What is a “hot” roof? A “hot roof” means that insulation is installed closely beneath the roof decking, without space for ventilation. … Depending on the quality of the insulation, hot air from outside can permeate the insulation and warm the conditioned space, raising energy bills and making HVAC units work overtime.
Do you need to ventilate a warm pitched roof?
The enclosed void of a warm pitched roof does not require to be ventilated. … Rather than actively ventilating to the outside, entrapped water vapour diffuses through the vapour permeable underlay; negating the need for forming cavities or voids below the underlay.
Do you vent a hot roof?
A hot-roof is one where there is no ventilation required as the insulation is directly attached to the roof sheathing.
Do I need a Vapour barrier on a warm roof?
Warm deck flat roofs can be constructed on most modern construction material types such as concrete, timber and timber based sheets. … A vapour barrier will then need to be installed to reduce condensation in the roof structure.
How do you insulate a pitched warm roof?
To create a warm pitched roof, insulation such as Kingspan Kooltherm K7 Pitched Roof Board, should be fitted between and over the rafters. As this requires fitting insulation above the rafters the roof covering will have to be removed in order to fit the insulation.
Does spray insulation removes the need for roof ventilation?
The final thing about closed cell spray foam is that it will not allow moisture across it, which means that you will need to consider ventilation in the loft space to prevent build up of condensation.
What is a warm pitched roof?
Warm pitched roof
It has s insulation layer above the rafters, and immediately below its weatherproof membrane. … A warm roof construction allows heat to be conserved within a property – without the need for a ventilation system.
How do you vent hot air from a cathedral ceiling?
Several simple fixes can add circulation to a home with a vaulted ceiling.
- Ceiling Fan. Add a ceiling fan a few feet below the ceiling. …
- Whole House Fan. Install a whole house fan. …
- Attic Vents and Fan. Add the appropriate attic and roof vents to help remove hot air from the home. …
- Doorway and Circulating Fans.
What happens if a roof is not vented?
They say that poor or non-existent ventilation might cause attic temperatures to rise to 150 degrees or higher in the summer. That can lead to damaged shingles and other roofing materials as well as a buildup of condensation and development of mildew and mold.
Can a roof have too much ventilation?
Dangers of Too Much Ventilation
The two main dangers associated with too much ventilation involve roof damage and increased utility bills. If you have too much air circulating, your roof will collect moisture causing damages that will weaken spots and then cause leaking.
Can roofing felt be used as a Vapour barrier?
Plastic housewraps have largely replaced asphalt felt as the water-resistive barrier required by codes. … Fortunately a number of materials, including traditional asphalt felt (tar paper) have this ability to stop liquid water while remaining “permeable” to water vapor.
What is the difference between a breather membrane and a Vapour barrier?
The job of a vapour control layer, or VCL, reduces the water vapour transfer through any building and reduces the risk of condensation forming. … A breather membrane is positioned on the outer side of the insulation, allowing vapour to escape from inside while repelling any water that tries to enter.
How thick should the insulation be on a warm roof?
The thickness of insulation required will vary depending on the material you decide to use and the manufacturer’s specification. A ventilation gap, usually 50mm, should be provided between the top of the insulation and underside of the roof covering to allow the air to flow across.
Should you insulate between roof rafters?
Insulating between the joists of your loft will keep your house warmer, but make the roof space above colder. This means pipes and water tanks in the loft space could be more likely to freeze, so you will need to insulate them.
How do you insulate an existing roof?
Remove existing roofing and non-adhered underlayment to expose roof sheathing. Apply continuous air control membrane to existing roof sheathing or implement continuous air control at roof sheathing. Install rigid insulation board in multiple layers with joints offset vertically and horizontally between adjacent layers.