Roof Ventilation Buyer’s Guide

A cold roof is the traditional form of roof. Loft spaces for decades have been dominated by this type of roof and continue to do so today. In the modern day, they are commonly insulated at ceiling level using fibreglass insulation laid across ceiling joists. So what is the point of roof vents? In this guide you can learn what roof vents are, types and more to help you install the ideal ones in the roof of your home.

  1. What are roof vents
  2. Benefits of roof vents
  3. What issues occur from lack of ventilation?tile-vent
    a. Damp
    b. Unpleasant smell
  4. Types of vents
    a. Roof tile vents 
    b. Slate tile vents
    c. Lap vents
    d. Soffit vents
    e. Fascia vents
    f. Dry ridge vents
    g. Through wall extraction vents
    h. Vent turbines
  5. How many roof tile vents do I need? 
  6. What does “wind tunnelling” mean? 
  7. Roof vent compatibility 

What are roof vents and why do we need them?

Roof vents are applied to the roofing of properties today to help with reducing weather affecting the function of a home. You can find many amazing types of roof vent. If your property is older, it might not be required. Older houses were never truly built with proper roof vents, but it’s worth considering if your property suffers.

Having said this, you will need to consider that applying modern ventilation might not work with the classic model home. Discover a wide variety of roof vents in our range, including brands such as Redland, Britlock and many more major manufacturers in the roofing industry.


What are the benefits of roof vents?

There are many benefits to ventilation aside from reducing condensation and improving temperature control in the property. Two others are the following:

Energy costs reduced

Vented roofs allow heat to escape the space more easily. This can in turn reduce the need for such solutions of air conditioning for lower bills.

Life of roof extended

One issue that can arise, that many may not not know the name of, is “ice damming”. This is when heat from inside the attic combines with heat from the sun. This melts the snow and ice on your heated roof. As a result, water runs to the edge of the roof and begins to refreeze.

One this happens, ice and water builds up at the edges of the roof. It backs up behind or underneath the roofing materials, causing damage to your whole roof system. The damage can also be the result in your attic and the inside walls of your property.


What other issues occur from lack of ventilation?

There are multiple issues that can occur is ventilation isn’t correctly applied to the property. The two main ones are damp and condensation. However, there is a third which can be simply named as a strange smell which usually occurs in severely hot weathers. Here are some explanations of issues roofs can have without ventilation.

Damp

Loft damp is the result of warm, moist air being trapped in loft space that isn’t ventilated or cannot ventilate fast enough. Warm moist air can be created by showering, drying clothes indoors or even cooking. How damp forms is the warm, moist air condensates on the cold spots of your loft. It then turns back to a liquid state, where it will form small or large drops of water on the cold surface.

Unpleasant smell

Hot weather doesn’t stop issues arising. Although there isn’t common appearance of damp or condensation, there is a link between the hot weather and the roofing material. Black bitumen-based roofing felts get very warm and emit a bituminous. This isn’t a common smell, so many won’t realise this is the issue until later on when they hire a professional that is used to the smell. A strong smell can indicate lack of fresh air through air movement, so it’s important to get ventilation installed as soon as possible.

Lack of ventilation in hotter weather can also increase heat volumes in the house. Summers can be hot, but they can be even hotter without correct ventilation. How it develops is the sun heats the roof and loft space during the day, creating ‘solar grain’. This is when large volumes of hot, trapped stale air stops any heat from rising up and away from rooms below the loft space. It’s great for winter, but not so great in the heated summer weathers.  


Types of vents

There are a wide variety of roofing vent types available. Here is a brief overview of the most common.

Roof tile vent

A roof tile vent can be universal and very handy when incorporating ventilation into your roof. They can be easy to replace and, due to their universal manufacturing, they can added to any brand of roof vent compatible with tiles you choose.

You can find a wide range of roof tile vents here, as well as double roman, roll and much more. Each offer a style of ventilation to suit as much or as little as you need.

Slate tile vent

Slate roof vents are also ideal for their installation and range of designs available. They can blend in nicely with slate tiles. So if you would like something that suits the slate style roof, consider this solution.

