When we had our first Dehumidifier many years ago ( on our third one now, we have only had compressor based ones, because it it gets below 5degC inside your house you have a bigger problem than humidity, and dessicant ones are quite expensive to run because the dessicant has to be dried out inside the machine using a heater ) I was shocked by the amount of water it was collecting, we had to empty the 3 litre ( IIRC ) a couple of times a day for first few days, then the time to empty the tank increased and eventually we could run the machine for over a week to collect 3 litres. Ours is a modern house as well, I hate to think how much moisture is locked up in the building fabric of older houses with solid stone walls, especially sandstone. The contractors who were fitting insulation were supposed to do a survey of walls to make sure they were suitable to insulate, but they never seemed to, and just pumped the stuff in willy-nilly, our walls already had the cavity partly closed off with expanded polystyrene boards when houses were built, so where the new insulation was going to go was anyones guess. I think Pikeys were the main contractors and they were payed by the job by government, so they took about as much care as they do when fixing potholes for the council or laying a new drive with an inch of hardcore and half an inch of tarmac.
If you look at my earlier post about loft insulation- where did the advice to put 300mm of glass fibre in the loft come from when the optimum is 150mm ( and maybe 100mm if insulation is sealed in with chipboard, which limits air movement. 300mm makes the loft pretty much unusable and is well past the point of diminishing returns, it looks to me like lobbying from the insulation industry to increase their sales and gives no real benefit as far as heat loss is concerned.