A cold roof in a flat roofing scenario is the one whose thermal insulator is below or inside the structure of the roof. The temperature of the roof structure is almost the same as the outside. The definition of a warm roof on pitched roofs relates to the space between the pitch of the roof and the ceiling.
What is the difference between a hot roof and a cold roof?
Cold roof: As the majority of the insulation is between the rafters, the overall build-up of the roof is often less. Warm roof: The insulation is laid above the substrate layer so the overall roof construction is generally deeper.
Why is warm roof better than cold roof?
Warm roof insulation ensures the entire roof structure is insulated, meaning a warm deck roof is more energy efficient than a cold roof.
What is a cold roof system?
A cold roof is one of a couple of different roof construction options for houses in order to insulate them effectively. Also sometimes referred to as a cold deck roof, it’s a roof where the insulation sits directly on top of the ceiling plasterboard, usually nestled between the floor rafters.
What is a warm roof system?
Warm roof systems for flat roofs are assemblies where the thermal insulation is installed on top of the roof structure. This keeps the structural decking, usually constructed from timber, steel or concrete, at the same temperature levels as the internal temperature of the building.
Do cold roofs need ventilation?
Cold Roofs
A cold roof is where all of the insulation is placed either between and under or completely under the joists or deck. No insulation is on top. In this way the roof itself is kept cold. You only need ventilation in a cold roof.
Should a loft be hot or cold?
The majority of us just use the loft space for storage so normally a cold loft will more than suffice, but for some we use the loft space for a games room or a study. To be honest, insulating your loft as a cold loft is far easier than trying to produce a warm loft – mainly because you don’t need to fight gravity.
Can you insulate a cold roof?
Installing or upgrading loft insulation is probably the quickest and most efficient method of improving the thermal performance of an existing building.
Does a cold roof need a vapour barrier?
Wrong! sadly, it’s often the way – out of sight, out of mind, but the humble VCL is actually a very important part of the roof build-up. Be it a cold or warm roof construction, the primary function of a VCL is to keep warm moist air from inside the building – inside the building.
Can you insulate under a warm roof?
The general advice we give is that you should always insulate between and above the rafters (warm roof) or between and under the rafters (cold roof).
What kind of insulation do you use for a warm roof?
Flat roof insulation is used to enable a room to feel warmer in the winter and cooler in the summer months. Wood fibre, cellular glass and polystyrene (EPS or XPS) all have good insulation properties, but foam works particularly well and is often found in modern constructions.
How is a warm roof constructed?
A warm flat roof is formed by placing a layer of insulation over the top of the roof structure. Due to the insulation being over the top of the roof, the timber structure beneath is warm, which is why the term ‘Warm Roof’ is formed.
How do you ventilate a cold flat roof?
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What happens if a roof is not vented?
Roof vents create proper air flow, which reduces moisture that can build up inside an attic. Extra, unneeded moisture can damage almost any and every area of your roof. Also, attics without proper ventilation see mold grow as moisture is not expelled.
How much insulation do I need for a cold flat roof?
An uninsulated flat roof has a U-Value of around 1.5 W/m2K. When insulating one, you’re aiming for a value of 0.25 W/m2K or less. To achieve this, you should insulate your flat roof with insulation boards totalling around 150mm thickness.
Do I need soffit vents on a flat roof?
It’s almost always needed, except for houses that already have warm flat roofs. As for cold flat roofs, which are more common, they need this type of ventilation because they collect higher amounts of condensation during the winter.
What is a mushroom vent?
Turbine roof vents – turbines are mushroom-shaped vents that spin with the wind currents and help to expel hot air from your attic.
Does a warm flat roof need to be ventilated?
Your flat roof needs the ventilation to keep, more or less, the inside of the roof the same temperature as the outside. This is the easiest way to prevent condensation, and there we are all aware of how much damage moisture can be to a roof.
