In Lhasa city, because of the abundant solar radiation, different direction walls absorb very different amount of solar energy. For the more efficient using of solar radiation, this difference should be reflected in the insulation design. By analysis on the typical year climate data, the absorption of solar radiation of different direction walls is clear. Compared with the inland city, Lhasa has more abundant solar energy and the bigger difference of direction, which means, the non-balance insulation is meaningful. The local test verifies the result of south and north room’s big difference thermal environment in the target building. By analyzing the permissible value of net heat loss by the envelope, the suggested limited value of overall heat transfer coefficient is proposed.