Ice damming’ occurs when heat from inside the attic combines with the sun’s heat. It melts the snow and ice on your heated roof, letting the water run to the edge of the roof and begins to refreeze. In cases of severe condensation or for large roofs where the distance between eaves exceeds 10m (30ft), or the roof pitch is steeper than 35o, then it is recommended that an additional row of ventilation panels be fitted into the highest line of roofing felt or underlay lap closest to the ridge on both sides of the roof. On a cold day there will be condensation on the roof felt – this will be droplets running downs the underside of the roof felt It is recommended that one ventilator panel is fitted between each rafter in the lowest underlay lap above the level of the insulation layer in the loft on both sides of the roof (see product brochure fig. 1).

It is very important that your loft is ventilated. As we have discussed, poor ventilation leads to condensation forming and this condensation can soon rot roof timbers and cause structural damage. How to Spot Signs of Condensation and Damp in the Loft? Ventilation ridge placed on roof with slit cut into felt to allow warm air out. Images courtesy of roofing ventilation.co.uk Wind tunnelling is when the air will through one vent and out through another. Perhaps via one vent from one side of the roof to another. This can be useful if your property is at risk of high condensation in the loft as air can pass through without affecting the circulation. I just bought a load of 200mm insulation to top up the loft to see if that would help with the problem. I cleared everything out yesterday and when I went to start rolling it out today I have noticed that the roof is covered in beads of condensation and some of the wood is damp. I'm assuming from the sub zero temperatures last night as there wasnt any rain.Alongside the tile and slate vents, Danelaw offers a range of eaves and soffit vents, CON6+ and CLAY6+; the ventilated dry fix ridge and hip systems. Ridge tile vents are placed on the ridge, at the very peak of the roof to allow warm air to escape rather than condense in the roof space. The vent ridge replaces a normal ridge tile and the felt below the vent ridge is cut to allow the air out through a sleeve which comes with the ridge tile. Ridge tile vents can, by adding a pipe adapter, also be used to fix an extractor fan hose to.

At this point (called the eaves) there should be a gap between the underside of the roof and the outside wall. This gap should be about 50 – 75mm wide and will usually have a meshed grill within it stopping insects and birds getting in. We are quite used to seeing condensation in the bathroom, firstly in the form of hot steam as we shower or bathe, but then, as the bathroom cools, the steam condenses on the ceiling, cold water pipes, tiles etc. It is not so obvious in the loft. A rule of thumb is that, for a normal double pitched roof (IE sloping on both sides) of 15 degrees slope or over, you would need (to vent it properly) a continuous 10mm opening all along the ridge. This would give you a “free” air flow per m, of 1m (=1,000mm) multiplied by 10mm = 10,000mm2. One issue that can arise is “ice damming”. Many homeowners and professionals who are familiar with these lofts issues know of this problem.There are many benefits of roof vents. From reducing condensation to improving temperature control in the property, they’re admirable for many reasons. Two others are the following: Energy costs are reduced When upgrading roof space insulation, it is important to consider the effect on the roof and ensure that adequate levels of roofing ventilation is provided or maintained to avoid damage and the decay caused by the increased risk of condensation. Hambleside Danelaw have produced a short article about the ventilation requirements for cold and warm pitched roofs which is featured on Roofing Today. Ensuring familiarity with the roofing ventilation requirements will assist in constructing an appropriately ventilated roof. A dry ridge vent system is mandatory for all new roof installations in the UK. They are installed without the use of mortar. A mortar is a wet ridge used to support this type of vent. There is a calculation that is use to work out the airflow required but it is based on a given airflow requirement. This is determined by building control or another expert, and typically not available if you are trying to find a solution to the ventilation problem retrospectively. Danelaw® offers a wide range of roofing ventilation products covering a wide range of tile types and construction details, from new build developments to refurbishment.