Roof Vents to Prevent Condensation

Over the last 16 years I have installed new roofline fascia boards to hundreds of houses, I always install roof vents with each installation to help prevent condensation. This page is for those of you who suffer from loft/roof condensation.

It is always worse in winter isn’t it? As a roofing contractor I always get a surge of phone calls whenever the temperature drops below freezing.

Here is an example of a typical question I am often asked:

It was fine all year, now my loft is damp and there are water droplets on the underside of the felt. What is causing it?

Another Common Concern I Often Hear:

I see mould, green and black marks on the walls/ceilings and near the window frames, what is causing it?

If the temperature has recently dropped below freezing then this is a BIG CLUE as to what the problem is, I will explain:
In winter we keep our windows closed to keep warm, this causes a build up of moisture in the home, think about it; that shower you just had, the kettle you just boiled, the dinner you prepared in the kitchen, the wet clothes you just put on the hot radiator, the washing machine dryer pumping out steam, even the iron.

Moisture Has to go Somewhere

Moisture will stay in your home until it comes into contact with a cold surface, it will then condensate and turn to water, that’s when mould and other problems start to appear. This can happen all year round but is far more common in winter when it is colder. Here is a list of common areas where you will see water droplets or damp issues in winter months:

  • In the loft – hot, warm air rises until it goes into the cold loft and condensates, if you see water droplets on the underside of the felt this is a symptom of the problem
  • On walls that are cold – External walls are often very cold in winter and become a point of condensation, expect water marks on the walls and damp or mouldy patches/spots
  • Window frames and ceilings – the ceiling tends to suffer more in the corners or where it meets the walls (always external walls). Single glazed windows are a nightmare for condensation in winter

Prevent Loft Condensation – Solutions

You need to ventilate the loft so moisture is allowed to escape whilst insulating the walls and ceiling to prevent any cold “areas” within the habitable part of the home.

Good quality insulation on the ceiling followed by some roof vents should help, however if you are still pumping out moisture (kettle shower bath etc) in your home then you will need to make some lifestyle changes, these can really reduce the amount of mould/black spots/damp your property will suffer from in winter months.

Remember – smaller homes like flats and bedsits etc are more likely to suffer from lifestyle-type condensation.

Tile for venting roofs and lofts

Lifestyle Changes

Keep the bathroom door shut when bathing or showering, then when you are done, open the window for a short while so moisture can escape.

Don’t hang clothes on the radiators during cold weather spells, use a clothes rack like this one put it in a single room near the hot radiator, also open a window so moisture can escape.

When cooking keep the kitchen door shut and make use of the extractor fan, also open the window slightly.

Go into your loft and ensure that the water tank has a suitable cover and there is nothing up there that is faulty, such as a faulty water heater or broken vent pipe etc

Roof Vent

A roof vent will allow airflow through the loft and will help to reduce condensation.

When ventilating a roof every homeowner needs to be aware that installing vents on properties with little or no ceiling insulation may result in issues arising:

1) Drop in overall house temperature

2) Increase in heating costs.

This is the result of the warm air generated by the central heating being allowed to escape through the roof.

There are several ways to vent a roof, however ensuring that the ceiling has insulation is ESSENTIAL.

Tile Vents

A tile vent can be installed to either new or existing roofs.

It is not always a good idea to vent the roof at the highest point – two thirds of the way up the roof is fine. Usually 2-3 vents per side of a roof are required however that is based on an average 7m x 4m roof side.

Vents should not be placed parallel to each other but should be stepped so true air circulation in the loft can be achieved.

The vents can be installed by following these instructions:

  • Remove tiles and timber batten to area
  • With a pencil and using the vent as a template draw an outline – avoid timber rafters!
  • Using a sharp knife cut the hole into the felt
  • The vent pipe is then pushed through the hole and secured via the fixing holes
  • Roof tiles are then re-laid and cut around the vent pipe – easy

On the Ridge

As an alternative to roof tile vents, a pre-vented ridge tile can be fitted which works equally well.

The vent is in most cases cemented to the existing roof, just as a standard non vented ridge tile would be.

Because the vent is placed at the highest level of the home it will allow warm air to escape with ease.

Vents for ridge tiles.

Eaves Vents

There are various eaves vents that can be installed to help reduce condensation in the eaves section of the roof.

Soffit vents and fascia strips can both be installed to both new and existing roof-line boards. These can be used in conjunction with other types of ventilation or as a stand alone product.

Our eave vent page contains more useful information.

vented soffit board

One Response to “Roof Vents to Prevent Condensation”

  1. Alison Miles12/10/2012 at 12:19 pm #

    Hi Daniel

    Can I ask you as a house owner, is it a good idea to have venting tiles in the roof in the following circumstances – I have a water tank and water pipes in the loft so worry about them freezing (I live in Scotland!), I have no central heating so keeping house warm with electric heaters and coal fires and have limited loft insulation which I can’t afford to improve.

    Has been suggested as had wet beams in loft last year but I thought may have been due to badly broken ridge tiles which builder didn’t return to repair so were like that all year.

    Any advice gratefully appreciated.