Building Energy Efficiency in Skillion Roofs. - Roof Ventilation

Create a healthy and energy efficient home by complementing your insulation with a passive Vent system.

Skillion roofs create a fantastic sense of space in a new build and an elevated, modern design, but they can be prone to moisture build up thanks to the minimal gap between the roof cladding and the ceiling.

New Zealand’s low overnight temperatures ensure we often reach dew point at night, and without airflow, dew point condensation settles onto building structures and materials, causing irreparable mould damage in roofing designs with minimal cavity space.

Read on to find out how a cost effective, passive ventilation system by Vent can protect your new build from moisture damage and create unmatched energy efficiency.

What defines a skillion roof?

Skillion roofs are characterised by their single-pitched design, they create high internal ceilings and are commonly used architecturally for a sense of space in the kitchen and living areas. The ceiling and roof run parallel to each other leaving little space for airflow. Minimum 25mm of space without any air openings top and bottom are typical, leading to trapped hot air and moisture issues, especially in New Zealand’s temperate climate.

Vent x Skillion Roof: An Application.

Vent products were specified as a complete system to create passive airflow in this new build recently. The high pitched ceilings provide a great design feature internally but leave little room for airflow between the membrane and the roofing in the roof cavity.

Skillion Roof design in Black Coloursteel.

In this project’s case, the insulation is 5mm thicker than the roof cavity. Without a passive ventilation system in the roof cavity there would have been damaging contact between the roofing materials, and no possible way for vapour to exit the roof space creating high risks of condensation build up and avoidable damage to a brand new home.

This project also specified a black Coloursteel roof and a black non-breathable membrane. Black attracts the heat of the sun and without a breathable membrane, even though this structure is completely compliant, it’s at high risk of sweating and ultimately damaging mould issues.

Vent’s Passive Ventilation Solutions

To mitigate moisture issues in skillion roof projects like the one above, Vent offers a range of passive ventilation products that work together to create airflow and a more energy efficient home. Vent products don’t require an energy source to activate and work across multiple types of roof cladding.

The Skillion Vent System, includes:

VENT G2500N Over Fascia Vent

The G2500N can be installed on top of metal or timber fascia to achieve continuous and calculated airflow of 25,000mm² per linear metre. The G25000 releases hot air from roof voids and manages moisture discreetly as it’s hidden by the gutter and spouting. It’s the only ventilation solution available for builds with no eaves. The G2500 vents are slim enough to stop birds and large insects accessing the roof cavity but wide enough to create airflow.

Installation:
Screw or nail to the top of the fascia through the fixing holes provided along the full length of the eaves. Compatible with steel or timber structures, the G2500N will fix along the top edge of any flat top fascia profile.

Ventilation & Drainage Batten 20mm – VB20

The BRANZ approved VB20 is a 20mm Polypropylene Ventilation and Drainage Batten designed to facilitate 16,000mm² per linear metre of passive airflow in the cavity between the roofing underlay and roof purlins.

Installation:
The VB20 comes with an adhesive underside for easy fixing to either steel or timber purlin, add nails or screws where required. The battens are 1800mm in length for easy handling.

Ventilation & Drainage Batten 10mm – VB10

The VB10 is designed to create a gap between roof cladding the roofing membrane to prevent the transfer of dew point condensation from the underside of the roof cladding to the underside of the roofing underlay or membrane. When the steel cladding is in contact with the roofing membrane, as the steel cladding cools, it transfers this cooler temperature to the membrane, causing condensation when it eventually drops below the air temperature. The VB10 batten is a simple solution to provide a space between cladding and membrane, mitigating contact and cool transfer.

Installation:
Strong and durable and produced in 1800mm lengths for easy handling, Install VB10s along the purlin runs by peeling away the backing to reveal an adhesive backing, eliminating the need for excess screws and nails.

Optional: Ridge Vent – RV10P

The RV10 is designed to release 8000mm per lineal square metre of warm air from each side of the roof void using the natural convection of rising warm air or through negative pressure created by wind blowing over the roof. The RV10 has an adhesive and flexible aluminium flashing which is adaptable to roofing profiles to prevent water ingress on any pitch roof.

We recommend:
RV10P for cladding profiles with a through depth < 34mm
RV10DT for cladding profiles with a through depth 34mm – 38mm

Installation:
Ensure underlay ends at the last purlin. Cut the ridge vent in half along the fold and place it into position on a barge or apron, peel the tape and push down into the roof profiles so it’s secure. Snip tape if needed to ensure a snug fit. Make sure the temperature is above 5 degree Celsius when installing.

Together, these products create an energy efficient home with consistent airflow when cavity space is tight. The Vent system ensures the moist air escapes while preventing cold air from entering, essential in mitigating dew point condensation.

RV10P

RV10DT

Installation Tips & Videos.

The complete Vent system is purposefully designed for quick and easy install without compromising strength and durability. We’ve created a system that protects your future build and maximises energy efficiency while ensuring your labour and material costs are minimal.

For more information on how to install a passive Vent system into your skillion roof check out this installation guide.

And, give us a call if you have any questions.