How do I stop condensation in loft ?

[kelfoan]

I have noticed droplets of water on the roof felt inside the loft. Is there any way of stopping it ?

[dot.hawkes]

ventilation

[kelfoan]

How do I ventilate a loft? Would adding insulation to the roof such as polystyrene blocks help?

[KARL]

Condensation generally occurs when air comes into contact with a colder surface but it can also occur if the air itself is cooled to dew point or below - this also leading to it dumping the moisture it contains onto everything around it. Ventilation is not the only answer, and often not a desirable one if that means introducing heat loss. By far the best solution is insulation and draught proofing - a very foreign concept in Britain where the traditional answer is to lower the overall temperature through letting the wind whistle through (which admittedly works, as it did in times before effective heating was attempted). You do not describe the situation you have, but assuming it is a simple void with a "naked" roof above a ceiling, then you could consider applying insulation to the inside of the roof. You can use sheet foam which is precisely trimmed and fitted to the sarking (timber or other between/across rafters, if you have it) or either rock wool or glass wool with a facing of vapour barrier material (fixed to rafters, membrane side facing into the void). There are also contractors who will spray foam onto the underside of your roof - this acts as insulation and vapour barrier in one (as would foam sheeting). Adequate access to do the work is essential.

[buildersmate]

Good answer, Karl, except the last bit (IMHO). I fundamentally disgree with you about spraying the tiles with foam. It locks them in place and makes later renovation very difficult.

The other answer, of course, is better forced extraction in the rooms that are creating the water vapour in the first place. Mainly bathrooms (especially shower-rooms), kitchens, and wherever you hang the clothes to dry in winter.