Just coming across some interesting discussions Thermal Insulation of Solid-Walls is Underestimated
Very interesting. The article describes my “solid” masonry walls quite accurately but doesn’t take any account of moisture in them.
I am wondering if generalised surveys that use average values of components are much value and we really should be moving to actual readings of ventilation heat loss humidity and proposing appropriate sets of solutions. The almost identical handed terraced property next to us has a very recent rating but its aspect allows it far more solar gain.
It must be personalised. For example
There are two separate issues here. The house/residence as it stands and its occupants needs.
I don’t think that one certification should cover both. The energy and perhaps water needs survey is a general document useful to all (or at least it should be).
The special needs survey is of interest to a minority and each special need is unique.
My house has an access ramp, is wheelchair accessible on the ground floor, with a wet room for bathing. That will mean nothing to the typical buyer but cost a lot to implement.
The full version of SAP used for design purposes and the projected EPC of new builds has a database of components with their U & λ values. The normal rdSAP used for existing properties doesn’t, hence the “rd”, which stands for “reduced data”.
PHPP has even more stringent specifications but is not in general use in this country.
There is only a vague correlation between rdSAP and PHPP results. A Passivhaus will often get a poorer than expected EPC.