The human body, as we all know, is an incredible piece of biological engineering. And the body needs to deliver oxygen to the blood, so it can survive. A house, although not a living organism is much the same – it needs to breathe. Without ventilation the air is trapped inside and condenses. If there is any moisture in that air, especially warm air then water is produced.
The roofing area and your loft is a prime area of this condensation effect. Many roofs in the UK have insulation at the floor level, as opposed to in the rafters. This means that cold and damp air is allowed to seep in. This means two things can happen
- If damp air comes in then you now have moisture coming into your property. This obviously leads to problems such as mould, decay and disintegration of materials like wood and brick.
- With the warm air from your heating rising up through the floor and coming into contact with the cold air in your loft, this immediately condenses into water.
A poorly insulated floor will have gaps and will let the heated air from below into your roof space. Then the fibre glass insulation that 90% of British households have, will absorb the moisture and become damp.
Then of course, if you have a damp insulation product, this will actually conduct the heat through instead of trapping it below. This is a ever decreasing cycle of insulation and condensation. Most roofers will tell you that proper ventilation will stop this effect and keep the roof space dry. This also helps to protect the battens, the sarking (felt) and the rafters.
The worst case of this I have seen was when the insulation on the loft floor was piled in about 3 feet thick. This was great at keeping the heat below, but made an extremely cold loft. The roofing tiles had no tile vents, and the soffit vents had been covered by the insulation. There was literally no air flow at all, the resulting condensation had caused all sorts of damage.
First of all the insulation was incredibly damp on the top, showing 20% of moisture. But the most expensive issue was the rotting timber. Over the years, since the insulation and air tight roof had been installed, the water had absorbed into the woodwork of the rafters.
If you are afraid this is happening in your roof space, a simple check will tell you. If your rafters have white stains and visibly look like they are damp its pretty easy to tell. But buying a simple moisture monitor will give you the whole story even when the visible signs have not developed yet. This monitor can be stuck into any material and will give you the exact moisture level. Anything over 10% moisture is showing signs of too much moisture being absorbed.
So how do you ventilate your roof?
There are several ways that air flow can be encouraged by different types of vents
- Tile Vents
These can be installed by a professional roofer quite easily. They simply remove one of your existing tiles and replace it with a tile vent. 2 or 3 on each side of your roof will usually be enough to ventilate an average size property.
- Soffit Ventilation
Another good way of drawing out the cold air in your loft is adding vent to the soffits. This is the part of your roofing which overhangs the property wall. Cold air essentially flows downwards so giving that air somewhere to go.
- Gable End Air flow
Putting a vent on the top of gable end wall (The wall part of your loft at each end) will allow ventilation through the roof area.
Making sure a roof is well ventilated is a basic industry standard which should be taken into account every time a building is put up or a new roof is installed. However it is amazing how often it is not done correctly.
Here at Roofersbristoluk.co.uk we have over 25 years’ experience of installing roofing on new build projects as well as replacing on older buildings. We supply the domestic and commercial sectors with the correct materials and roofing products ensuring a consistent and well received service. As we have the know-how on properly ventilating a property, our customers find that their materials will stand the test of time and not cause any headaches in the years to come.
If you need any roofing work or advice click onto our home page, read our reviews and contact us for a first class roofing service that no other company in Bristol can match!