BOOK Here's a good example of insulation and draught issues in a modern home (built in 2012). During a full house survey we identified cold air entering into the utility room, not just from the door but from under the sink.
The camera was set to show the temperatures below 14 degrees and you can see the cold air leaking into the house. On inspection, under the utility units, the drainage pipe from the upstairs toilet was entering the void below the floor and wasn't sealed. The supply pipes to the sink and the sink drainage also weren't sealed with cold air entering from below the house. The outside temperature for this inspection was 6 degrees.
The drainage downpipe and sink pipes were sealed and insulation was packed under the utility units. That made a big difference to the temperature within the room. The outside temperature had dropped to 4 degrees by this point. But you can still see a draught from below the door.
Adding a draught excluder to the bottom of the door completed the job. The temperature in the room was clearing higher with some simple diy insulation and draught exclusion.