Check out the sleek style slate vents from brands like Klober, Manthorpe and other well known manufactures.

Lap

These particular types of vent, also known as “felt lap” vents, they are another easy solution for ventilation problems. Especially in poorly vented areas of the property.

Though they are more commonly used on older roofs with bitumen ‘felt’ undersarking (waterproofing layers), they can also be fitted to roof membranes if needed.

Soffit

There are two main types you can find at soffit vents – circular and continuous.

This type a vent may also be referred to as eaves vents. These vents can be found installed in many modern houses and normally built into the soffit. The result of this is continuous 10 – 25 mm ventilation at low level around eaves of a property.

Manthorpe Continuous Soffit Vent (10,000mm2) - 2.44m Black

Fascia

Fascia ventilation allows air to pass into the roof space between felt and fascia board.

“Over vent” fascia is another good solution when it comes to problematic roofing spaces, but does not offer as easy of an installation process. However, the mesh grill design keeps out bugs, insects and is ideal for those who desire a hidden solution unlike soffit vents.

Dry ridge

Dry ridge is a mandatory for all new roof installations in the UK. They are installed without the use of mortar. Mortar is wet ridge, which is used to support this type of vent.

The dry ridge system is the innovative style of ventilation, combating the traditional method of using mortar and sand during the installation of ridge and hip tiles.

An ideal part of this type of ventilation is that there is little to no maintenance required. If, however, they have been applied with sand and mortar, then they will need to be replaced with mortar bonds.

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Through wall extraction

The through wall extraction vent isn’t limited to one style. Two main types are wall vents that are used to provide background ventilation and wall vents that are use to provide air to a room with heat-producing appliances (e.g gas appliances or central heating boilers).

Vent turbines

The vent turbine is a fantastic solution for those looking for a more eco-friendly source of ventilation. Not only does it use the wind rotate the ventilated air in and out of the roof space, as a result this can be fantastic for reducing your electrical costs.


How many roof tile vents do I need?

The way to figure this out will depend on the age and type of property. You can figure this out yourself or consult with a professional roofing expert. If you do decide to work out vent amount yourself, consider adding a bit more to the overall total. Don’t go insane, however, as this can be difficult to remove in future.

Ideally you will want to have the perfect balance. So try to consider what is needed and what might help further in specific weathers. Here are calculations you can make to figure out the number of vents you need for your roof:

1.Find total airflow required.  Discover the length of the ridge of the roof in MM. 

Length(mm) x continuous airflow required 

Example: For 10m long roof requiring 5mm continuous airflow –

10m x 1000 = 10,000mm long roof followed.

Then 10,000mm x 5mm = 50,000mm2 airflow.

2. Work out number of vents required, asking how many vents it would take to provide the same amount of airflow. 

Total airflow (provided by first calculation) ÷ airflow per vent 

Example: For CV20K vent with an airflow of 20,000mm2

50,000mm2 ÷ 20,000mm2 = 2.5 (which would require half vents or three vents if unavailable). 

3. Calculate centre centres of the vents, checking how far they need to be. 

Length of roof ÷ number of vents

Following above example: 10,000mm long roof ÷ 3 = centres 3,333mm.


What does “wind tunnelling” mean?

Wind tunnelling is when 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.

Having said this if you have added or are planning to add roof vents for clean air in the loft space, you may not care for such a solution.

In fact, another solution is tile vents. These can be fitted lower down a roof and combined with lap, dry ridge, ridge tile vents and roof tile vents fitted higher up the roof surface to improve air circulation.


Can roof vents fit with any tiles?

Some roof tile vents are only compatible with certain materials. This is often referred to in the name of the product, but if you’re unsure it’s worth double checking in the product description. Slate roofs, clay tile roofs and concrete tile roofs have different needs which shape and size tile vents will cater to.

Some roof tiles might also only be usable for high level roof ventilation, while others for low level ventilation. You can find a wide range of tiles with various information regarding their compatibility through our product range here.


If you would like more information, you can check out our website or speak to our experts via live chat or calling 01752 692 760 .

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