Home > Danelaw Pitched Roofing > FAQS > Ventilation

Ventilation

Do you offer a universal tile vent?

No. This is something that we have considered, however all universal designs are a compromise and usually considered quite unsightly when installed.

We do offer a wide range of discreet flush fitting tile ventilators to suit most applications.

When installing tile vents in a roof with sark boarding, does the board need to be cut?

Yes, a hole that corresponds with the rear spigot or aperture of any vent should be cut in the sarking board when the vent is being used to deliver ventilating air into the roof void.

The underlay should be cut and dressed around the opening to divert any rainwater or condensate around the opening in the roof.

What is the airflow of your tile vents when used for extraction terminals?

Generally, the airflow is restricted by the length, size and straightness of the ducting being used, and the adaptor that connects the pipework.

We can only quote the pressure resistance created by the baffles and louvres in vent design. The extractor fan should be selected to suit the variables found in each different application, and as advised by the extractor fan manufacturer.

My roof is covered with hand-made clay tiles therefore I need a tile ventilator that doesn’t show when installed. What can I use?

The Danelaw HD 10/10 plain tile ventilator is designed to carry small cuts of the same tile that is being used on the roof, and therefore is not visible on the completed roof except for the small black ventilation slot that must remain exposed.

What is the minimum roof pitch for your slate and tile vents?

This depends on the individual product. All of our slate and tile roof vents are designed to suit the minimum pitch of the slates or tiles that they are intended to be used with.

Do I cut the roofing underlay at ridge when using your CON6+ dry fix ventilated ridge system?

Where ridge ventilation is being provided for, the underlay may be terminated short of the truss or rafter apex on both sides of the roof or laid over the apex and cut afterwards.

It is important to ensure that the drape or sag in the underlay does not cause the opening at the apex to become restricted. Best practice is to cut the underlay along the ridge line and tack folded back to prevent this.

Why is my vent leaking?

No good quality roof vents leak when installed correctly. If a slate or tile vent is suspected of leaking, the circumstances should be considered.

It is possible for rainwater and condensation to run down the roofing underlay and drip though the opening cut into the underlay. This will usually be apparent on the outside of the vent, or on the underlay. To prevent this, the underlay should be cut and dressed around the opening to divert any rainwater or condensation around the opening in the roof.

If water is draining through a ceiling extractor fan, it is most likely that it is condensation forming in the ducting and draining back to the fan. To minimise this, the ducting should be as short as possible and lagged with insulation where it passes through a cold roof space. If this is not possible, or the problem persists and a condensation trap has not been fitted above the extractor fan, then this should be done.

In very extreme conditions, such as experienced during the ‘Beast from the East’ in 2018, extremely low temperatures combined with fine dry powdery show can create a situation where small amounts may enter through the ventilator. It is not possible to produce a ventilator cost effectively that will allow the free flow of ventilating air and not the very fine snowflakes.

In these situations, in-line or flush fitting ventilators often perform better due to an internal rainwater trap rather than those that rely on a covering hood or cowl.

How do I ventilate a cold roof?

Ventilation openings can be provided at the eaves over a fascia, through a soffit or at a brick corbel, at low or high level through the roof surface using slate or tile ventilators, or high level using a mechanically fixed dry ridge system.

The actual requirements will depend on the pitch of the roof and the span of the roof.

How do I ventilate a warm roof?

Warm roofs generally do not require ventilation as there should be an Air & Vapour Control Layer (AVCL) or vapour barrier on the warm side of the insulation to prevent the passage of warm moisture laden air to the colder uninsulated parts of the roof.

Where the insulation follows the line of the rafters, often referred to as a ‘hybrid’ roof, this may or may not require ventilation depending upon the design detail and the roof covering type.

How many tile or slate vents will I need per metre to ventilate a roof space?

This will depend on the opening area equivalent. At the eaves, it will be either 10,000mm² per metre or 25,000mm² per metre of eaves and 5,000mm² at the ridge or on both sides of the ridge depending upon the situation.

The calculation is:            area opening requirement (mm²/m)  x  length of eaves (or ridge) in metres.

vent airflow area opening (mm²)

Can I use you plain tile vents for mechanical extraction in a vertical application?

We would not recommend this as it is likely that high levels of moisture in the form of vapour would flow under the tiles in the courses above and condense on the underside of the tiles, battens and wall facing material.

Can I use one of your tile vents for a cooker hood extractor terminal?

Technically yes, however because it is not usually possible to access, dismantle and clean a roof ventilation terminal of any build-up of grease etc, we would not recommend it.


Danelaw merchants stockists pitched roofing products Danelaw merchants stockists pitched roofing products

Danelaw Stockist

We have a comprehensive list of merchants across the UK that stock our Danelaw roofing products. Search using location, and discover a list of stockists in that area with contact information of the branch and your local area Sales Manager, who can help you with any questions you may have.

View Stockist


Download a brochure

Download the Danelaw Brochure or Pocket Product Guide

Need advice?

If you need any advice just contact our dedicated technical team who’ll be glad to help

Want to book a CPD seminar?

You can fill out our online booking form and select the appropriate seminar for you

Share this page on your social networks

Main Hambleside Danelaw logo
Hambleside Danelaw Limited
Long March, Daventry, Northamptonshire, NN11 4NR, UK
+44 (0) 1327 701 900   |   +44 (0) 1327 701 909
iso-certification

© Hambleside Danelaw Limited