Answer: When the temperature increases, the air can contain more water. At the same time, there is less need for room heating, and with less heating, indoor air humidity will increase, especially in winter. This could mean better living conditions for mould and house dust mite and therefore a poorer indoor climate and more incidents of allergies.
Answer: Complying with the building regulations will get you far. The most important thing is that joints and constructions are correct, and that gables, roof tiles, the facade, windows and doors have been properly fitted and secured. If individual roof tiles become detached during a storm, this could give the wind access to the attic, where pressure might build up. Combined with low pressure on the lee side of the house, this could lead to further damage to the roof.
Answer: Rainwater and meltwater must be led away from the house quickly and effectively. This is done e.g. by ensuring the ground is adequately levelled and by cleaning out gutters and drain covers, so that leaves and similar do not clog the drains or in other ways impede the flow of water. Snow and sleet piled against the house should be removed to avoid wet exterior walls and to keep any ventilation holes free. Furthermore, snow carried by the wind into the attic or other such places should be removed to avoid eventual moisture or water damage.