Roof Ventilation - The Only Guide You Need to Read

Words: 2137 💻 Read time: 10 mins 📚 

Writer: Scott Beddoes 👨🏻‍💻

Roof ventilation is one of those problems you know you should sort out, but you ignore it until it's too late.

You know those things that always seem to stay at the bottom of your to-do list?

Roof ventilation is the definition of one of those things!

And if it stays at the bottom, you could be running the risk of condensation and damp.

So it's important that you get roof ventilation right.

This Roof Ventilation Guide will show you everything you need to know, in one neat place.

And, you'll find out how to choose the best option for you and your home.

 

Roof Ventilation Requirements UK

To meet UK roof ventilation requirements, provide enough ventilation to avoid condensation in the roof space.

Ridge or high-level ventilation should be equivalent to a continuous opening of 5mm at the highest point of each roof slope.

For a roof pitch of 15° or more, provide ventilation equivalent to a 10mm slot running the full length of the eaves.

And for a mono-pitch roof, you need cross-ventilation, plus the equivalent of a continuous 5mm slot and some eaves ventilation.

We refer to the cold roof section in the ventilation segment of 7.2.15 by the National House Building Council (NHBC).

 

The Problem with Roof Ventilation

Quick history: when houses used to be built, the roof was installed over a breathable membrane.

As the name suggests, a breathable membrane is designed to let your home “breathe”.

But in recent years, the effectiveness of these membranes has been questioned.

The introduction of loft insulation has done wonders for keeping our homes warmer. But it can also reduce the effectiveness of eaves vents — sometimes blocking them completely.

And a warmer house means more potential for condensation.

 

Condensation in Loft - What Causes It?

So what actually happens when you don’t have enough roof ventilation?

Well, firstly, warm air rises and meets the inside surface of the roof.

Then the temperature difference causes the moisture to condense forming condensation.

Heat and moisture is produced by 3 main activities:

1️⃣ Cooking

2️⃣ Drying your clothes

3️⃣ Hot baths or showers (see our in-depth post for reducing bathroom condensation)

Without the right amount of roof ventilation, it won't be long before daily activities start contributing to condensation or damp.

In an ideal world, you want to catch it and take measures to prevent it before it develops any further.

Because the longer you leave it, the more costly the damage can be.

 

Damp Problems in the House

Damp in your house can cause these 3 problems:

✅ Wood rot

✅ Black spot mould 

✅ Health risk for people with respiratory problems

Thankfully, condensation and damp can be treated fairly easily.

You might even be able prevent the problems before they develop. 

 

Loft Condensation Solutions

There are 2 main solutions to the problem of loft condensation:

1️⃣  Vapour barrier membrane
2️⃣  Roof vents

Vapour Barrier Membrane

A vapour barrier membrane is a thin layer placed under the insulation between your loft and your upstairs rooms.

It is designed to prevent warm moist air from moving up from the house into the roof space. And it does that job well.

However, there are still points like the edges where air can still get through.

And when it comes to improving ventilation or adding extraction (which we'll go into later), you're going to need some type of roof vent. 

 

Roof Vents for Houses (Best Types)

Today, new builds require roof tile ventilation to pass building regulations, and owners of older homes are installing roof vents to improve ventilation.

There are many different types of roof vent for houses on the market. And each option has it’s good and bad points.

But which type of roof vent is the best?

Let's quickly go through them here to save you some time.

I'll tell you the pros and cons of each and give it a star rating out of 5.

Soffit Vent

Soffit vents are installed under the eaves of a roof. They let fresh air up into the loft to improve air circulation. This prevents loft air from going stale. When combined with roof ventilation tiles they work efficiently to draw air in through the soffit vents and exhaust warmer air through the ventilation tiles.

Pros	Cons
Easy to install	Designed for air intake
Unlikely to be blocked by snow	Different roof vents needed to exhaust air

 Product rating: ⭐⭐ 

 

Fascia Vent

Fascia vents are installed over the fascia boards to provide low level ventilation. They could offer a better alternative to soffit vents, because soffit vents can accumulate dust and debris. This can require regular maintenance and cleaning work.

