What is the difference between a cold roof and a warm 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.
Which is better warm or cold flat roof?
A warm roof is the easiest and most cost effective type of insulation and is an ideal choice for pitched roofs. On some flat roof extensions and balconies, a warm roof would increase the height and isn't possible, in this scenario you should choose a cold roof insulation.
What is a warm roof construction?
A warm roof is a type of roof construction which has an insulation layer above the rafters, and immediately below its weatherproof membrane.
What is a cold roof assembly?
A vented or “cold” roof has been the traditional roofing assembly for many years. A cold roof implies that the attic is not within the conditioned space of the home. Instead, the attic has insulation on the floor that separates air between the conditioned and attic spaces.
Do cold roofs need ventilation?
Cold deck roof construction The cold deck roof as shown above has the insulation at ceiling level and must have a ventilated cavity of at least 50mm. The cavity must be ventilated on two opposing sides by a continuous ventilation gap of 25mm.
What is the purpose of a cold roof?
A cold roof offers a house good insulation, meaning that the rooms below it stay warmer than the space above. Warm or damp air is able to rise up through the ceiling and above into the ventilation space within the roof and circulate out as opposed to causing condensation.
What are the 4 types of roofs?
4 Types of RoofsGable Roof. This roof type is known for its distinguishable triangular shape feature. ... Mansard Roof. This roof type was adapted from the French and has a much steeper lower slope. ... Flat Roof. This roof type may not be entirely flat but have a low-sloped pitch that makes them appear flat. ... Hip Roof.
Does a cold roof need a Vapour barrier?
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 convert cold roof to warm roof?
It is often preferable to convert an existing cold roof to a warm roof construction, as this greatly reduces the problem of thermal bridging.
How do you frame a cold roof?
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How much insulation should be in a cold 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.
Are cold flat roofs allowed?
Cold roofs must have ventilation. Warm roofs must have a VCL bonded to the deck. Roofs must be wind resistant and strong enough to walk on.
Does warm flat roof need ventilation?
A warm flat roof usually does not require ventilation. What space do I need to allow for the ventilation? To ensure sufficient ventilation, enough space must be provided to allow for the movement of air, preventing the risk of condensation forming within the roof.
How much more efficient is a warm roof?
The warm roof can come in many different styles and with different materials. We spoke to Warmer Roof in Somerset; they use a timber build for their warm roof and they tell us “Our Warmer Roof is at least 5 times more energy-efficient than traditional glazed conservatory roofs.
Why use a warm roof?
A warm roof will make the entire structure of the building warm in an attempt to avoid any cold bridging. It has a continuous insulation layer above the rafters and immediately below its weatherproof membrane.
Are cold flat roofs allowed?
Cold roofs must have ventilation. Warm roofs must have a VCL bonded to the deck. Roofs must be wind resistant and strong enough to walk on.
How does a cold roof work?
The cold roof is very similar to traditional ventilated roofs in the sense that air is allowed to enter the eaves of the roof through a vent. The air travels up the roof pitch and exits at the roof peak. To accomplish this we install 1×3 pine strapping along the roof every 18″.
Why use a ventilated cold roof?
Ventilated roofs are nothing new, however ventilated cold roof are used on SIP roofs in order to prevent ice dams, damage from trapped moisture and a second layer of defense for roof leaks. In this article I’ll show you how we use ventilated cold roofs on timber framed homes that have SIP’s roof panels.
What is a SIP roof?
The SIP’s are 6-1/2″ thick Urethane foam panels that create an amazing insulation layer and a great vapor barrier. While Urethane insulation can stop interior water vapor from hitting the cold roof surface these panels do have joints that could possibly let air through. If water laden air passes through joints in the SIP’s it could hit the cold roofing surface and condense leading to possible rotting problems on the SIP panels.
What size vents are used on a 5/8 roof?
The soffit detail for this house will include a 2″ wide continuous strip vent. The ridge of the roof will include a traditional ridge vent.
Why is venting important in the attic?
It prevents condensation and dry rot within the attic wood structure and wood substrates, prevents mould, and prevents warping of the plywood. Proper venting also extends the life of the shingles and roof membranes. Provide ventilation in a ratio of approximately 1:300 of the insulated area. Ideally air should enter the vented soffit, rise as heated in the attic, and exit near the peak of the roof.
Why is it necessary to ice a roof?
