guitarsammy

I live in a 1985 Barratt house in Northern England, a 4-bedroom detached property in an exposed location. Despite having relatively new double glazing, ample loft insulation, and previously insulated cavity walls, I am looking to enhance warmth and reduce gas consumption. Through my basic thermal camera survey, I've pinpointed key areas for improvement: Downstairs is noticeably colder than upstairs, attributed in part to the uninsulated floors over a ventilated cavity. External walls exhibit a 'hollow' sound upon knocking, presumably due to plasterboard with a cavity between it and the blockwork. However, certain spots, particularly around windows like lintels, act as cold bridges. Considering the long-term nature of this project, I have a few questions to kickstart my planning: Insulating the floors seems potentially expensive and disruptive. Would lifting and insulating beneath the engineered wood flooring/Weyroc be the only viable option, or is there an alternative method? Despite having cavity wall insulation, would injecting insulation into the hollow spaces behind the plasterboard on external walls be beneficial by further enhancing u-value? Could this cause condensation issues? Alternatively, is it more practical to remove the plasterboard entirely and replace it with insulated plasterboard to address thermal bridging in those areas where the masonry is solid?