Why Do I Need Ventilation in the Roof Space?

Draughty houses are mainly a thing of the past. The problem is that all that moisture-laden air that used to escape with the draughts now only has one way to go — up into the roof space. Therefore, to avoid the build-up of that moisture-laden air and the problem of condensation and mould that comes with it, we need to look at loft ventilation options.

damp and mould on ceiling
Too much condensation in the loft can form mould on the ceilings directly below the loft space

Condensation and the Roof Space

Condensation happens because cold air can’t hold as much moisture as warm air. This means that, when warm air containing a lot of moisture meets a cold surface (such as your roof in winter), it cools down and deposits drops of water everywhere.

This is a problem not only because it makes your loft a less pleasant place to visit, but also because of the long-term effects of dampness. If left unchecked, you’ll likely find mould spreading over both the underside of the roof and anything you have stored in the loft. Even more seriously, it could create rot in the timbers, and you could end up with major structural repairs.

The good news is that most homes already have some ventilation in the form of gaps under the eaves of the roof which allow air to enter the loft space, flow across it, and remove some of that warm air with it. As long as there’s nothing blocking that flow such as poorly laid insulation of course. This built-in ventilation probably wont be enough to handle all of that humid air though so other methods are usually required – and this is where roof ventilation methods come into play.

How to Ventilate Your Loft Space

Roof Ventilation

One way of adding extra ventilation in your loft is to install roof windows. These have many benefits, but unfortunately, they may have a limited effect on condensation because the problem’s worst in cold weather, when you won’t want the windows open.

A better solution is to install roof vents. If you live in a modern house, they should have been built in. If you don’t already have them, though, you can combine loft vent installation with repairs to your roof or roofline.

The main types of roof space ventilation solutions are:

  • Soffit vents are fitted to the soffits, on the underside of the roofline. They can either be continuous strips along the soffit or a series of circular vents. If the vents were included when the house was built, they’re likely to be soffit vents.
  • Over fascia vents fit at the top of the roofline, instead of underneath. Though not as good at catching updraughts, they don’t attract as much dirt as soffit vents.
  • Roof tile/slate vents can be fitted in place of a tile or slate, and it’s even possible to combine them with a bathroom extractor for added effect.
  • Ridge tile vent is a vent fitted to the roof ridge instead of a tile, perfect for allowing the damp air to be pushed up and out by the draughts.
  • Lap vents are fitted from inside the loft to the roof’s undersarking. Unlike the other options, which require professionals, lap vents can be fitted by an expert DIYer.

Another solution to the problem of humid air build-up in the loft is the LoftZone floor-raising system which is designed to keep an air gap above the insulation and allow for air to flow through the loft. Using this in combination with air vents and/or loft windows is a great way of handling loft ventilation problems.


Hopefully, it’s now really clear why airflow within the flow is so important. The problems associated with poor airflow can be serious and even damage your health so it’s something every homeowner needs to consider.

If you want to know more about ventilating your loft space or are unsure of what you need, feel free to get in touch for a chat or ask a question.