Most houses in the UK are not energy efficient and have little purpose of energy rentention i.e using insulators or double glazed windows. To some, there is no need for this as the cost of proper insulation or double glazed windows are probably more than what they pay in a year to utility companies, still it is very expensive to do without proper energy retention schemes in homes. Although, there are a few tricks like putting cling film on windows and making sure no cold drafts in and around the house. This helps retain the heat in the house, meaning you do not have to switch on the heating for long hours, reducing your co2 emissions and the amount you spend on gas and electricity. This might not cost you money, it’ll certainly cost you your time. There are other ways to heat your house, like if you have a mobile electricity heater, you can use it in one room where you are at the moment. Anyway you look at it, cheap? cost you your time, expensive? cost you money. Finding the balance between the two is crucial, assuming you already have a good type of supply with your utility company.