As loft insulation has improved over the years, our homes lose far less heat through the roof than they used to. This is fantastic for reducing energy bills, but it has caused another problem - condensation. 

If you’ve noticed it in your loft, roof vents will help improve air circulation and reduce condensation problems. But how much does it cost? We’ll explain everything in this guide.

How much does it cost to install roof vents?

How much it costs to install roof vents depends on the type of roof vent you need, whether you need scaffolding and roofer rates in your area, but here are the average costs:

*All prices are estimates based on the hourly or day rate of roofers and offers on materials.

Factors affecting the cost of roof vent installation

There are a few factors that will affect the final cost of roof vent installation:

• Type of vent: Different vent types can take varying amounts of time to install. Standard roof tile vents are usually the easiest and quickest to install, while ridge vents can take longer as the roof ridge is harder to access.
• Roof type and material: Slate, tile and flat roofs require different installation methods, which affect labour costs.
• Number of vents needed: More vents increase material and labour costs, but you may save money on the per-unit price.
• Scaffolding requirements: If access is difficult or over a certain height, scaffolding may be needed. This can add £500-£1,000 to the overall cost.
• Roof condition: If you need roof repairs carried out before vent installation, costs will increase. However, this could save you money on scaffolding as you can get both jobs done at the same time.

Image	Name	Cost
	70mm Timloc Push-in Soffit Vent x 20	£50.00
	Klober Uni-Plain Tile Vent KG9918 x 4	£116.00
	Klober Single Pantile Tile Vent KG9860 x 4	£123.00

What are roof vents and what do they do?

Roof vents help fresh air to circulate through your roof, which prevents condensation and moisture build-up in your loft. It’s important to have good airflow in your loft to stop mould and rot to your roof structure.

If you notice water droplets on the underside of the roof in your loft or even on things you’re storing in there, the chances are you don’t have enough ventilation in your roof space. If left to get worse, a poorly ventilated roof can lead to rotting joists and mould on your belongings that are stored in the loft - and in worst cases, it can spread to your ceiling or walls directly below the roof.

Modern houses have roof vents installed as standard, but many homes built even 20-30 years ago may not have them. There are many different types of roof vents available to work with different types of roof:

• Ridge vents: Installed along the roof ridge, providing continuous ventilation.
• Soffit vents: Circular vents placed under the eaves to allow fresh air to enter the loft.
• Eaves vents: Long, rectangular vents that are installed under the eaves.
• Tile vents: Individual vents that replace roof tiles, suiting a variety of homes.

A roofer will be able to tell you which type of roof vent is suitable for your home. Often tile or ridge vents are used alongside soffit or eaves vents to provide the best ventilation.

Why should you have roof vents installed?

If you’re noticing condensation in your loft, that’s a good sign that you should have roof vents installed. There are lots of benefits to roof vents:

• Prevents condensation: The added ventilation reduces the risk of damp and mould growth in the loft.
• Extends roof lifespan: Moisture build-up can weaken rafters and insulation over time.
• Regulates temperature: Stops the roof space from getting too hot or too cold, reducing the build-up of moisture.
• Improves energy efficiency: Helps maintain a stable home temperature, potentially reducing your energy bills.
• Protects insulation: Moisture-damaged insulation loses effectiveness, leading to higher energy bills.

While you may wonder whether roof vents are really needed, most homes can benefit from them. Any roof needs proper ventilation and without it, your home could suffer from damp and mould problems in the future. It’s always best to try to get ahead of potential issues before they arise to prevent damage to your property.

How are roof vents installed?

How roof vents are installed depends on the type of vent, but they all need to be installed via the outside of the roof, not the inside. If a roofer says that they can fit them from the inside of your loft to save money on scaffolding, be wary as they may not complete the job properly.

Tiled vents can replace one or two tiles, so are relatively easy to install. A roofer should cut a section of your roof’s felt underlay out, then fit the vent in the same way that they would a normal roof tile.

Ridge vents are secured to your roof ridge in a similar way to tiled vents. The roofer should cut away some of the roof felt then fit the vent into a gap where a ridge tile used to be.

Eaves vents can be used with tile or ridge vents to provide better ventilation. They can be as long as your roof’s soffits, which can mean removing many roof tiles and felt to install them. 

Soffit vents should be installed in the soffits at the halfway point between your roof joists. The roofer may use silicone to fill in any gaps before screwing the vent into the soffit.

How to work out how many roof vents you need

Your roofer will be able to advise you on how many roof vents you need, but you can use this calculation to give you a rough estimate of how many you require:

Length of roof x continuous airflow = total airflow

Domestic properties often require a continuous airflow of 10mm. So, measure the length of your roof in mm and multiply it by the continuous airflow:

20,000 (length of roof) x 10 (continuous airflow) = 250,000 (total airflow)

The number of roof vents you need will depend on the type you’re having installed, as each vent has its own ventilation area. You need to divide the total airflow by the ventilation area of the vent you’re using:

Total airflow ÷ ventilation area of the vent = vents required

As an example, a Klober universal tile vent has a ventilation area of 6,000mm². As your home requires a total airflow of 250,000mm, you will need 34 of these tile vents:

200,000 (total airflow) ÷ 6,000 (ventilation area of tile) = 33.33

It’s best to leave it to your roofer to advise on how many vents you need, as every vent has its own ventilation area, and they will know the best ones for your property.

How long do roof vents last?

As long as your roof vents are installed properly, you can expect them to last between 15-20 years. Aluminium roof vents tend to last longer than plastic ones as the material is more durable. 

Asking a roofer to inspect your roof vents any time you require any maintenance work done is a good idea. This can help you to spot problems before they get worse, and gives your roofer the opportunity to clean off any debris that may stop them from working effectively. 

If you notice that your roof has started to ‘sweat’ with condensation after you’ve had your vents installed for a few years, the chances are they are beginning to fail. It’s worth asking a roofer to take a look and see if your roof vents need repairing or replacing.

If you’re ready to install roof vents on your property, get multiple quotes from local roofing specialists to compare prices. Post a job on HaMuch now to find the best professionals in your area.

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