On of our departures from the Passivhaus, or EnerPHit standard is that we do not plan to spend time doing numerical energy models, such as PHPP, which would be needed for certification. Our only thermal calculations to date have been for thermal bridge analysis, known as Ψ-values, and U-values for determining the thickness and extent of insulation to be used for our walls, floors and roofs, junctions, etc. Our scope is limited by the existing structure and there are elements of work that are not justifiable right now. For example, our roof junctions are a weak thermal point, but the roof is in sound condition. It does not make any economical sense to take it off solely to improve its thermal performance at the eaves and verge. In the time that we plan to live here, there may be a ‘blue moon’ opportunity when we do need to do some major work on the roof and the comparative cost of dealing with the thermal weak points will be <10% of the roof work costs.