After reading about 'earthship'house construction using thermal mass as its sometimes only form of heating/ cooling,i set about building this tunnel house, built on the same principals.I started with 6 railway sleepers for each of the middle hoops and 4 power poles, 2 each end, these were all cemented in to place,large bolts inserted and 6mm wire netting added between for reinforcement.One ton of cement and a hell of a lot rocks from our local river went into the four walls,then soil added to the sides and planted in native grass.
In winter with outside frost temp down to -8 C/-18 F,inside has not gone below 4 C/40 F, some tomatos"black krim" did make it though winter and have just starting to come away again now.In the summer we average day time highs of 30 C/83 F but when it gets hotter the inside/outside temperates tend even up.
This tunnel house gives me about a 9 month growing season and has helped expand the outside gardens season also.My thoughts now are towards building a second larger one with solar and woodburner for heating.
We have had about a years worth of rain in the last two weeks, thats why there water inside
its all ground water its just coming up from below