Forums DIY Ground Source Heat Pumps Reply To: Ground Source Heat Pumps October 25, 2018 at 2:36 pm #431 FUZZY 15 Posts Simple stuff like thick curtains, draft excluders and substantial underlay can make a big difference. If you can manage it, move the radiators from the usual, maximum inefficiency position beneath the windows to internal walls where a substantial portion of the heat generated won’t be immediately leeched outside.