　Published　by　Elsevier　Ltd.