Without this detail the roof could be prone to ice dams from sun induced melting and possible water damage from leaking water vapor hitting the cold surface of the SIP’s . This may seem like an extra, expensive step but it’s absolutely necessary in order to prolong the life of the roof and provide a maintenance free roof.
Does a vent work on a roof?
It won’t work correctly. Air needs to come in at the eave and travel up the roof and vent at the top.
Why is closed cell spray foam used on a hot roof?
Because closed-cell spray foam is a vapor and air barrier, the theory is that air and water vapor will never make their way to the roof sheathing, thereby eliminating the need for a vented roof section . The problem with a hot roof assembly is that it relies on a perfect installation of the two-part insulation foam.
What causes a loss of integrity in a roof?
However, any number of factors could potentially create a loss of integrity in the system, including, but not limited to, the following: Improper temperature of the substrate that is being sprayed with insulation ( in this case the underside of the roof deck ) Improper temperature of the spray-foam chemical parts.
Can hot roofs shrink?
Furthermore, a hot roof assembly also relies on the premise that the framing lumber will never shrink, twist, or otherwise change its shape. If this phenomenon occurs, there is a potential for micro-channels to form.
What is cold roof construction?
What does it involve? Cold roof construction, is what is found on most older flat roof buildings and almost all houses both old and new.
What is the second type of roof?
The second type of roof construction is the warm roof.
How does condensation form on a roof?
Warm , moisture-laden air is allowed to flow through the insulation and when it comes in contact with the colder sub-structure of the roof , condensation can form on the structure of the roof. Proper ventilation is required to remove any air that infiltrates the space above the insulation thus preventing condensation from forming.
When designing a warm roof, the architect must take the added weight of the insulation into consideration.?
This is especially true in residential construction of a sloped roof. A sloped roof done with standard construction is not capable of handling the additional weight of insulation so stronger roof trusses must be used.
Can you re-roof a warm roof?
If you are thinking of re-roofing your home or building, the option of a cold or warm roof is already done for you. The roof must be designed to withstand the additional weight of the warm roof or the entire roof must be reconstructed . In most situations you have to live with whatever roof your building or house came with.
Do flat roofs need to be ventilated?
A flat roof installation, due to the warm air being held below the solid surface of the roof, does not need to be ventilated. There is no air-space between the roof and the warm air, thus there is no condensation. When designing a warm roof, the architect must take the added weight of the insulation into consideration.
Can flat roofs be cold?
When you think of roofs, chances are you believe the only way they could be warm or cold is in the summer or winter. The truth is, flat roofs come in two different configurations depending on how the architect designed it.
What is a hot roof?
A “hot roof” means that insulation is installed closely beneath the roof decking, without space for ventilation. In some cases, this design allows the attic space to be usable like any other room in the house by bringing it into the thermal envelope of the home. Since there is no intentional ventilation between the insulation and the roof decking, ...
What is a rafter baffle?
Rafter baffles are an inexpensive component of a vented roof. When it comes to cost-effectiveness, energy bills are the final factor in deciding what type of roof is best. A vented roof will keep a home cooler in the summer, lowering cooling costs, and keep the roof cool in the winter, preventing costly ice dams.
Why is the attic warmer in the summer?
The attic may become warmer during the summer as the insulation conducts heat into the attic. During the winter, an unvented attic will remain warmer. But without ventilation, the chance for ice damming, mold, and moisture accumulation is higher. With an unvented roof, these damages are less easy to notice.
What is Accublock insulation?
AccuBlock is designed for unvented roofing assemblies, but it serves a function in vented roofs, too. In an unvented roof, it acts as a template for spray foam insulation to prevent overspray and to allow the insulation blanket to cover the top plate.
Do you need a ridge vent for an attic?
Instead, the attic has insulation on the floor that separates air between the conditioned and attic spaces. For this type of roof, you’ll need to have proper soffit vents, a ridge or gable vent, and ventilation baffles. AccuVent rafter baffles are compatible with all types of insulation, including spray foam.
Can an unvented roof be used as an attic?
Air sealing, proper insulation density, and vapor retarders all come at a cost, but depending on your climate, an unvented roof done right can make your attic space livable and keep conditioned air inside where it belongs. A vented or “cold” roof has been the traditional roofing assembly for many years.
Does a hot roof allow air exchange?
During the summer, a hot roof does not allow for air exchange between exterior and interior air.
