Humidity/damp and exessive heat are both issues from insulation not being done properly.Excessively insulated eh?
Thats an interesting concept, can you give your understanding of it?
Gas central heating should not cause condensation inside if it's a main installation as the boiler and heaters will vent outside. However, it's entirely possible to be using a gas cooker without extraction if the house was built before cooker extraction was required. Again, some folks have those mobile Calor gas type heaters, which vent inside so all water from burning gas is inside, or they have a cheap front-venting tumble drier, or they dry clothes on radiators, or use a shower with no/substandard extraction. All of those things need quite a bit of ventilation to avoid a rise in humidity, and extractor fans need to be combined with vents to draw in fresh air to be effective.
What has happened in many cases is that insulation was put into older properties (often via grants) but the ventilation wasn't sorted out, so the combination of moisture from people and also from the things I highlighted above cause condensation issues. Getting the ventilation right ventilation can cost as much as the insulation if new windows and extraction systems are needed..... so often this is overlooked in grant schemes.
Also, some properties have a lot of sun gain at some times of year, so the heat gets in and cannot get out again. Lack of ventilation and people keeping windows closed for security reasons being main reasons.
Insulation needs to be seen as part of a system but unfortunately with grant incentives to "insulate" without considering the system, there's a bunch of situations where insulating an older property has caused excessive summer heat or damp from condensation.
GC