It is called recuperator. If it is possible to retrofit i suggest to use mounted in attic (it will be silent). Otherwise, if you want higher quality not and th

It is called recuperator. If it is possible to retrofit i suggest to use mounted in attic (it will be silent). Otherwise, if you want higher quality not and these `breathing` types the box will have similar size like air conditioner (search: mitsubishi vl-100eu5-e)