I hear you about foil backed insulation, but the walls are relatively thin which means than any signal that gets through the windows can reach reach most of a room. I usually get good reception in new builds, compared to the centuries-old limestone buildings round here. Floor to ceiling glazed patio doors can't hurt signal in new build houses, either.
What is criminal is building a new house without whacking a load of Cat6 cable in the walls prior to plastering - it'd be far cheaper than powerline or WiFi repeaters, and cause less RF interference too.