Pros	Cons
Can't see them like soffit vents	Not an easy DIY option
Mesh keeps out insects	Can leave little space for guttering install
	Can be blocked by loft insulation

 Product rating: ⭐⭐ 

 

Cowl Vent

A cowl vent is a hooded roof tile vent designed to replace existing roof tiles. They can also be connected to a bathroom extractor fan using a flexible pipe adaptor.

Pros	Cons
Easy to install	Doesn't look great
Prevents draughts and wind-driven rain	Breaks appearance of roof
Prevents entry of bugs and insects

 Product rating: ⭐⭐⭐⭐

 

Lap Vent

Lap vents slip in between an overlap in the horizontal under-sarking inside the loft, providing an air path for the wind blowing up the face of the roof outside.

Pros	Cons
Simple, easy, and effective	Safe floor in loft needed to work on for internal fitting
Can install from inside - no need for external access or getting on the ladder	Might not provide as much ventilation as roof ventilation tiles

 Product rating: ⭐⭐⭐

 

Dry Ridge Vent

Dry ridge vents can be used on the apex of a roof to provide high level ventilation and exhaust moisture. Dry ridge vents aren’t really designed to be used as vents alone. They are more of an exit point than a source of ventilation. They can be used in combination with other forms of lower level ventilation such as eaves vents or soffit vents, fascia vents, or roof ventilation tiles.

Pros	Cons
If positioned on the apex of the roof with the felt or under-sarking suitably cut immediately beneath, they do provide excellent natural air movement	If you live in an exposed location and have large soffit vents as well, ridge tile vents have been known to cause too much ventilation on very windy days, possibly blowing the insulation about near the edges

 Product rating: ⭐⭐

 

Slate Vents

Slate vents are designed to replace existing roof slates. Slates come in 2 standard sizes - 600 x 300mm (24 x 12 inch) and 500 x 250 mm (20 x 10 inch).

You can get them in plastic and sometimes real slate. They have a grille and underbase that allow air to flow through the vent and out of the roof. Most slate vents have the option of a pipe adaptor fitting to create a connection for bathroom extractor fans and soil vent pipes.

Pros	Cons
Easy to fit	Must be fitted from the outside
Look better than cowl vents

 Product rating: ⭐⭐⭐⭐⭐

 

Roof Tile Vents

Roof tile vents are by far the easiest professional solution to roof ventilation problems.

They are easy to fit either during the process of installing a new roof, or retrofitting to older existing roofs. One vent replaces one tile.

There are roof tile vents designed to fit most tile profiles on the market.

You can buy them in the same colour as your existing roof tiles to maintain the appearance of your roof.

If you're venting your extractor fan through your roof, a roof tile vent is almost certainly your best solution.

How Roof Tile Vents Work

Pros	Cons
Easy to install	Must be fitted externally
Look good with multiple colour options
Available for most types of roof tile

Product rating: ⭐⭐⭐⭐⭐

Which Roof Tile Vent Do I Need?

There are 5 ways you can find out which roof tile vent you need.

1. Find a spare tile and check the back for brand name and model.
2. Ask a professional roofer.
3. Use Google images to look for similar roof tiles.
4. Visit tile manufacturer websites such as Marley, Redland and Sandtoft.
5. Send a photo via the Contact Us page at https://beddoesproducts.com/

Roof Tile Vent Dimensions

Tile Name	Length (mm)	Width (mm)	Roof Tile Vent
Marley Modern	420	330	Marley Modern Vent Tile
Marley Ludlow Plus	387	230	Marley Ludlow Plus Vent Tile
Marley Ludlow Major	420	330	Marley Ludlow Major Vent Tile
Marley Mendip	420	330	Marley Mendip Vent Tile
Marley Wessex	420	330	Marley Wessex Vent Tile
Marley Plain Tile	267	165	Plain Tile Vent
Marley Edgemere	420	330	Marley Edgemere Vent Tile
Marley Double Roman	420	330	Marley Double Roman Vent Tile
Redland 49	382	226	Redland 49 Vent Tile
Redland Renown	418	332	Redland Renown Vent Tile
Redland Mini Stonewold	418	334	Redland Mini Stonewold Vent Tile
Redland 50 Double Roman	418	332	Redland Double Roman Vent Tile
Redland Delta	430	380	Redland Delta Roof Tile Vent
Redland Grovebury	418	332	Redland Grovebury Vent Tile
Redland Plain Tile	268	165	Plain Tile Vent
Redland Stonewold Mk2	430	380	Redland Stonewold Mk2 Vent Tile

Let's use the example of the Marley Ludlow Major roof tile:

Find the Ludlow Major tile on the Marley website here: Marley Ludlow Major

Let's say you decide using the photos that you have the 'Dark Red' version.

