Condensation in the loft? Why do I get it? How do I prevent it?
Winter is the time of year when the temperatures can suddenly drop dramatically and rise quickly due to the sun coming out.
The sudden change in the weather means our loft spaces start to get colder, and the immediate heat generated by the sun hitting the roof will generate warm air quickly before the loft space has adjusted to it. Warm air contains moisture, so warm air plus cold surface equals condensation!
Moisture can form on the underside of the roof felt/membrane/wood to form droplets of water. This is especially common with older houses, but can also be present in newer properties.
So what is the cause? Well, some percentage of warm air hitting a cold surface is to blame, so make sure your loft is well insulated (government recommended level is 270mm). Check you have a quality draft sealed and insulated loft hatch. If you have an old wood one, check the seal is tight and make sure there is insulation on top of it. It's best to have it replaced with a modern one though, as the old ones tend to leak badly, letting warm air in to your loft. No point having loads of insulation, when the heat is seeping out through your hatch.
Check for any old holes left in ceilings and walls by workmen, where old pipes/cables used to be and seal these up.
Never block the eaves of your loft as this will stop vital air circulation.
The biggest culprit for condensation is the lack of air circulation.
Fit some soffit vents or slate/tile vents and clear the eaves so air can flow correctly. DO NOT board directly on to your ceiling joists and DO NOT squash your insulation to board for storage. This will cause or add to the problem, as well as reducing the efficiency of your insulation by up to 50% or more. The best way to get around this so you can add some loft boarding, is to install a raised storage area at least 50mm clear of the top of the insulation level, so that air can circulate around and underneath the boarded area without being restricted. It's best to use a raised loft floor system like LoftZone Raised Loft Floor to do this job correctly and professionally, or you can use a timber trussed raised sub-frame if the LoftZone system is not suitable.
Also, look for other heat generating appliances in your loft, such as unlagged hot pipes from boilers etc.
Add more soffit vents, wall or roof vents to help create air flow, unblock the eaves & check the seal on your loft hatch. If your loft is already boarded, check to see if it squashing your insulation. There should be at least 50mm above the insulation of clear space.
Some simple checks could solve this problem. In some small cases it could simply be bad design, but it is more commonly blocked soffit & air vents or suffocating loft insulation.
Here is a link to raised loft floors
All about sub-frames
More news here