heating technology assumptions (house type, existing/new, decentral gas boilers)

for many technologies there are different assumptions in DEA depending on the house type (e.g one family house/apartment complex) and for new and existing buildings.
Currently the assumptions for existing one family houses are assumed (I have checked for some technologies the investment costs per MW, they don't change much between one family houses and apartment complexes). In general, one could assume a certain percentage of new buildings for the cost assumptions.

For decentral gas boilers there are investment costs and possible additional investments which apply for grid connection if the house is not connected yet
those costs are currently excluded with the assumption that there are no new
decentral gas boilers build in houses with no gas grid connection. This results in high FOM of 10.5% which should be discussed.

The issue names no file, test, or entry point. First clarify the intended assumptions for house types, building age, and decentral gas boiler grid-connection costs with the project maintainers. Done means the agreed assumptions and their treatment in the technology data are documented and consistently applied.