Now go to the Beddoes Products website for the Marley Ludlow Major Vent Tile here: Marley Ludlow Major Vent Tile and select the 'Red - sanded' option.

 

What Colour Should I Choose?

Roof ventilation tiles come in 5 basic colours:

• Grey
• Terracotta
• Brown
• Red
• Black

Most manufacturers produce tile vents in smooth plastic in these colours.

Some roof tiles are different. They might be a mixture of 2 colours or old and weathered, causing the colour to change.

In these situations, the basic colours can stick out among your roof tiles like a sore thumb.

 

How Can I Colour Match My Roof Tiles?

At Beddoes Products, we manufacture everything in-house. Our products come in any colour in smooth or granular finishes. We can also colour match to existing tiles. All you need to do is send us a photo.

Check your tile manufacturers’ website and search for your tile. Some brands use different names for similar colours to their competitors. For example, Marley Old English Dark Red is a close match to Redland Farmhouse Red.

Send us an email to ask for advice about your colour, or leave a note with your order.

 

How Many Roof Tile Vents Do I Need?

Finding the right number of roof tile vents can be more of an art than a science. It depends on your house’s age, property type and location. 

It would be useful to ask for advice from a professional roofing expert, but you might want to make your own estimate.

Consider adding slightly more ventilation than is needed to allow for extreme weather conditions, while keeping costs as low as possible. Try to find a balance.

 

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

 Length (mm) x continuous airflow required.

 Example: 10m long roof requiring 5mm continuous airflow.

 10 metres  = 10,000mm long roof followed.

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

 

2. Work out the 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 the Beddoes Products Plain Tile Vent with an airflow of 7,500mm2

50,000mm2 ÷ 7,500mm2 = 6.67 vents (which would require 7 vents).

 

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

Length of roof ÷ number of vents

Following the above example: 10,000mm long roof ÷ 7 = Centres of 1,429mm.

Instead of putting 7 on one side of the roof, you would stagger them on opposite sides to get the best airflow.

Staggering would mean placing 4 vents on one side at 3 metre centres. Then placing the remaining 3 vents on the opposite side at 3 metre centres, but in between the 4 on the other side.

Think of it like this. If you were to draw a line between the vents on both sides, it would look like a zigzag.

 

How to Fit Roof Tile Vents 

The informative video below from the Fixmyroof YouTube channel demonstrates how to fit roof tile vents.

These are the simple steps described in the video:

• Remove roof tiles from the area where vent will be fitted
• Make a cross-cut in the underlay
• Fold out the top piece of felt and nail securely
• Prepare pipe adaptor and flexi pipe for connection (if installing for bathroom extractor fan)
• Re-position and nail tiles around the vent area
• Position and nail roof ventilation tile
• Complete positioning of remaining roof tiles

Keep in mind that these are the instructions for the Marley Ludlow Plus Vent Tile and Redland 49 Vent Tile.

Other vents will be similar but may vary slightly. 

Where Can You Buy Roof Tile Vents?

Builders Merchants and DIY Stores

Buying in-store can be good if you’re lucky. You can see the product close-up to check suitability and quality.

The problem is most stores only have a small range of products with limited stock. Colour choices will also be limited.

eBay

eBay has more product options than most builders merchants. If you search regularly, you might pick up some cheap deals from someone selling old stock.

 

Online Stores

Online roof tile vent stores have the biggest range of products with the best colour flexibility.

You could go directly to the big roofing stores. However, it might be better to Google search specific terms like “Marley Ludlow Major Vent Tile” to find exactly what you’re looking for.

I prefer this method because it means less pages to click through trying to find the right product category on bigger roofing websites.

 

Conclusion

In this guide, you've learnt how to decide whether you need roof ventilation, how to choose the best roof ventilation tiles for your home, how to select the right roof tile vent, how to find your colour and where to buy from.

Now it's time to apply everything.

Browse our roof tile vents full range.

📚 Further reading: How to Stop Bathroom Condensation

Need help? Head over to our Contact page.